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• Development of the use lightweight aggregates as PCM carriers. • Characterisation of PCM impregnated lightweight aggregates. • Coating materials for PCM impregnated lightweight aggregates. • Performance of cement mortar mixes incorporating PCM lightweight aggregates. This paper initially reports on development of lightweight aggregates impregnated with phase change material (LWA-PCM), for application in mortars, plasters and other building materials. This is followed by a study into the development and characterisation of prototype cement mortars using the LWA-PCMs. The work has developed methodologies for efficiently impregnating and hosting phase change materials (PCMs) into lightweight aggregates (LWAs), including aerated concrete particles (ACG) and perlite. PCMs can store and release energy within a given temperature range, moderating thermal fluctuations, resulting in the reduction of energy lost in buildings and increasing thermal comfort. Three commercial PCMs, with melting points between 18 °C and 25 °C, were used in this study. Methods, including vacuum impregnation and immersion, and conditions for optimal absorption of the PCMs into ACG, were developed and evaluated experimentally. Different coating materials, to limit leakage of PCMs from the aggregates, were also trialled as part of this study. Compared to immersion, vacuum impregnation resulted in an increased absorption by up to 15.6 % depending on the type and viscosity of the PCMs. The impregnated aggregates were incorporated into cement mortar mixes, at replacement rates between 10% and 50% (by volume). The effects of PCM impregnated particles on both the mechanical and thermal properties of the cement mortars have been evaluated. Increasing the amount of PCM loaded particles decreased both the flexural and compressive strengths of the cement mortars, by up to 38% and 49% respectively. However, the volumetric heat capacity of the materials increased by nearly 60%. This paper presents a new approach for the design of PCM-loaded aggregate particles, with the potential to be incorporated into different construction materials to improve the energy efficiency and resilience of buildings. [ABSTRACT FROM AUTHOR]

• Numerical modelling of CRM strengthened masonry elements using the OOFEM code. • Simulation of diagonal compression tests, in-plane and out-of-plane bending tests. • Detail level modelling approach independently calibrated and validated. • Nonlinear static analysis including material and interfaces nonlinearities. • Experimental outcomes used for comparison and sensitivity analysis. The paper concerns the modelling of masonry elements strengthened through Textile Reinforced Mortar (TRM), a near surface system made of fiber-based grids or textiles embedded in mortar layers. Recently, the author, focusing on the mechanical characterization of TRM composites, developed a detailed level modelling approach by using the free, open-source Finite-Element code OOFEM, for the simulation of experimental tests on TRM coupons (pull-out tests, tensile tests, shear bond tests and in-plane shear tests). The model was capable to account for the failure of single components (e.g. the fibers tensile failure, the mortar cracking and crushing), as well as of their interactions (the debonding of the fibers from the mortar and of the mortar from the masonry substrate). In this paper, the detailed-level modelling approach is applied to the simulation of TRM strengthened masonry elements subjected to diagonal compression, in-plane and out-of-plane bending tests, investigating on the typical failure modes of masonry. Non-linear static analyses are performed, with nonlinearities of materials and interfaces deduced from experimental evidences. The comparison with some experimental results and a parametric study allowed to evidence the reliability of the models and their sensitivity to the main components characteristics. [ABSTRACT FROM AUTHOR]

Concrete is one of the most abundant construction and demolition wastes. It can be crushed to produce Recycled Concrete Aggregates (RCA) that can eventually be recycled for the manufacture of new concrete. However, the presence of adherent cement paste leads to higher alkalis content in these aggregates that could increase the risk to observe Alkali Silica Reaction (ASR). Moreover, the origin of natural aggregates in the RCA is generally unknown and these aggregates can potentially be reactive concerning ASR. Among standards which qualify the risk of ASR for natural aggregates, two main tests are used in this paper to evaluate the risk of ASR of RCA: tests on mortars and tests on microbars. In these tests, the water absorption of aggregates is not taken into consideration for the effective water calculation. However, in the case of absorbing aggregates like RCA, absorption water cannot be neglected. It could change significantly the effective water to cement ratio, and then influence the measured expansion. The first aim of this paper is to study the influences of absorption water and initial saturation state of RCA on the expansion of mortars and microbars. The second objective is to propose a new simple method for the assessment of water absorption coefficient of the fine granular fraction 0.16/0.63 mm used for the manufacture of microbars. It is shown that absorption water has a strong influence on the expansion of mortars and microbars made with RCA, and that it has to be taken into account in the composition of the mixes. The initial state of saturation of RCA is less influential. The proposed method for the water absorption coefficient determination of fraction 0.16/0.63 mm is based on the correlation between water absorption and cement paste content. The estimation of the latter from the mass loss between 105 and 475 °C for two fractions of RCA, allows for an accurate determination of the water absorption coefficient of the fine fraction. [ABSTRACT FROM AUTHOR]

Concrete highway and airport pavements are designed to be long lasting; however, some concrete pavements have shown premature deterioration at the cracks and joints. It has been hypothesized that one cause of this deterioration is associated with fluid ingress, especially in cases where those fluids contain deicing salts. This paper examines fluid ingress in mortar using a cross-sectional geometry that is similar to a typical concrete pavement joint. Time-dependent and spatial aspects of fluid ingress are examined using neutron radiography (NR), which was performed using the thermal neutron radiography station at the neutron spallation source at the Paul Scherrer Institut (PSI). Specifically, this paper examines the role of the initial relative humidity (or degree of saturation) and air content on the fluid ingress. The work indicates that the initial fluid ingress reaches a specific degree of saturation relatively rapidly, where the large capillary and gel pores appear to be filled in (commonly referred to as the nick point in sorption tests) and the entrapped and entrained air pores fill in more slowly over time. [ABSTRACT FROM AUTHOR]

This paper aims at investigating the development mechanism of early-stage strength for cold recycled asphalt mixture using emulsion asphalt. The influence parameters of early-stage strength development for cold recycled mixture by emulsion and cement (CRME) is firstly studied, and then the direct tensile test is used to determine the early-stage strength development law of emulsion asphalt–cement mortar. Lastly, the image analysis is used to identify the fracture morphology of cross-section of cold recycled mixture, and the development mechanism of cold recycled mixture is revealed. The results indicate that the cement plays the predominant role in strength of CRME in first 3 days, while emulsion asphalt plays the predominant role in both early-stage and final strength. Moreover, the adhesion between mortar and aggregate provide the strength for CRME in earth-stage, while the cohesion in emulsion–cement mortar provides the strength for CRME after curing. The findings in the paper provide new approaches to improve the early-stage strength of CRME. [ABSTRACT FROM AUTHOR]

The purpose of this paper is an investigation of the possible role of zeolite and powdered Bayburt stones on the fresh and hardened properties of hydrated lime (CL90) mortars. Parameters studied in this paper form the main barriers to the use of hydrated lime in construction practice. Enhancement of these parameters is vital for mortar/substrate optimisation in masonry construction. The major concern of this paper therefore is the combination of wet mortar and brick substrate and most significantly the interaction between them at fresh and hardened states. The results show that transfer sorptivity and time to dewater hydrated lime mortars can be manipulated when zeolite and powdered Bayburt stones are used as replacement materials to the binder. Long setting time of CL90 mortars is decreased with the increasing replacement levels of both zeolite and powdered Bayburt stones. Experimental results also showed that the increasing replacement levels of zeolite and powdered Bayburt stones resulted in a dramatic increase in compressive strength and these results are also supported with the microstructural images. The ability to enhance water transport kinetics and mechanical properties of hydrated lime mortars with zeolite and powdered Bayburt stones should not be underestimated as this enables such materials to be used in construction practice more competently. These results have important practical consequences, not only in the initial adhesion of the mortar to the substrate but also in the strength of the set material and therefore the use of hydrated lime mortars may be encouraged if zeolite and Bayburt stones can improve the fresh and hardened state properties of these mortars. [ABSTRACT FROM AUTHOR]

• Accelerated hydration of PS via activation methods is reviewed. • Review on using PS as blended cement in SCM and as a precursor in AAM. • Combined activation method has the best performance despite high PS as cement replacement. Supplementary cementitious materials (SCM) and alkali activated materials (AAM) are widely researched as alternative binder in concrete due to potential for reducing greenhouse gas emissions by utilizing industrial by-products. Phosphorus slag (PS) is the by-product of yellow phosphorus industry, which can partially substitute ordinary Portland cement (OPC) and reduce carbon footprint. This paper provides a comprehensive review of different activation methods (mechanical, thermal, chemical and alkali activation) to study the factors affecting the mechanical properties and underlying mechanism of PS as binder in SCM and precursor in AAM. The major drawback of PS in cement-based materials or concrete is the low early strength and long setting time due to the presence of P 2 O 5 , and this intensifies as the PS replacement amount increases. The mechanical activation by increasing the fineness, utilization of chemical activators and elevated curing temperature to improve the early-age performance of PS blended cement (PSC) are summarized. Specifically, the effect of these activation methods with different PS replacement level on cement paste, mortar or concrete are discussed in terms of compressive strength, setting time and microstructure. Combined activation gives the best outcome in improving early age properties of PSC. The composition of PS, replacement level and fineness of PS, curing temperature and method, type and dosage of activator are highlighted in this paper. Generally, the optimal PS replacement level is 30 – 40% in non-activated PSC, while activated PSC with proper activators can increase the PS replacement level to 35% – 80% or even fully replace OPC in AAM system. [ABSTRACT FROM AUTHOR]

• Setting time and engineering properties of BCSA concrete are studied. • Citric acid delays initial set from 15 min to as long as 3.5 h. • Retarding hydration does not affect the mechanical strength. • Design codes accurately predict the modulus of elasticity and tensile strength. This paper discusses the setting time and engineering properties (compressive strength, tensile strength, and modulus of elasticity) of belitic calcium sulfoaluminate (BCSA) cement and concrete. BCSA is an emerging alternative cement known for, among other things, its rapid setting behavior. This has long supported its use as a concrete repair material, but BCSA is also attractive for structural applications. Nevertheless, little information is available on the engineering properties of BCSA concrete. This paper quantifies the influence of mixture parameters on BCSA cement setting times, showing that they can be tightly controlled by altering the dosage of a citric acid retarder. It also quantifies the influence of mixture parameters and curing age on compressive strength, proposing predictive models and showing that retarding the hydration of BCSA does not affect its long-term strength. Finally, this paper measures the modulus of elasticity and tensile strength of BCSA concrete and attempts to predict these properties based on the compressive strength. Results suggest that predictive equations from ACI 318, CSA A23, and Eurocode-2 tend to predict the engineering properties of BCSA cement rather well. Together, these results support the feasibility of integrating BCSA cement into practical concrete construction. [ABSTRACT FROM AUTHOR]

• Mixture proportion characteristics of anti-washout concrete; • Fresh-state properties of anti-washout concrete; • Hardened-state properties of anti-washout concrete; • Test methods for anti-washout concrete. Anti-washout concrete (AWC) is a special cement-based material that can be directly employed in underwater environments without dispersion. It was developed around 50 years ago, and more than 150 journal articles and technical reports have been published. This paper provides a holistic review about the basic fresh-state and hardened-state properties of the AWC, such as water (washout) resistance, consistency, bleeding and segregation resistance, mechanical properties, and durability, as well as relevant testing methods. The discrepancies between AWC's characteristics and those of conventional concrete are clearly presented. The mixture compositions, supplementary cementitious materials (SCMs), and other conditions that affect AWC's performance are also elaborated. Finally, the paper discusses the specific performance requirements of AWC and corresponding construction strategies for its different applications, including normal construction, marine engineering, bulk filling, and repair practices. Future research needs to stimulate the development of AWC are also discussed. [ABSTRACT FROM AUTHOR]

The ongoing use of various mineral additions along with chemical admixtures such as superplasticizers justifies the need for further research. Understanding and quantifying their effects and possible synergies on the fresh and hardened properties of cement-based materials is necessary, especially if some of these components are known to have a pozzolanic effect. This paper describes and models the fresh and hardened properties of cement mortars including nanosilica and fly ash, and relates their properties to the proportioning of these materials and the superplasticizer dosage. Mini-slump, Marsh cone and Lombardi cone tests were used to examine the properties of the fresh mortars, and to assess density, plastic shrinkage, and drying shrinkage up to 20 days. The equations presented in this paper make it possible to optimize mortar proportionings to the required levels of performance in both fresh and hardened states. [ABSTRACT FROM AUTHOR]

• The potential of brick waste recycling and its use in aerial lime-based mortars is investigated. • The incorporation of brick dust in lime mortars generated a pozzolanic reaction. • Brick dust improved the compressive strength. • Brick dust increased the hygric and hydric expansion of lime-based mortars. To preserve architectural heritage for future generations, restoration materials such as mortars should be compatible with the historic substrate. Pozzolanic mortars are a compromise solution between Portland cement-based mortars and aerial lime-based mortars. This paper investigates the recycling of brick waste in the Meknes region of Morocco to formulate pozzolanic mortars. Nine different mortars were made using aerial lime, sand and brick dust. They were characterized in terms of shrinkage, color, mechanical and hydric properties. The study revealed that Meknes brick dust exhibits a pozzolanic activity and reduces shrinkage. Moreover, it increases hydric and hygric expansion, enhances mechanical strength and affects the color of mortars. An appropriate recipe for restoration mortars could then be proposed to restore regional architectural heritages, depending on the properties of their historic substrates. [ABSTRACT FROM AUTHOR]

• SB-AER can as an admixture to improve the chloride ion penetration resistance of mortar. • A ternary blends (containing SF, FA, and SB-AER) with a particle size 75 um or less can be prepared by ball milling. • The ternary blends can improve the chloride ion penetration resistance and mechanical properties of the mortar. How to improve the chloride penetration resistance of reinforced concrete in marine environment has always been an important research topic. In this paper, based on the adsorption properties of strong basic anion exchange resin (SB-AER) for chloride ion, SB-AER, silica fume (SF) and fly ash (FA) were milled into ternary admixtures with particle size less than 75 μm. The effect of SB-AER on chloride ion penetration resistance of mortar was studied. In this experiment, the mechanical properties and compactness of mortar with different SB-AER content were tested by pressure testing machine and ultrasonic nondestructive flaw detector. The microstructure of mortar was observed by scanning electron microscope (SEM). The chloride ion binding capacity of mortar with different SB-AER content was qualitatively and quantitatively analyzed by chloride ion selective electrode method. All the results show that under the appropriate SB-AER content, the ternary admixture can effectively improve the chloride penetration resistance and mechanical properties of mortar. SB-AER-3 group (SB-AER, SF and FA are 3%, 5% and 10% of cement weight, respectively) has the best performance in these two aspects. [ABSTRACT FROM AUTHOR]

• Study of the influence of superplasticizers on the fresh and hardened state characteristics of lime mortars. • Superplasticizers based on polycarboxylate ether (PCE) and on polynaphthalene sulfonate (PNS) were used. • PCE was found to be more effective (higher dispersing ability) and efficient (less quantity needed) than PNS. • Both superplasticizers led to a vast strength increase and only small changes in the porous structure. • Resulting lime mortars with superplasticizer have potential to be used in restoration. Water-reducing admixtures have the potential to minimize the disadvantages that typically discourage the use of lime in restoration works. However, the knowledge on the effect of these admixtures on the properties of lime mortars is not as consolidated as it is for cement-based materials. Therefore, this paper aims at studying the influence of two types of superplasticizer, one based on polycarboxylate ether (PCE) and the other on polynaphthalene sulfonate (PNS), on the fresh and hardened state properties of lime mortars. PCE was found to be more effective (higher dispersing ability) and efficient (less quantity needed) than PNS, leading to a lower fluidity loss over time, but to a higher tendency towards bleeding. Both admixtures led to a substantial mechanical strength increase, even at early ages, and just to small changes in the porous structure of the mortars, which suggests that lime mortars with superplasticizer have potential to be used in restoration. [ABSTRACT FROM AUTHOR]

• The use of Spanish Broom fibers for improving mechanical properties of mortar has been studied. • Maceration of summer harvesting with sea water and 5% NaOH gave the best results. • Fiber maceration with sea water is a cheaper and more environmentally friendly. • The results on 56-day old reinforced samples show better results then etalon. • The samples with 30 mm-long fibers gave the highest flexural strength values. This paper investigated the use of Spanish Broom fibers for cement mortar reinforcement. The characterization of the fibers separated with different separation methods was carried out through FTIR and TG/DTG analysis. The influence of harvesting time, fiber processing method, fiber length and amount of fibers on the mechanical characteristics of cement composite have been studied. Compressive and flexural strengths of cement mortar specimens were determined after 28 days and compared with reference mortar. Five specimens were also tested after 56 days and obtained results are opposed to the results on 28-day old samples. According to the results obtained Spanish Broom fibers are very strong and able to reinforce cement matrix at micro level. Fibers picked in summer will result in better mechanical properties of mortars than fibers picked in fall. Considering the maceration method, it is concluded that fiber maceration with sea water is as effective as chemical treatment with NaOH but cheaper and more environment-friendly. [ABSTRACT FROM AUTHOR]

• Cement mortars were cured in frozen sands to mimic the influence of permafrost. • Temperature profiles in calcium sulfoaluminate (CSA) cement mortar were recorded. • Hydration reaction of CSA cement cured at cold temperatures was investigated. • Hydration reaction of CSA cement was fast regardless of cold curing temperatures. • CSA-based mortar achieved fast strength development even at −5 °C and −10 °C. The objective of this paper is to investigate the hydration reaction and strength development of calcium sulfoaluminate (CSA) cement mortar cured in various cold temperatures (i.e., 5 °C, 0 °C, −5 °C and −10 °C). In this study, both CSA cement-based and GU (General Use) cement-based mortar samples were cured in wet sands at temperatures of 5 °C, 0 °C, −5 °C and −10 °C. During the investigation, the temperature profiles in both sands and the centers of mortar samples were recorded. In addition, thermogravimetric analysis (TGA) and unconfined compressive strength (UCS) tests were conducted on the samples at 1, 3, 7 and 28 days. The TGA results showed that the hydration reaction rate of GU cement was slow at cold temperatures and decreased with a drop in the curing temperature. However, the hydration reaction of CSA cement was very fast—it was mostly completed within the first 24 h—regardless of the curing temperatures. The UCS test results indicated that the strength development of CSA-based mortar was much faster than that of GU-based mortar. The CSA-based mortar achieved rapid strength development even cured in frozen sands with temperatures at −5 °C and −10 °C. In conclusion, CSA cement can be substituted for GU cement to accelerate the strength development of cement-based materials constructed in cold temperatures. [ABSTRACT FROM AUTHOR]

• The effects of bentonite on the pore structure of cement mortar were given. • The permeability of mortar could be reduced significantly by bentonite. • The waterproofing process and mechanism of bentonite particles were proposed. The pore structure and permeability of cement-based materials have great influence on the durability of application of this materials. The effects of bentonite on the pore structure and permeability of cement mortar were investigated in this paper. Bentonite, as a swelling potential clay, was added to mortar at content 0, 4 and 8% by weight of cement. The compressive strength, flexural strength, and impermeability pressure were determined for cement mortar with bentonite and compared with plain cement mortar specimens. Test results showed that the addition of 8% bentonite could cause a significant increase of 61.48%, 42.09% and 76.47% for compressive strength, flexural strength, and impermeability pressure, respectively. The enhancement of impermeability is mainly due to the pore structure refinement by the bentonite, which is validated by test results of the Mercury intrusion porosimetry (MIP). Moreover, needle-like and amorphous hydration products grow on the surface or edge of bentonite resulting in more tortuous penetration path to improve the barrier performance of cement mortar. [ABSTRACT FROM AUTHOR]

• This paper first reports the influence of nano-silica on high strength mortar. • Pore system was refined and more disconnected. • Compressive strength and transport properties were improved. • Drying shrinkage was reduced due to the refined microstructure. • The enhancing efficiency was compared in high strength and normal strength mortar. Recent studies have demonstrated the advantages of using nano-silica in building materials such as concrete due to its nano-filler effect as well as the pozzolanic reaction. However, most of the previous findings are based on normal strength cement composites. In this study, a wide range of properties of high performance cement composites are investigated with addition of colloidal nano-silica (CNS) at dosage of 0.5%, 1.0%, 1.5% and 2.0%. Attributed to the pozzolanic reaction of CNS, the microstructures are denser and more homogenous. SEM observation, accelerated hydration rate and reduced Portlandite content verify this beneficial reaction. Hence, the CNS can help produce cement composites with higher mechanical strength and better durability regards to the impermeability to water and chloride ions. Also, it is found that the influence of CNS is more pronounced for composites with lower water-cement ratio at 0.30, in comparison with those at 0.50. [ABSTRACT FROM AUTHOR]

Fly ash is known as a common geopolymer precursor. However, it is important to search for suitable alternatives as the availability of fly ash will reduce with the move to more renewable energies. This paper evaluates the feasibility of using waste clay brick powder (WCBP) as a partial alternative for fly ash in geopolymer mortars with ground granulated blast furnace slag (GGBFS), under ambient and heat curing conditions. The physical, mechanical, and mineralogical properties of geopolymer mortar with 10 to 40% WCBP were investigated. Microstructural properties of WCBP and geopolymer mortars were investigated using X-ray fluorescence (XRF), X-ray diffraction (XRD), tescan integrated mineral analyzer (TIMA), scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). Reductions of the flow of fresh mortar were observed with the increase of WCBP. The highest 28 days compressive strengths were obtained in the mortars containing 40% WCBP, both at ambient and heat curing conditions. Microstructural analysis highlighted compact structure and reduced porosity, which are attributed to the role of WCBP in enhancing fly ash-GGBFS mortar properties by promoting geopolymer gel formation. • Characterization of Waste Clay Brick Powder (WCBP) showed its potential use as a geopolymer precursor. • The effect of WCBP on the mechanical and mineralogical properties of fly ash-GGBFS-WCBP geopolymer mortar was investigated. • High strength and a compact microstructure development could be achieved by using up to 40% WCBP. [ABSTRACT FROM AUTHOR]

Due to high Cl- content and porosity in coral, coral-aggregate concretes usually present poor durability and mechanical properties. In this paper, two types of materials, polyvinyl alcohol (PVA) and Calcium Sulphoaluminate (CSA) clinker, were used to modify properties of coral sand and consequently inhibit leaching of Cl- from coral and improve mechanical properties of yield mortar. Results showed that the smaller the particle size, the greater Cl- dissolution rate of crushed coral sand. PVA and CSA materials could effectively inhibit the Cl- dissolution, and the most obvious decrease could reach 6% and 23%, respectively, in comparison of 35% prior to the modifications. However, mechanical properties of these two modified coral sand mortars were unsatisfactory under standard curing, which the CSA-modified specimens generate thaumasite resulting in a strength decrease and could be improved by a slight increase in curing temperature to 35 ℃. • PVA and CSA were used to improve mechanical and chloride dissolution of crushed coral sand. • PVA decreases number of pores for entire diameter, CSA divided bigger pores into smaller ones. • Both the PVA and CSA modifications inhibit dissolution of Cl from coral sand. • CSA modified coral sand mortar needs a higher curing temperature for satisfactory strength. [ABSTRACT FROM AUTHOR]

Cement-based materials prepared with manufactured sand can exhibit quick loss of fluidity. However, the estimation of the flow loss remains difficult given the variable contents and physiochemical properties of the microfines in various sands. This paper studies the fluidity loss of mortar mixtures made with different manufactured sands varying in mineral composition and content of microfines. The effect of microfines on accelerating the early-age hydration of cement before the deceleration period was evaluated by quantifying the generation of early hydration products. Test results show that the growth of yield stress corresponding to the loss of mini-slump flow of mortar mixtures were mainly determined by the formation of early hydration products, in addition to the volume fraction and packing density of aggregate grains and powder particles. An approach was then proposed that can assess the loss of mini-slump flow of mortar mixtures prepared with manufactured sand, regardless of the type and content of the microfine materials in the sand. • Manufactured sand with a relatively high content of microfines does not necessarily cause low fluidity of mortar. • Manufactured sand with a high fine content and MB would cause fast growth of rheological properties. • Flow loss of mortar with manufactured sand can be assessed by evaluating the generation of early hydrates. [ABSTRACT FROM AUTHOR]

This paper focuses on the development of environmentally friendly, easy to use and cost-effective construction and demolition waste (CDW)-based geopolymer mortars activated solely with low-alkalinity NaOH and along with large share of recycled concrete aggregates (RCAs). The low-activity CDW-based precursors used in this study included brick waste and concrete waste. Additionally, slag and silica fume were utilized as industrial waste-based precursors to provide additional sources of Ca and Si, promoting enhanced geopolymerization. NaOH was utilized at molarity levels of 4, 5, 6, 7, and 8 M. The study employed a comprehensive test methodology, enabling a thorough investigation of the different properties and performance of the geopolymer mixtures, ultimately achieving the goals set for this research. The results indicated that the 4 M NaOH concentration was insufficient for early strength development of CDW-based geopolymer systems, although it eventually provided adequate alkalinity for strength development at later ages (e.g., compressive strength of 7.2 Mpa at the end of 28-day). While higher NaOH concentrations generally improved performance, the optimal choice was found to be 5 M NaOH. Nevertheless, 100% CDW-based geopolymer mixtures activated solely with low molarity NaOH solutions showed lower performance (compressive strength of 10.5 Mpa and flexural strength of 2.3 Mpa at the end of 28-day) and were found to be susceptible to water ingression and unable to withstand freeze-thaw cycling. Incorporation of slag significantly enhanced the mechanical and durability properties of CDW-based geopolymer regardless of alkaline content. The inclusion of coarser RCAs (0–4.75 mm) and a higher amount of finer RCAs (0–2 mm) resulted reduction in the performance of the mixtures. Nevertheless, the observed negative impacts were mitigated through 5% silica fume substitution. The findings of the study indicate that low-alkaline activated CDW-based geopolymer mortars can achieve an impressive compressive strength of 24.9 MPa and flexural strength of 4.7 Mpa along with superior durability performance. • Rheology of geopolymer can be customized by adjusting NaOH, precursor & aggregate content. • Slag can enhance the mechanical, transport and durability properties of geopolymer. • NaOH molarity of 5 M was optimal for activating the CDW-based geopolymer. [ABSTRACT FROM AUTHOR]

As a non-homogeneous porous material, the microstructure of cementitious composites critically affects the mechanical and durability properties. This paper aims to analyze the effect mechanism of cement replacement by zeolite powder on the microscopic pore structure characteristics, macroscopic mechanical behavior, and durability of mortar to reduce cement consumption and improve mortar performance. The compressive strength and chloride ion permeability of mortar incorporated with zeolite powder were experimentally determined, and the effects of zeolite powder content on the composition of cement hydration products and pore structure were further analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and mercury intrusion porosimetry (MIP). The pore structure characteristics were quantitatively analyzed by fractal theory. The results shows that incorporating zeolite powder in cement mortar fills the pores, promotes secondary hydrate formation, reduces the Ca/Si ratio, refines the pore size, and reduces the porosity of large pores. Thus, the internal pore structure of the matrix is significantly improved, reducing the pore fractal dimension and improving the compressive strength and chloride ion penetration resistance. 15% cement replacement zeolite powder has been found optimal in reducing the porosity and chloride ion permeability coefficient while enhancing the compressive strength. The pore structure fractal dimensions calculated by the Menger sponge fractal model can quantitatively describe the pore structure distribution characteristics, which can help ascertain the relationship between zeolite powder content, pore structure quantitative characteristics, and macroscopic mechanical behaviors. • The effect of zeolite on the property and pore structure of the mortar is tested. • Zeolite can enhance the strength, compactness and chloride impermeability. • Using fractal dimension to quantify the pore structure characteristic of mortar. • A relationship model between property and pore fractal characteristic is proposed. • The zeolite content should not exceed 15% to avoid damaging properties. [ABSTRACT FROM AUTHOR]

The safeguard of existing masonry buildings requires a meticulous characterisation of the component materials (units and mortar) by using in-situ minimally intrusive techniques. This need is especially prominent in the case of heritage buildings in order to minimize their damage and alteration. This paper presents a research on some minor destructive techniques (MDT) for the in-situ evaluation of the mechanical properties of masonry components. In the research, the results derived from MDT were empirically correlated with the compressive strength obtained by using well-known destructive testing (DT) techniques executed in the laboratory. The experimental campaign focused on two different MDT techniques, namely the Pin Penetration Test (PPT) and the Helix screw Pull-out Test (HPT). The PPT is based on the measurement of the depth of penetration of a steel pin. The HPT is based on the measurement of the pull-out load necessary to extract a steel tie inserted into a hole drilled in a brick or in a mortar joint. The experimental campaign also included an evaluation of the Double Punch Test (DPT) by comparison with strength values obtained from mortar specimens prepared and tested following the standard EN 1015–11. The experimental results show a satisfactory agreement between the MDT measurements and the compressive strength obtained with DT. Although both the PPT and HPT are useful for the evaluation of the compressive strength of masonry components, the former exhibits a lower scattering in the experimental measurements. • 541 destructive tests on modern and historical solid clay bricks and mortar joints. • 741 minor destructive tests on solid fired clay bricks and mortar joints. • Compressive strength in mortar using Double Punch Test and EN 1015–11 procedure. • Compressive strength evaluation of specimens using the Pin Penetration Technique. • Compressive strength evaluation of specimens using the Helix screw Pull-out Test. [ABSTRACT FROM AUTHOR]

Polyethylene Terephthalate (PET) is commonly used to manufacture plastic products such as beverage bottles, food packaging, and clothing fibers. It is the most widely used plastic in the world and accounts for about 60% of all plastics. Being non-biodegradable, the accumulation of waste PET presents a significant environmental challenge. Conversely, recycling PET has long been recognized as an optimal strategy for mitigating these environmental concerns. In recent years, recycled PET has gained attention as a potential additive in construction materials, including asphalt mixtures and cement concrete. This paper provides a comprehensive literature review on incorporating waste PET in asphalt mixtures, examining its utilization as an asphalt binder modifier, a partial or complete aggregate substitute, and a partial asphalt binder replacement. The focus is on investigating the mechanical properties of these mixtures, including moisture susceptibility, fatigue resistance, rutting performance, and fracture resistance. The findings from the reviewed studies indicate that the inclusion of PET in asphalt mixtures enhances the mixture's stability, improves resistance to moisture susceptibility, increases resistance to rutting deformation, and improves the asphalt mixture's fracture resistance. However, certain studies have highlighted a decline in the mechanical properties of asphalt mixtures when PET is used in large quantities. • PET Incorporation Methods in Asphalt Mixtures : There are three primary methods in which PET can be added into asphalt mixture namely wet, dry, and modified dry methods. Wet and dry techniques are most commonly used, offering versatility based on the melting points of the plastics involved. • PET utilization in asphalt mixture: PET can be utilized in asphalt binder, either by modifying the binder's properties or by partially replacing the asphalt binder. It can also be used as a substitute for traditional aggregates in asphalt mixtures. • Enhanced Performance PET-modified asphalt mixtures : PET inclusion in asphalt mixtures significantly improves resistance to moisture-induced damage, rutting deformation, fracture resistance, and fatigue cracking, contributing to longer-lasting and more durable pavements. • Form and sizes of the PET utilized : The sizes and forms of PET utilized play a crucial role in determining the properties of the asphalt mixture. Fine-grade PET particles increase moisture resistance, coarser particles increase bulk density, and longer PET fibers increase fracture and fatigue resistance. • Economic and environmental benefits. Economically, it reduces material costs by recycling readily available PET waste, cutting expenses associated with virgin materials. Environmentally, it diverts plastic waste from landfills and incineration, conserving natural resources and reducing environmental pollution. [ABSTRACT FROM AUTHOR]

Graphene has been considerably studied as a reinforcing nanomaterial in cementitious composites to improve their mechanical properties under quasi-static loading. However, there is still lack of knowledge in graphene cementitious composites under high strain rate loadings. This paper reports the reinforcing effect of graphene on the mechanical behaviour of mortar at high strain rates. Different graphene contents were incorporated into the mortar to study their effect on the behaviour of mortar quasi-statically and dynamically. Compressive and split tensile strengths were measured under low and high strain rates using a universal testing machine and split-Hopkinson pressure bar (SHPB), respectively. It was found that adding 0.05% and 0.01% of graphene to the mortar enhanced the dynamic compressive and split tensile strengths up to 30% and 9.5% at 175 s-1 and 2–5 s-1 strain rates, respectively. Moreover, to understand the macroscale mechanical behaviour of the graphene mortar, Scanning Electron Microscopy (SEM), Energy Dispersive Spectrometer (EDS) and Mercury Intrusion Porosimeter (MIP) were employed to explore the morphology, porosity and hydration products of graphene mortar. The results indicated that graphene acted to fill the voids as well as to impede the crack path. • Mechanical properties of graphene mortar were evaluated at high strain rates. • Graphene can enhance the strengths of mortar quasi-statically and dynamically. • Dynamic increase factors were determined for both compression and tension. • Microscopic analysis proved graphene fills the voids and impedes the crack path. [ABSTRACT FROM AUTHOR]

For fiber reinforced permeable concrete, numerical simulation method have been applied to reduce the time consumption of physical experiments and to study the mesostructure of the material. In this paper, polyacrylonitrile fiber reinforced permeable concrete (PANFRPC) is considered to consist of aggregate, mortar (containing fibers inside), interface transition zone (ITZ) and pores in 3D mesostructure model generated from computer tomography (CT) images. For the numerical simulation of the, material properties of each component in the model are assigned according to physical experimental results. The failure curve of the mortar in PANFRPC is determined by physical test results to reflect the effect of fibers. The simulation results show that the model has similar mechanical properties to the actual specimen and can be used to simulate the elastic stage of the uniaxial compression process and predict the strength with an error of less than 15% despite the simplification of fiber. the accuracy and reliability of the model have also been verified by the distribution pattern of vertical caraks and x-shaped shear cracks from macro and meso perspectives. • CT scanning and digital image processing technology are applied to extract the mesoscopic components of PANFRPC specimen. • 3D mesostructure model of PANFRPC is established for numerical analysis of uniaxial compression process. • The accuracy and reliability of the numerical model construction method are verified by simulation results. [ABSTRACT FROM AUTHOR]

This paper investigates the adhesive properties of fresh mortar with manufactured sand (Msand) as replacement of river sand (Rsand). Adhesive properties were evaluated by normal force evolution curves from the tack test. Both static and dynamic yield stress were measured to elaborate the influence of Msand replacing Rsand on the adhesive properties. Results indicate that Msand increases the adhesive force, critical displacement, stiffness, and adhesive failure energy whereas shortens the debonding duration. Replacement of Rsand by Msand gradually promotes the transition of failure mode from cohesive rupture to adhesive rupture. The adhesive force of mixtures showing cohesive rupture is highly related to their static yield stress values. • Adhesive properties of mortar with Msand were evaluated by the tack test. • MS increases the adhesive force, stiffness, and adhesive failure energy. • MS promotes the transition of failure mode from cohesive rupture to adhesive rupture. • The adhesive force of mixtures showing cohesive rupture is related to their static yield stress. [ABSTRACT FROM AUTHOR]

Microwave-assisted breakage of cementitious materials has emerged as a promising green and low-carbon method for dismantling cementitious structures. To understand the mechanism of microwave-induced cracking in structures, it is essential to study the thermal behaviors of cement and mortar under microwave treatment. In this paper, the effects of mixture ratio, water content, and microwave power on the microwave heating characteristics of cement and mortar specimens were investigated through real-time temperature and mass monitoring. In particular, the influence of microwave power on the bursting effect of cement and mortar specimens was analysed, and the mechanism of specimen bursting was explained. The results show that moisture content, water-cement ratio, and microwave power significantly impact the heating rate and mass loss of cement and mortar during microwave treatment. Based on the heating rate, the heating process of cement and mortar under microwave treatment can be divided into three to four stages, depending on the moisture content. The primary reasons for variations in the heating rate are water evaporation and the decomposition of hydrolysis products. The thin-wall ball model based on steam pressure theory can explain the bursting of cement and mortar specimens. Our findings suggest that increasing microwave power and water content in mortar specimens can lead to microwave-induced cracking. • Instantaneously measured the temperature and mass changes of cement and mortar while microwave heating. • Investigated the influence of mix ratio, water content and power on microwave heating and bursting of cement and mortar. • Examined the thermal decomposition kinematics of cement hydration products while microwave heating. • Reveals the dual role of water in the microwave heating process. [ABSTRACT FROM AUTHOR]

Permeability is an important factor affecting the durability as the connection between pores provides a channel for water and ion permeation. However, the mechanism governing the influence of inter-pore connection is still unclear. This paper quantitatively calculates the connectivity and complexity of inter-pore connections based on pore structure scan images, and investigates the effect of different aggregates on the resistance of mortar to chloride-ion migration. Seawater ordinary mortar (SOM) and seawater iron tailings mortar (STM) were prepared. Pore scans and tests for chloride migration coefficient and chloride-ion content were conducted. Based on the maximum Feret diameter of the pores, the complexity index, K ci , was defined to characterize the complexity of inter-pore connections, and this extends existing calculation methods from one-dimensional to two-dimensional in nature. However,the complexity index correlates with the chloride migration coefficient and chloride-ion content well for seawater ordinary mortar only but not for seawater iron tailings mortar. Therefore, the critical image diameter, d ic , was defined to characterize the connectivity of pores. This also overcomes the shortcomings of the MIP method, which does not give the spatial pore distribution. Last, the modified complexity index, K mci , which modifies the complexity index using the critical image diameter, was presented. It is shown to correlate with test results well for both seawater ordinary and iron tailings mortars. Replacing K ci with K mci greatly improves the linear correlation of complexity of inter-pore connection with chloride penetration resistance for seawater iron tailings mortar, with the correlation coefficient R increasing from 0.45 to 0.88. • Quantitative characterization for complexity and connectivity of inter-pore connection. • Critical image diameter is defined to characterize the connectivity. • Modified complexity by connectivity to characterize chloride permeate resistance. [ABSTRACT FROM AUTHOR]

Shortly after the mixing of ultra-high performance concrete (UHPC), a viscoplastic layer forms on the surface, which is often colloquially called elephant skin. This layer can hinder the venting, through which air bubbles accumulate below the concrete surface, causing poor surface quality and aesthetics after finishing or resulting in an inferior composite in the case of multi-layer structural components. This paper aims to improve the surface performance of UHPC by reducing the effect of elephant skin. In the present work, the influence of various factors on the "elephant skin" formation on UHPC surface is firstly investigated using a newly developed test method that measures the development of the surface resistance of "elephant skin" on UHPC with time, based on the Vicat apparatus for testing the setting time of cement. Then, the formation mechanism of "elephant skin" on the surface of UHPC is discussed. Finally, some measures to minimize the effect of "elephant skin" on the UHPC surface are proposed. The results reveal that next to controlling the ambient relative humidity (RH) and temperature, an optimization of the concrete mix composition and manufacturing process, such as an increase of superplasticizer (SP) dosage, paste content and water-to-binder (W/B) ratio can help to slow down the "elephant skin" formation on UHPC surface, minimizing its negative effect while without significantly compromising the concrete compressive strength. • Formation of "elephant skin" reduces UHPC surface properties. • A new method is used to examine the formation speed of "elephant skin". • Formation of "elephant skin" is caused by surface evaporation and rising of internal moisture. • Ambient temperature and humidity can influence the formation of "elephant skin". • Improving the UHPC mix proportion can slow down the formation of "elephant skin". [ABSTRACT FROM AUTHOR]

• Valorization of dredged sediments and excavated clays in geopolymer formulations. • Adapting flash calcination at 750 °C as a pre-thermal technique for dredged sediments. • Durability of flash-calcined sediment/flash-calcined clay – Metakaolin – Slag geopolymer. This paper focuses on the development of a geopolymer (GP) mortar that can be cured under ambient conditions using flash-calcined dredged sediment (FCS) and flash-calcined excavated clay (FCC), as a substitute for Metakaolin (MK). Granulated blast furnace slag (GBFS) is also added to some of the GP mixes to study its effect on GP performance. Potassium silicate (K 2 SiO 2) was used as an alkaline reagent (AR). Therefore, this study investigates the effect of binder composition on the mechanical and durability performance of the GP mortar samples. Acid attack test, high-temperature resistance test, and microstructural analysis tests such as X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were conducted to compare the reference mix with other substitute mixes containing FCS and FCC. Finally, the nuclear magnetic resonance (NMR) test is done on all GP mixes to verify their network classification. The results show that using FCS/FCC and only 10–20 % wt. of GBFS in the GP mortar mixes can result in similar or better properties in terms of strength and durability, while the NMR test identifies their tetrahedral network can vary between formulations. [ABSTRACT FROM AUTHOR]

• A numerical simulation method based on computational fluid dynamics (CFD) and DDPM for the free flow of fresh concrete in the long-distance chute is established. • The movement characteristics of aggregate in fresh concrete during chute transportation are studied on the mesoscale. • According to the results of numerical simulation, the optimum angle of concrete transfer in chute and the optimum mortar viscosity to effectively suppress aggregate segregation are proposed. The movement behavior of fresh concrete greatly affects the change of concrete properties and the wear of pipelines during transportation. This paper aims to predict the movement of aggregates in fresh concrete during transporting on a mesoscopic scale. A dense discrete phase model (DDPM) was utilized to describe fresh concrete, which treats fresh concrete as a double-phase fluid composed of matrix mortar and dense spherical aggregate particles that had grading particle size, random distribution, and different densities from matrix mortar. The correctness of this method was verified by comparing it with the experimental results. Then, based on the Computational Fluid Dynamics (CFD) and the DDPM, the free flow of fresh concrete in the long-distance chute was simulated. Flow behavior of fresh concrete in the chute with different inclination angles and movement characteristics of fresh concrete with different viscosities at an optimal angle were investigated, respectively. Moreover, recommended parameters for the maintenance of concrete workability in the project were provided, and it is believed that a mortar viscosity of around 50 Pa·s can effectively suppress aggregate segregation, ensuring the consistency of concrete properties during transportation. [ABSTRACT FROM AUTHOR]

• The effect of thermal preconditioning on carbon FRCM was investigated. • Bare and epoxy-coated textiles were considered. • The thermal preconditioning included heating ramps up to 300 °C. • The matrix prevents the organic coating from carbonizing. • Textile impregnation improved the FRCM properties even after thermal exposure. Fabric-reinforced cementitious matrix (FRCM) composites often include polymer-impregnated bundles to improve the exploitation of the textile mechanical properties. However, organic components may degrade when exposed to elevated temperature. In this paper, the bond behavior of a carbon FRCM applied to a masonry substrate and exposed to a thermal preconditioning up to 300 °C for 250 min is investigated. Tensile tests on the textile and flexural and compression tests on the mortar matrix, as well as single-lap direct shear tests of FRCM-masonry joints with bare and impregnated textiles, are performed. Results show that the polymeric impregnation improves the mechanical properties of the FRCM even after thermal preconditioning. [ABSTRACT FROM AUTHOR]

• The out of plane behavior of T-shaped masonry walls is experimentally investigated. • Twisted bars or adhesive with rebars are used to improve the T-connection. • The cyclic behavior of the retrofitted structure is tested. • Twisted bars significantly improved the dissipation capacity. • Rebars with adhesive allowed to achieve the monolithic behavior of the specimen. The damage observed after the recent earthquakes showed that the most common failures for masonry buildings involve out-of-plane mechanisms associated to the ineffective connection between walls. For this reason, retrofitting techniques aiming to achieve a box-like behavior are of great interest. This paper presents the results of an experimental study conducted to investigate two different retrofitting solutions used to improve the structural connection between orthogonal walls: a mechanical connection by means of twisted bars and a fastening solution with rebars and injection mortar. Two full-scale T-shaped masonry specimens were realized in solid clay brick, with a "weak" connection between the front and the back wall. The specimens were tested in unreinforced and strengthened configurations, considering different retrofitting layouts. An out-of-plane load was applied on the front wall, together with a vertical prestress to simulate the gravity load coming from the floors and walls above. Each specimen was tested in three consecutive runs: a monotonic one on the unreinforced masonry, a first cyclic run with the wall intersection reinforced with twisted bars, and a second cyclic run on the wall retrofitted with rebars and injection mortar, after the removal of the twisted bars. The twisted bar solution resulted in a significant increase of the dissipative capacity of the wall despite the number of adopted bars, while, in the case of rebars and adhesive, a higher resistance was achieved together with a perfect box-like behavior. [ABSTRACT FROM AUTHOR]

• MPC was prepared using red mud waste, and the 28-day compressive strength exceed 80 MPa. • The effects of red mud substitution on the performance of fresh and hardened properties of MPC were investigated. • Qualitative and quantitative analyses of the hydration products and microstructure were carried out. • The rheological properties of fresh MPC pastes blended with red mud was determined. Alumina and iron oxide which constitute significant components of red mud can participate in the hydration reaction with phosphate. This paper partially replaced magnesia with red mud in the preparation of magnesium phosphate cement (MPC) and investigated the effects of red mud substitution on the performance of fresh and hardened properties of the MPC. The fresh properties of MPC were analyzed by measuring the setting time, fluidity, early hydration heat release and rheological properties, while the hardened mechanical properties were characterized by compressive strength measurement. The phase composition and micro-morphology were examined by XRD, SEM, EDS, and TG-DTA. The experimental results demonstrated that the incorporation of red mud prolonged the setting time, and postponed the occurrence of the peak temperature, and reduced the hydration reaction intensity. Regarding to the rheological properties, an increase in the dynamic yield stress was followed by a decline with gradually addition of red mud. Conversely, the plastic viscosity increased consistently. Concerning hardened properties, adding appropriate amount of red mud powders to MPC can significantly improve the compressive strength of hardened MPC mortars. The samples containing 15 % red mud yield the highest compressive strength, especially in the early strength, it was even more pronouncedly improved by 14.8 % comparing to the controlled samples at 3 h. Furthermore, detailed information about the modification effects of red mud on the MPC microstructure has been studied. The density of the MPC matrix was improved, microcracks and gaps appeared less, and some new hydrates could be determined, which is responsible for the improvement of the MPC's mechanical properties. [ABSTRACT FROM AUTHOR]

• Demolished concrete waste can be potentially utilised as recycled aggregates (RA). • Multi-stage processing and mechano-chemical treatment enhances the quality of concrete RA. • RAC incorporating treated RA shows better mechanical and durability properties. • Additional C S H formation is observed for RAC incorporating 35% treated RA. On account of the shortage of naturally occurring coarse aggregate, recycled aggregate (RA) made from crushed concrete debris is now used in the construction industry. With this rise in the utilisation of recycled aggregate in the construction sector, there has been extensive research into ways to improve its quality. The significant fraction of mortar remains that are left on the RA surface is the primary factor that affects its quality. Concrete made from RA loses strength and mechanical performance due to the attached mortar's increased porosity and water absorption values and the frailer transition region between the new mortar and aggregates. In order to minimise the old cement fractions and increase the quality, this paper studies the effect of concrete incorporating multi-stage processed RA from demolished concrete waste, followed by treatment with mechanical abrasion and sodium silicate immersion. The recycled aggregates were produced through multi-stage jaw crushing, followed by utilising natural aggregate, recycled aggregate, and recycled aggregate obtained after mechanical abrasion, followed by sodium silicate treatment for concrete mix design at various substitution percentages as coarse aggregates. The experimental investigation further progresses with the evaluation of mechanical and durability properties of concrete mixes, which is additionally followed by microstructural studies such as scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDAX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Thermogravimetry-differential thermal analysis (TG-DTA). The outcomes demonstrate that two-stage treatment, such as mechanical abrasion followed by sodium silicate immersion, yields superior-quality RA. Recycled aggregate concrete (RAC) made with these treated aggregates illustrated an increase in workability and density with respect to an untreated RAC mix. Furthermore, comparable strengths in compression, flexure, and tension are found in treated RAC mixes, particularly at 35% replacement levels, with respect to concrete mixes comprised of natural aggregates. A similar trend is detected in the chloride penetration tests and water sorptivity tests. In addition, the microstructural investigation confirmed the formation of additional calcium silicate hydrate for treated RAC mixes, particularly for the 35% substituted RA mix. On the basis of the results, it is suggested that multi-stage jaw crushing followed by treatment through mechanical abrasion and sodium silicate can potentially enhance the mechanical, microstructural, and durability performance of RAC. [ABSTRACT FROM AUTHOR]

• SCGF is developed to promote the utilization of industrial solid waste. • Attention-based tree models are adopted to predict the mechanical properties of SCGF. • An intelligent design method of SCGF is proposed and verified. To promote the utilization of industrial solid waste, a new green binder system namely SCGF for sustainable concrete is developed, in which slag-fly ash is activated by soda residue-carbide slag. However, the mix design of the SCGF is challenging due to heavy workload and the lack of theoretical basis. The relationship between mix proportion and mechanical properties of SCGF needs to be accurately expressed. In this paper, an intelligent design method of SCGF is proposed by coupling the attention mechanism, machine learning and multi-objective heuristic optimization algorithm. After training with experimental data, the prediction performance of attention-based tree model is evaluated. Multiple Pareto optimal solutions can be obtained by the proposed intelligent mix proportion design method. The results show that attention-based tree models perform higher accuracy (accuracy > 95 %) and better measures than that of classical tree models. Compared the strength and cost of SCGF to cement mortar, the mix proportion designed in this study has obvious advantages in environmental protection and economy (>50 % cost saving). Therefore, the proposed method can provide a theoretical basis for the recycling and utilization of industrial solid wastes. [ABSTRACT FROM AUTHOR]

• A comprehensive bibliometric analysis of the applications of zeolite in concrete. • Leveraging natural zeolite as a replacement for cement to improve concrete sustainability. • Exploring future prospects on the innovative use of natural zeolite in cementitious composites. Pozzolanic materials or industrial wastes can be used to partially replace cement, minimizing the carbon footprint of concrete structures. Zeolite, silica fume, fly ash, and metakaolin are some of the most frequently used supplementary materials that reduce the concrete's permeability and, therefore, play a significant role in improving its durability and strength. Among the available alternatives, the application of natural zeolite as a pozzolanic material, in concrete has increased in recent years. In particular, a range of studies have focused on including natural zeolite to produce mortar and concrete with a reduced cement content, and thus, environmental impact. Through a consistent and comprehensive blended evaluation method, this research aims to evaluate past studies that utilized natural zeolite for various concrete applications. A total of close to 2,000 papers were screened, and more than 60 of them were selected for relevance. Bibliometric mapping was used for keyword occurrences and zeolite-related details. This study provides a state-of-the-art review of research on natural zeolite through a critical analysis of various research studies carried out in the past. The ultimate goal is to provide an in-depth understanding of the effects of zeolite on the performance of concrete mixtures, in terms of workability, strength, and durability. Furthermore, the current challenges and future prospects of using natural zeolite have been outlined, paving the way to expand the use of this category of supplementary materials. [ABSTRACT FROM AUTHOR]

• The study focuses on a high-volume fly ash cement mortar hybrid containing nano-silica ftabledioxide and steel fibers. • The addition of NS and SF significantly enhanced the flexural and compressive strength of high-volume fly ash mortar. • Adding 1.0 vol% SF and 2.0 wt% NS increased flexural and compressive strength by 70.6% and 53.7% at 28 days. • Hybrid NS and SF improved sulfate resistance, reduced mass loss rate, and enhanced residual strength after sulfate attack. • NS and SF refine pores in high-volume fly ash mortar, reducing average pore diameter. The flexural strength, compressive strength, water absorption, and sulfate resistance of high-volume fly ash cement mortar hybrid containing 0–2.5 wt% nano-silica dioxide (Nano-SiO 2 , NS) and 0–2.0 vol% steel fibers (SF) were studied in this paper. Fly ash (FA) was used to replace 50 wt% of Portland cement. The resistance to sulfate attack was tested by exposing the specimens to 5.0 wt% sodium sulfate solution, and the flexural strength, compressive strength, and mass loss after 3, 6, and 9 months of erosion were determined. Specimens cured at normal condition were tested at the same ages for comparison. Moreover, the microstructure and pore structure were also investigated. The test results show that the combined addition of NS and SF significantly enhanced the flexural and compressive strength of high-volume fly ash mortar and significantly reduced its water absorption. Compared with control mortar, the addition of 1.0 vol% SF and 2.0 wt% NS increased the flexural and compressive strength by 70.6 % and 53.7 % respectively at the age of 28 days, and the water absorption of mortar was decreased by 45.0 % at the age of 90 days. The hybrid addition of NS and SF improved the sulfate resistance of mortar, reduced the mass loss rate of sulfate attack, and enhanced the residual strength of mortar after sulfate attack. In addition, the mercury injection test showed that adding NS and SF can obviously refine the pores of high-volume fly ash mortar, and reduce the internal average pore diameter. [ABSTRACT FROM AUTHOR]

• The health condition of on-site coral reef sand concrete breakwater structures is investigated. • The deterioration mechanism of coral reef sand concrete under scouring and abrasion environment is revealed. • The mechanism of fly ash and silica fume improving the abrasion resistance of coral reef sand concrete is revealed from different scales. • Relevant engineering measures are put forward to improve the abrasion resistance of coral reef sand concrete. In complex marine environment, coral reef sand concrete structures such as breakwaters are subjected to abrasion by sand-containing currents, which seriously shortens the service life and cycle of structures. Therefore, this paper investigates the health status of on-site breakwaters, moreover, reveals the damage mechanism of coral reef sand concrete (CRSC) under scour and abrasion environments in combination with indoor macroscopic and microscopic experiments. In addition, the effects of fly ash (FA) and silica fume (SF) on the mechanics and durability, hydration and hydration products of CRSC are investigated so that corresponding measures can be proposed to improve the service performance of breakwaters. The results demonstrate the indentation hardness of coral aggregate is greater than that of ITZ and cement stone matrix. Therefore, the ITZ and cement stone matrix with lower hardness are scoured and abraded by water flow containing coral reef blocks with high hardness, resulting in abrasion failure of CRSC. FA and SF prolong the induction period of cement, and reduce the hydration rate and accumulated heat of the accelerated period and second peak. The hydration reaction between the supplementary cementitious material and Ca(OH) 2 occurred within 20–40 h, resulting in the third exothermic peak of the system. The hydration process of the admixture-cement system goes through three stages: crystallization nucleation and crystal growth (NG), phase boundary reaction (I) and diffusion (D). FA mainly plays a physical filling role in the early stage, and it reduces the early C-S-H polymerization degree and the total volume of C-S-H phase, but slightly increases C-S-H polymerization degree in later stage. However, SF is involved in hydration reaction in the early stage, and increases the C-S-H polymerization degree and total volume of C-S-H phase. [ABSTRACT FROM AUTHOR]

• Mortars from the Roman Forum of Carthago Nova show a clear multilayered structure. • The mortars' composition varies considerably across layers (top to bottom). • TG allows quantification of cerussite, whose origin is uncertain in Roman mortars. • Hydroxyapatite linked to combustion of animals' bones was found in black pigments. • The materials are well preserved, and some mortars were likely coated (wax). This paper aims to study the construction technique and characterisation of original mortars and wall paintings at the Roman Forum district of Carthago Nova (Spain). A multi-analytical approach was conducted on original fragments using Optical Microscopy (OM), Field Emission Scanning Electron Microscopy (FESEM), colour tests (CIE L*a*b*) and contact angle measurements. Besides, the chemical composition was studied by X-fluorescence (XRF), Thermogravimetry (TG), X-ray diffraction (XRD) and Infrared spectroscopy using attenuated total reflectance (ATR-FTIR). The mortars showed a multi-layered pattern consisting of three distinguishable layers that were decorated with low-thickness coatings. The top layer composition was eminently calcitic, while the central and bottom layers were probably elaborated with pozzolanic materials. It is worth noting that unusual minerals as cerussite (PbCO 3) were identified in some layers, and probably associated to subsequent activities carried out in the site after Roman times. The top coating was made of hematite (Fe 2 O 3) for red decoration, whereas graphite (C) and hydroxyapatite (Ca 5 (PO 4) 3 (OH)) were identified in black coatings, which suggests the use of animal bones in the production of black pigments. In addition, the outer surface of some fragments was most likely coated with organic substances to enhance colour and durability. Finally, SEM examination and EDX analyses also confirmed some of the above findings and the existence of NaCl surface crusts due to natural weathering. [ABSTRACT FROM AUTHOR]

• The preparation method of Cu(OH) 2 nanoarray cement mortar was provided. • The effect of Cu(OH) 2 nanoarray on properties of cement mortar was discussed. • The mechanism of Cu(OH) 2 nanoarray on cement mortar was discussed. • Within the scope of this experiment, the optimal dosage of Cu(OH) 2 nanoarray is 0.5%. This experiment investigates the effect of Cu(OH) 2 nanoarray on the properties of cementitious materials. Cu(OH) 2 nanoarray is a novel nanomaterial with excellent electrical conductivity and chemical stability. At present, the interaction mechanism between Cu(OH) 2 nanoarray and cementitious materials has not been explored. In this paper, the effect of Cu(OH) 2 nanoarray on the properties of cement mortar was investigated by testing the mechanical strength and electrical conductivity of Cu(OH) 2 nanoarray. The microstructure of Cu(OH) 2 nanoarray cement mortar and the development of hydration products were analyzed using XRD, SEM, EDS and MIP tests. The results showed that when 0.5% Cu(OH) 2 nanoarray was added, the 28d compressive strength and flexural strength of the cement mortar increased by 50.29% and 41.28%, respectively, and its electrical resistivity decreased by 50%. The Cu(OH) 2 nanoarray optimized the mechanical strength and workability of the cement mortar by modulating the hydration products and improving the microstructure. [ABSTRACT FROM AUTHOR]

• Crumb rubber was bio-functionalized using polydopamine. • The wettability of crumb rubber was improved by the deposition of polydopamine film. • By using polydopamine-functionalized crumb rubber, the 28d compressive strength of rubberized mortars was improved by 37–68%. • The interface transition zone of rubberized mortars was densified owing to the chelation of polydopamine with Ca2+. This paper explores a biomolecule, dopamine, to functionalize crumb rubber (CR) to enhance the performance of cement mortars made with the CR. This is inspired by marine mussels, which can attach to various substrates underwater using the adhesive protein L-3,4-dihydroxyphenylalanine in its byssus. Dopamine is a mimic of the adhesive protein of mussel. At pH = 8.5, dopamine can spontaneously self-polymerize on the CR surface through the oxidation and the subsequent cross-linking of the catechol structure to form uniform polydopamine (PDA) film. This can enhance the wettability of the CR, leading to higher fluidities of the produced mortar. More importantly, the PDA film can chelate with Ca2+, promoting the formation of a denser interface transition zone between the CR and the cement paste and accelerating the hydration of the cement. As a result, the compressive strengths of the produced mortars were improved by 1–24 % at 3d, 13–52 % at 7d, and 37–68 % at 28d. The capillary water absorptions of mortars were also reduced by 28.6–41.8 %, significantly enhancing the durability of the mortar. [ABSTRACT FROM AUTHOR]

• The bonding properties between FCNTs repair mortar and fire exposed old mortar substrate has been investigated. • The bonding strength and microscopic test were performed to determine the reinforcing mechanism of FCNTs in the ITZ. • An effective prediction model is proposed to quantify the effects of porosity and different FCNTs on the interfacial bonding strength of composite specimens. Reinforced concrete structures need to be repaired after exposure to fire, in which the weakness of the interfacial transition zone between the repair mortar and the old concrete substrate is a crucial problem. Carbon nanotube can be added into repair mortar to address the above-mentioned problem because of its bridging, pore filling and nucleation effects. However, the bonding mechanism of functionalized carbon nanotube repair mortar and the old concrete is not yet fully understood. Therefore, this study investigates the bonding performance between different functionalized carbon nanotube repair mortar and old mortar substrate exposed to high temperature. Firstly, to evaluate the roughness of old mortar exposed to high temperature, three-dimensional microscope and mercury intrusion porosimetry were performed in this paper. Secondly, thermogravimetric analysis and X-ray diffraction were carried out to further analyze the phase composition of the repair mortar. Thirdly, microstructure of the interfacial transition zone was investigated by electron backscatter diffraction characterization and microhardness measurements. Fourthly, the bonding mechanism of interface between new and old mortar was discussed. The results show that the surface roughness of the old mortar can gradually increase with increasing of temperature, which improves the interfacial mechanical interlocking. The functionalized carbon nanotube can reduce the content and orientation of calcium hydroxide and improve the microhardness of the interfacial transition zone. Finally, an interfacial bonding strength prediction model considering porosity and the reinforcing effects of different functionalized carbon nanotube is proposed. The findings of current study can benefit further research and application of nanomaterials in the field of structural repair and maintenance. [ABSTRACT FROM AUTHOR]

[Display omitted] • The heat welding method can be used as a green, easily available, and economical way to modify the polypropylene (PP) surface. • The fly ash fixed on the surface of PP by heat welding can effectively improve its wettability and pozzolanic activity. • With the addition of F@PP, the microscopic pore structure of the mortar is more compact, and the mechanical properties are greatly enhanced. • The hydration products of the F@PP interface play the role of "micro-pile" in connecting the paste and PP. The weak bonding of plastic/paste caused by the hydrophobicity of plastic surface is a significant bottleneck for the large-scale application of plastics in concrete, which seriously affects the macro and micro structure of plastic concrete. To address this issue, a heat welding modification method was proposed in this paper, which utilized the thermoplastic of the plastic, fly ash was welded to the polypropylene (PP) surface to form a composite aggregate with fly ash properties (F@PP). Experimental results revealed that F@PP exhibited better wettability (contact angle = 75°) and pozzolanic activity compared to unmodified PP. Moreover, compared to PP mortar or F/PP mortar (simply add fly ash to PP mortar), the microscopic interface of F@PP/paste was more compact and its Ca/Si was mostly reduced to less than 2.0. The porosity of F@PP mortar was significantly reduced by 50–57% at 28d and the compressive strength was increased by 11–28% at 3d, 7d, and 28d. These findings highlight the effectiveness of the proposed heat weld method in enhancing the plastic/paste interface and the performance of plastic mortars. [ABSTRACT FROM AUTHOR]

• Withdrawal performance of screws anchored in mortar are remarkably increased. • Withdrawal capacity and mortar ratio a of hybrid anchorage are linearly related. • Coefficient k is defined to predict withdrawal capacity of hybrid anchored screws. In steel-timber composite floors, the screw connection between the H-steel and timber slab is vitally important, and the accurate calculation of the withdrawal performance of screws is one of the keys to accurately evaluating the shear performance of screw connections. In this paper, 20 groups of pull-out experiments were performed for mortar-glulam hybrid anchored screws. The differences in the withdrawal performance of glulam-anchored screws, mortar-anchored screws and mortar-glulam hybrid anchored screws were evaluated, and the effects of the screw diameter, effective anchorage length, and mortar anchorage ratio on the withdrawal performance of screws were analyzed. First, compared with glulam anchorage, the withdrawal strength and withdrawal stiffness of mortar anchorage increased by 54.7% and 33.0%, respectively. Second, when the total effective anchorage length was constant, as the mortar anchorage length increased, the withdrawal stiffness and withdrawal resistance of mortar-glulam hybrid anchored screws increased linearly. Finally, the calculation method of the modified effective anchorage length for mortar-glulam hybrid anchored screws was proposed, which improved the accuracy of the standards for calculating the withdrawal resistance of hybrid anchored screws by approximately 20%. [ABSTRACT FROM AUTHOR]

• Including SF into the AAFA mixture decreased workability, whilst STPP increased it. • Including 5–15% SF or/and 4% STPP in AAFA increased compressive strength. • Exposing specimens to outdoor natural weathering showed an adverse effect on their strength. • The adverse effect of weathering could be decreased with including up to 15% SF and 4% STPP. As known, exposure of any material to outdoor natural weathering, which has varied changes in temperature, relative humidity, percentage of sunny/cloudy, precipitation, CO 2 and polluted air may adversely affect its properties compared to its unexposed counterpart cured at the lab. This paper aims to evaluate the effect of one year of outdoor natural weathering exposure on the properties of neat alkali-activated fly ash (AAFA) mortars and those modified with silica fume (SF) and sodium tripolyphosphate (STPP). To increase the resistivity of AAFA mortars to weathering exposure, the FA was partially substituted with 5–20 wt% SF. To further improvement, a fixed ratio of 4% STPP was added to the neat FA mortar specimens and those containing SF. After initial curing, half of the specimens were cured inside the lab for one year (unexposed specimens), whilst the other half were exposed to outdoor natural weathering conditions for the same period. The variations in the compressive strength, mineral composition, hydration products and microstructure were compared. The results showed that exposing specimens to natural weathering has a negative effect on their compressive strength. This negative effect can be mitigated by introducing SF up to 15%. To further reduce this negative effect, 4% STPP can be added. [ABSTRACT FROM AUTHOR]

• Various disposal techniques for recycling discarded masks were summarized. • Current status of recycle of discarded masks in civil engineering were studied. • Mechanical properties of slurry with silane coupling agent modified discarded masks. In recent years, with the heightened of public health protection awareness, masks have become an important protective equipment. The accumulation of discarded masks (DM) poses an impact to environment and resource. Recycling DM has become a prime focus of sustainable development research. This investigation introduces a review of the recycling of DM in civil engineering and presents a novel modification of discarded mask fibers (DMF) to enhance the mechanical property of cement paste. In the review section: (1) The masks are divided into three classes by integrating relevant standards and considering mask protective characteristics; (2) Various disposal techniques for recycling DM are categorized in shredding, hot processing, paper shredding, and crushing; (3) The impact of incorporating DMF in concrete, mortar, asphalt, road subbases and base courses are discussed. The enhancement of applying DMF into composite materials varies depending on the specific application. In the experimental research section, the silane coupling agent (SCA) is introduced as a modification to improve the weak bonding between DMF and composite materials. The SCA-modified polypropylene (PP) fibers were conducted as a control group. The results indicate that the compressive strength of cement paste with both SCA-modified DMF and PP fibers increased by 12.29 % and 26.10 %, respectively. Finally, several future opportunities in recycling of DM in Civil Engineering were drawn. [ABSTRACT FROM AUTHOR]

• The properties of magnesium oxychloride cement containing engineering spoil (ES) were investigated. • 3D printable magnesium cement (MC-3DP) was developed. • The influence of the ES content on the MC-3DP paste and mortar was investigated. • The 3D printing properties and hardened strength of the MC-3DP paste were evaluated. Using magnesium cement to solidify engineering spoil (ES) is an eco-friendly option for disposing of solid waste. This paper proposes a novel type of magnesium cement for 3D printing (MC-3DP) using ES as an additive to magnesium oxychloride cement (MOC). The effect of the ES on the mechanical properties and water resistance of the MC-3DP paste and mortar were investigated. The MC-3DP paste was subjected to a hydration heat test and microscopic tests (X-ray diffraction and scanning electron microscopy). The 3D printing properties of the MC-3DP paste were evaluated, including the open time, flowability, extrudability, buildability, and hardened properties. The results showed that the ES improved the MC-3DP's mechanical properties and water resistance. The results of the hydration heat test, XRD analysis, and SEM analysis revealed that the addition of ES did not result in new hydration products in the MC-3DP paste. Instead, the ES served as a filler and improved the performance of MC-3DP. Additionally, the ES addition significantly improved the printing properties of the MC-3DP paste, and the degree of improvement increased with the ES content. Our results provide new insights into developing methods to upcycle ES. [ABSTRACT FROM AUTHOR]

• The white deposits were newly formed carbonized products C 4 A C ¯ H 11 and CaCO 3. • SB had a good inhibiting effect on the early and long-term whitening of CAC mortar. • C 4 A C ¯ H 11 was no longer generated resulting in no visible whitening with 12% SB addition. • Capillary water absorption was closely related to the whitening of CAC mortar. • SB affects cement hydration, hydrophobicity and capillary water adsorption of CAC mortar. This paper was based on the results of the research group's previous research on early whitening of mortars. The inhibition of whitening and changes of white deposit on the surface of calcium aluminate cement (CAC) mortar with styrene-butadiene copolymer (SB) were studied using a long-term accelerated whitening method under conditions of (20 ± 2) ℃ and (60 ± 5)% RH. The whitening phenomenon and white deposits of CAC mortars were studied using digital processing of images, optical microscopy (OM) and scanning electron microscopy (SEM). The results indicate that the white deposit on the surface of CAC mortar primarily consists of newly formed carbonation products, calcium carboaluminate hydrate (C 4 A C ¯ H 11) and calcium carbonate (CaCO 3), and with the extension of this exposure time, C 4 A C ¯ H 11 will be carbonized to generate CaCO 3 and Al(OH) 3 (AH 3). It is interesting to note that SB reduces the production of C 4 A C ¯ H 11 and CaCO 3 and that at SB dosing levels above 12% the C 4 A C ¯ H 11 disappears and there is hardly whitening of mortar at this time. The inhibition mechanism of SB on the whitening of CAC mortar was investigated using X-ray diffraction (XRD), capillary water absorption and water contact angle tests. The analysis reveals that hydration product of CAC is mainly CAH 10 after curing at 20 ℃ for 1 d, and the addition of SB did not change the type of CAC hydration products. Furthermore, incorporating SB enhances the hydrophobicity and reduces the capillary water absorption in CAC mortar, and forms a polymer film in CAC mortar. They prevent the transfer of ions from the interior of CAC mortar to the exterior and the contact of CO 2 from the air with the cement hydrate on the surface of CAC mortar, thus reduces the production of white deposit on the mortar surface and inhibits the whitening of CAC mortar. [ABSTRACT FROM AUTHOR]