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The aim of this study was to evaluate some physical and mechanical properties of the paper mill (PMS) and spruce planer shaving added cement boards. Also the effect of sludge type in consequence of waste water treatment technique on properties of wood-cement boards (WCB) was investigated. The wood/cement ratios were used as 1/3, based on the oven dry weight for the WCB manufacture. PMS was used up to 20% wt of total composite based on organic (wood) and inorganic (cement) amounts. Black sludge has shown more improvement than grey sludge on properties of WCBs, which indicates the anaerobic waste treatment technique is more effective for additive in WCB. The modulus of rupture and elasticity values of the WCBs with 5% of grey sludge, 5% and 10% of mixture of grey and black sludge were acceptable limits according to EN 634-2 standard. The mechanical strengths of all WCBs with black sludge were found above the specified EN standard. This suggests that PMS depending on sludge type may be used up to 20% wt of total composite weight for the commercial production of WCBs, which could expand the raw material base for this panel product. [ABSTRACT FROM AUTHOR]

In the present work, unshredded waste newspaper based composites have been prepared in polyester resin matrix. Reinforcing material, waste newspaper is characterized by chemically, X-ray diffraction (XRD) methods, Fourier transform infrared spectroscopy (FTIR) and tensile properties. Three different fibre content composite samples, namely 25%, 34%, and 50% (by weight) are prepared by hand lay-up techniques. Water absorption and thickness swelling tests are conducted by immersing composite samples in distilled water at room temperature. It is found that the percentage of moisture uptake and thickness swelling are increased as the fibre volume fraction is increased due to the high cellulose content. The tensile, flexural and interlaminar shear strength properties of water immersed samples are investigated and compared with dry composite samples. It is observed that after swelling the mechanical properties of composites are found to decrease with increase in percentage moisture uptake. [ABSTRACT FROM AUTHOR]

• The waste paper is transformed into Aggregates of Waste Paper (AWP). • New biocomposite based on the Aggregates of Waste Paper and Lime (AWPL) is formulated and characterized. • The microstructure of the new composite AWPL is characterized by high open porosity. • The thermal conductivity of the material AWPL are ranging between 0.097 and 0.012 W/mK. • The compressive strength of the material AWPL is ranging between 4.2 and 10.95 MPa. • The new material AWPL can be used as structural material and thermal insulation. In the aim of the valorisation of waste paper, an experimental study of a new biocomposite (AWPL) dedicated to building based on Aggregates of Waste Paper and Lime is performed. The waste paper used in this work is transformed to Aggregates of Waste Paper (AWP), the physical, thermal and morphological properties were carried out. Five combinations of (AWP – Lime) have been prepared and the weight ratios of lime used are 20, 30, 40, 50, and 60 wt% correspond. Experimental investigations of physical, mechanical, thermal and morphological characterizations of AWPL were carried out in order to determine: the apparent density, the open porosity, the water absorption, the ultrasound pulse velocity, the flexural and compressive strengths and the thermal conductivity. Furthermore, a characterization by Scanning Electron Microscopy (SEM) was realized to observe the AWP/lime bond. The results of characterization of AWPL show good mechanical properties as flexural and as compressive, these results are confirmed by the analysis SEM, that shown good adhesion of the AWP/Lime interface. The thermal characterization tests of AWPL have shown an important thermal insulation capacity linked to the low values of the thermal conductivity, these low values can be explained by the high porosity of AWPL. As a result, the AWPL could be classified as a structural and thermal insulation material for buildings according to the RILEM classification. [ABSTRACT FROM AUTHOR]

The rapid solidification and significant shrinkage of alkali-activated slag cement are key issues that restrict its practical engineering application. This paper explores the composition design of alkali-activated cements (AAC) with slow coagulation and shrinkage reduction. This paper adjusts the proportion of slag (SG) and calcined coal gangue powder (CCGP), regulates the content of Na 2 O·2.4SiO 2 -NaOH-Na 2 CO 3 ternary activator components, and uses calcium carbonate whiskers (CW) instead of SG to prepare AAC with slow coagulation and shrinkage reduction. When the activator is composed of (66 %) Na 2 O·2.4 SiO 2 -(2 %) NaOH-(32 %) Na 2 CO 3 mixed composition, the CO 3 2- and Ca2+ in the system react preferentially to produce CaCO 3. The decrease of Ca2+ concentration delays the formation of C-(A)-S-H, resulting in the initial and final setting time of AAC reaching 334 min and 346 min, respectively. When the CW substitution rate is 3 %, the 28d compressive strength of AAC reaches 102.2 MPa. The 49d drying shrinkage of the AAC is 7020μm/m and the 49d autogenous shrinkage is 2387μm/m. This is attributed to the combined effect of enhancement mechanisms such as whisker bridging, crack deflection, whisker pullout, whisker–matrix coalition pullout and whisker breakage. This study establishes the relationship between the composition and performance of high performance AAC, which is significance for the resource utilization of coal gangue and the practical engineering application of AAC. • The composition of Na 2 O·2.4SiO 2 -NaOH-Na 2 CO 3 ternary mixed activator was designed. • Calcium carbonate whisker (CW) was used to reduce the shrinkage of AAC. • The retarding mechanism of Na 2 CO 3 was clarified. • The microscopic enhancement mechanisms of CW were explored. [ABSTRACT FROM AUTHOR]

3D printing technology, as a rapid prototyping method, can accurately reconstruct the internal structural characteristics of samples, making it highly promising for rock engineering applications. However, current 3D printing materials used to reconstruct rocks suffer from low strength and high ductility, which is inconsistent with the high strength and brittleness of natural rocks. This paper explores the use of silane coupling agents KH550 (γ-aminopropyl triethoxysilane) and KH570 (γ-methacryloxypropyl trimethoxysilane) to modify nano SiO 2 powder. Through sample preparation and uniaxial compression tests, the mechanical properties and failure characteristics of the modified nano SiO 2 powder were analyzed. The results indicate that, using the preparation method with a mass ratio of E-44 epoxy resin, KH550 modified nano SiO 2 powder, and 593 curing agent at 80:40:26, the samples achieved an uniaxial compressive strength of up to 30.55 MPa without enhanced brittle post-processing. The failure characteristics exhibited significant axial tensile damage. Additionally, combining CT scanning technology demonstrated that the structural and mechanical properties of the samples can be effectively reproduced. Therefore, the 3D printing materials discussed in this paper provide a viable reference for accurately reconstructing high-strength and high-brittleness rock masses. • New printing material can model the high strength and brittleness of rocks. • Different silane coupling agents on nano SiO 2 -modified E-44 epoxy resin. • Mechanical properties and failure modes of samples with varying mass ratio. [ABSTRACT FROM AUTHOR]

Eucalyptus is one of the most important plantation species in South China. Alternate applications of plantation grown hardwood such as eucalyptus need to be developed due to decreased demands of fibers for pulp and paper industry. The feasibility of manufacturing three-layer cross-laminated timber (CLT) using fast-grown small diameter eucalyptus wood ( Eucalyptus urophylla × Eucalyptus grandis ) was evaluated in this study. L 9 (3 3 ) orthogonal tests with three factors and three levels were adopted to study the effects of adhesive spread rate, pressure, and pressing time duration on the block shear strength (BSS), wood failure percentage (WFP), and rate of delamination (RD) of CLT via block shear tests and cyclic delamination tests. The results indicated that the optimal pressing parameters were adhesive spread rate of 160 g/m 2 , pressing pressure of 0.8 MPa, and pressing time duration of 200 min with one-component polyurethane adhesive used. The values of modulus of elasticity (MOE) and modulus of rupture (MOR) in the major and minor strength directions of CLT were 11,466 MPa, 24.5 MPa, 681 MPa, and 8.6 MPa, respectively. The values of transverse shear moduli and interlaminar shear strength in the major and minor strength directions of CLT were 91.8 MPa, 1.3 MPa, 241.6 MPa, and 0.5 MPa, respectively. The mechanical properties of eucalyptus CLT were equivalent to those of commercially available softwood CLT. These results indicate CLT panels manufactured from fast-grown small diameter eucalyptus lumber is promising for structural applications. [ABSTRACT FROM AUTHOR]

Recycled Aggregate Concrete (RAC) has attracted considerable attention for its potential to conserve natural resources and mitigate carbon emissions. Nevertheless, the widespread adoption of RAC in the construction industry faces challenges associated with its inherent performance deficiencies, including the formation of pores and microcracks in the recycled aggregate (RA) generated during the crushing process, as well as the presence of dual interfacial transition zones (ITZ) within the internal structure of RAC. The incorporation of fibres as reinforcement offers a promising solution to improve the performance of RAC. The paper begins with a comprehensive examination of various fibre properties and recycled aggregates. Then, summarizing the impact of fibres on RAC's performance. Special emphasis is placed on analyzing the influence of mixed fibres on the mechanical properties of RAC. The introduction of a blend of low-strength and high-strength fibres demonstrates the potential for further improving the mechanical properties of RAC beyond the benefits offered by individual fibres. This blending strategy also enhances the multiscale crack resistance of RAC, attributed to the collaborative effects of various fibres at different load stages. The reinforcing mechanism at the micro-scale of RAC is also discussed. Finally, the paper outlines perspectives for future research. [Display omitted] • A comprehensive review of hybrid fibre reinforced recycled aggregate concrete. • The effects of a single type of fibre on mechanical properties and microstructure. • Combining high-strength and low-strength fibres shows positive effects. • Blended fibres induce a dense C-S-H gel phase, enhancing cracking resistance. • The economic and environmental impacts are discussed. [ABSTRACT FROM AUTHOR]

The outbreak of the COVID-19 epidemic has led to a large number of waste disposable medical face masks (DMFMs) worldwide, which seriously pollute the environment and threaten human health. In this paper, waste DMFMs were recycled as mask fiber and mixed into self-compacting recycled aggregates concrete (SCRAC) to form a mask fiber reinforced self-compacting recycled aggregates concrete (FRSCRAC). The effects of recycled coarse aggregate (RCA) replacement ratio, DMFM fiber content, and length on the working and mechanical properties of FRSCRAC were investigated. The results show that the specimens meet the requirements of self-compacting concrete (SCC) in terms of working and mechanical performance, but the RCA and DMFM fiber could reduce the workability of the FRSCRAC, and the higher the amount of RCA and DMFM fiber, the more obvious the reduction. At the same time, the mechanical properties of FRSCRAC increased as the decreasing RCA replacement ratio and growing DMFM fiber content. Compared with specimens without DMFM fiber reinforcement, the compressive strength, split tensile strength, flexural strength, and elastic modulus were increased by 1.3%-9.6%, 1.46%-8.6%, 24.4%-54.69%, and 0.65%-4.73%, respectively. Moreover, the reduction of the DMFM fiber length is favorable to the mechanical properties of FRSCRAC as well. Furthermore, the X-ray CT and scanning electron microscope (SEM-EDS) techniques were applied to analyze the microstructure of typical specimens. The results showed that the DMFM fiber and surrounding mortar could form a multiphase composite, which reduces the porosity and improves interfacial stress transfer efficiency, thus enhancing the mechanical properties of FRSCRAC. In addition, based on the experimental results, the mechanical strength index of FRSCRAC and the calculation formula of its mutual conversion relationship were proposed. The research conclusions of this paper can provide a reference for the application of waste DMFM fibers in FRSCRAC. • Waste disposable medical face masks were recycled as fiber and mixed into self-compacting recycled aggregate concrete. • Parameters were investigated to make clear the influential mechanisms of waste fiber on recycled concrete performance. • The mechanical strength index of FRSCRAC and the calculation formula of its mutual conversion relationship were proposed. [ABSTRACT FROM AUTHOR]

Engineered Cementitious Composites (ECC) utilize the bridging effect of high toughness fibers to improve the brittle failure of concrete materials, achieve the effective control of cracks in cementitious materials, and significantly improve the deformation capacity. In view of the multi-stage crack-blocking effect of different fibers incorporated in ECC materials, 91 ECC specimens of steel-polypropylene hybrid fiber by mixing steel fiber (SF) and polypropylene fiber (PPF) into cement-base are made in this paper. The specimens are tested in compression, tensile, bending and damping properties, respectively, which is of great significance to study the response of ECC structures under the earthquake action. The effects of the volume content of SF and PPF on the mechanical properties of ECC are studied in this paper. The results show that the cube specimen has better ductility than the prismatic specimen under monotonic compression, and there is no obvious brittle failure. With the increase of the volume content of SF to PPF, the compressive strength and elastic modulus of hybrid fiber ECC gradually increase, while the corresponding strain and axial compressive toughness gradually decrease; the tensile strength and tensile modulus increase, while the bending strength and damping ratio decrease. According to the test results, constitutive models of monotonic and repeated loading of hybrid fiber ECC suitable for finite element (FE) analysis are proposed. This investigation provides a theoretical basis and an experimental reference for further study of steel-polypropylene hybrid fiber ECC. • Steel fiber and polypropylene fiber are mixed as hybrid fiber of ECC. • The mechanical properties of ECC are investigate. • Volume content of steel-polypropylene hybrid fiber has influence on concrete material. • The hybrid fiber ECC cube has better ductility than that of prismatic. • Constitutive models of hybrid fiber ECC are suitable for finite element analysis. [ABSTRACT FROM AUTHOR]

This paper presents a thorough investigation into utilizing hybrid fibers, comprising both steel and polymeric fibers, to enhance the compressive and tensile behaviors of ultra-high-performance concrete (UHPC). Flowability tests revealed potential usability challenges with polymeric fibers, emphasizing the necessity for careful consideration. Compressive strength results demonstrated that hybridizing straight steel fibers with short hooked steel fibers results in performance similar to that of reduced steel fiber content. Elastic modulus trends correspond with those of the compressive strength, and unexpectedly positive effects on the ultimate strain capacity under compression are observed with long polyvinyl alcohol fibers. Tensile behavior analysis highlights the superiority of both short and long hooked steel fibers, with the latter contributing the highest tensile strength. However, the use of polymeric fibers significantly decreases the tensile strength owing to insufficient dispersion and low tensile strength. Scanning electron microscopy images of UHPC with polymeric fibers reveal debonding and surface damage, with potential advantages observed for polypropylene fibers through methods such as surface moisture coating. In conclusion, this paper provides insights into optimizing fiber content and types for UHPC, emphasizing a balance between reduced fiber content and maintained performance. The proposed hybrid reinforcement approach, particularly with short hooked fibers, is promising for practical usability and cost-effectiveness in construction applications. • Addition of hybrid fibers, particularly polymeric fibers, results in a decrease in flowability. • Hybridizing with hooked fibers decreases the fiber content by 0.5 % given similar strength levels. • Long PVA fiber is effective in increasing elastic modulus of UHPC due to limited deformation. • Hybrid use of straight and hooked steel fibers exhibits improved tensile performance of UHPC. • Introduction of PVA and PP fibers causes a decrease in the tensile strength of UHPC. [ABSTRACT FROM AUTHOR]

Fully utilizing regional resources such as marine sand, coral, and desert sand, along with a diverse range of solid wastes from industries, agriculture, and urban areas, not only effectively reduces the costs and carbon footprint of construction activities but also contributes to achieving sustainable development in the building sector. Despite earlier studies focusing on the feasibility of solid waste as lightweight aggregates, the comprehensive evaluation of the performance of alternative aggregates in such innovative materials as geopolymers and ultra-high-performance concrete remains significantly limited amid their rapid development. Therefore, this paper concentrates on a thorough exploration of regional sand and gravel resources, as well as efficient and value-added approaches to incorporating solid wastes from industries, agriculture, and urban areas as alternative aggregates in construction. It provides a comprehensive review of the physical properties of alternative aggregates and their impacts on the workability, mechanical properties, and durability of concrete. Additionally, the paper offers a detailed assessment of the production processes and performance of sintered and cold-bonded artificial aggregates. This research provides valuable insights for researchers and practitioners in the fields of construction, sustainable waste management, resource conservation, and recycling. • Regional resources, industrial and agricultural and urban solid wastes are used as clean aggregates. • Potential legal challenges to the use of clean aggregates are revealed. • Reviewed the modification methods of granular solid waste. • Reviewed artificial agglomeration techniques and potential challenges for powdered solid waste. [ABSTRACT FROM AUTHOR]

Basalt fiber (BF) is an emerging environmentally-friendly fiber. Adding basalt fiber can improve the deficient recycled concrete's poor mechanical properties and durability. By reviewing nearly 120 related papers, the effects of variables such as BF content and length (0–1.5%, 9–18 mm), recycled aggregate substitution rate (0–100%), and cement mix ratio (w/b, 0.25–0.45) on the mechanical and durability properties of basalt fiber-reinforced recycled concrete (BFRAC) were discussed. Due to the presence of vulnerable interfacial transition zones, the mechanical properties of recycled concrete (RAC) continuously deteriorate over time. However, by adding an appropriate amount of basalt fiber, it is possible to improve these structural defects by forming a network structure that enhances cracking resistance within the matrix and improves interface bonding strength among other benefits. Consequently, this significantly improves the overall mechanical properties of RAC. Additionally, while incorporating recycled aggregate (RA) may reduce compressive strength initially, this deficiency can be mitigated through the proper inclusion of fibers in RAC mixtures. Optimal compressive strength for RAC is achieved with a replacement ratio between 25–50% and a fiber content ranging from 0.2–0.3%. Furthermore, properly incorporating fibers into RAC greatly enhances splitting tensile strength and flexural strength as well; specifically achieving optimal splitting tensile strength with a replacement ratio between 40%− 50%, a fiber content at 0.3%, and utilizing fibers with lengths measuring approximately 12 mm long. The primary cause for poor frost resistance in RAC lies within numerous micro-cracks and pores present in RA aggregates which lead to high water absorption rates ultimately reaching critical water saturation points resulting in freeze-thaw damage occurrences during exposure to freezing conditions. When exposed to sulfate attack, RAC undergoes a chemical reaction with sulfate ions present in the concrete, leading to the formation of numerous expansion products that negatively impact concrete performance. Progressive dehydration of hydration products under high-temperature conditions leads to a porous structure within the concrete matrix. Incorporating fibers can impede microcrack expansion during freeze-thaw, sulfate attack, and high-temperature environments, thus enhancing the erosion resistance of RAC. Compared to conventional concrete, interfacial bonding in RAC is less tight and more vulnerable to damage in complex environments. Current research on RAC suggests that the mechanism behind its damage under complex freeze-thaw load coupling environments remains unclear. It is recommended that future studies combine large-scale component tests with computational simulations to address this issue. • This paper discusses the mechanical properties and durability of BFRAC. • Numerous micro-cracks and pores in RA cause high water absorption. • When exposed to sulfate attack, CH reacts with SO2- 4 to form expansion products. • Hydration products' dehydration at high temperatures results in loose of concrete. • BF inhibits the growth of microcracks and enhances its erosion resistance. [ABSTRACT FROM AUTHOR]

Mesoscale modelling is a promising tool to analyse the phenomenological causes of mechanical failure of recycled aggregate concrete (RAC). Most mesoscale models of RAC are two-dimensional (2D) and 3D models are lacking. This prevents the full understanding of the behaviour of each mesoscopic phase. This paper presents a 3D model of RAC and analyses its mechanical behaviour based on mesoscale phenomena. The analyses concern three types of tests carried out in concrete specimens: uniaxial compressive, uniaxial tensile and splitting tensile strength tests. The mechanical response and fracture behaviour of each mesoscopic phase is analysed in relation to the response of RAC specimen. The comparisons between uniaxial behaviour of 3D and 2D modelling as well as between uniaxial and splitting tensile behaviour of RAC are presented. The main findings of the paper are: (1) the full curve of uniaxial stress-strain response from 3D modelling is comparable to that from 2D modelling for RAC (therefore, 2D models are validated for RAC modelling); (2) the overall behaviour of the concrete elements remains elastic regardless of the fracture development in the ITZ and attached mortar of recycled aggregates until damage propagates to the new mortar matrix; (3) a relationship between modelled uniaxial and splitting strength of RAC is established and validated. [Display omitted] • Realistic mesostructural model of RAC - particle size, attached mortar content and ITZ with real thickness. • Replicate the strength test of uniaxial compression, uniaxial tension, and splitting tension. • Validate the use of 2D model through comparison of the outcomes from 2D and 3D models. • The influence of each mesoscopic phase on the overall mechanical behaviour of RAC. • Establish the relationships between the modelled uniaxial and splitting tensile strength. [ABSTRACT FROM AUTHOR]

[Display omitted] • This is a state-of-art review of rubberized recycled aggregate concrete (RRAC) and fiber-reinforced rubberized recycled aggregate concrete (FRRAC). • Different mechanical properties, microstructural analysis, and life cycle assessment of RRAC and FRRAC have been reviewed. • Extensive regression analysis has been conducted to predict different mechanical properties of RRAC and FRRAC. • Crumb rubber (CR) and recycled coarse aggregate (RCA) reduced the strength, however, fiber addition could have a positive response. • Addition of CR and fibers enhanced the toughness and ductility of RRAC; however, excessive amount of CR negatively affected the toughness. • RCA and CR can be used up to 30% and 10%, respectively. The growing population demands rapid development of infrastructures. However, the construction industry is searching for environmentally sustainable and eco-friendly building materials to fight climate change. Millions of tires are discarded globally, and only certain percentages are recycled. The use of rubber tires as a natural aggregate replacement in concrete has gained popularity among the research community in the past few years, primarily due to its ductility and toughness properties. A significant number of investigations have been reported in the past using recycled coarse aggregates (RCA), crumb rubber (CR), and fibers separately in concrete. The results revealed that the addition of rubber particles along with RCA in concrete reduced the strength. However, the inclusion of fibers in the same mixtures significantly improved the mechanical properties of concrete by acting as a bridge within the concrete matrix for the surrounding cracks. In this review paper, over 220 research articles from the last 30 years reporting the effect of RCA, CR, and fibers on the mechanical and physical properties of rubberized recycled aggregate concrete (RRAC) and fiber-reinforced rubberized recycled aggregate concrete (FRRAC) are summarized. This paper presents in detail the influencing factors that affect the physical and mechanical properties of RRAC and FRRAC. The performance of FRRAC depends on the types of fiber and CR, treatment of CR, RCA sources, and the mix design of concrete. Based on the review, recommendations are provided for optimized FRRAC production. Simplified equations have been proposed to predict the tensile and flexural strength and modulus of elasticity of RRAC and FRRAC. An overview of predicting the mechanical properties of rubberized concrete using different machine-learning algorithms has been presented. Finally, this review paper will help scholars understand the use of RCA and CR in concrete as aggregate replacement materials and create waste material utilization opportunities for the sustainable green construction industry. [ABSTRACT FROM AUTHOR]

Magnesium potassium phosphate cement (MKPC) is susceptible to high-temperature damage when used as a fireproofing coating or structural repair material and as a nuclear waste encapsulation shell, and the strength loss and dimensional shrinkage at about 100 °C severely limit the application of MKPC. Therefore, in this paper, the macroscopic properties, physical phase composition and microscopic morphology of sucrose-modified MKPC at room and high temperatures (20°C, 50°C, 120°C) are investigated from the perspective of modified retarder, and the mechanism of sucrose's influence on MKPC at high temperatures and the optimal dosage are speculated, and the Pearson correlation analysis is performed on the various macroscopic and microscopic indexes. The results showed that 2.5 % sucrose doping could reduce dimensional shrinkage by 59.6 % and increase late strength by 21.8 % at high temperatures, significantly optimizing the macroscopic properties of MKPC. The inhibition of the high-temperature decomposition product MgKPO 4 ·H 2 O by sucrose and the reduction of pores formed by water evaporation are among the main reasons for the optimization of the properties. Additionally, the adsorption of amorphous products to form new polymers that fill the pores is also an important reason for the optimization of performance. However, Pearson's correlation analysis showed that too much sucrose contributed to the reduction of pulp strength, and its optimal dosage should be between 2 % and 3 %. • Experiments on the effect of sucrose on MKPC performance at high temperature. • Sucrose optimizes high-temperature-induced dimensional shrinkage of MKPC. • Sucrose at high temperature significantly reduced the late strength loss of MKPC. • Sucrose forms polymers to fill MKPC pores and improve densification. • The optimal range of sucrose dosing is 2∼3 %. [ABSTRACT FROM AUTHOR]

Compared to ordinary Portland cement (OPC), sulphoaluminate/ferroaluminate cement (SAC/FAC) and aluminate cement (CAC) are the most promising repair materials due to their excellent early strengths, but the later strengths of SAC/FAC develop slowly, and the later strengths of CAC are obviously declined. This paper studied the effects of nano-SiO 2 and nano-ZnO on the physical properties, mechanical properties and early hydration processes of three special cement-based materials and compared them with OPC-based materials. The strength development and early hydration mechanism were revealed by hydration heat, scanning electron microscopy and X-ray diffraction. The test results showed that with the increasing content of nano-SiO 2 , the setting time of the four cement pastes was gradually shortened, the fluidity of four fresh mortars was gradually reduced, and their compressive and flexural strengths at all ages were improved to different degrees. Nano-ZnO significantly prolonged the setting time of OPC paste and increased the fluidity of OPC mortar, which had a negative effect on its early compressive and flexural strengths, but enhanced its late strengths. After the addition of 1 % nano-ZnO, the initial and final setting time of OPC were about 12 times and 13.4 times that of ordinary OPC paste, respectively. The effect of incorporating nano-ZnO on the physico-mechanical properties of three special cements was similar to that of nano-SiO 2. The strength loss of CAC mortar with two kinds of nanoparticles was greatly reduced. The incorporation of nano-SiO 2 and nano-ZnO could promote the hydration process of three special cements, resulting in the denser microstructure and higher crystallinity of hydration products. • Effect of nanoparticles on the properties of three special cementitious materials. • The strength development law of three kinds of special cement was found. • The early hydration mechanism of three kinds of special cement was revealed. • Nano-ZnO retarded the hydration process of ordinary Portland cement. [ABSTRACT FROM AUTHOR]

In this paper, the effects of the content of steel fiber and lightweight aggregate types on the mechanical properties of lightweight engineered geopolymer composites (LW-EGC) were investigated by uniaxial compression tests. The effect on compressive strength, stress-strain curves, elasticity modulus, peak strain, and energy absorption were discussed. The results showed that the type of lightweight aggregate had a significant effect on the mechanical properties of LW-EGC. LW-EGC-C had higher compressive strength, elasticity modulus, and energy absorption capacity. LW-EGC-S had a higher peak strain. Adding steel fibers could greatly increase the compressive strength, peak strain, and energy absorption. Meanwhile, there was an optimal range for the volume content of steel fiber, so the best improvement effect was achieved when the content of steel fiber was 1.0 %. Compared with LW-EGC-M, the above mechanical properties were improved by 39.28 %, 15.32 %, and 26.17 %, respectively. In addition, based on the existing constitutive models and test results, a stress-strain model for LW-EGC suitable for incorporating steel fibers is proposed. The constitutive model was divided into a rising phase and a falling phase, which could describe the falling curve more accurately than the existing constitutive models, indicating that it could reliably describe the compressive stress-strain response of LW-EGC. • Effects of steel fiber content and ceramsite types on the compressive properties of LW-EGC were studied. • The effect on compressive strength, stress-strain curves, elasticity modulus, peak strain, and energy absorption were analyzed in detail. • When the steel fiber content was 1.0 %, the mechanical properties of LW-EGC were best improved. • A stress-strain model suitable for LW-EGC has been proposed considering the effect of steel fiber content. [ABSTRACT FROM AUTHOR]

Circulating fluidized bed fly ash (CFA) is a waste emitted from coal combustion process in circulating fluidized bed boilers. The high SO 3 and f-CaO content severely limits its application in building materials. The purpose of this study is to explore the possibility of large-scale application of CFA in autoclaved aerated concrete (AAC). The preparation parameters of AAC were discussed and the performance was optimized. Moreover, the workability and environmental properties of AAC were explored. The results indicated that AAC was well adapted to high CFA content, although a high CFA content caused a higher water demand as well as a reduction in the silicon content. The introduction of quartz sand and blast furnace slag effectively addressed the problems of insufficient active silica and high specific gravity. When the CFA doping was 50 %, H4 sample showed the best mechanical properties (3.82 MPa and 641 kg/m3), which meet the requests of A3.5, B06 in the Chinese national standard GB/T 11968–2020. Moreover, the toxicity leaching results showed that H4 sample was green and harmless. During the performance optimization process, more well-crystallized tobermorite was produced, whose crystal form changed from acicular to slat. Massive C-S-H gels and better crystallinity of tobermorite were observed, where were bonded and intercalated with each other, thus enhancing the properties. The paper may provide guidance for high dosing of CFA in AAC. • The potential for extensive use of CFA in AAC was verified. • The mechanical, durability and microscopic properties of CFA-based AAC were studied. • The utilization rate of CFA in building materials was increased to 50 wt%. • CFA-based AAC was a green material whose heavy metals were well consolidated. [ABSTRACT FROM AUTHOR]

Based on the thermal activation method, utilizing fine particles of waste concrete to prepare low-carbon recycled cement (RC) is currently one of the research hotspots. Based on existing literature research results, this paper identifies four calcination temperature conditions (120, 450, 750, 1000 ℃) and uses replacement rates of 10 %, 30 %, 50 %, 70 %, and 100 % of RC to replace ordinary Portland cement (OPC).The main physical properties, hydration characteristics, mechanical properties, and microstructure of RC are studied. The study elucidated the influence of RC thermal activation temperature, replacement rate, fineness, and age on its hydration characteristics, mechanical properties, and microstructure, establishing a macro-micro correlation for RC and revealing the mechanism of improvement in mechanical properties of thermal-activated RC. The research indicates that in the initial stage of hydration, RC exhibits a relatively fast hydration rate, with higher initial total heat release than OPC. Hydration products include internal hydration products (formation of C-(A)-S-H gel) and external hydration products (formation of plate-shaped AFm). Furthermore, RC exhibits a faster hydration rate at a hot activation temperature of 750°C, with CH and C-S-H gel transforming into the highly hydrated α´L-C 2 S, forming a denser microstructure at an early stage. Moreover, at a replacement rate of 30 %, the compressive strength of cement mortar reaches its optimum at 28 days, achieving 13.81 MPa, equivalent to 60.7 % of OPC cement mortar, with a 66.67 % reduction in carbon emissions. Microstructure analysis reveals that when the temperature reaches 1000°C, excessive combustion of RC leads to the formation of low-reactivity C 2 AS and β-C 2 S, resulting in a decrease in macroscopic mechanical properties. Additionally, increasing the fineness of RC significantly enhances its rehydration capability, especially as the age increases. This study is of great significance for the preparation of green cement-based composite cementitious materials. • Studied the impact of thermal activation, substitution rate, and fineness on RC's mechanical properties. • The hydration characteristics of RC under different thermal activation temperatures were discussed. • The microstructure and mechanism analysis of thermally activated RC were explored. • The carbon emissions of RC at different thermal activation temperatures were compared to identify the optimal temperature. [ABSTRACT FROM AUTHOR]

Cemented paste backfill technology is a green and advanced backfilling method. However, its reliance on cement as a binder has become one of the key constraints to its widespread application due to the high cost of cement. This paper utilized solid waste materials, including anhydrous phosphogypsum (APG), blast furnace slag (BFS), and carbide slag (CS), to prepare a low-cost binder for backfilling. The working performance, physical and mechanical properties, and hydration mechanism of the ABCB (ABCB) were analyzed, along with an assessment of its environmental and economic benefits. The results showed that: (1) The binder composed of 35 % APG, 60 % BFS, and 5 % CS exhibited the optimal ratio, with good working performance. Its 28-day flexural strength and compressive strength reach 7.22 MPa and 51.42 MPa, respectively, with a water absorption of only 1.98 % and a softening coefficient of 0.926. (2) CS effectively promoted the hydration of APG and BFS, reducing porosity and enhancing strength development. However, excessive CS adversely affected the binder's strength. (3) The phosphorus and heavy metal content leached from the binder met the standard requirements. Compared to cement, the binder prepared with the optimal ratio reduced prices by 220 RMB/t, decreased carbon emissions by 756.9 kg/t, and lowered energy consumption by 4420 MJ/t. Therefore, applying the ABCB in backfill mining can significantly enhance both environmental and economic benefits for mines. • A full-solid waste binder composed of APG, BFS, and CS for cemented paste backfill was developed. • The working performance and physical-mechanical properties of APG-BFS-CS cementitious material were analyzed. • The hydration mechanism of APG-BFS-CS cementitious material was analyzed by SEM, EDS, and XRD. • The economic and environmental benefits analysis was performed on the APG-BFS-CS binder. [ABSTRACT FROM AUTHOR]

This paper performed the research on the autogenous shrinkage mitigation mechanism and mechanical properties of alkali-activated high strength mortar (AAHSM) incorporating hydroxypropyl methylcellulose (HPMC). The increase in HPMC content causes the lower slump flow and the longer setting time of AAHSM due to the flocculation effect of HPMC. Because of strong interaction between the hydroxyls of HPMC and water, the higher internal relative humidity is achieved, leading to the much lower capillary pressure. The unreacted precursors and reaction products are wrapped by the HPMC molecular network, causing that the depolymerization-polymerization reaction is prevented, which leads to the lower reaction degree. The increase in HPMC content promotes less generation of C(N)-A-S-H gels and more generation of hydrotalcite. The adhesion forces between reaction products particles are enhanced by the flocculation effect caused by the HPMC molecular network, indicating that the AAHSM containing HPMC has larger resistance to the deformation. Adding HPMC has a slight effect on the element compositions of reaction products and the pore types and a slight adverse effect on the Yang's modulus of reaction products micro region. Thus, the 56 days autogenous shrinkage of AAHSM is reduced by 22.2 % when the HPMC content is 2.0 wt%. Although the proportion of meso pore is increased by adding HPMC, the higher porosity and coarser pore structure are achieved, thus the autogenous shrinkage is still reduced. The lower reaction degree and generation of C(N)-A-S-H gels caused by adding HPMC lead to the higher porosity, which is related to the lower compressive and flexural strength. When the HPMC content is 2.0 wt%, the 28 days compressive and flexural strength of AAHSM are 89.2 MPa and 8.2 MPa, which are decreased by 17.3 % and 16.3 % compared to that of AAHSM without HPMC. At longer curing age, the reaction degree is improved and more Ca-rich C(N)-A-S-H gels are generated regardless of with or without HPMC, causing the lower porosity and higher Yang's modulus of reaction products micro region, which leads to the improvement of mechanical properties. ● Alkali-activated high-strength mortar (AAHSM) with strength of over 90 MPa was prepared. ● Autogenous shrinkage mitigation mechanism of HPMC for AAHSM was revealed. ● Mechanical properties effects of HPMC for AAHSM was studied. ● Compressive strength of AAHSM was slight reduced and the flexural strength and toughness were improved by HPMC. ● Autogenous shrinkage of AAHSM was reduced due to the lower capillary pressure and stronger adhesive force between gel particles caused by HPMC. [ABSTRACT FROM AUTHOR]

Fiber reinforced thermoplastic composites have many advantages, such as repeated molding, high toughness, durability and recyclability, which made them a potential substitute as engineering strengthening materials for thermosetting composites. However, their long-term performances under complex service environments are not well understood, hindering its durability design. In the present paper, glass fiber reinforced polypropylene (GFRPP) plate was studied on its mechanical property evaluation subjected to water immersion (distilled water) and bending (bending strains of 0.54 % and 1.04 %) at elevated temperatures (40 °C, 60 °C and 80 °C) up to 180 days. Water uptake, mechanical properties, thermal properties and microstructure tests were further carried out to reveal the effects of water uptake content, immersed temperature and bending loading level on the properties. The results showed the water absorption curve at three temperatures presents a two-stage diffusion behavior. After the longest immersion time of 180 days, the strength retention of plate at 40 °C, 60 °C and 80 °C were 88.2 %, 58.3 % and 31.8 % for tensile strength, 83.6 %, 67.8 % and 47.9 % for flexural strength and 70.6 %, 61.7 % and 41.4 % for in-plane shear strength. Higher immersion temperature accelerated the swelling effects of polypropylene. Higher bending loading levels accelerated the crack or defects formation and propagation in the resin as well as at the interface. When the strength retention rates were 50 %, the longest service life of plate exposed in service environment of Da Lian (T=9.2 °C) were 23.9 years (tensile strength), 12.8 years (flexural strength) and 3.0 years (in-plane shear strength) without the bending strain. Through comparing with thermosetting composites, glass fiber reinforced polypropylene has almost close or higher tensile strength retention rate and service life for certain service conditions. • The maximum water absorption and diffusion coefficient of composites were lower than epoxy or polyurethane based composites. • Higher immersion temperature accelerated the swelling effects of polypropylene. • Higher bending loading levels accelerated the crack or defects propagation in the resin as well as at the interface. • When the strength retention rates were 50 %, the longest service life of tensile strength were 23.9 years. [ABSTRACT FROM AUTHOR]

Even though the demand for utilizing geopolymers is growing, the need for current standard guidelines to regulate compliance to address the complexity of the mix design could be one of the major hurdles of utilizing geopolymers vastly in construction. There is no straightforward standard that addresses the complexity of the mix design of geopolymers. Thus, this work addresses main factors affecting the compressive strength of slag based geopolymers and provide a tool for predicting it. This article includes experimental work to evaluate the properties of slag-based geopolymer binders and the development of a model using Artificial Neural Network (ANN) algorithms for predicting the performance of these slag-based geopolymer binders. In this paper, we have utilized and developed ANN models for optimizing slag-based geopolymer mixes based on precursor materials' physiochemical properties and activation solutions constituents that can enhance performance compressive strength prediction in construction applications. • A high-accuracy DOE model was developed and used to characterize the Geopolymeric paste. • A developed ANN model was superior in forecasting the compressive strength of AAS systems. • The choice of the alkali activator has minimal impact on the compressive strength. • The optimal water-to-slag ratio is approximately 0.28. • The optimal alkali oxide concentration is 6 %. [ABSTRACT FROM AUTHOR]

Adding a certain amount of steel fibers can overcome the brittleness defects in geopolymer concrete and improve the mechanical properties, which has a broader application prospect. However, the research on the material properties of steel fiber-reinforced geopolymer concrete (SFGPC) after high temperature exposure is still very limited. Therefore, tests on 114 cubes and 57 prisms after exposure to high temperatures were conducted in this paper. The main variables were temperature (20 °C, 200 °C, 400 °C, 600 °C, and 800 °C), steel fiber volume content (0, 1 %, and 2 %), and concrete type (SFGPC and steel fiber-reinforced ordinary Portland cement concrete (SFOPC)). The results indicated that SFGPC with a steel fiber content of 1 % at 800 °C experienced a 53.6 % reduction in compressive strength, a 58 % reduction in splitting tensile strength, a 93.9 % reduction in elastic modulus, a 45.9 % reduction in toughness index, and a 274.5 % increase in peak strain, compared with room temperature. The 1 % fiber content enhanced the compressive strength by 10.3 %−36.5 %, the splitting tensile strength by more than 16 %, the peak strain by 9.6 %−32.7 %, and the toughness index by 24.4 %−64.6 % compared to the absence of fiber content. Based on the room temperature model, a constitutive model of SFGPC under uniaxial compression after high temperatures was developed. • Cubes and prisms of SFGPC after high temperature exposure were tested. • High temperature reduced the strength, elastic modulus, and toughness index. • Increasing fiber content enhanced the mechanical behavior of SFGPC. • A constitutive model under compression after high temperatures was developed. [ABSTRACT FROM AUTHOR]

Glass fiber reinforced plastics (GFRP) have been widely used in the field of civil engineering infrastructure, while it also generating a large amount of waste glass fibers simultaneously. This paper uses waste glass fiber in self compacting recycled concrete (SCRC), forming a kind of waste glass fiber reinforced self-compacting recycled concrete (RGF-SCRC). The effects of recycled coarse aggregate (RCA) replacement ratio, water to binder (W/B) ratio, the content and type of glass fiber on the working and mechanical properties of RGF-SCRC were investigated. The results showed that the specimens could meet the requirements of self-compacting concrete (SCC) in terms of working performance, but the addition of RCA and glass fiber could reduce the workability of RGF-SCRC, when RCA is replaced with 100 % and the fiber content reaches 10 kg/m3, the slump expansion is reduced by 9.5 % and 12.4 %, respectively. The mechanical properties of RGF-SCRC decreased as the growing value of RCA replacement ratio and the W/B ratio, among them, the elastic modulus decreased the most, by 40.4 % and 30.0 %, respectively. Compared with the results of the control specimen, the properties could be improved significantly under an appropriate content of waste glass fiber: the cube compressive strength, splitting tensile strength, flexural strength, and elastic modulus of RGF-SCRC were increased by 1.3∼9.6 %, 13.5∼59.4 %, 17.8∼40.9 %, and 3.3∼13.4 %, respectively. However, excessive fiber content showed a negative effect on the mechanical properties. Specimens with the 7.5 kg/m3 alkali resistant glass fiber content showed the best mechanical properties. Moreover, the X-ray CT and scanning electron microscope (SEM) techniques were applied to explore the influencing mechanism of waste glass fibers on RGF-SCRC. The results showed that after adding an appropriate content of waste glass fiber, the porosity and the number of large pores decreased, and the pore size and distribution became more reasonable, which enhanced the compactness of RGF-SCRC to some extent. The mechanical force and friction force anchored at the fiber end at the interface with the concrete matrix increase the bonding strength, thereby enhancing the mechanical properties of RGF-SCRC. This study achieve the resource utilization of waste glass fiber and improve the mechanical properties of concrete and the research results can provide a reference for the practical application of RGF-SCRC in civil engineering. • The waste glass fiber was applied in self compacting recycled concrete (SCRC). • Various parameters were investigated to make clear the influential mechanisms of glass fiber on the working and mechanical properties of waste glass fiber reinforced self-compacting recycled concrete. • The enhanced mechanism of fiber addition on SCRC was illustrated by the microstructure method and analysis. [ABSTRACT FROM AUTHOR]

Chloride-induced deterioration of reinforcing steel bars has become a densely researched topic over the past several decades because of the severe ramifications to the structural reliability of aging infrastructure. The ever-growing volume of experimental and field data continually enables advances in the field through deeper micro-macro analyses and various modeling applications. The purpose of this paper is twofold. First, an experimental program is introduced, describing the tensile testing of 284 artificially corroded, 25 mm diameter deformed Grade500E reinforcing bars. Secondly, the mechanical characteristics of corroded bars are predicted through a collection of regression-based machine learning algorithms. Models are trained and tested on a database of 1387 tensile tests compiled from 25 other experimental programs available in the literature. The complete database includes 19 input parameters used to predict nine key mechanical properties of the corroded steel bars. Nine machine learning models were selected from a balanced assortment of algorithm typologies to determine the most appropriate methodology for each response variable. The adaptive-neuro fuzzy inference system (ANFIS) model was found to have the strongest individual predictive ability across all models. Meanwhile, ensemble tree-based learning algorithms categorically provided the most consistently high-performing models over the selected response variables. • Monotonic tensile testing was performed on 284 artificially corroded steel rebars. • A database of 1387 tensile tests is compiled from 26 experimental programs. • Comparative analysis on the predictive capability of nine machine learning methodologies. • Adaptive-neuro fuzzy inference systems demonstrate the strongest individual ability. • Tree-based models categorically provide the most consistently high-performing models. [ABSTRACT FROM AUTHOR]

When constructing concrete structures using 3D printing, it is important to consider the anisotropy due to the printing process. The print path influences the formation of layer interfaces and inter-filament voids, and the fracture propagation behavior of the printed specimen. In this paper, the fracture propagation behavior of printed mortar specimens under compressive, tensile, and bending stresses is evaluated for different print paths. X-ray computed tomography visualizes the interior of printed specimens and shows that the pressure during material extrusion elongates the intra-filament voids. The inter-filament void structure is influenced by the print path, forming an aligned structure in one direction or a complex lattice-like structure. Anisotropy in the deformation direction under compressive stress, which is influenced by the inter-filament void structure, is assessed by 3D scanning. Under tensile stress, Digital Image Correlation (DIC) visualizes that tensile stress is concentrated in the layer interface, causing cracks to propagate along the layer interface. Under bending stress, DIC evaluates the effect of the print path on fracture propagation behavior. The results show that the mechanical properties and fracture propagation behavior of printed specimens are affected by the arrangement of the layer interface and inter-filament void, which is governed by the print path. (200 words) • Layer interface arrangement and inter-filament void structure, influenced by print path, affect the mechanical properties of 3D printed concrete. • Anisotropic deformation of 3D printed specimens due to print paths can be evaluated by 3D scanning surfaces before and after loading. • DIC with a high-speed camera evaluates instantaneous bending fracture, strain distribution, and crack propagation behavior in printed specimens. [ABSTRACT FROM AUTHOR]

• Multivariate optimisation and statistical analyses were conducted on scaffold boards. • Effects of the selected wood defects on the performance of boards were investigated. • 0.3 TKAR and 0.1–0.17 MKAR were determined as the most critical values. • Failure is independent from knot defects for the low density and growth rate boards. The uncertainties involved in the prediction of scaffold material performance in the machine grading process have brought forth the necessity to identify the level of influence of wood defects on the scaffold performance required to be optimised for its intended use as a construction material. This paper tackled this important aspect by employing multivariate optimisation and statistical analyses on the previously reported experimental results in the literature on the machine graded scaffold boards from UK Sitka spruce (picea sitchensis) softwoods. Initially, nonlinear multivariate regression analyses were performed for the responses of such variables as failure load, displacement, extreme fibre stress and the critical failure distance to several wood characteristics as contributing factors. The extension of the statistical analysis to the multi-objective optimisation study was accomplished using Response Surface Method (RSM) by considering the mutual interactions between the factors including total and margin knot area ratios, density, rate of growth and slope of grain. This paper represented graphically how the load bearing capacity, the deformation characteristics and the critical failure location points are influenced by the considered factors. The significance of factors and their relative influence on the performance optimisation were finally discussed by providing the essential information on the future use of scaffold board products as construction material. [ABSTRACT FROM AUTHOR]

Highlights • CNTs and CNFs are both the nano-structured fibrous materials with excellent properties. • The dispersion of CNTs/CNFs is the decisive factor affecting the performance of composites. • The incorporation of CNTs and CNFs affects the variety performance of cement-based materials. • CNTs/CNFs-modified cement-based composites have broad application prospects. Abstract CNTs and CNFs are drawing widespread attention due to the unique structure and excellent properties, such as the mechanical property and the electrical property. It will significantly improve the cement-based composites' properties when adding CNTs/CNFs into composites. This paper briefly introduces the CNTs'/CNFs' basic properties and dispersion methods, and elucidates the properties of cement-based composites recombining CNTs/CNFs, including the mechanical property, the deformation property, the durability property, the thermal conductivities and electrical conductivities. This paper also summarizes the problems existing in present research, and gives some proposes for future study. [ABSTRACT FROM AUTHOR]

Highlights • Mechanical characterization of fibers are described. • Papers of HMA reinforced with fibers were reviewed. • Fibers improve the viscoelastic behaviour of asphalt binder. • Fibers improve the mechanical performance of hot mix asphalt. • Fibers reinforce HMA through a tridimensional network and increasing adhesion in the mix. Abstract The use of fibers in hot mix asphalt (HMA) has become a much more attractive alternative for the construction of road pavements. Numerous studies have shown that the incorporation of fibers in the mixture improves fatigue resistance, permanent deformation and stiffness. The aim of this paper is to present a review of the mechanical impact of fibers in HMA by analyzing their reinforcement effect in a qualitative and quantitative manner. Fiber properties and characterization tests on fiber-modified bitumen are discussed. Quantities, blending procedures and performance of bituminous mixtures with different types of fibers are presented. Results of mechanical improvement are displayed. Based on the current research results, depending on the properties and the type of mixture in which they are used, each type of fiber seems to improve certain parameters more than others. Coconut fibers and waste fibers are described as environmentally friendly alternatives. [ABSTRACT FROM AUTHOR]

Highlights • Concrete with higher seashell ratio has lower physical and mechanical properties. • Ground seashell aggregate can replace up to 20% natural fine aggregate in concrete. • Up to 50% seashell as a partial coarse aggregate can give normal-weight concrete. • Current data on durability of seashell aggregate concrete indicate varied effects. • Sound absorption and thermal insulation studies of seashell concrete are required. Abstract Trends in concrete technology are currently directed towards sourcing alternative sustainable materials for concrete in order to minimise over-reliance on natural resources. Many of the substitute materials used for producing green concrete are recycled materials obtained from industrial wastes and by-products. A promising solution to the challenge of seashell waste management involves utilising seashells as construction materials in concrete. Experimental investigations have been carried out on the use of mollusc seashells such as periwinkle shell, mussel shell, oyster shell, cockle shell, crepidula shell, clam shell and scallop shell as aggregate replacement materials in concrete. The seashells were utilised as partial or total replacement of fine and coarse aggregates in concrete. This paper is a literature review of seashell aggregate concrete. The paper first presents an overview of the physical, mechanical and chemical properties of the seashells. This is followed by a discussion of the physical, mechanical and durability properties of seashell aggregate concrete in fresh and hardened states. Possible applications in the construction industry are also highlighted. Mollusc seashells have similar chemical composition with limestone-type aggregates but characteristically contain traces of chloride and sulphate salts. Although inclusion of seashell aggregate reduces the physico-mechanical properties of concrete, utilising some seashells as partial coarse aggregate at up to 50% substitution level can produce normal-weight concrete for non-structural and low-strength structural functions. The current understanding of seashell aggregate concrete provides a basis for further research on various aspects of its behaviour including the sound absorption and thermal insulation properties. [ABSTRACT FROM AUTHOR]

• This investigation shows the mechanical performance of starch-hemp agro-composite materials for thirty different compositions. • The failure of the starch-hemp composite materials is due to the great displacement. • The stereoscopic images of agro-composite in compression (ARAMIS système) show that the gradient of the strain is neither homogeneous and nor regular. • The obtained results reveal an optimal composition for this agro-composite building materials. The use of Hemp/Lime concrete has gained popularity due to its lightweight, low thermal conductivity, and good sound absorption properties. However, the emission of CO 2 from lime and the non-durability and non-recyclability of lime-hemp concrete make it less sustainable. In this paper, we studied new Starch/Hemp agro-composite materials as an alternative building material. The physical and mechanical properties of these materials strongly depend on the mixture of hemp shive and binder, making it challenging to determine the optimal composition for specific applications. This paper presents the experimental results obtained from one hundred and eighty specimens for the optimal composition. We used thirty different mixtures, including three Hemp/Starch (H/S) ratios of 6, 8, and 10, and five mixtures with hemp shive sizes of 5 mm (H k), 15 mm (H i), and 20 mm (H j). We studied and analyzed the influence of the H/S ratio and hemp shive size (H k , H i , H j) on mechanical properties, including density, flexural tensile strength, compressive strength, Young's modulus, and Poisson's ratio. The experimental results demonstrate that the starch-based binder allows for the transfer of mechanical strength to the hemp shive and gives the desired shape to the agro-composite material. The equations describing the evolution of the physical and mechanical characteristics (ρ, σ c , σ t , E, ν) should help researchers and building professionals manufacture this agro-resource and determine the optimal composition for building based on intended applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Physicochemical characterization, toxicity and applications of FGD gypsum. • Properties of FGD gypsum crucial for its application as building material. • Advantages and disadvantages of FGD gypsum in construction are discussed. Flue Gas Desulphurized Gypsum (FGDG) is a by-product generated by the thermal power industry to remove sulfur dioxide (SO 2) from flue gas emissions. This paper provides a comprehensive review of flue gas desulphurized (FGD) gypsum production, property, and applications in the construction industry. In 2020, global FGD gypsum production reached an estimated 255 million tons, primarily in Asia (55%), followed by Europe (22%), North America (18%), and the rest of the world (5%). The paper discusses the chemical and physical properties of FGD gypsum, including its composition, crystal structure, particle size, and moisture content. It also reviews the various applications of FGD gypsum, such as in cement and concrete production, agriculture, and gypsum board manufacturing. In the construction industry, FGD gypsum is widely used as a raw material for producing gypsum products, such as plasterboard and cement, due to its high purity and low cost. Moreover, FGD gypsum is increasingly used in agriculture as a soil amendment, which can improve soil structure, increase water retention, and provide essential nutrients to plants. The potential for FGD gypsum to be reused and recycled is also discussed, as well as its environmental impact. FGD gypsum can be safely disposed of in landfills or used for backfilling, with appropriate measures to prevent the leaching of heavy metals and other contaminants. It also delves into the potential benefits of FGD gypsum for improving fire resistance, and acoustic properties, and reducing material waste. With its high purity level and lower cost compared to natural gypsum, FGD gypsum is a viable alternative that can transform the construction industry. This paper also discusses its major drawbacks, such as high SO 3 content, dissolution in water, and ettringite formation. This review suggests that there is potential to improve the properties of FGD gypsum further and increase its use as a sustainable construction material in the future. [ABSTRACT FROM AUTHOR]

Foamed concrete (FC) offers many advantages and has been widely applied in the construction industry. However, its unique porous structure leads to poor mechanical properties, making it prone to cracking and fracturing during service. To address this issue, ultra-high molecular weight polyethylene (UHMWPE) fibers, modified with tannic acid (TA) and ethanolamine (EA), were applied to reinforce FC to improve its mechanical performance in this research. The effects of TA/EA modification on UHMWPE fibers were investigated, and the impacts of modified UHMWPE fibers on FC were explored, including workability, physical properties, mechanical properties, and microstructural characteristics. The fibers were added in the dosages corresponding to 0.1 %, 0.3 %, 0.5 %, and 0.7 % of the mass of cementitious material. The experimental results show that modified UHMWPE fibers exhibit good thermal stability and improve adhesion with FC. Regardless of modification, UHMWPE fibers can enhance mechanical properties of FC at all dosages investigated. When the dosage of modified UHMWPE fibers is 0.5 %, the enhancement of mechanical properties of FC is most eminent. Compared to control group, the drying shrinkage decreases by 20.6 %, and the compressive, flexural, and tensile strengths increase by 216 %, 688 %, and 120 %, respectively. The bend-press ratio reaches 1/4, outperforming that of the ordinary FC. The analysis of microstructural properties reveals the underlying mechanisms behind the enhanced mechanical properties of FC. The fiber modification methods discussed in this paper can strengthen the bond between the fibers and the cement matrix, thereby enhancing the reinforcing effect of the fibers in FC. These findings provide a new insight into the efficient applications of fibers that bind poorly to cement-based materials in FC. • TA/EA improved the hydrophilicity of the UHMWPE fibers through modification. • Modification enhanced adhesion between UHMWPE fibers and cement matrix. • Fracture mode of modified UHMWPE fibers in cement matrix in FC revealed. [ABSTRACT FROM AUTHOR]

In this paper, the influence of rice husk ash (RHA) and super-absorbent polymer (SAP) on the properties of cement-based composites was investigated by mono or compound incorporating different dosages of RHA and SAP. In addition, the modification mechanism of RHA and SAP on cement-based composites was studied by analyzing microstructural evolution, the heat of hydration, the composition of hydration products, and the pore structures. The results indicate that the 28 days strength of cement-based composites improved with increasing SAP dosage, while the early strength decreased. The addition of RHA slightly enhanced the mechanical strength of cement-based composites. The 28 days compressive strength and flexural strength of SAP and RHA were not lower than that of the reference group under different combining conditions. The strength of the cement-based composites was highest when the dosage amount of SAP was 0.15 % and that of RHA was 5 %. The small particle size of RHA can fill the pores formed by SAP after water release, which helps to improve the microstructure of the concrete. Furthermore, the non-crystalline SiO 2 in RHA reacts with Ca(OH) 2 to produce C-S-H gels in the cement-based composites. The combination of SAP and RHA decreases the heat generated during hydration and reduces the negative capillary pressure of cement-based composites, which helps to prevent the initiation and early development of cracks. Therefore, the addition of SAP and RHA consistently enhances the production of cement hydration products, such as hydrated calcium silicate gel, thereby refining the pore structure and improving the density of the cement-based composites. This study enhances the understanding of the influence of SAP and RHA on the basic properties of cement-based composites, providing new insights into the development of a sustainable built environment by combined use of RHA and SAP. • 0.15 % SAP compounded with 5 % RHA significantly increased the strength of concrete and optimized its microstructure. • The compounding of SAP with RHA reduces the heat of hydration and prevents early cracking. • The compounding of SAP and RHA is beneficial in reducing the capillary pressure in the plastic phase of cementitious materials. • The compounding of 0.15 % SAP with 5 % RHA increases the yield of hydrated calcium silicate gels and makes cementitious composites denser. [ABSTRACT FROM AUTHOR]

Fire-resistant steel (YSt-355FR (0.1 % Mo)) has become the most utilized structural steel due to its superior performance at elevated temperatures compared to traditional structural steel at both the material and structural levels. However, its performance after exposure to fire remains questionable. This study investigates the post-fire performance of cold-formed fire-resistant steel at the material level. A total of 132 steel coupons and 84 Charpy test specimens were exposed to temperatures ranging from 100°C to 1000°C. These temperature-exposed steel coupons were subjected to four different cooling conditions: furnace cooling (FC), air cooling (AC), water-jet cooling (WJC), and water cooling (WC). Tensile tests were performed on the cooled steel coupons to obtain post-fire stress-strain curves, from which the residual mechanical properties were determined. Charpy impact tests were also conducted on the cooled steel specimens to obtain impact energies and identify the fracture patterns. Key observations regarding the post-fire behavior of fire-resistant steel in terms of strength, deformability, stiffness, and toughness parameters were made. Both the exposure temperature and the cooling condition significantly influence the post-fire performance of fire-resistant steel. Fire-resistant steel demonstrates superior post-fire behavior compared to traditional structural steel. Constitutive equations were proposed to predict the mechanical properties of fire-resistant steel under various post-fire conditions, and a sound reliability analysis was performed to examine the reliability of the predicted design parameters compared to the test results. The findings presented in this paper are significant as no prior investigation has assessed the post-fire performance of fire-resistant steel; thus, they may encourage the steel construction industry to prefer fire-resistant steel over traditional structural steels and promote the reuse of temperature-exposed fire-resistant steel for sustainable construction. [Display omitted] • Post-fire material behavior of YSt-355FR (0.1 % Mo) fire-resistant steel presented. • Effect of temperature and different cooling methods on post-fire mechanical properties quantified. • Postulation of partial reversibility of mechanical properties of YSt-355FR confirmed. • Constitutive equations for post-fire mechanical properties of YSt-355FR proposed. • A sound reliability analysis for the constitutive equations performed. [ABSTRACT FROM AUTHOR]

Long-term durability of concrete has been of interest for researchers in past decades, and throughout their numerous research endeavors, they have tried to improve durability with the application of different methods. One technique is the integration of a new material into the concrete. One material that has attracted great attention of researchers is nano-SiO 2 (NS). Its considerable performance in the enhancement of durability properties of concrete and mortar provides reasonable specifications satisfaction for scholars. In this paper, important durability characteristics of concrete, including the chloride ion penetration, electrical resistivity, water penetration, water absorption, the pore size distribution, the carbonation, the sulfate resistance, frost resistance, shrinkage, and thermal properties were explored. Additionally, the effects on the microstructure of concrete and mortar in the previous studies were discussed. Mechanical properties, such as compressive strength, flexural strength, tensile strength, and abrasion resistivity were also investigated in the past and most recent papers. [ABSTRACT FROM AUTHOR]

At meso-scale, Calcium Silicate Hydrate (C-S-H) can be considered as randomly packed globules (about 4.2 nm), which forms the basic unit cell, with water molecules and voids. In this paper, the nanostructures for the globules are developed based on some plausible atomic structures of C-S-H. The mechanical properties for the C-S-H globules are determined through molecular dynamics simulation. Interfaces between the C-S-H globules are also simulated with different amount of water molecules. Key material parameters, e.g., Young’s modulus, strength and fracture energy, are obtained. It has been found that longer mean chain length of silicate tends to increase the strength of C-S-H and change the fracture behavior from brittle to ductile failure, in the chain length direction. In the other direction, however, silicate chains do not play an important role while interlayer structure matters. Moreover, pores in the C-S-H nanostructures can considerably reduce the strength of the globule structures in the normal direction to silicate chain but the weakening effect becomes substantially less in silicate chain direction. Further, it has been found that for all types of the interfaces between C-S-H globules, the interface with no extra water molecules has the greatest tensile/shear strength. The mechanical properties obtained in this paper for C-S-H nanostructures and interfaces could be necessary inputs to the meso-scale modelling of C-S-H via either granular mechanics, i.e., DEM, or continuum mechanics, i.e., FEM. [ABSTRACT FROM AUTHOR]

This paper presents the stress-strain behavior of CRC with rubber replacement percentages of 6%, 12% and 18%. The peak stress, strain at peak stress, modulus of elasticity, energy dissipation ability and the constitutive model under uniaxial compression were examined. Constitutive models for traditional concrete (TC) were applied to both TC and CRC. Comparisons between experimental results and the models were made. A constitutive model for unconfined CRC was then developed. A numerical study on the flexural behavior of reinforced CRC slabs was conducted with the application of the stress-strain model developed in the paper and the results agreed well with experimental tests. [ABSTRACT FROM AUTHOR]

Cold-formed steel hollow sections are extensively used in building construction due to their potential benefits over hot-rolled and open cold-formed steel sections. Their performance in fire is important for successful structural applications while their post-fire residual capacities are also important to assess the extent of their fire damage and reusability with and without strength enhancing techniques. This paper presents the details of an experimental investigation on the post-fire mechanical properties of cold-formed steel hollow sections. Tensile tests were performed on coupons exposed to elevated temperatures varying from 100 to 800 °C and then cooled down to room temperature. These coupons were cut from cold-formed steel square and rectangular hollow sections with varying thicknesses and grades. The results from this investigation provided post-fire stress-strain curves, yield strengths, ultimate strengths and elastic modulus, and their reduction pattern. They show that the post-fire mechanical properties of cold-formed steel hollow sections are different to those of open cold-formed channel and hot-rolled sections. New predictive equations were proposed to determine the post-fire mechanical property reduction factors. Post-fire mechanical properties were also compared with their elevated temperature mechanical properties to evaluate their strength gain after cooling down. This paper also evaluates various strength enhancement techniques for use with fire damaged cold-formed steel hollow sections. [ABSTRACT FROM AUTHOR]

To further enhance our understanding of the microstructure of SRM and its intrinsic relationship with macroscopic properties, this paper conducted indoor freeze-thaw cycles, EIS and uniaxial compression tests. The results indicated that the number of freeze-thaw cycles has a significant exponential relationship with R CPP , R CPP 1 and C DSRP. As the number of cycles increased, R CPP and R CPP 1 exhibited a decreasing trend, whereas C DSRP showed an increasing pattern. The freeze-thaw cycles led to the expansion and connection of different pores, resulting in the widening or multiplication of channels in CPP , leading to a decrease in both R CPP and R CPP 1. However, in DSRPP , the liquid-filled pores underwent radial expansion during freeze-thaw cycles, connecting with gas-filled pores around them. This transition led the conductive path to transform into CPP , reducing the accumulated thickness of non-continuous points. Consequently, C DSRP exhibited an increasing trend. Furthermore, the increase in porosity weakened the deformation resistance, increasing the compaction stage of pores and the peak strain, while reducing its peak strength and secant modulus. The peak strength, strain and secant modulus also exhibited significant exponential relationships with different cycles. There was a good exponential correlation between ∆ R CPP of CPP and the uniaxial strength, and the freeze-thaw deterioration model constructed with it as an influence factor could better assess its peak mechanical strength after freezing and thawing. • An electrochemical circuit model for different conductive paths was proposed. • The microstructure was characterized by EIS parameters of the equivalent model. • The influence and mechanism of freeze-thaw cycles on EIS parameters were analyzed. • A degradation model for the uniaxial strength was established with EIS parameters. [ABSTRACT FROM AUTHOR]

In the exploration of the moon and outer space, our preliminary mission lies in the construction of lunar base. To make lunar concrete with local materials on the moon becomes the key technology to promote the construction of lunar bases. In order to further study the feasibility of using lunar in-situ resources to prepare concrete and build a lunar base, the environment and resources on the lunar surface are analyzed, and the severe challenges brought by extreme environment to concrete preparation and the prerequisites of in-situ resources are clarified. In this paper, the research progress of lunar concrete is summarized from the aspects of raw material acquisition, concrete preparation methods and performance, and the comparative analysis of cement concrete, sulfur concrete, geopolymer concrete and polymer concrete is carried out. Existing studies have shown that in the acquisition of raw materials, sulfur concrete has more advantages, cement concrete and geopolymer concrete are also feasible, but polymer, as a scarce resource on the moon, is difficult to obtain. In terms of preparation methods, cement concrete and geopolymer concrete are more suitable for the production of prefabricated components in artificial environment due to the limitation of external environment and the demand of water circulation, while the in-situ preparation methods represented by sulfur concrete and polymer concrete can be used for the connection and node reinforcement of prefabricated components on the moon. In terms of performance, the mechanical properties of the four kinds of concrete all meet the basic requirements, but the service performance in the harsh environment of the moon needs to be further studied. Meanwhile, the key location characteristics for lunar base construction in different regions are analyzed in terms of topography, environment and in-situ resources. Finally, the future exploration direction of the construction of the lunar bases is proposed. • Comparative study on lunar concretes: cement, sulfur, geopolymer, and polymer. • Sulfur concrete's raw material acquisition advantage; polymer's scarcity on moon. • Prefabrication versus in-situ production methods for lunar habitat construction. [ABSTRACT FROM AUTHOR]

Sand instability is always an intractable problem in geotechnical engineering and its reinforcement using additives is an effective method. This paper introduces the organic polymer reinforcer (OPR) and the recycled polypropylene fiber (RPF) to modify sand. The unconfined compression and corresponding numerical tests were performed to investigate mechanical properties, deformation failure behavior, and microscopic response. Results showed that both materials positively affect the mechanical and deformation properties of modified sand synergistically. Optimized particle structure by the inter-particle polymer membrane linked the loose sand into a whole with fibers as a framework. Strain-softening properties were reduced with less strain localization under loading. This is also clearly related to the improvement of the micro-damage based on numerical results. OPR-RPF reinforcement transformed the bond failure from unidirectional concentration to multilocal dispersion by improving force chain construction, microcrack propagation, and energy allocation. Thus, the failure of modified sand showed a macroscopic progression from shear-faulting via ductile-faulting to ductile flow. Future research lies in further considering the particle shape and pore structure variations to provide new insights for a deeper understanding of sand stabilization mechanisms and engineering applications. [Display omitted] • OPR-RPF treatment synergistically enhances sand's strength and failure resistance. • OPR and RPF content each influenced the micro-damage response of the modified sand. • Multiple interactions improve force chain, cracking, and energy response. • The bonding and framework effects favored homogeneity mitigating strain localization. [ABSTRACT FROM AUTHOR]

A type of new stainless steel, namely QN1803, has been developed in recent years. The elevated temperature mechanical properties of QN1803 stainless steel were experimentally investigated and presented in this paper. The test programme includes a series of elevated temperature material tests and some room temperature material tests as control groups. The elevated temperature tests adopted the steady-state testing method and transient-state testing method. In the steady-state tests, nine temperature levels ranging from 100 °C to 900 °C with 100 °C interval were considered. In the transient-state tests, ten stress levels ranging from 0.1 f p,0.2 to 1.0 f p,0.2 with 0.1 f p,0.2 interval were considered. Key mechanical properties were obtained from the tensile coupon tests, and the results from the two different testing methods were compared. The reduction factors of the key mechanical properties and a two-stage R-O material model was provided for QN1803 stainless steel based on the obtained test results. These outcomes provide a fundamental reference for further research studies on the structural behaviour of QN1803 stainless steel in fire. • Elevated temperature mechanical properties of QN1803 stainless steel were firstly investigated. • Steady-state tests and transient-state tests were conducted. • Reduction factors of key mechanical properties were provided. • An elevated temperature material model was suggested for QN1803 stainless steel. [ABSTRACT FROM AUTHOR]

The low water-cement ratio has a significant effect on increasing the compacted density of the concrete, thereby enhancing its mechanical properties and microstructures. This paper introduces an innovative approach of utilizing the cold isostatic pressing method to prepare reactive powder concrete (RPC) specimens with an ultra-low water-cement ratio which not exceeds 0.16. And it is compared with the specimens prepared by the traditional vibrational method which conversely requires the minimum water-cement ratio of 0.21. The results show that the RPC specimens under cold isostatic pressing exhibit enhanced compressive strength and microhardness, as well as improved matrix compactness. Conversely, the RPC matrix produced under the vibrational method not only contains a small number of air-entrained bubbles that can influence the strength of matrix but also exhibits a significantly larger cumulative volume of harmful pores that affect the performance of RPC compared to cold isostatic pressing. Therefore, cold isostatic pressing technology based on all-directional hydroforming is a powerful tool for the preparation of high-strength RPC, which significantly reduces the internal defects of the specimen, and the prepared RPC has superior mechanical properties and matrix structure. • Significant increase in the compressive strength of RPC has been achieved by cold isostatic pressing. • The molding method has a significant influence on the Vickers hardness of RPC. • The hydration reaction of cold isostatic pressing specimens after autoclave curing is still incomplete. • Specimens prepared by cold isostatic pressing exhibit dense matrix without air-entrained bubble observed. [ABSTRACT FROM AUTHOR]

Fiber reinforced thermoplastic composite bars offered the advantages of repeated molding, high toughness, and recyclability, making them a promising alternative to steel bars. For the stirrups applications in concrete structures, it was essential to develop efficient bending technologies for producing high-quality thermoplastic bending bars. In the present paper, the bending properties of glass fiber reinforced polypropylene (GFRPP) composite bars were investigated by experimental and theoretical methods. A novel bending fixture of GFRPP bars was specifically designed for GFRPP bars to ensure the reliable bending of the bars. Finite element simulation was employed to analyze the stress distribution of GFRPP bars, providing valuable insights into their mechanical behavior. Additionally, a bending strength model was developed based on the material mechanics, offering a theoretical framework for understanding and predicting the bending strength of GFRPP bars. Finally, the bending mechanism of bars was further revealed according to experimental and theoretical findings. The results of the study demonstrated that the specially designed bending fixture was successful in minimizing damage to the bending section of the GFRPP bars, leading to a significant improvement in bending strength retention of up to 43.2 %. Furthermore, the theoretical results and experimental test have a good agreement in terms of stress distribution and failure mode. The maximum strain in the transition zone between the straight section and the bending section of the GFRPP bars was nearly double that of the straight section at the same stress levels. With the increase of bending radius to diameter ratio from 3.0 to 7.0, the tensile strength of GFRPP bending bars increased by ∼7.9 %. The study identified the transition area between the bending section and straight section of GFRPP bars as the most critical failure point. The strength degradation mechanism during the bending were attributed to the shrinkage and torsion of inner fibers owing to the compression caused the local stress concentration, which caused the inner resin matrix to crack and interface debonding of fiber/resin, leading to the premature tensile failure. • The bending fixture can achieve the high bending strength retention up to 43.2 %. • Theoretical and experimental results verified the most unfavorable failure point. • Larger bending radius contributed to the decrease ∼7.9 % of tensile strength. • Fiber distortion and interface debonding led to tensile failure of bending bars. [ABSTRACT FROM AUTHOR]

The construction industry seeks innovative solutions like smart concrete. Traditional concrete faces durability issues, environmental impact, and high rehabilitation costs. To address this, smart concrete combines eco-friendly materials with advanced nano-technology, featuring self-sensing and self-healing properties to detect damage early and autonomously repair cracks. Researchers explore methods to reduce concrete's carbon impact through clinker replacement and alternative binders. The industry moves toward sustainable and technologically advanced practices, where "smart concrete" marks a transformative shift in construction, promising eco-conscious, technology-driven building methods. This review explores smart technology in concrete construction, focusing on structural health monitoring and autonomous crack repair advancements. It consolidates diverse self-sensing and self-healing mechanisms, emphasizing their role in viable construction goals. The paper delves into the impact of nanomaterial on the mechanical and durability of self-sensing, self-healing, and self-adjusting concrete, showcasing smart concrete's potential for transformative construction practices. Biomimetic Structural Health Monitoring (SHM) systems using self-sensing concrete and nanomaterials detect strain changes independently, which is vital for effective monitoring. Real-time Structural Health Monitoring using embedded sensors aids in timely decision-making for asset management and ensures continued structural safety. Self-activated bacteria in concrete provide an eco-friendly solution for crack healing by producing calcium carbonate and reinforcing structural integrity. Bacteria-based agents show promise in enhancing concrete's crack repair potential, aligning with better construction practices. In conclusion, smart concrete presents a significant opportunity to transform the construction sector, emphasizing eco-friendliness, resource optimization, and robust infrastructure. • Smart concrete features self-sensing and self-healing properties to detect damage early. • Researchers are exploring methods to improve the properties of smart concrete through alternative binders. • Structural Health Monitoring (SHM) systems using self-sensing concrete aid in effective monitoring. • Self-activated bacteria in concrete provide a solution for crack healing, enhancing construction practices. [ABSTRACT FROM AUTHOR]

Rock formations naturally contain intricate internal fractures due to various environmental factors. Such fractures result in significant weakening of the mechanical properties of the rock mass. As factures have different geometric features and fill material characteristics, it is difficult to replicate their complex behavior in the laboratory. This poses a serious limitation on the experimental investigation of the mechanical properties of fractured rocks. Sand powder 3D printing (3DP) can overcome the limitations of casting methods in preparing samples with complex fractures and thus is widely applied in soft rock mechanics experiments. This paper utilizes Computer Tomography (CT) scanning to obtain the probability distribution patterns of fractures in fractured rock samples. Additionally, it combines sand powder 3DP technology to generate soft rock-like samples with internal networks of filled fractures. Uniaxial compression experiments employing digital image correlation (DIC) and acoustic emission (AE) techniques are used to investigate the mechanical properties, deformation characteristics, and fracture evolution patterns of samples with different fracture densities. By increasing the fracture density, the peak strength of the soft rock-like samples exponentially decreases, and the deformation characteristics linearly decrease. Crack propagation paths mostly follow the prefabricated fracture trajectories and loading direction. An RA-AF analysis suggests that the failure mode of the soft rock-like samples transitions from diagonal shear failure to block-shaped shear failure with increasing fracture density. These research findings represent a novel sand powder 3DP approach for studying the complex mechanics of complex fractured rocks. • A novel method to generate rock analogs with filled internal fractures is proposed. • Internal fracture density has great effect on the mechanical properties of samples. • Effect of fracture density on failure patterns are investigated with DIC and AE. [ABSTRACT FROM AUTHOR]

Application of nano-SiO 2 (NS) particles to reinforce high performance concrete (HPC) has received widespread attention from both construction industry and researchers due to their interface improving effect, small size effect, filling effect and surface effect. This paper critically reviews previous research carried out on the effect of NS on properties of HPC. Detailed review on the fresh properties, mechanical properties and durability of high performance concrete containing NS particles are presented. Through 76 recent and past literatures, the influence of SiO 2 nano-particles on workability and setting time of fresh mixture, compressive strength, flexural properties, fracture properties, water anti-permeability, chloride permeability, abrasion resistance, frost resistance, water absorption capacity, resistance to high temperatures and microstructure of HPC is discussed in this paper. The properties of NS modified concrete are compared with control concrete. Furthermore, this paper presents on the benefits and advantages to improve the HPC by using NS. It is shown that, in general, the incorporation of SiO 2 nano-particles significantly improves the mechanical properties and durability of HPC though the flowability of the fresh concrete is decreased by the usage of NS. This literature review also aims to provide a comprehensive insight into possible application of NS modified concrete in the construction industry today. [ABSTRACT FROM AUTHOR]

Reactive powder concrete (RPC) is highly susceptible to serious damages and explosive spalling during high temperature owing to its dense microstructure. Over the past few years, the demand of RPC in construction industry increased due to ultra-high strength and durability requirements. This raises concerns about fire resistance of RPC. Recently, numerous studies have been carried out to explore the residual and hot-temperature performance of RPC. Within this framework, the experimental results about the thermal, mechanical and deformation properties of RPC at both test modalities are compiled and compared. Important mechanical properties focused in this paper are compressive strength, tensile strength, flexural strength, elastic modulus and stress-strain behaviour. Among thermal and deformation properties; thermal conductivity, specific heat capacity, mass loss, free thermal strain and load-induced thermal strain are discussed. Meanwhile, mechanism of fire induced spalling and its influencing factors like moisture content, water-binder ratio, fibres and supplementary cementitious materials are studied as well. A relationship among spalling critical temperature and standard cube compressive strength has been developed. Furthermore, the relationship among spalling resistant steel fibres dosage with standard cube compressive strength has been obtained. A comparison of compiled fire resistance data of RPC with existing code provisions is also presented. These code provisions are found to be more conservative for residual test data rather than hot-temperature test data. The residual strength of RPC after exposure to high temperature was relatively higher than hot-temperature strength at most temperature ranges. This study shows a lack of experimental data about deformation and thermal properties of RPC exposed to high temperature. Overall, those factors have been highlighted in the paper that improve high temperature performance of RPC. [ABSTRACT FROM AUTHOR]