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In the paper, the impact of paper production waste (primary sludge, or PS) on the properties of cement pastes and mortars is discussed upon. Some specimens were formed with fine PS fraction that replaced a part of cement content in them (5%, 10%, 15%, or 20%); in other specimens, coarse fraction of sludge (2/4) was used and a part of content of fine filler (sand) was replaced by PS. The properties of mixtures, such as water content required for cement paste of normal consistence, the setting time, exothermic temperature, flow diameter and plunger penetration, were established. In addition, the properties of hardened mortar, such as its density, flexural strength and compressive strength, were established. The microstructure of hardened specimens was examined as well. It was found that PS retarded hydration processes and reduced exothermic temperature; in addition, it reduced the flow diameter and the plunger penetration. While assessing the properties of hardened mortar, it may be stated that 5% PS waste might be used for replacement of a part of cement content. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents results of an investigation into the potential use of recycling paper mill waste-water to replace mixing water in cement mortar systems for manufacturing concrete masonry products. The physical and mechanical properties of mortar containing various amounts of de-inking waste-water were consequently investigated. A key finding of this study was that replacing mortar mixing water with waste-water significantly improved workability and consistency of cement mortar mixtures. In particular the flow of mortar mixtures increased with increase of waste-water content up to 50% and then levelled off when waste-water content exceeded 50%. Correspondingly, the flow of mortar mix with 100% waste-water replacement at water/cement ratio of 0.50 was found to be equivalent to that of the reference mortar mix with 100% potable water at water/cement ratio of 0.60, indicating potential use of de-inking waste-water as water reducing admixture. The enhanced workability arising from waste-water addition however induced changes in mechanical properties of the hardened material. Compared to reference mortar, replacing 10% and 100% potable water respectively resulted in 19% and 60% reduction of compressive strength, with a corresponding 5% and 16% drop in bulk density, and up to 19% increase in drying shrinkage. Also, water absorption and volume of permeable voids increased with increasing waste-water dosage, albeit marginally. The benefits derived from rheology improvements compared to compromises in mechanical properties due to de-inking waste-water addition strongly indicate clear potential of using de-inking waste-water in production of lightweight cementitious building and masonry elements. [Copyright &y& Elsevier]

Highlights: [•] APS-FA blended cement mortars showed good resistance to freeze/thaw cycles. [•] Blended mortars perform better than OPC mortars in marine environments. [•] Resistance of blended and OPC mortars to Spanish’s plateau conditions are similar. [Copyright &y& Elsevier]

Abstract: Making use of industrial by-product or waste clay to partially replace cement in concrete has greatly contributed to sustainable development of environment. This study investigated the optimal activation condition for producing high reactivity metakaolin (MK) by using kaolin by-products (KB) from paper industry. Initially, the material properties of KB were analyzed in this study and the results indicated its great potential to be treated by calcination to be a very effective pozzolan. Afterwards, MK samples produced from different activation treatments of KB, including different calcining temperature, calcining duration, initial temperature rise rime and grinding particle size, were applied in mortar to determine their pozzolanic effect. Results indicated that the optimal activation condition for KB to high reactivity MK conversion is 2-h calcining duration at 750°C and with 7μm grinding particle size. Finally, compressive and flexural strengths of mortar samples produced by replacing cement with 0–25% MK content were tested and the results showed that 15% was the optimal cement replacement level of MK and the mortar so produced exhibited 20% improvement in compressive strength compared to control mortar. [ABSTRACT FROM AUTHOR]

Highlights: [•] A beneficial reuse application for two industrial wastes, EPS and PSA, is reported. [•] Lightweight cement mortars containing PSA and EPS have low density and low thermal conductivity. [•] Ground EPS resulted in lower thermal conductivity than powdered EPS. [•] Mortars containing EPS and PSA meet the EU standards for rendering, masonry and plastering. [Copyright &y& Elsevier]

• Calcareous sludge is used as filler in geopolymeric mortars. • Biomass fly ash is used as main alumina-silicate source (70 wt%). • Used wastes derive from a Kraft pulp industry. • Manufacture is simple and highly sustainable and reproducible. • Novel geopolymeric mortars are suitable for construction applications. Calcareous sludge is an alkaline waste produced by the paper pulp industry that is commonly disposed of in land-fill. However, recent studies and the European regulations discourage such practice. This work investigates an alternative and innovative way to recycle and reuse this waste, as filler, in the production of green geopolymeric mortars intended for applications in construction. This is the first time that this calcareous sludge is used to produce novel waste-based materials, in both construction and geopolymer technology. The novel alkali-activated mortar also uses biomass fly ash – another slightly investigated waste stream – to substitute the metakaolin (70 wt% substitution) and the manufacture process is performed at ambient conditions. All of that reduces the overall process footprint. The implemented mix design is aimed at maximising the waste incorporation and improving the material properties, such as workability and mechanical performance. The main results demonstrate that 10 wt% of calcareous sludge can be efficaciously used as filler in the geopolymeric mortars, generating up to 30% improvement in the mechanical resistance. This alternative use of such wastes will contribute to increase the sustainability of the novel construction materials also granting environmental advantages and a financial surplus for the industry. [ABSTRACT FROM AUTHOR]

Coating mortars are essential for passive fire protection (PFP) in structures, preventing spalling. The present study explored the factors that affect the performance of mortars under fire or high temperatures through a systematic literature review. We used the Scopus database, and surveyed articles published in the past 15 years (2008–2023) resulting in 102 papers that were read completely. Most works investigated the effects of carbon nanotubes (CNTs), supplementary cementitious materials (SCMs), fibers, and phase change materials (PCMs) on the residual mechanical properties of mortars after elevated temperatures. We summarized the influence of these materials, with most results indicating that they are promising strategies to improve the fire resistance of mortars. More specifically for coating mortars, few studies have been conducted on their physical and mechanical characterization, with gaps being observed primarily in terms of thermal characterization and performance with a curing age greater than 90 days. Thus, this research contributes to the advancement of more reliable and efficient construction materials, while ensuring the safety of buildings and people. ● We reviewed 102 papers on the physicochemical behavior of mortars under high temperature. ● Coating mortars provides relevant passive fire protection. ● Carbon nanotubes (ideally less than 0.4 %) can improve mortar performance. ● Research gaps: performance with curing age > 90 days, behavior of post-fire curing. [ABSTRACT FROM AUTHOR]

Self-heating electrically conductive cementitious composites (ECCCs) represent an innovative advancement in civil engineering materials, offering a variety of functionalities including deicing, electrical curing, and facilitating concrete casting in cold weather. This paper presents a comprehensive review of self-heating ECCCs, focusing on electrical/ohmic curing and deicing. After an in-depth review of previous research, effective dispersion techniques, such as combinations of surfactants and admixtures, were found to be critical for establishing robust electrical conductivity and self-heating performance in ECCCs. The study also shows that the self-heating performance of ECCCs is influenced by several factors, such as filler properties, mixture design, moisture content, temperature, and curing conditions. The effects of moisture are controversial; while some studies suggest it improves self-heating, others indicate that it may disrupt conductive pathways through unwanted hydration. Generally, this paper presents an overall review of self-heating ECCCs research ranging from the raw materials, fabrications, mechanisms, and test methods to case studies on their performances. Finally, remaining issues and future directions for the advancements of ECCCs to extend their applicability are discussed. • The use of self-heating ECCCs for deicing and electrical curing was discussed. • Effective filler dispersion is crucial for electrical and self-heating performance. • Percolation thresholds, contact resistance, and tunneling enable resistive heating. • Optimizing combinations of surfactants and admixtures is essential for effective dispersion. • Various factors influencing self-heating performance were examined. [ABSTRACT FROM AUTHOR]

• A method for batch calculation of aggregate shape parameters was proposed based DIP. • The numerical model of mortar fluidity test was successfully established by DEM. • The increase in flake particle content leads to greater elongation of machined sand. • High flaky particle content can lead to poor flowability of mortar. • There is a correlation between the aggregate shape parameters and the fluidity. This paper combined digital image processing (DIP) and discrete element method (DEM) to investigate the relationship between the particle characteristics of manufactured sand and the flow ability of mortar, and clarified the key characteristics parameters of particle shape influencing the flow ability of mortar. A method for batch calculation of shape characteristic parameters (elongation n e , angularity index n a and fullness ratio n f) of aggregates based on DIP was proposed. The fluidity tests and corresponding simulations of mortar at different water-cement ratios were carried out respectively, and the results showed that the errors of simulated fluidity (f m) were around 7%. The simulation results demonstrated that the f m decreased with increasing content of large-size aggregates in the mortar. The augment of both n e and n a reduced the flowability of mortar. The magnitude of rolling/sliding friction coefficients of aggregates are the important parameters that determine the flowability of mortar. [ABSTRACT FROM AUTHOR]

In February 2024, Construction and Building Materials published the paper "Nondestructive measurement of the capillary water absorption coefficient and water transport behaviors of porous building materials by using single-sided NMR", which claims to measure the capillary absorption of moisture in brick, sandstone, mortar and concrete by means of moisture content profiling with the 'NMR mouse', a low-field, single-sided, open-magnet NMR instrument. This critique formulates several serious concerns on the study's outcomes and conclusions. The excessively large similarity of the capillary absorption behaviour of the four materials is peculiar, since it disregards the differences in their open porosities and pore sizes. The overly large capillary moisture contents are equally abnormal, as they exceed the moisture storage limit of the material's pore structure. There appears to be an inconsistency between the moisture content profiles and the overall moisture masses. Finally, it is shown that the lengthy time interval necessary for a single NMR pass limits the applicability of the NMR mouse for capillary absorption coefficients of porous building materials. • this post-publication review formulates concerns on a previously published paper. • several of the study's quantitative outcomes are physically/internally inconsistent. • the paper's method moreover is solely fit for implausibly slow capillary absorption. [ABSTRACT FROM AUTHOR]

This paper studies the effect of high temperatures (20℃, 200℃, 400℃, and 600℃) and stress ratios ( σ 2 / σ 3 ) (0.15, 0.3, 0.45, and 0.60) on biaxial compressive strength and strain development patterns of high-strength geopolymer concrete (HGPC). Experimental observations indicate that HGPC exhibits laminar damage similar to ordinary Portland concrete (OPC) before and after exposure to high temperatures, under biaxial compression. Unlike OPC, damage in HGPC initially passes through coarse aggregates at room temperature but shifts predominantly to the aggregate-mortar interface at 600℃. The biaxial compressive strength envelope of HGPC expands with rising temperatures. The increased multiple of biaxial compressive strength ( σ 3 / f m ) for HGPC at room temperature rises and then falls with increasing stress ratios, peaking at a stress ratio of 0.45 and surpassing the values for OPC and high-strength concrete (HSC). Before high temperature, the modulus of elasticity of HGPC is higher than that of OPC and decreases with increasing temperature, decreasing by about 45–60% for every 200°C increase, and the reduction is greater than that of OPC. The existing failure criterion is not suitable for HGPC after high temperature, this paper develops a new biaxial compression failure criterion for HGPC before and after high temperature based on Kupfer's criterion, taking into account the effect of temperature. The proposed failure criterion calculation results are well in agreement with the experimental data. A damage constitutive model for HGPC considering the effect of temperature and lateral pressure is also proposed, combining the Weibull distribution model for the ascending branch and a modified empirical model for the descending branch. This combined model effectively predicts the stress-strain relationship of HGPC under various temperature conditions. • The axial behavior of HGPC is tested at different temperatures and lateral pressures. • A failure criterion for biaxial compression of HGPC taking into account the effect of temperature is proposed. • A damage constitutive model of HGPC considering the effect of temperature and lateral pressure is established. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the variation rule of coarse aggregate and pore structure of shotcrete by adding MWCNTs. In the paper, X-ray computed tomography scans are used to study the coarse aggregate distribution and pore structure of the preparation of shotcrete, high-temperature curing shotcrete and shotcrete with MWCNTs. The distribution pattern of coarse aggregate and pore of shotcrete is obtained. The results show that: the coarse aggregate loss of shotcrete is serious within 30 mm from the wall and the coarse aggregate increases significantly in 30–70 mm. The addition of 0.03% MWCNTs increased the coarse aggregate of shotcrete by 36.63% and the volume of coarse aggregate by 25.64%. The largest increase is in coarse aggregates of 5–7 mm. This show that MWCNTs can improve mortar adhesion and reduce aggregate rebound. The number of shotcrete pores decreases with the increase of pore diameter. The proportion of small pores is up to 85%, the proportion of large pores is only 2%, but the volume of large pores reaches 87%. The addition of 0.03% MWCNTs can reduce the number of small pores in the shotcrete and reduce the mean pore diameter, resulting in a decrease in the porosity of the shotcrete. When the curing temperature is 80℃, the porosity of shotcrete increases, and the pores decrease due to interconnection. The pores around the coarse aggregate account for over 70% of the total porosity, with pores larger than 1 mm accounting for 75%. This paper has a good reference value for the development of shotcrete and the selection of coarse aggregate in the actual working conditions. • The coarse aggregate distribution and pore structure characteristics of shotcrete were revealed. • The influence of MWCNTs on the rebound of shotcrete coarse aggregate was analyzed. • The relationship between pore distribution of shotcrete and coarse aggregate distribution is discussed. [ABSTRACT FROM AUTHOR]

Utilizing nano-SiO 2 (NS) to reinforce the old mortar and the weak interfacial transition zone (ITZ) in recycled coarse aggregate (RCA) is a productive approach to enhance the quality of RCA. Throughout this paper, RCA was immersed in NS solutions with different concentrations (2, 5, 10 and 30 wt%). Subsequently, a systematic evaluation of the crushing index and water absorption of the treated NS modified recycled coarse aggregate (SRCA) was conducted. In addition, the calcium hydroxide (CH) content of RCA before and after modification was analyzed by Thermogravimetric and Differential Thermal Analysis (TG-DTA) curves. This study finds that the performance of SRCA modified with 2% concentration achieves comparable modification effects to other concentrations. Additionally, this paper delves into the impact of NS powder on the slump characteristics and compressive strength of concrete. Considering the above research and economic costs, this study adopts 2% concentration of NS for RCA modification and further investigates the stress-strain relationship of NS modified recycled aggregate concrete (SRAC) with various SRCA replacement ratios. Moreover, this paper establishes mesoscopic models of SRAC for various replacement rates and proposes constitutive models corresponding to these rates. The results indicate that when the SRCA replacement rate is within 60%, the stress-strain curve shape of SRAC closely resembles that of natural aggregate concrete (NAC); when the replacement rate exceeds 60%, the descending segment of the SRAC stress-strain curve becomes more precipitous, showing a higher tendency towards fragility in the concrete. ● Nano-SiO 2 can be used to improve the properties of recycled coarse aggregates. ● NS powder affects the slump and compressive strength of recycled concrete. ● As the concentration of NS solution increases, the compressive strength of concrete increases. ● Mesoscopic models of modified recycled concrete were established and constitutive models were proposed. [ABSTRACT FROM AUTHOR]

Since 3D printed concrete has a promising application in engineering, the combination of 3D printing concrete and other building materials has become a hot research topic.This paper investigates the shear properties of 3DPM-NM specimens which use 3D printed mortar (3DPM) as the precast part and normal mortar(NM) as the cast-in-place part. Four different types of interfacial locking design were analyzed in this paper, including L-shaped, C-shaped, S-shaped and K-shaped. The shear damage law of the specimens was analyzed using digital image correlation (DIC) technology. The results show that L-shaped specimens are basically damaged along the shear surface during the loading process. Most of the initial cracks in the C-shaped, S-shaped and K-shaped specimens appeared along the interfacial bonding surface during the loading process. Then, the cracks in the C, S and K-shaped specimens continued to develop along the interfacial bonding surface or spilt through the specimens directly. The results show the shear properties of the C-shaped specimens are similar to those of L-shaped specimens. And the mechanical properties of S-shaped and K-shaped specimens are better than those of L-shaped specimens which increased by 96% (S-shaped), 78% (K-shaped) respectively. The mean slip is increased by 10% in S-shaped specimens and 28% in K-shaped specimens compared with that of L-shaped specimens. According to the AASHTO GSCB INTERIM-2003 specification, the modified formula for the shear bearing capacity of 3DPM-NM specimens is proposed in this study. The calculated resultsare in good agreement with the test results, which theoretically provide guidance for the application of 3DPM, lay the foundation for its feasibility as a structural body of a building. • Specimens with 3D printed mortar (3DPM) as a precast component and normal mortar(NM) as a cast-in-place part were tested. • Comparison of the shear performance of specimens with different types of interfacial locking design were conducted. • Theoretical analysis and modified calculations of shear strength for 3DPM-NM interfacial locking specimens were carried out. [ABSTRACT FROM AUTHOR]

In this paper an overview is presented on the use of diatomaceous earth (DE) as a partial substitute for binder and fine aggregate in mortars. For this purpose, this paper was divided into two sections. In the first one, concepts related to physical, chemical and microstructural properties of DE, as well as results of previous studies about its reactivity used in different construction materials (cement, concrete, mortar, bricks, phase change materials etc.) were summarized and discussed. In the next section, the effects of using DE on the fresh, hardening and durability properties of cement and lime-based mortars were discussed. In general, the results suggest that increasing DE content may reduce mortar performance due to the high porosity of its particles. However, this deficiency was observed for DE contents higher than 20%, which, however, can be compensated for by using superplasticizer additives or by volumetric dosage instead of by weight one. This critical value of up to 20% of DE was calculated using T2 statistical on the scores of principal components analysis obtained from the results collected from publish manuscripts. Nevertheless, the results of this review research may contribute to provide information on an under-explored alternative source of supplementary cementitious materials (SCMs) and therefore help mitigate the negative effects generated by the cement industry and assist in the production of mortars with a lower carbon footprint that can play an important role in the thermal behavior of buildings. • State of the art systematic review of diatomaceous earth (DE) for mortar production. • Statistical analysis of the mechanical properties of mortar with DE. • Understanding the effects of DE on properties of mortars. • When up to 20% DE is used, the mechanical behavior of mortars can be improved. • Paths for the development of new studies on mortars incorporating DE are shown. [ABSTRACT FROM AUTHOR]

To address the challenge posed by traditional methods of modifying recycled concrete aggregates (RCA), which struggle to achieve properties comparable to natural coarse aggregates (NCA) while ensuring a high utilization rate, this paper proposes a combination of freeze-thaw modification and sodium silicate modification. The process subjects the RCA to freeze-thaw cycles (FTC) to detach the attached mortar, which results in the extraction of recycled aggregates (Near-NCA) with properties similar to NCA, along with the spalling mortar (SM). These materials are used in the recycled concrete and mortar, respectively. Considering the inferior properties of SM, sodium silicate solutions are employed to modify it, serving as a replacement for river sand in the recycled mortar. The outcomes reveal that concrete cast using Near-NCA demonstrates mechanical properties comparable to ordinary concrete. Furthermore, the sodium silicate proves to be effective in modifying SM, reducing its crushed index and water absorption by approximately 30%. Through the SEM and XRD, it is determined that these improvements can be attributed to the formation of C-S-H gel. Finally, a multi-objective model is developed to consider modification effects, carbon emissions, energy consumption, economic and time costs, with the utilization of TOPSIS for determining the optimal modification plan. • This paper proposes a method that combines freeze-thaw modification with mineralization strengthening. • Modifying spalling mortar with sodium silicate solution can improve its various properties. • The modification mechanism of sodium silicate is investigated through microscopic tests. • The TOPSIS method is utilized to obtain the optimal modification scheme considering multiple objectives. [ABSTRACT FROM AUTHOR]

The hydrophobicity nature of the waste carbon fiber felt (WCF) surface results in the formation of a weak interface with the paste during the curing process of WCF concrete, which seriously affects the performance of WCF concrete and the reuse of WCF. To address this problem, this paper utilized polydopamine (PDA) for the functionalization of WCF to enhance bonding between WCF and paste. The wettability, Ca2+ complexation, and functional groups of PDA coating on WCF were analyzed by contact angle, ICP-OES, and XPS, respectively. Additionally, the effects of incorporating PDA-functionalized WCF on the flowability, compressive strength, hydration kinetics, pore structure, water absorption capillary, and SEM of mortars were tested. Experimental results showed that the PDA coating improved the wettability of WCF and enhanced the flowability of WCF mortar. What's more, the PDA coating could chelate Ca2+ and promote the formation and deposition of hydration products on the WCF surface, resulting in a denser interfacial transition zone (ITZ). Compared with ordinary WCF mortar, the compressive strength of the PDA-modified WCF mortar was increased by 18% at 28d. Furthermore, the capillary water absorption of the modified group mortar was also decreased by up to 13%, significantly enhancing the durability of mortars. This paper presents a green and simple bio-inspired method to strengthen the ITZ between WCF and paste, which is fundamentally different from the traditional modification methods, and also offers a theoretical basis and technical foundation for the sustainable utilization of WCF. • Introducing hydroxyl and amino groups on WCF using PDA. • The contact angle of WCF was maximum decreased to 40.49°. • The interface gap of WCF/paste was enhanced owing to the chelation of PDA with Ca2+. • The compressive strength of WCF mortars modified by PDA was improved from 39.43 MPa to 46.52 MPa at 28d. [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]

• LSS used as a NS substitute in FA/GGBS-based mortar increases compressive strength. • GO-modified mortars show superior viscosity recovery to NC-modified ones. • LSS mortars offer higher strength and lower drying shrinkage than NS mortars. • Formwork-free conditions increase drying shrinkage in 3D printed mortars. • High temperature & humidity reduce drying shrinkage in printed GO/NC modified mortar. The environmental impact of concrete 3D printing (C3DP) has become a concern due to its large cement consumption and over-exploitation of natural resources. This study investigates the viability of using geopolymer mixtures in C3DP prepared with fly ash (FA)/ground granulated blast furnace slag (GGBS) and underutilised aggregate as substitutes for ordinary Portland cement (OPC) and natural aggregate, respectively. This paper focuses on the rheological, mechanical, and shrinkage properties of FA/GGBS-based geopolymer mortar with lead smelter slag (LSS) as natural sand (NS) substitute and the impact of adding nanoclay (NC) and graphene oxide (GO), as thixotropy agents, on the yield stress development and viscosity recovery properties of the mixtures. The effect of various outdoor environmental conditions of 24 °C -50 %RH, 35 °C -90 %RH and 35 °C -50 %RH on pore water evaporation and 28-day drying shrinkage of 3D printable geopolymer mortar was studied, considering the effect of NS, LSS, NC and GO in free-formed and control conditions. LSS GO-modified mortars exhibited superior viscosity recovery capacity and yield stress evolution compared to their NC-modified counterparts. Moreover, using LSS instead of NS resulted in increased 28-day compressive strength under various environmental conditions, and LSS mortars exhibited lower drying shrinkage in both conventional casting and free-formed conditions. The findings of this paper will serve as a benchmark for further studies on the effect of different curing techniques (internal or external) on the hardened state dimensional stability of 3D printed products using alkali-activated binder systems to improve the structural integrity by controlling the water evaporation and drying shrinkage development. [ABSTRACT FROM AUTHOR]

This paper presents an innovative hierarchical meta-modelling approach for predicting the effective elastic properties of stone injected with composite cement grouts containing Carbon NanoTubes (CNTs) for structural rehabilitation purposes. The study first addresses the homogenization of the nano- and micro-scales through numerical representative volume elements. The first numerical model focuses on the cement matrix doped with randomly oriented CNTs, while the second model represents the porous stone with CNT/cement grout filling the pores. However, the computational burden associated with these models poses a significant limitation when analysing large-scale macrostructural elements. To overcome this challenge, a hierarchical meta-modelling approach based on two nested Kriging surrogate models is proposed. This approach offers a fast and accurate alternative to bypass the time-consuming numerical homogenization process. The first surrogate model establishes a connection between the microstructural characteristics of the CNTs and cement and the effective elastic properties of the composite grout. Subsequently, a second meta-model expands over the first one by introducing two additional variables: the elastic modulus of the stone and the porosity, allowing for estimation of the overall elastic properties of CNT/cement/stone composites. The accuracy and efficiency of the proposed hierarchical meta-model is demonstrated through detailed parametric analyses. To showcase its potential for optimizing rehabilitation interventions, the paper is closed with its application to a benchmark case study of a stone column injected with CNT/cement grout. • Composite CNT/cement grouts are investigated for the first in the literature. • A novel nested surrogate modelling approach is proposed for multi-scale composites. • Fast stiffness estimates of porous stone injected with CNT/cement grout are obtained. • The proposed approach is used to assess the performance of grout injected columns. [ABSTRACT FROM AUTHOR]

• Pumpability and buildability of Portland cement/GGBS binders presented. • Pumpability correlates with w/b ratio, whereas buildability with w/b ratio and printing speed. • Process of crack formation presented to provide insights into structural behaviours of 3D printed arch truss. • Estimation of tensile strength of 3D printed truss elements should consider restrained shrinkage effects. • Potential of GGBS for reducing the embodied carbon of 3DP cementitious binder highlighted. The work presented in this paper forms part of a wider research programme being undertaken on the development of low-carbon cementitious mortars for 3D printing applications. Specifically, this paper investigates the potential of ground granulated blast-furnace slag (GGBS) as a partial replacement for Portland cement. Five mortar mixes with varying water/binder (w/b) ratios (0.35 to 0.45) were tested, and to investigate their pumpability and buildability, a series of wall-like specimens were printed using a custom-built 3D printer under a range of speeds of 2 to 4 m/min. Pumpability was found to be directly related to w/b ratio, whereas buildability was found to be dependent upon both test parameters. Mortar mixes with w/b ratios in the range 0.37 to 0.40 demonstrated promising pumpability and buildability characteristics when extruded at the optimum printing speed of 2.5 m/min. Moreover, to demonstrate the application of the optimised mix, an arch truss prototype was printed and subsequently tested to failure to provide insights into the structural behaviour of a 3D printed arch truss member. From the process of crack formation and accompanying analysis, it was found that although the development of tensile stresses in the 3D printed prototype was minimal (a direct result of the arch geometry), it still governed the overall member behaviour due to the presence of internal stresses induced by restrained shrinkage. [ABSTRACT FROM AUTHOR]

Stereotaxically-constructed graphene (SCG) endows it with significantly different porosity, adsorption, and promoting effect on cement hydration compared to sheet-like graphene. However, the dispersibility of SCG is still a key factor affecting the performance of its reinforced cement-based materials (CBMs). To produce a stable and well dispersed SCG solution, in this paper a combined method of polycarboxylate superplasticizer and dilute hydrochloric acid was used to graft carboxyl groups around SCG that are conducive to dispersion, significantly improving the dispersibility of SCG in the solution and reducing the optimal content of SCG in cement mortar. After modification, only 0.01 % SCG can increase the compressive strength of cement mortar by 25 %, and improve the elastic modulus and energy dissipation of cement mortar, as well as improving the crack distribution during the failure process of cement mortar. Furthermore, it was found that the SCG grafted with carboxyl groups (PSCG) promoted the hydration reaction of cement, generated more calcium hydroxide, significantly increased the elastic modulus of high-density and low-density C-S-H, and the resistance of cement mortar to chloride ion diffusion was enhanced by improving the pore structure. • Improved crack resistance by 0.03 % modified graphene content. • Modified graphene can significantly enhance C-S-H. • The microstructure of cement-based material matrix is denser. [ABSTRACT FROM AUTHOR]

This study investigates the acid corrosion resistance of an alkaline-activated material (AAM) composed of ground granulated blast-furnace slag (GGBFS) and water treatment residue (WTR) as precursors. WTR, a byproduct of the drinking water treatment process rich in aluminium and silicon, proves to be a suitable precursor for AAM after cost-effective pre-treatment involving calcination and grinding. As its low-Ca content and aluminosilicate nature of the treated WTR, the AAM incorporating WTR exhibits significant potential for improving acid resistance. This is attributed to the formation of less acid-reactive N-A-S-H gels than C-A-S-H gels in high-Ca AAMs, indicating its applicability in concrete sewage pipes where microbiologically generated acid corrosion is prevalent. In the paper, a comprehensive analysis, including mechanical performance, ion leaching behaviour, and microstructural characteristics, was conducted on mortar samples containing varying WTR/GGBFS ratios before and after exposure to sulfuric acid. Incorporating WTR up to 40 % effectively reduced acid-induced strength loss compared to neat-GGBFS AAM. The obtained results reveal that high-Ca AAMs facilitate gypsum formation during acid attack, leading to mechanical degradation. The inclusion of WTR induces a Si-rich transition layer between the corroded and intact matrix, mitigating sulfate diffusion. The release of aluminium from WTR promotes secondary precipitation of aluminosilicate, beneficially increasing the thickness of the transition layer. This thicker transition layer in the higher WTR samples is advantageous in reducing the likelihood of cracks and reducing the sulfate transportation into the intact matrix. [Display omitted] • Alkaline-activated material from water treatment waste showed great acid resistance • Less amount of harmful gypsum was formed in the samples with higher WTR content • A Si-rich transition layer was found to prevent sulfate transportation • Involving WTR could increase the thickness of the transition layer [ABSTRACT FROM AUTHOR]

Cracking is a widespread phenomenon throughout the service of concrete structures for marine and offshore engineering. In this paper, the effect of sulfate ions and related cations on the crack closure behavior of cracked mortar in chloride-containing environments was studied. To this end, the mortars are cracked before transferring to the pure chloride solution as well as composite chloride and sulfate solutions (CNS and CMS series). The self-healing behavior is assessed by the evolution of crack width, water absorption, and nondestructive ultrasonic detection. The Vickers hardness test is applied to evaluate the micro-hardness of self-healing products generated in the crack gaps. Thermodynamic modeling of the phase volume expansion from the mortar matrix to the crack surface is conducted using Gibb's free energy theory to explore the self-healing mechanisms. Experiment results suggest that the existence of sulfate ions in chloride-containing solutions is beneficial for crack closure, and self-healing could be more obvious if the cations that bind to sulfate are magnesium ions. The distributions of Vickers hardness on the mortar surface across the crack reveal that the brucite layer diminishes the overall Vickers hardness of the mortar matrix, whereas it is favorable for the micro-hardness enhancement of self-healing products in the CMS series. Thermodynamic modeling interprets the expansion rates relative to the original unhydrated cement under the action of different soaking solutions. • Double or triple layer precipitates were found in CMS series. • Healing efficiency ordered as CMS-2 > CMS-1 > CNS-2 > CNS-1 > pure chloride. • Waveform evolution of ultrasonic pulse signals improved in the self-healing process. • Brucite layer was favorable for the micro-hardness enhancement of healing products. • Thermodynamic modeling confirmed the volume expansion in CNS and CMS series. [ABSTRACT FROM AUTHOR]

In this paper, the fracture performance of nano-metakaolin (NMK) cement mortar during early hydration period was investigated. Different NMK contents (0 %, 3 %, 5 %, 7 %) were considered, and three-point bending tests were conducted. The digital image correlation technology and acoustic emission technology were utilized to analyze P -CMOD curves, initial fracture toughness, unstable fracture toughness, fracture energy, cumulative AE hits, and cumulative AE energy, AE source locations of cement mortar at early hydration stages. Furthermore, SEM experiments were utilized to analyze the mechanism by which NMK affects fracture performance of cement mortar. The results indicate that the incorporation of NMK enhances the fracture properties of cement mortar, with the most suitable NMK content being 5 %. The addition of NMK increases the cracking load, peak load, and the CMOD at the peak load of the cement mortar at 3 d, 7 d, and 14 d. The cracking load and fracture energy of the cement mortar with 5 % NMK increase by 22.5 % and 35.7 % respectively, compared to ordinary cement mortar at 14 d. NMK enhances the initial fracture toughness and unstable fracture toughness of the cement mortar, improving its crack propagation resistance. The unstable fracture toughness of the cement mortar is the largest when the NMK content is 5 % at 14 d, which is 31.6 % higher than that of ordinary cement mortar. Furthermore, NMK increases the cumulative AE energy and fracture energy of the cement mortar, increasing the cumulative ring counts and cumulative AE hits, causing the crack propagation path to deviate and resulting in improved crack resistance. The cumulative ring counts and AE hits for the cement mortar with 5 % NMK are 42.9 % and 66.2 % higher, respectively, than those for ordinary cement mortar at 14 d. NMK significantly modifies the cement matrix, thereby enhancing the fracture resistance of cement mortar. • NMK enhances the fracture resistance of cement mortar at early hydration age. • NMK causes the crack propagation path of cement mortar to deviate. • NMK increases the energy required for the fracture of cement mortar. • The propagation process of cracks in NMK cement mortar is investigated. [ABSTRACT FROM AUTHOR]

In the Marine environment, cracked concrete was eroded by sea water, resulting in the structural durability reduction. In this paper, a new type of protective cement-based material combining microbe with magnesium aluminum layered double hydroxide (MgAl-LDH) was studied. Automatic crack sealing and corrosion inhibition of cement-based materials were realized. Moreover, the effectiveness of the protective cement-based material was demonstrated through engineering application. Firstly, a core-shell structure admixture (SHG) was prepared by combining microorganisms, magnesium source and aluminum source. By adding SHG, protective mortar with the ability to autonomously seal cracks was produced. The sealing effect of cracks was systematically characterized through tests of area sealing ration, ultrasonic pulse velocity, and water impermeability. The test results indicated excellent sealing effect of the cracks. A physical barrier was constructed to block seawater from entering the crack interval. Secondly, by verifying the influence of different doses of SHG on the strength of mortar specimens, the optimal amount of SHG was selected. Finally, the sealing products of cracks were studied in detail in the laboratory. The experimental results indicated that MgAl-LDH were formed in the concrete crack zone due to the magnesium and aluminum sources in the SHG. Therefore, the pH in the crack zone was reduced, promoting the ability of microorganisms to mineralize CaCO 3 Furthermore, the formed MgAl-LDH in the product also possessed a unique ability to immobilize eroding ions in seawater. A chemical barrier to neutralize eroding ions was constructed. Based on the successful laboratory results, SHG was applied in actual engineering projects, and the specific performance was carefully investigated. The protective concrete prepared using SHG exhibited excellent sealing effects on cracks. The leakage was effectively reduced. This study provided new insights into the protective of concrete structures in marine environments. • Crack filled and corrosive ions immobilized were realized simultaneously. • Crack sealing depth were enhanced due to the modification of bimetallic hydroxide. • Engineering application was conducted, and excellent effect was demonstrated. [ABSTRACT FROM AUTHOR]

Eggshell is a waste of poultry and the proper disposal of such waste products is a worldwide issue. Alkaline activation of calcium-rich eggshell powder (ESP) as a binder with a suitable aluminosilicate source offers the opportunity to produce viable materials. Thus, this paper reports the innovative use of ESP as a precursor in metakaolin (MK)-based one-part alkali-activated materials (AAMs). The impact of ESP on the fresh, physical, mechanical, and microstructural properties of one-part AAMs was studied. Upon the addition of ESP, the setting time was extended and a consistent reduction in semi-adiabatic heat release was observed. ESP favored the rheological characteristics of the mixtures by lowering viscosity and yield stress which enabled a decrease in the water content of ESP containing mortars. The incorporation of ESP up to 40 % improved the compressive strength by 22 % and 46 % for paste and mortar samples, respectively, and resulted in a notable mitigation of mortar shrinkage (only 300 µɛ at 56th days). ESP plays dual function in microstructure of AAM as a binder and micro-aggregate. C-A-S-H type gels were observed in ESP-rich mixes due to its calcium-rich structure, and the contribution of ESP on the hydration reactions were clarified in detail via X-Ray diffraction and thermogravimetric analysis. Life cycle analysis results indicated that incorporating ESP could obtain similar compressive strength while reducing the ecological impact. • Investigation on metakaolin (MK) and eggshell powder (ESP) based one-part AAMs. • ESP extended setting times, reduced semi-adiabatic temperature, and modified rheology. • ESP inclusion up to 40 % increased compressive strength and reduced drying shrinkage. • ESP exhibited a dual role in the AAM microstructure as a binder and micro-aggregate. • CO 2 emission of one-part mortars consistently reduced with an increase in ESP ratio. [ABSTRACT FROM AUTHOR]

Limited in-depth literature reviews have been conducted on the history, synthesis, hydration kinetics, and carbon footprint of limestone calcined clay cement (LC3). This review paper extensively surveys, for the first time, the impact of various critical parameters on the performance of LC3 paste, mortar, and concrete. BFBF These parameters include the role of supplementary cementitious materials (SCMs)-based wastes as an alternative to calcined clay (CC), the addition of nanomaterials, alkali-activator content, and sulfation, the addition of calcium silicate hydrate (C-S-H) seeds, curing temperature, and the reactivity and content of CC. The study found that incorporating SCMs-based wastes reduced the demand for superplasticizer, improved workability, and mitigated the CO 2 emissions of LC3. While nanosilica and alkali-activator based on alkali sulfate salts accelerated the early hydration rate of LC3, they slowed down its later hydration rate. Nano halloysite and zeolitic imidazolate improved the early and later strength despite decreasing the flowability of LC3. Incorporating C-S-H seeds, increasing curing temperature, and increasing CC reactivity improved the hydration rate of LC3, reduced pore volume, and enhanced electrical resistivity. The use of blast-furnace slag (BFS) as a partial alternative source to CC is recommended, as it reduces the demand for superplasticizer, improves workability, increases both early and later compressive strength and durability, and reduces processing costs and carbon footprint. Overall, LC3 with different OPC replacement materials presents a sustainable and high-performance substitute for OPC, effectively decreasing the environmental impact of cement production by reducing its carbon footprint • The impact of critical parameters on the LC3 performance was deeply reviewed. • It includes SCMs-based wastes, the addition of nanomaterials, alkali-activator content, and sulfation. • In addition to calcium silicate hydrate seeds, curing temperature and the reactivity and content of calcined clay • SCMs-based wastes reduced the SP demand, improved workability, and mitigated CO 2 emissions of LC3. • Nanosilica and alkali-activator accelerated the early hydration of LC3. [ABSTRACT FROM AUTHOR]

The benefits of limestone waste as a partial replacement of cement have been well established. In this paper, to better understand the effect of limestone waste on the properties of cement-based materials, the hydration process and microstructural properties of cement are evaluated. The results showed that the limestone waste decreased the fluidity of cement mortar, while the mortar having up to 10 % limestone waste provided competitive properties with pure cement mortar. It is concluded that the presence of limestone waste has both negative and positive effects simultaneously on the hydration and microstructural properties of the cement paste. During the hydration process, the net reaction heat of limestone waste in the cement blends ranged from 0.38 J/g to 4.1 J/g. In addition, the thermodynamic modeling and XRD indicated that the monocarbonate and hemicarbonate were stable in the limestone-cement blends, and the limestone waste increased the stability of ettringite. • The effect of limestone waste on the hydration and strength development of cement was investigated. • The net reaction heat of the limestone fines in the cement system was 3.5 J/g∼4.1 J/g. • An appropriate content of the limestone waste improves the chemical shrinkage of cement. [ABSTRACT FROM AUTHOR]

The use of Recycled Fine Aggregate (RFA) combined with Limestone-Calcined Clay Cement (LC3) is one of the low-carbon options for replacing ordinary mortar, leading to an eco-friendly and sustainable construction material, and providing a solution for waste management. In this paper, a comprehensive investigation concerning the mechanical properties and microstructural characteristics of LC3 mortar, using different proportions of limestone, calcined clay, cement clinker, and two types of RFA (namely RS1 and RS2), was carried out. The results highlight that a binder with 17.55 wt% calcined clay, 8.77 wt% limestone, and 73.68 wt% CEM I shows superior mechanical properties compared to CEM I with both natural sand and high-quality recycled sand, and similarly it shows better mechanical properties than CEM II at all levels of substitution of natural sand with recycle sands of high and normal quality. The replacement of commercial cement with LC3 mitigates the negative impact of RFA on water absorption, enhances pore size distribution, reduces total porosity, and boosts mechanical strength. The combination of RFA with LC3 is an effective approach to reduce the environmental impacts of cement production, to well manage wastes generated by construction and demolition, and to improve material's performances. • Mortar's workability remains unaffected using volume-based sand replacement of NS with RS. • Compressive strength of LC3 containing 70 % of clinker is higher than CEM I and CEM II at 28 days. • LC3 reduces the water absorption rate, fully compensating the negative effect of RS. • MIP and TD NMR measurements revealed a finer pore structure in mortar containing CC. [ABSTRACT FROM AUTHOR]

In the history of our civilization, masonry structures date back thousands of years. Considering the different types, geometries, and arrangements of masonry components, as well as the mortar properties, defining "masonry" precisely is challenging. Construction of masonry structures relies on layering single components and binding them using mortar or crafting them with stones without mortar. Despite many advantages, masonry structures remain one of the most vulnerable construction types. Many of these structures have not been designed to withstand seismic loads. Generally, their structural systems have been designed primarily to withstand gravity loads. Consequently, moderate earthquakes can cause extensive damage and destroy entire cities. Therefore, the assessment, repair, and retrofitting of these structures is vital to society's well-being. First, this study describes masonry structures and their mechanical and structural characteristics. Next, methods for detecting and classifying common types of damage are presented. Subsequently, a comprehensive review of assessment, repair, and retrofitting methods for masonry structures is provided. Machine learning (ML) techniques have proven to be exceptional tools for providing accurate and reliable information. In this paper, descriptions and recent advances in ML techniques for the assessment, repair, and retrofitting of masonry structures are presented. These models can be utilized for several predictive applications, such as determining possible damage scenarios in heritage buildings, assessing seismic vulnerability, detecting superficial surface damage, and selecting mortar compositions for optimal mechanical properties. Furthermore, structural health monitoring (SHM) methods applicable to masonry structures are discussed. The study concludes with case studies, and an extensive discussion of existing methods, challenges, and recommendations for future work. • Smart materials offer safety and cost benefits for masonry structures. • Retrofitting URMs crucial for climate change resilience. • Post-tensioning discouraged in rural areas due to material quality. • Retrofitting must enhance out-of-plane behavior to reduce earthquake fatalities. [ABSTRACT FROM AUTHOR]

In this paper, a high-performance strong base anion exchange resin (HP-SBAER) suitable as a modifying additive for alkali excited materials (AEM) was prepared. The interaction between the independent variables (cross-linking degree, porosity and dispersibility) was explored by means of Box-Behnken Design (BBD) in Response Surface Methodology (RSM). HP-SBAER demonstrated a significant improvement of 8.01 % in mechanical properties and 41.57 % in Cl- solidification ability compared to SBAER. In addition, HP-SBAER had strong resistance to failure and stable Cl- solidification ability. HP-SBAER doping into AEM released OH-, which ensured the alkaline environment of AEM and promoted the condensation of AEM. The intergranular spacing of the crystal molecules decreased and the crystallinity improved. In addition, the newly generated C(N)-A-S-H gel filled the pores, and the pore size distribution developed toward harmless pores. The incorporation of HP-SBAER into M-AEM mortar modulated its fluidity and initial setting time, while having minimal impact on the final setting time. The optimal doping of HP-SBAER was determined to be 3 wt%. At this doping amount, the fluidity of the M-AEM mortar was 245 mm, and the initial and final setting times were 51 min and 80 min, respectively. Under a Cl-environment, the mechanical properties of the M-AEM improved by 25.66 %, and the Cl- solidification ratio increased by 115.38 % in the Cl- environment. The performance advantage of the M-AEM was more obvious in a high Cl- environment. • A high-performance resin modifier (HP-SBAER) was prepared to improve the durability of AEM in Cl- environments. • HP-SBAER enhanced alkaline environment and improved AEM microstructure and crystal structure. • HP-SBAER significantly improved the Cl- solidification properties of AEM and reduced the rate of strength loss in Cl- environments. [ABSTRACT FROM AUTHOR]

This paper focuses on the study of the reaction between limestone and sodium hydroxide solution. This reaction is used to produce alkali-activated mortars after curing and in the presence of unreactive siliceous sand. The kinetics of this reaction is investigated by semi-adiabatic calorimetry experiments. The formulation parameters are fixed but the curing parameters are tested: temperature (38 and 45°C) and time of drying (14, 25, 27 and 28 days). Their impact on reaction products (identified by FTIR and thermal analysis), on microstructure (SEM observations and porosity measurements) and on mechanical strength (flexural and compressive tests) are determined. The reaction was fast and a temperature drying was required to obtain stabilized hydration products in mortars. The products of the alkali-activation of limestone are double sodium/calcium carbonate (mainly pirssonite and with specific conditions of curing gaylussite) and calcium hydroxide. The microstructure and the proportions of reaction products, impacted by drying conditions, influence the mechanical strength of mortars. With an appropriate time (25 days) and temperature of drying (45°C), the compressive strength reached, after 28 days, almost 25 MPa. • The reaction between limestone and sodium hydroxide solution take place in two stages. • FTIR measurements allow the identification of stages of the reaction process. • Drying in the curing process is necessary to end the crystallization stage. • Curing temperature plays an important part in the nature of reaction products. • The microstructure and the strength of alkali-activated mortars are linked to the curing process (time and temperature). [ABSTRACT FROM AUTHOR]

Successful implementation of microbial self-healing cementitious materials requires the provision of a suitable incubation environment, which activates the bacteria to produce calcium carbonate sealing the cracks. Affecting microbial mineralization, incubation temperature determines the self-healing efficiency of microbial cement which limits its widespread application. To investigate the effect of incubation temperature on the self-healing abilities, laboratory experiments were conducted on polyvinyl alcohol (PVA) fiber reinforced cement mortar impregnated with Sporosarcina pasteurii. The mortar specimens were initially cracked by three point bending to generate 0.4 mm width cracks at the bottom and then sprayed the calcium chloride and urea solution periodically for 2 days and immersed in the water for 28 days at ambient temperatures of 20 ∘ C, 25 ∘ C, 30 ∘ C, and 35 ∘ C. The cracks were inspected regularly which were further analyzed via deep learning to evaluate the crack healing ratio and sealing rate. The cracks failed to completely repair at 20 ∘ C, while cracks at 30 ∘ C requires only 4 days to seal. The crack healing rate accelerated with increasing temperature from 20 ∘ C to 30 ∘ C, exhibiting a trend of initial increase followed by decrease across all temperatures. The bacterial-repaired mortar specimens exhibited a recovery in flexural strength, with a regained strength ratio of approximately 7.184 % at 30 ∘ C. Supported by Scanning Electron Microscope (SEM) and X-ray diffractometer (XRD), the results revealed that the higher temperature actives larger particle CaCO 3 with mainly vaterite and some calcite morphology. The interaction mechanism of temperature effect on bacterial self-healing capabilities was revealed by the comprehensive assessment between the microbial activity, crack width evolution and mechanical performance. This paper may shed some light on the engineering application of microbial cementitious material resilient infrastructures with desirable healing efficiency under real ambient temperatures during service. • The optimal incubation temperature is 30 °C taking 3 days for complete healing. • Crack width sealing rates displayed an initial increase followed by a decrease. • Wider cracks exhibited faster sealing rates due to more friendly ecological niches. [ABSTRACT FROM AUTHOR]

This paper investigates the synergic effect of both hydrated lime and guar gum stabilisation on the mechanical, thermal and hygroscopic properties of a compressed earth material for building applications. The stiffness, strength and compression energy at failure of both unstabilised and stabilised earth samples were measured at different curing times by means of compression tests. The moisture-dependent thermal conductivity was instead determined via the hot disk technique at a constant temperature of 25 °C and at the three different relative humidity levels of 0 %, 50 % and 95 %. The specific heat capacity was measured by means of calorimetry tests at the three temperature levels of 32–34 °C, 34–36 °C and 36–38 °C. The moisture adsorption-desorption curves were measured by performing a cyclic variation of relative humidity between 0 % and 95 % at a constant temperature of 25 °C via the dynamic vapour sorption (DVS) technique. Results from the experimental campaign show that the proposed stabilisation methods increase both the peak compressive strength and compression energy at failure while the addition of the biopolymer guar gum induces a progressive reduction of stiffness. The thermal properties of the earth are only marginally affected by the addition of hydrated lime and guar gum, with stabilised samples exhibiting similar levels of thermal conductivity and specific heat capacity to those of the unstabilised ones. Finally, the biopolymer stabilised samples exhibited a similar hygroscopic behaviour to that of unstabilised ones, whereas the addition of hydrated lime deteriorates the moisture adsorption capacity of the material. • Earth samples are stabilised with hydrated lime and the biopolymer guar gam. • Biopolymer stabilisation increases strength and compression energy while reducing stiffness. • Lime stabilisation increases stiffness and strength but reduces ductility. • Lime and guar gum stabilisations marginally affect the thermal properties of the earth. • Moisture adsorption is preserved by guar gum stabilisation and reduced by lime stabilisation. [ABSTRACT FROM AUTHOR]

The residential market consumes nearly half of the world's concrete production, and it is anticipated that 68 % of the global population will reside in urban areas by 2050. Researchers have focused their efforts on exploring alternative options to natural aggregates in concrete and mortar. In line with the principles of circular economy, construction and demolition waste has been repurposed for the manufacture of cement-based materials. Volcanic products, which are abundant but underutilized, have been identified as an alternative to recycled aggregates. They offer several advantages over natural river aggregates, including reduced weight, enhanced thermal and acoustic insulation, improved fire resistance and pozzolanic characteristics. While there has been a significant amount of research on the use of expanded perlite as a supplementary cementitious material, studies involving the use of expanded perlite aggregates (EPA) in cement-based construction materials are relatively limited. This paper seeks to address this knowledge gap by investigating the use of EPA in cement-based mortar at both room and elevated temperatures. The study examines the impact of varying replacement percentages (10 %, 20 % and 30 % - by volume) of natural sand with EPA having a maximum grain size of 4 mm, and the exposure temperature of mortar prisms at the age of 28 days. Specifically, temperatures of 100ºC, 150ºC and 200ºC were selected for analysis. The impact of these parameters on the flexural and compressive strength of mortar, as well as its dynamic elastic properties, was experimentally determined. The findings indicate that, at room temperature, higher replacement percentages of natural sand by EPA result in decreased flexural and compressive strengths, by as much as 50 % and 30.71 %, respectively. However, the dynamic moduli values for replacement percentages up to 20 % are similar to those of the reference mix. Conversely, when subjected to temperatures up to 200ºC, significant improvements were observed in the flexural strength values, e.g. over 20 % for temperatures of 150°C and 200°C, with only marginal improvements in compressive strength, 3 % ÷ 20 % for temperatures of 150°C and 200°C, compared to values obtained at room temperature. • Expanded perlite aggregates replace sand in cement-based mortar up to 30 % by volume. • Proposed equation correlates dynamic modulus of elasticity with compressive strength. • Flexural strength of perlite aggregate mortars increases at elevated temperatures. • Compressive strength improves for perlite mortars subjected to temperatures up to 200°C. [ABSTRACT FROM AUTHOR]

Reinforced concrete structures are susceptible to reduced service life owing to the erosion caused by the of chlorine-containing, external environment and internal chloride. In this paper, a superhydrophobic hydrotalcite cement mortar was studied with internal and external cooperation against chloride ion erosion. The effect of different hydrotalcite substitution amounts on the chlorine corrosion resistance of the mortar was investigated. The mortar exhibited good resistance to chlorine corrosion, and the corrosion resistance rate increased by 91.83 %. The free chloride ion concentration measurement and rapid chloride migration test exhibited that the prepared mortar effectively resisted chloride ion invasion and reduced the content of free chloride ions in the mortar. The proposed anticorrosion method is expected to have potential application prospects for concrete structures under chloride salt environments. • An anti-corrosion cement mortar is proposed to resist both external and internal chloride ion erosion. • The effect for the different hydrotalcite substitution amount on the chlorine corrosion resistance of mortar was analyzed. • The prepared cement mortar improved the anti-corrosion property of reinforced concrete in chlorine salt environment. [ABSTRACT FROM AUTHOR]

• TRs and RG were co-treated to produce a new blended binder with good mechanical strength and water resistance. • RG and CRG can effectively activate the hydraulic property of TRs by electrodeless resistivity test. • This paper provides a cost-effective method to recycling TRs and RG. The huge accumulations of Ti-extracted residues (TRs) and red gypsum (RG), which are the solid by-products from TiO 2 pigment industry, have caused a series of on-site and off-site environmental problems. This work is concerned with the feasible recycling of TRs, RG, calcined RG (CRG) as main components in the production of a novel cementing material. The resulting mechanical strength, softening coefficient, hydration behavior (electrical resistivity) and microstructure (porosity and hydration products) of this binder were investigated. It was found that the flexural strength, compressive strength and softening coefficient of mortar samples at 28 days can reach up to 6.3 MPa, 47.9 MPa and 0.87, respectively. An electrodeless resistivity test, over a period of 72 h was also conducted: an increasing content of RG from 0 to 40% retarded the hydration within the first 24 h, whereas both the binders incorporating 20% CRG plus 20% RG and 40% RG were responsible for the later accelerating hydration. Moreover, an increase of RG's content (from 10% to 40%) and the substitution of CRG for RG decreased total porosity and narrowed pore size distribution of mortar samples. Results from X-ray diffraction and morphology analysis revealed that the intertwined hydrated products in the hardened binders were needle-like ettringite, unreacted bar-like gypsum and filamentous C-(A)-S-H, ensuring the blends with a good water resistance. In summary, this paper provides a cost-effective approach for utilizing TRs and RG to produce a high-strength cementing material as an alternative to ordinary Portland cement. [ABSTRACT FROM AUTHOR]

• This paper investigated the performance of mortars containing steel scale. • Taguchi based grey relational analysis method was applied in this study. • Water/cement ratio was found the most important parameter on the responses. • The addition of scale has improved mechanical strengths and porosity of the mortars. This paper examined the performance of cement mortars containing steel scale as experimentally and statistically. To this end, mortar samples with different levels of fine scale (0%, 5%, 10%, 15%), coarse scale (0%, 5%, 10%, 15%), water/cement ratio (0.5, 0.6) and cement dosage (400 kg/m3, 500 kg/m3) were produced and their compressive strength, flexural tensile strength and porosity value were determined. Taguchi based grey relational analysis method was performed to obtain optimal parameter levels for simultaneously achieving the desired properties of the mortars. L 16 (42 × 22) orthogonal array table was chosen for the tests according to the Taguchi quality design concept. ANOVA (Analysis of variance) method was applied to determine statistically effects of the parameters. Optimization results were compared with initial parameters (control sample) and it was concluded that there was a good fit between them. Based on the overall observations, it is recommended that the Taguchi based grey relational analysis method could be effectively used in such studies. [ABSTRACT FROM AUTHOR]

Highlights • Shrinkage and expansion of various glass aggregate mortars are presented in this paper. • Crushed glass, glass beads, and expanded glass were used to replace natural sand. • Crushed glass and glass beads in mortar improved plastic and drying shrinkage. • Mortar bar tests confirmed deleterious nature of glass, except for expanded glass. Abstract This paper presents the effect of various glass aggregates on plastic and drying shrinkage and alkali silica reaction (ASR) expansion of cement mortar. The study was done by substituting a portion of sand with expanded glass, crushed glass, and glass bead aggregates. The low absorption capacity of glass, except expanded glass, enhanced the dimensional stability of the mixtures, minimizing volumetric contraction associated with shrinkage. Presence of finer glass particles in the mortar resulted in a large benefit in ASR expansion. The study found that cement mortar with glass aggregates can be beneficial if aggregate type and amount is chosen appropriately. [ABSTRACT FROM AUTHOR]

Highlights • The cracking behavior of cementitious materials can be monitored by EIS. • The semi-circle in Nyquist plot is present in the cracked mortar at high frequency, • R ct in Nyquist plots, Z and θ° in Bode plots sensitively reflect the cracking behavior. • The stability and smoothness (fluctuation) of Bode plot can response the cracking degree. Abstract In this paper, electrochemical impedance spectroscopy (EIS) is used as a non-destructive testing method for investigating the cracking behavior of two kinds of cement-based materials with/without fiber, which are engineered cementitious composites (ECC) and plain mortar. The experimental results show that the cracking patterns and deflection-load curves of plain mortar and ECC are different when the external load reaches to the first-cracking load and ultimate load. The EIS results show that the parameter value of R ct and plural modulus value Z in fractured mortar increase several hundred times compared with correspondingly origin plain mortar. Moreover, the semi-circle presents in the fractured mortar at high frequency and the diagonal lines are deviated from less than 45 deg at low frequency, and the phase angle (θ°) in cracked mortar decreases as the frequency decreases in Bode plots. However, the values of R ct and Z in cracked ECC increase dozens of times compared to origin ECC, and the phase angle decreases as the frequency decreases. The variation of R ct in Nyquist plots, and the stability and smoothness of Bode plot sensitively reflect the cracking degree of cementitious system. In this paper, it is proposed that as a non-destructive method, electrochemical impedance measurement can be used to evaluate the cracking behavior of cement-based materials. [ABSTRACT FROM AUTHOR]

Highlights • Brick masonry blocks were reinforced with FRCM composites. • Two different mortar matrices (natural hydraulic lime and Portland cement) were used. • Wetting-drying cycles in water and saline solution were carried out. • The bond behavior of FRCM-masonry joints and the materials deterioration were investigated. • The matrix played a key role in the debonding mechanism and in the salt crystallization pattern. Abstract Fiber-reinforced cementitious matrix (FRCM) composites are a new category of composites recently proposed for seismic strengthening of historical masonry structures, to provide a more compatible solution compared with fiber-reinforced polymer (FRP) composites. Despite the rapidly increasing number of research papers dealing with the mechanical behavior of FRCM composites applied to masonry, their long-term performance and susceptibility to weathering processes are still largely unexplored. In this paper, the response of FRCM-masonry joints to accelerated weathering is investigated. A laboratory testing procedure, previously developed by the authors, which involves wetting-drying cycles in water and saline solutions, is employed. Two different types of mortars (based on natural hydraulic lime and Portland cement) were used for the composite matrix, without changing the geometry, the type of masonry substrate and the fibers (galvanized steel cords), in order to assess the role of the matrix in the FRCM-masonry joint bond behavior and deterioration processes. Results show that the matrix played a key role in the debonding mechanism of the FRCM-masonry joints as well as in the capillary absorption of water and in the resulting salt crystallization patterns. [ABSTRACT FROM AUTHOR]

Highlights • Effects of glass fiber on mechanical properties of MPC were studied. • The addition of glass fiber improved the water resistance of MPCs. • The flexibility and deformation behavior of MPC can be improved by using glass fiber. • The mechanism of glass fiber improving water resistance of MPC was analyzed. Abstract This paper describes an experimental investigation into the compressive strength, the flexural strength and the water resistance of magnesium phosphate cement (MPC) mortar reinforced by glass fiber. Fiber volume fractions of 1.5%, 2.5%, 3%, 3.5% and binder/aggregate ratios of 1:1, 1:1.2 and 1:1.5 were designed for the experiments. The microstructural, mechanical and water resistance properties of fiber-reinforced MPCs were evaluated with respects to the variance in the fiber volume fraction, the ratio of binder/aggregate. The results showed that the glass fibers have more pronounced effects on the flexural strength compared to compressive strength. The optimum volume fraction of glass fiber is reported at 2.5%. Furthermore, the effect of glass fiber on the water resistance of MPC is discussed, and a "reserving" method to resist the strength loss by water has been proposed. In addition, the paper provides a possible explanation of the fiber reinforcement mechanism which is in agreement with the experimental results. [ABSTRACT FROM AUTHOR]

• The morphologies of aggregates can be quantified using photography and processed through ImageJ. • The number of aggregates and volume of mortar in an asphalt mixture is enough to predict its porosity, stiffness, stability, and flow. • New design models enable to select optimal aggregate's number and mortar's volume to achieve desired performance of asphalt mixtures. • New design models help checking whether one asphalt mixture fulfils performance requirements. Conventional asphalt mix design methods require numerous experiments to verify the efficacy of various recipes, resulting in significant time and labour costs. Therefore, there is a need for an alternative method that is both efficient and convenient. To address this issue, this paper proposes a novel asphalt mix design method that reduces the reliance on time-consuming and resource-intensive physical and mechanical tests to determine the properties of new asphalt mixtures. The method focuses on the quantity of aggregates and the volume of mortar to estimate the air voids content, resilient stiffness modulus, Marshall stability, and flow requirements in accordance with industry standards. Statistical analysis shows that the key properties of asphalt mixtures are primarily influenced by the number of aggregates and volume of mortar. Nomographs are provided to predict these properties based on the mixture's gradation and mortar volume. The proposed method's feasibility is demonstrated by accurately predicting the gradations and properties of six different mixtures. Additionally, the paper suggests the use of 3D models for asphalt mixtures, allowing for the observation of aggregate distribution and air voids before testing the mixtures' mechanical properties. [ABSTRACT FROM AUTHOR]

• In this paper, the effects of water–binder ratios and curing ages on the axial tensile stress–strain curves of mortar, new–old mortar interface and RAC were investigated experimentally. • Based on the experimental results and the random aggregate model, the manuscript explores the tensile damage development of RAC and analyzes the law and mechanism of the influence of the properties of old mortar on the axial tensile stress–strain curves of RAC. • In this paper, the tensile constitutive relationship of RAC is proposed based on the tensile constitutive relationship of ordinary concrete, combined with experimental results and numerical analysis results. The tensile constitutive relationship is essential for determining the ductility and restoring force characteristics of seismic-resistant concrete structures and studying the mechanisms causing damage and fracture to concrete structures. This study investigates the axial tensile stress–strain curves of mortar, the interface between new and old mortar, and recycled aggregate concrete (RAC) with different water-binder ratios and ages. First, the tensile constitutive relationships of mortar and new-old mortar interface were established. Then, based on the experimental results and the random aggregate model, a double-interface numerical model of RAC was established to investigate the development of tensile damage in RAC and the influence law and mechanism of the old mortar strength, thickness and curing age on the curve of the tensile stress–strain of RAC. The results are a comparison of the peak tensile strengths at the same age and water-binder ratio for the above three mortar types, where new mortar > RAC > new-old mortar interface. Under the same thickness of old mortar, the peak stress, elastic modulus and peak cutline modulus of RAC increased with the increase of old mortar strength, and the amplitude of change increased with the increase of mortar thickness. Based on the tensile constitutive relationship of ordinary concrete, the tensile constitutive relationship of recycled coarse aggregate concrete is proposed by combining the experimental results and numerical analysis results. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Patch repairs are widely used for local damage in RC columns. • 15 patch-repaired RC columns were tested at the ICITECH. • The paper analyses the effectiveness of patch repairs on RC columns. • Patch repair is compared with: all-four-sides and one-side repair. Abstract This paper describes an experimental study on patch-repaired reinforced concrete columns subjected to axial loads until failure. The behaviour of four series of columns repaired with Class R3 and R4 cement-based mortar was analysed both with and without a bonding agent. The results obtained were compared with control series of undamaged and damaged but unrepaired columns to determine the effectiveness of the repairs and the subsequent improvement in the behaviour of the columns. The results of this study were compared with those of previous work by the authors on the analysis of all-four-side repairs and one-side repairs. The conclusion reached was that patch repairs are highly effective as compared to the other techniques studied and that using Class R3 mortar achieves better results on damaged columns made with low-quality concrete. It was also concluded that applying a bonding agent does not improve the results, although this element was found to be necessary to prevent the premature detachment of the repair when there is a substantial difference between the stiffness of the column concrete and that of the mortar used in the repairs. [ABSTRACT FROM AUTHOR]

The mechanical response of stone masonry depends on the properties of the components and also on the typology created by the stone units and the mortar joints. While the influence of the component strength on masonry is relatively well studied, few studies have been devoted to its influence on masonry properties mainly because of the difficulty of varying the masonry typology systematically. This paper focuses on generation and calibration of masonry typologies, which serves as foundation for further numerical investigation. To this purpose, we develop a typology generator based on relevant research in computer vision. To characterize different typologies quantitatively, we also develop an objective method to compute the line of minimum trace directly from the image of stone masonry based on graph theory. The code and recommendations for the parameter choices are publicly available online. Altogether, this paper provides a useful tool for researchers to study systematically the influence of historical stone masonry typologies. [ABSTRACT FROM AUTHOR]

This paper discusses masonry buildings constructed in Pernambuco and their relationship to several failures that have occurred, some of which included the death of inhabitants. Topics such as the main features of this building technique and its peculiarities that played an important role in its structural behaviour are discussed in detail. Additionally, the paper presents a large characterization of materials and components used constituting the most important current research on this topic in Brazil. Its content analyses in depth, experimentally, the behaviour of single bricks, prisms and wallets that allow the identification and quantification of the influence of several mortar rendering layers on the load capacity of elements tested. A critical analysis concerning the factors that contribute to the performance observed is presented from which it was possible to realize a significant variability of results. A summary with the main results of all experimental tests is presented. [ABSTRACT FROM AUTHOR]

The heterogeneity of a cement-based material results in a random spatial distribution of carbonation depth. Currently, there is a lack of both experimental and numerical investigations aiming at a statistical understanding of this important phenomenon. This paper presents both experimental and numerical supercritical carbonation test results of cement mortar blocks. The carbonation depths are measured along the carbonation boundary by the proposed rapid image processing technique, which are then statistically studied by calculating, e.g., their probability density and power spectral density (PSD). The results indicate that the distribution of the carbonation depth can be approximately represented by a lognormal distribution function and the PSD has quantitative correlation with some of the statistic parameters used in the simulations. In particular, the effects of the autocorrelation lengths and the coefficient of variation of porosity, which are used to define the random porosity field, on the irregularity of carbonation depth are analyzed numerically in details and validated by experimental results. The study has shown that using a random field of porosity with due consideration of spatial correlation and variance, the irregularity of carbonation depth can be realistically captured by the numerical model. The numerical results confirm that lognormal distributions represent the random nature of carbonation depth well and the average and variance of the irregular carbonation depth increase with the increase of carbonation time, autocorrelation length and coefficient of variation of porosity. The study also offers a potential method to numerically calibrate some of the statistic parameters required by a numerical carbonation model through comparing the PSD with that from experimental tests. Overall the methodology adopted in the paper can provide a foundation for future investigations on probability analysis of carbonation depth and other similar work based on multi-scale and -physics modelling. [ABSTRACT FROM AUTHOR]

Roller compacted concrete (RCC) is constructed in layers. It is a dry and lean concrete with the interlayer being generally weak. In this paper, the shear strength of RCC interlayer under different time intervals and interlayer treatments are studied, and the corresponding change laws of shear behaviors are analyzed. Through the comparison of the test results at different time intervals, it was found that the peak shear strength decreases with increases to the time interval. Before the initial setting, the influence of time interval is relatively small. Between the initial setting and before the final setting, the influence of time interval becomes evident, and after the final setting it is seen that the influence of the time interval is much greater. Three interlayer treatments are tested, namely, mortar, expansion agent with mortar, and nano SiO 2 with mortar. It was seen that treatments with the expansion agent and the nano SiO 2 improve shear strength more than that of mortar alone. The cohesive stress c and friction coefficient f of the RCC interlayer are calculated for each case. At peak stress, f keeps steady and c decreases with the increase of the time interval. For treatments with nano SiO 2 , values of c were observed to be improved while for treatments with the expansion agent, higher values of f were seen. The shear strength of RCC interlayer can be well explained by using test results of scanning electron microscope to provide a view of the structure on the mesoscopic scale. The results of this paper are helpful to understand the influence laws of shear strength of RCC interlayer, and it has significance for the improvement of interlayer construction technology of RCC. [ABSTRACT FROM AUTHOR]