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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]

• 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]

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]

Recycled aggregate (RA) is generated through the crushing process of Construction and Demolition Waste (CDW). Although there has been extensive research on the mechanical properties of recycled aggregate asphalt mixture (RAAM), the impact of recycled aggregate (RA) on its rheological characteristics remains underexplored. This paper aims to assess the rheological properties of recycled aggregate asphalt mixture (RAAM) during the processes of mixing and compaction. Firstly, different percentages of recycled aggregate (RA) were utilized in the design of the recycled aggregate asphalt mixture (RAAM), and rheological behaviors of RAAM during the mixing and compaction stage were characterized by mixing torque and compaction energy, respectively. Then, high-precision three-dimensional models of RA were reconstructed utilizing CT images, and four indices were established to quantitatively assess the macro shape and micro-morphology of RA particles, utilizing the spatial model data for precise measurements. Finally, a correlation was found between rheological properties of RAAM and RA morphology through a comprehensive analysis of laboratory test results and spatial model indicators. Results show that aggregate particles' microstructural morphology significantly influences asphalt mixture's rheological behavior during mixing and compaction. Additionally, the 3D spherical degree and Needle-flake index performed more significant correlations with mixing and compaction than the 3D angular index and 3D texture index. As opposed to natural aggregate, RA exhibits more intricate morphological characteristics stemming from its porous cement mortar composition. Increasing the RA content causes more energy consumption and increases the thickness of asphalt mortar film during the compaction process. In general, methods established in this study offer an efficient mean of quantifying the morphological characteristics of aggregate particles, thereby enabling the assessment of the impact of RA on the rheological properties of asphalt mixtures. • A quantitative method for microstructural morphology of aggregate particle is proposed. • Rheological properties of asphalt mixture containing recycled aggregates are measured. • The relationship between rheological properties and morphological indicators is obtained. [ABSTRACT FROM AUTHOR]

The fatigue life of the cement asphalt (CA) mortar in the slab track of the China Railway Track System (CRTS) II is crucial to the smooth and safe operation of high-speed railways. To investigate the fatigue life of the CA mortar under the combined thermal action and vehicle loads, this paper develops a new coupled thermal-mechanical finite element (FE) model for the concrete slab track at the mesoscale. First, the meteorology and heat transfer principle are adopted to simulate the temperature distribution of the concrete slab track. The heterogeneous characteristics of the concrete of the precast slab are modelled by the three-phase composite material at the mesoscale using the new developed random aggregate algorithm. Then, the energy-based exponential cohesive zone model is adopted to simulate the interface between the CA mortar and the precast concrete slab. The proposed mesoscale numerical model can provide reliable predictions for the temperature distribution and the deformation of the precast concrete slab under thermal action, which are confirmed by the relevant field measurements. Finally, the fatigue life of the CA mortar is estimated by the nonlinear damage cumulative method associated with the stress time history under the combined thermal action and vehicle load. From the obtained results for the numerical example, the thermal action can decrease severely the fatigue life of the CA mortar, and the fatigue life varies significantly at different positions, with the most vulnerable zone located near but not directly below the rails. • Proposing the coupled thermal-mechanical FE numerical modelling for railway concrete slab tracks. • Developing new random aggregate algorithm for modelling heterogeneous concrete at the mesoscale. • Predicting reliably CA mortar fatigue life using nonlinear damage cumulative method under combined action. [ABSTRACT FROM AUTHOR]

The alternative patch repair derived from hybrid alkali-activated binders (HAAB) were investigated in this paper. The HAAB mortar was produced with fly ash (FA), Portland cement (PC), and polymer-modified material (PMM). The additives (PC and PMMs) were used to replace FA at the dosage of 30 % by weight of binder. The proportions of PC-to-PMM at 30:0, 20:10, 10:20, and 0:30 were investigated. Sodium silicate (NS) and sodium hydroxide (NH) solutions were used as the alkaline activators. Constant NS-to-NH ratio of 2.0 and liquid/solid binder ratio of 0.60 were used for all mixtures. Experimental results showed that the setting time, compressive and shear bond strengths of the HAAB mortars met the requirement for repair material as specified by ASTM standard. The 7-day bond strength increased with increasing PMM replacement up to an optimum level; thereafter, it started to decline. A combination of PC and PMM in FA-based HAAB enhanced the adhesion at contact zone. Moreover, the HAAB mortars showed greater durability compared to conventional PMMs after immersion in sulfate and acid solutions, as evidenced by its relatively low strength loss. The increased formation of ettringite might be the main factor for the substantial reduction in the strength of PMM mixes. Therefore, the HAAB mortar is an attractive choice for patch repair material in terms of excellent durability, high bond strength, cost-effectiveness, and low carbon footprint compared to conventional PMM. • FA-PC-based HAAB with 10–15 % PMM satisfied the minimum 7-d compressive and bond strengths requirement as per ASTM standard. • Compressive strength of FA-PC-based HAAB decreased as PMM content increased. • Reaction product was mainly formation of hybrid C-(N)-A-S-H. • HAAB showed excellent durability, high bond strength, cost-effectiveness, and low carbon footprint compared to PMM mortar. [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]

Manufactured sand (MS) is increasingly used in massive concrete structures, but research on hydration of cementitious materials containing MS from diverse lithologies remains limited. In this paper, the hydration process of cementitious materials incorporating diverse lithologic MS powder and particles is examined, and the coupled effect of sand particles and stone powder as well as the differential effect of CaO-MgO blind expansion agent (CMEA) on diverse lithologic MS mortar hydration is analyzed. Results show that limestone and tuff stone powders similarly promote cement paste hydration, whereas only tuff MS significantly promotes mortar hydration. Compared to limestone MS, tuff MS has a greater effect on the initial Transverse relaxation time (T 2) distribution of cement paste and mortar. However, the main peak position remains unaffected by stone powder or sand particles once hydration stabilized. Natural sand (NS) particles also influence cement hydration, and the coupled effect of tuff MS particles and stone powder on hydration is the most significant. This influence is most evident in early-age hydration, gradually attenuating with reaction progression. Furthermore, low-field nuclear magnetic resonance investigations suggest CMEA reaction mechanisms in tuff MS mortar may diverge from those in NS mortar and limestone MS mortar systems. • Hydration process of cement-based materials with diverse lithologic MS is researched. • Effects of MS lithology on cementitious materials water evolution are analyzed. • Coupled effects of diverse lithologic MS particles and powder on hydration are discussed. • Differential effects of CMEA on hydration of various lithologic MS mortar are analyzed. [ABSTRACT FROM AUTHOR]

In this paper, the slag powder (SP) and belite calcium sulfoaluminate (BCSA) were added into Portland cement (PC) to study the properties of composite cementitious system (SBP). The hydration mechanism of the SBP was studied by the setting time, the heat of hydration, X-ray diffraction (XRD), thermogravimetric (TG), and Fourier transform infrared (FTIR) spectroscopy. The properties of the SBP mortar were tested by mechanical properties, drying shrinkage, and pore size distribution. The microscopic morphology of the SBP mortars was observed by scanning electron microscopy (SEM). The results showed that the setting time of the SBP paste was increased and then decreased with the increase in SP dosage. The increase in SP dosage promoted the pozzolanic effect, it led to a higher generation of the calcium silicate hydrate (C-S-H) gel and the Ettringite (AFt) under the excitation of the fluorine gypsum (FG). The porosity of the SBP mortar was reduced, and the density was increased with the increase in SP dosage. However, when the SP dosage exceeds 25%, the excess generation of the AFt leads to micro-cracks, increases the volume of the macro pores, and decreases the mechanical and drying shrinkage properties of the mortar. This study can provide a theoretical basis for applying the SBP in engineering. [Display omitted] • The hydration and properties of the Slag-BCSA-PC composite cementitious system (SBP) was studied. • The components of the SBP interact with each other to improve the properties of the mortar. • Quantified the ettringite (AFt) content using Fourier Transform Infrared (FTIR) spectroscopy. [ABSTRACT FROM AUTHOR]

This paper presents the results of an extensive experimental campaign related to the use of Coal Mining Waste Geomaterials (CMWGs) as recycled constituents (fine and coarse aggregates) in Ordinary Portland Cement mortars and concretes. To this purpose, a reference mix and other mixes with different percentages of replacement of natural aggregates by CMWGs, up to 40% by volume, were investigated. CMWGs came from different providers: Central Mining Institute (GIG), POLTEGOR, both in Poland, and SUBTERRA in Spain and tests were performed at two different laboratories working on similar, but not identical, compositions. This represents a novelty in the literature, generally focusing on one single-source waste and single-lab results. The physical and mechanical properties of all the mixes were evaluated and correlated with respect to the percentage of replacement of natural aggregates by CMWGs. While the presence of CMWGs, likely because of their grain size distribution, reduced the porosity of mortars (decrease of 9.5 and 20.4% for 10 and 20% of replacement respectively) and concretes (70% reduction for concretes with 10% of fines and 30% of coarse aggregates replaced by CMWGs), the mechanical properties decreased when natural aggregates were replaced with CMWGs, likely because of the reduced strength of the CMWGs aggregates. This decrease was found to be roughly proportional to the percentage of replacement of aggregates (for instance, a 12–23% reduction of flexural strength in mortars with 25% replacement of sand and, a decrease of 25% in concretes for a 25% replacement of fine and coarse aggregates); nonetheless the concrete performance remained in the range of applicability for several civil engineering applications without affecting their functionality. In conclusion, the replacement of natural aggregates by CMWGs has resulted an interesting option for real applications providing an added value to the implementation of circular economy concepts in the management and up-cycling of coal mine tailings and CMWGs. • Recycling Coal Mine Waste Geomaterials as partial replacement of fine and coarse aggregates in concrete is feasible.. • Complementarity and coherence of results from two different labs with aggregates from three sources validate the methodology. • Thin section analysis provides insight into microstructural reasons of macroscopic properties highlighting the interaction of CMWGs with cement paste. • Reduction in compressive strength induced by weaker CMWG aggregates does not jeopardize the possibility of producing concrete still retaining values of compressive strength fit for several structural applications. [ABSTRACT FROM AUTHOR]

This paper presents experimental and analytical investigations on the tensile and bond behaviour at elevated temperature of a polypara-phenylene-benzo-bisthiazole (PBO) fabric reinforced cementitious matrix (FRCM) system for strengthening concrete elements. Direct tensile (DT) and single lap direct shear tests (DS) were performed under steady-state conditions at the following temperatures: 20 °C, 85 °C, 150 °C, 230 °C and 300 °C. The results obtained were evaluated in terms of strength, stiffness, ultimate strain, load vs. slip response at the interface PBO FRCM/concrete and failure modes. Overall, the tensile and bond properties were significantly affected by the temperature increase. These results are mainly associated with the reductions of mechanical properties of the FRCM constituent materials as well as the degradation of the interaction between the fibres and the inorganic matrix at elevated temperatures. The experimental results were then used (i) to evaluate the suitability of the Aveston–Cooper–Kelly (ACK) model in describing the tensile response of FRCM at elevated temperatures and (ii) to calibrate temperature-dependent local shear bond stress vs. slip laws for the FRCM-concrete interaction. • PBO fibres, mortar, PBO FRCM coupons and PBO FRCM-to-concrete joints exposed to temperatures ranging from 20°C to 300°C; • Steady-state mechanical properties determined at : 20°C, 85°C; 150°C; 230°C and 300°C; • Results obtained evaluated in terms of strength, stiffness, ultimate strain, shear stress and slip; • Assessment of the Aveston-Cooper-Kelly model in describing the tensile response of the PBO FRCM at elevated temperatures. • Parameters of the local shear bond stress vs slip laws calibrated using 1 1 It is important to note that due to the proprietary nature of the patented product used herein, detailed information regarding its composition is not available. the experimental results. [ABSTRACT FROM AUTHOR]

As building solid waste, the replacement of brick powder for cement is conducive to reducing energy consumption and costs of building material. However, the low reactivity of BP cannot be ignored, as it negatively impacts the performance of mortar. To address this issue, this study incorporates a mixture of plant-based TA (Tannic) with BP into a pre-mixed paste and adds it to cement mortar. The porous structure of the BP facilitates the adhesion and complexation of polyphenol hydroxyl groups, enhancing the dispersion of BP in the cement paste. Moreover, the in-situ formation of nano-sized calcium-based complexes, as evidenced by AFM, XRD, TGA and SEM tests, provide excellent nucleation sites, which regulate cement hydration and enhance the mechanical properties of BP-cement mortar, significantly reducing the proportion of capillary pores and large pores in the mortar. By substituting 15% of cement with TA-modified BP, the compressive strength and flexural strength increased by 49.19% and 5.72%, respectively, and the shrinkage rate was reduced by 73.15%. Thus, this simple and green modification method will provide more inspiration for the efficient utilization of BP in cement-based materials. • The paper will provide more inspiration for the efficient utilization of BP in cement mortar. • The plant-based TA is attached to the surface of BP through complexation-adsorption. • TA-modification improve the dispersibility of BP-cement paste. • TA-modified BP mortar obtained higher strength and lower shrinkage, compared to untreated BP mortar. NOTE: BP mean brick powder. TA mean Tannin acid. [ABSTRACT FROM AUTHOR]

The paper presents an experimental program on the characterisation of the mechanical behaviour of perforated brick masonry (PBM) under uniaxial compression. The study is aimed to provide a better understanding on the compressive strength and elastic behaviour of a kind of masonry hardly dealt with in the literature. The mechanical response of the investigated masonry shows actually two complexities, linked respectively to the perforated nature of the bricks and the asymmetric cross-section of the units. The latter feature is particularly recurrent in exposed brickwork composed of perforated bricks, whenever one of the face shells has a larger thickness than the other one. For this purpose, an experimental campaign was carried out on units and PBM subjected to uniaxial compressive loading. The mechanical response of PBM is investigated to accurately determine the masonry Young's modulus and the compressive strength. Measurements obtained with conventional sensors are compared with those derived from the Digital Image Correlation (DIC) technique. Lastly, the experimental findings in terms of compressive strength and Young's modulus are cross-referenced with the estimations derived from empirical criteria available in Eurocode 6 and ACI 530.1–02. • Characterisation of the compressive response of Perforated Brick Masonry (PBM). • Derivation of compressive strength and Young's Modulus of asymmetric brick PBM. • Novel concept of co-barycentric area to calculate the compressive strength of PBM. •.DIC technique for the computation of Young's Modulus and Poisson's ratio of PBM • Comparison between experimental results and available empirical formulation. [ABSTRACT FROM AUTHOR]

Silica fume (SF) is widely used in the developing of high-performance geopolymer systems. Previous studies have shown that using different types of SF may have different influences on the performance of geopolymers. What are the key factors (affecting the properties of geopolymers) still need to be clarified? This paper investigated the effects of three types of silica fume (SF1− SF3) with various silica contents (98.0%, 94.7% and 53.1%) and particle sizes (D 50 : 3.3 μm, 3.1 μm and 11.8 μm) on the rheology and compressive strength of alkali-activated calcium alumina cement (CAC)/fly ash mortar. The incorporation of SF can significantly increase the plastic viscosity. The increase in plastic viscosity was due to the ball-bearing action of the spherical SF particles, which reduced the friction between the particles under shearing. Replacing 20% of the fly ash with SF1 and SF2 improved the compressive strength of geopolymer mortars while the incorporation of SF3 decreased the compressive strength at the same replacement ratio. Inductively coupled plasma (ICP) spectrometry results indicated that the amorphous silica in the SFs was dissolved in an alkali solution. Activators with high concentrations of monomer and dimmer silicon groups may promote the reaction between precursors and activators. The formation of additional aluminosilicate gels reduced the amount of large capillary pores (500 nm to 1000 nm), leading to improved strength. The incorporation of coarse SF3 introduced extra voids in the mixture, as suggested by calculations of packing density, leading to reduced strength. • From a chemical perspective, SF effect is governed by Si dissolution rate. • From a physical perspective, SF effect is governed by its PSD. • Low SiO 2 content SF increases strength of geopolymers at low dosage. • CPM can optimize mix composition of SF-geopolymer systems. [ABSTRACT FROM AUTHOR]

Spalling is the main problem concerning safety in concrete structures under rapid heating. Despite being studied for nearly a century, its prediction remains a challenge. In addition, the main recommendations for its prevention are merely the addition of a fixed amount of polypropylene fibres, without accounting for mix design. This paper presents an experimental study focusing on the thermo-hygral mechanism contribution to spalling. The use of mercury intrusion porosimetry and X-ray microtomography for the determination of pore connectivity is considered a key parameter. The results of the experiment are used for the development and calibration of an analytical equation capable of predicting spalling in concrete samples. The equation is then validated using over 100 examples extracted from literature, achieving an accuracy of 91.2%. Based on the validation, the proposed equation is a step forward in the prediction of concrete spalling based on the mix design parameters. • Development of analytical equation to predict concrete spalling. • Validation with more than 100 examples from literature reached 91% accuracy. • Experimental campaign emphasizing thermo-hygral contribution to spalling. • Definition and use of pore connectivity to predict spalling behaviour. [ABSTRACT FROM AUTHOR]

In this study, a standard pH test procedure, based on the high alkalinity of electric arc furnace oxidizing slag, was developed for rapid content evaluation of potentially hazardous slag in the fine aggregate and recommended standards are further proposed. The advantages of the developed procedure include easy equipment acquisition, simple test method, short time, and high accuracy. This study found that sample size, water source, and filtrate process were the factors affecting the pH test accuracy. In the test, the pH increased with a decrease in the aggregate size when the proportion of electric arc furnace oxidizing slag in aggregate was fixed, especially when the aggregate size was less than 0.225 mm. Upon comparison of the results of autoclaved mortar bar expansion tests, a good logarithmic relationship was observed between pH and electric arc furnace oxidizing slag content. It is suggested that pH 9.0 could be used as the standard to determine excessive electric arc furnace oxidizing slag in fine aggregate. • Proposed a standardized process for rapidly assessing pH in fine aggregates, addressing hazards from electric arc furnace oxidizing slag (EAFOS). • Optimized pH testing factors: D100 particles, RO water, 10 % solid content, filtration through 5A + 5B paper before measurement. • Sample pH values consistently showed a logarithmic relationship with EAFOS content proportion. • pH values over 9.0 indicate excessive EAFOS content in fine aggregates, making them unsuitable for further application. [ABSTRACT FROM AUTHOR]

In this paper, the method of dehydration condensation reaction was used to establish a superhydrophobic cement mortar surface with the contact angle of 159.3° and the slide angle of 6.1° by using organosilane and inorganic nanomaterials. The nanoparticles built roughness and the silane provided low surface energy, which in combination achieved self-cleaning, waterproof and durability improvement. The superhydrophobic coating with good penetration depth is able to show superhydrophobicity after simply brushing and curing at room temperature for 24 hours and maintain hydrophobicity after surface abrasion. A variety of liquid droplets can roll freely from the surface of superhydrophobic cement mortar and carry contaminants rolling down to show self-cleaning performance. In terms of durability, the coating appears good adhesion to the surface of cement mortar, which retained its hydrophobic property after tape-peeling tests and outdoor simulation tests. In addition, compared with ordinary cement mortar, the superhydrophobic cement mortar demonstrates excellent waterproof ability and freeze-thaw resistance through low water absorption and slow quality reduction after multiple freeze-thaw cycles. These key characteristics provide advantages for concrete protection applications in harsh environments. • A simple method for preparing superhydrophobic surface by brushing chemically-modified liquid is proposed. • The penetration depth of the superhydrophobic coating is 5 mm. • The coating optimizes pore structures and water absorption is reduced by 70.66%. • The coated mortar exhibits pretty icephobic performance and freeze-thaw resistance. [ABSTRACT FROM AUTHOR]

Ammonium carbonate was used as the carbonation accelerator for air-hardening lime mortars in this study. Various analytical methods, including XRD, IR, TGA-DSC and SEM were employed to access the phase transformation, degree of carbonation and microstructural features of the lime-based mortars. The paper explores the correlation between the mechanical strength, microstructure of cured lime mortars and the composition/carbonation degree with the crystallization behaviors in Ca(OH)2/CaCO3 binders. The results indicate that ammonium carbonate significantly accelerates the carbonation reaction and increases the early mechanical strength of air-hardening lime mortars. The mechanical strength of these modified lime mortars can be comparable to that of natural hydraulic lime (NHL). The aggregation behaviors of nano-CaCO3 under kinetic control, are believed to contribute much to the compact pore-structures and robust mechanical strength of lime mortars. This viable accelerating carbonation method holds promise for enhancing the properties of various lime-containing building materials in conservation and modern buildings. • Ammonium carbonate is effective in accelerating the carbonation of aerial lime. • Lime mortars modified by ammonium carbonate rival natural hydraulic lime (NHL). • The mechanical strength is highly related to carbonation degree and pore structure. • Nano-CaCO 3 play pivotal role in compacting the pore structure of lime mortar. [ABSTRACT FROM AUTHOR]

The porous hydrophilic nature of cement-based material is susceptible to water and corrosive media, severely reducing the durability. In this paper, methyl siloxane-based hydrophobic powder was prepared, and its effect on the physicochemical and anti-corrosion properties of mortar with different water-cement ratios were investigated. The results show that the addition of hydrophobic powder significantly improved the hydrophobic properties of mortars. Especially for the mortars with w/c ratios of 0.2 and 0.4, it showed superhydrophobicity with a water contact angle up to 156.5 ° and 152.3 ° respectively. Lower w/c ratio mortar has a denser microstructure, which reduces the water absorption rate of the mortar, and the hydrophobic powder enhances the hydrophobic effect of low w/c ratio mortar more significantly. The methyl siloxane groups in the hydrophobic powders will bind to the C-S-H gel in the mortar through Si-O bonding, preventing the C-S-H gel connections from forming a continuous network structure. This increased the pore volume and reduced the compressive strength by 14.6%-22.7%, but the total hydration degree was increased, and significant corrosion protection of the steel rebar was demonstrated. [Display omitted] • Super hydrophobicity of mortar was achieved by modification of hydrophobic powder. • Hydrophobic mortar with lower w/c ratio exhibits better anti-corrosion performance. • Methylsiloxane groups combine with C-S-H gel by Si-O enhancing hydrophobic properties of mortar. [ABSTRACT FROM AUTHOR]

This study investigated the changes in three characteristics, including phase compositions, microstructure, and microhardness, in the interfacial transition zone (ITZ) of high-ferrite cement (HFC) products when subjected to different curing systems. In addition, we explored the underlying mechanisms through which supplementary cementitious materials (SCMs) influence the ITZ under steam curing conditions. The characterization was performed through the application of test techniques such as X-ray diffraction analysis, backscattered electron, scanning electron microscopy, energy dispersive X-ray spectrometry, and microhardness. The findings demonstrated that the increase in the curing temperatures promoted the HFC mortar to generate an excellent ITZ performance compared to Portland cement and ground granulated blast furnace slag (GGBFS) showed an improvement in steam-cured HFC-ITZ better than. Specifically, optimal enhancement of the ITZ in steam-cured HFC cement-based materials was achieved through the 40% replacement of GGBFS where the calcium hydroxide (CH) content and orientation growth were reduced while the hydration product formation was increased, resulting in declined porosity. Furthermore, the incorporation of 20% replacement of fly ash (FA) led to the decrease in the CH content and porosity of the ITZ. However, due to the lower reaction activity, unreacted FA persisted in the paste even after 28 days of curing. Additionally, the uneven distribution of hydration products resulted in diminished microhardness. On the other hand, a 40% replacement of FA marginally improved the properties of the ITZ. Finally, the test data and conclusions in the paper can provide some evidence for the application of GGBFS and FA in HFC and HFC-based concrete. • At elevated curing temperatures, the ITZ in high-ferrite cement exhibits a denser microstructure. • The steam curing process, combined with a 40% addition of GGBFS, promotes the hydration to enhance the structure of ITZ. • The "filling effect" of FA reduces the porosity of HFC-ITZ, but the lower activity results a lower degree of pozzolanic reaction. [ABSTRACT FROM AUTHOR]

Residential construction materials have undergone a notable evolution within the construction sector. This paper extensively reviews various types of bricks and building materials commonly employed in house construction, categorizing them into classifications such as typical clay, concrete, fly ash, and new materials such as aerated concrete and recycled bricks. The study thoroughly investigates the mechanical, thermal, and environmental potentials of each material, also considering auxiliary building materials like mortar, cement, and bio-materials, which play vital roles in house construction. Its primary objective is to offer valuable insights to architects, engineers, builders, and researchers to facilitate informed decision-making in residential construction projects. It also considers factors such as sustainability and local availability. The research identifies Cellular Lightweight Concrete (CLC) bricks as the optimal choice for residential construction, given their compressive strength of up to 30–40% more than traditional bricks, along with excellent lateral load capacity and displacement ductility, also making them suitable for constructing partition walls. Modifications in composition, such as incorporating coconut and basalt fibres, result in a notable enhancement of approximately 17.4% in thermal insulation with minimal impact on thermal degradation. Ultimately, this review serves as a valuable reference for individuals seeking a deeper understanding of the diverse options available in bricks and building materials for modern residential construction. • Various bricks and building materials for residential construction are reviewed. • Investigate the mechanical, thermal and environmental potential of each material. • Alternative materials like fly ash, mycelium, geopolymer, LTC, and 3D-printed bricks were explored. • Insights into the potential of diverse bricks for sustainable and eco-friendly building practices. • Critically highlight research gaps and provide directions for future studies. [ABSTRACT FROM AUTHOR]

In the underlayment of a floor radiant heating system (FRHS), using gypsum-based self-levelling mortar (GSM) with high fluidity and early strength properties could save labor force and material costs. Combining phase change materials (PCMs) with FRHS is a promising way to improve energy efficiency and provide a comfortable thermal environment. This paper investigates the feasibility of preparing gypsum-based self-levelling energy storage mortar (GSEM) by incorporating fly ash cenospheres/paraffin (FACP) into GSM. The selection of fly ash cenospheres (FAC) particle size, the pre-treatment of FACP, the additional amount of FACP, and the thermal performance of FRHS containing GSEM are investigated. Results show that the selection of FAC should consider the influence of strength, fluidity, thermal property, and possible economic and environmental impacts. FAC 2 with a particle size (D50) of 110.5 µm is considered to be a suitable choice. FACP pre-treated with 52.5 cement could decrease paraffin leakage and increase the mechanical strength and fluidity of GSEM. With the sand replacement ratio (V f) increase, the mechanical strength of GSEM first increases and then decreases. When the V f is 100%, the compressive strength and flexural strength of GSEM are 18.8 MPa and 4.3Mpa; the thermal conductivity decreases by about 15.8% and the specific heat capacity increases by about 53.5%. For FRHS, the matching between the supply water temperature and the plate thickness should be considered in the design. Compared with the GSM plate, the GSEM plate could reduce about 2.4℃ temperature fluctuation, and the time at a comfortable temperature is extended by 60.8%. This finding indicates that the prepared GSEM could be applied to FRHS and has good potential to provide a comfortable thermal environment for buildings. [Display omitted] • Self-levelling mortar containing cenospheres/paraffin is prepared and studied. • Particle size and coating influence the properties of self-levelling mortar. • The mechanical strength of self-levelling mortar meets requirement of standard. • Self-levelling mortar can reduce temperature fluctuation, extend comfortable time. [ABSTRACT FROM AUTHOR]

This paper presents the effect of incorporating wollastonite microfibers and cellulose nanofibers on mechanical properties and microstructure of ultra-high-performance mortar (UHPM). Cellulose nanofibers of 0.005%, 0.015%, and 0.030% are combined with 4.8% wollastonite microfiber by weight of binder, which consists of 10% silica fume and 90% cement. Compressive and flexural strengths of the UHPM specimens are measured at 7 days. The microstructure is characterized in terms of SEM/EDX, XRD, FTIR, and nanoindentation. The results show the effectiveness of the fiber hybridization in enhancing the compressive and flexural strength of ultra-high-performance mortar with the improvement in flexural toughness and fracture energy by as much as 10% than control mortar. Moreover, hybrid fiber-reinforcement based on the microstructural analysis provided more synergic effect and uniform distribution of the fibers, thus developing an efficient micro crack bridging mechanism as well as resulting in enhanced toughening properties and an increased load carrying capacity. Additionally, the combination of wollastonite microfibers and cellulose nanofibers promoted the hydration reaction products and contributed a denser matrix between the fibers and cement matrix, resulting in an increase of the microstructure and interface area between the fibers and cement matrix. Nano indentation analysis also confirmed the increase of UHD C-S-H from 65% to 84% and lower percentage of anhydrous phase in ultra-high-performance matrix after combining wollastonite microfibers and cellulose nanofibers. • The hybridization of cellulose nano fiber with wollastonite microfiber increased the compressive strength of unreinforced mortar. • The greatest advantage in hybrid-reinforcement systems in ultra-high-performance mortar is the improvement in flexural toughness. • Hybrid reinforcement systems develop an efficient crack bridging mechanism as well as resulting in enhanced toughening properties and an increased load carry capacity. • The addition of wollastonite promoted a higher UHD C-S-H compared to the control specimen and other hybrid reinforced mortars. • Cellulose Nano Fibers enhance cement hydration due to the high specific surface area, in addition to the promotion of adhesion with cement paste and bonding properties when combined with wollastonite. [ABSTRACT FROM AUTHOR]

The paper presents the results of studies on based the universal morphology of recycled coarse aggregates in reality, an idealized model of recycled coarse aggregates was prepared using stones. Axial compressive strength tests were conducted on prism-shaped specimens of Modeled Recycled Coarse Aggregate Concrete (MRCAC), which were prepared with different old cement mortar coverages and aggregate arrangements. Through comparison with experimental data, the reliability of the finite element analysis model was determined. It was found that the arrangement of MRCA had a significant impact on the failure characteristics and elastic modulus of MRCAC. Thus, different arrangement modes affected the stress distribution within the specimens, resulting in significantly different axial compressive strength. • Studied the influence of aggregate arrangement on the stress characteristics of MRCAC. • Studied the influence of old cement mortar on the mechanical properties of MRCAC under different internal force transmissions. • Revealed the influence characteristics of old mortar on the stress-strain relationship in recycled concrete. [ABSTRACT FROM AUTHOR]

• Mechanical characterization of lime mortars by means of the Drilling Resistance Measuring System (DRMS). • Influence of penetration and rotational speed on drilling results. • Influence of penetration and rotational speed on correlations between UCS and drilling results. • Correlations between the mean of the drilling forces and the depth of cut per revolution. • Comparison between regression models developed using DRMS at a constant and variable depth of cut. The paper investigates the influence of the user-controlled variables on the results of the drilling test (DRMS) performed on lime mortars used for ancient buildings restoration. In particular, the ratio of the penetration and rotational speed (δ), namely the depth of cut per revolution, is considered. The experimental results show a relevant variation in the shapes of the drilling profiles with δ, especially in mortars with lower strengths. The efficacy of the regression models between the uniaxial compressive strength (UCS) and the drilling results changes with the depth of cut. An optimal range of δ to perform the DRMS test is identified for the analyzed mortars. The paper also investigates the possibility of performing the DRMS test according to another procedure poorly studied in the literature to evaluate the UCS of materials. It consists of making more holes in the same material at different values of δ. This method is based on the analytical and experimental results obtained with another scratching technique, the scratch test. The statistical analysis of results shows that the correlation between the mean of the drilling forces and δ can be described by linear regression in a limited range of δ. The slope of the linear regression has a high correlation with UCS. The obtained positive results move to deepen the experimental research on this topic. [ABSTRACT FROM AUTHOR]

[Display omitted] • PG improves the long-term compressive strength, the water resistance, and the microstructure of MOSC. • PG inhibits the crystallization of Mg(OH) 2 and promotes the formation of 5·1·7 phase. • Immobilization rates of MOSC on toxic elements in PG are ranked as P ≥ Cu ≥ Pb ≥ F. • PG-MOSC has the potential of environmental sustainability because of its low carbon emissions and efficient toxic fixation. Phosphogypsum (PG), an industrial waste containing phosphorus, has resulted in accumulation and environmental pollution because of its shallow utilization rate worldwide. In this paper, unpretreated PG is incorporated into magnesium oxysulfate cement (MOSC) as an insert fine aggregate at different dosing levels. The performance of the resulting mortar is evaluated by testing workability, volume stability, mechanical properties, water resistance, and sustainability. Results show that PG improved the water resistance, the long-term compressive strength, and the microstructure of MOSC. XRD/Rietveld analysis and TG-DSC demonstrated that the incorporation of PG inhibited the crystallization of Mg(OH) 2 and promoted the formation of 5 Mg(OH) 2 ·MgSO 4 ·7H 2 O (5·1·7 phase). Besides, some PG undergoes morphological changes that may disrupt the strength of MOSC. PG-MOSC has the potential for environmental sustainability because of its low carbon emissions and efficient toxic immobilization. The paper provides ideas and a reference for the resource utilization of PG. [ABSTRACT FROM AUTHOR]

Applying conductive cement-based anode is one of the commonly used methods to achieve uniform electrochemical protection for concrete structures. However, anodic acidification is a critical challenge limiting the effectiveness of electrochemical protection in concrete. Therefore, carbon fiber (CF) and expanded graphite (EG) were used in the current study as conductive materials to reduce the resistivity of cement-based anode by creating a "multi-scale" conductive grid within the anode, while slag powder was employed to enhance the anode resistance to chloride intrusion. This paper investigated the influence of slag powder on the mechanical properties, resistivity, and hydration products of carbon fiber-expanded-graphite conductive mortar (CECM) anodes. The results indicated an inverse relation between the slag powder content and the mechanical properties and resistivity of cement-based anodes. In general, the optimal dosage of slag powder is 20%, at which the compressive strength and resistivity of CECM decrease by 14.8% and 2.75%, respectively. Furthermore, a cubic function relation could be applied to correlate the slag powder content to the mechanical properties and electrical conductivity of the anodes. CF, EG, and slag powder created a composite structure within the hardened cement paste, and formed a multi-scale conductive grid that reduced the cement mortar's resistivity. Through XRD and FT-IR tests, it was found that during the testing period, the pozzolanic effect of slag powder was insufficient to compensate for the loss of strength resulted from the reduced amount of cement clinker. In addition, TGA-DTG results showed that the total amount of C-S-H in Group A increased from 14.31% to 22.86%, while in the Group B this amount increased from 20.74% to 25.94%. The optimal group had an increase from 20.21% to 24.59% in C-S-H content. These results confirm the similar hydration effect of slag powder on EG cement slurry compared to that on ordinary cement. It also indicates that the chloride ion resistance of cement-based anodes can be enhanced through the pozzolanic effect of slag powder, ultimately achieving long-term stable operation of cathodic protection system. • Slag powder is used to modify CECM. • Slag powder particles distributed in multi-scale conductive grids interlaced with EG and CF. • Quadratic surface can reflect the relation of Slag powder content and CECM's compressive strength and resistivity. • Slag powder's "secondary hydration" does not compensate for the strength loss caused by its "dilution effect". [ABSTRACT FROM AUTHOR]

Radiant floors' performance is highly dependent on the thermal properties of the heat transfer medium embedding the hydronic piping system for heating and cooling, which for wet construction is often a mortar. The objective of this paper is to study the effect that latent heat storage capacity and improved thermal conductivity have on the thermal performance of Radiant Floor Systems (RFS). To that end, two innovative mortars were developed: one incorporating Phase Change Materials (PCM); and another incorporating a dense by-product of the steel industry. The first mortar aims to provide the RFS with thermal energy storage capacity and the later has the goal of improving the mortar's thermal conductivity by incorporating this high-density aggregate into its composition. The methodologic approach comprises the characterization of the thermophysical properties of the mortars developed, as well as the subsequent application of the selected compositions into an experimental RFS apparatus to evaluate the thermal performance under continuous and intermittent heating. The selected mortar incorporating microencapsulated PCM (mPCM) exhibited a mechanical strength loss of 68.1% (compressive strength) and 47.5% (flexural strength) in relation to the reference mortar, thermal conductivity of 0.33 W·m−1·K−1 and specific heat capacity of 1222 J·Kg−1·°C−1. The selected mortar incorporating high-density aggregates revealed a reduction of 16.1% for compressive strength and an increase of 10.0% of flexural strength, in relation to the same reference. Its thermal conductivity resulted of 0.87 W·m−1·K−1 and specific heat capacity of 379 J·Kg−1·°C−1. The thermal behaviour of the RFS specimens revealed the potential of incorporating mPCM into RFS, when intermittent heating relying on night-time operation is adopted, considering the maximum temperature fluctuation of 4.02 °C (PCM-RFS). Mortars with high conductive matrixes portray suitable solutions for quicker thermal responses, exhibiting heating rates of up to 9.6 °C·h−1, if followed by a continuous heating strategy with lower supply water temperatures. • Development of mortar incorporating microencapsulated PCM for radiant floor systems. • Incorporation of steel industry by-product into mortar for increased thermal conductivity. • By-product increased the mortar thermal conductivity and mechanical performance. • PCM resulted beneficial when intermittent heating is used for radiant floor systems. • Mortars with higher thermal conductivity resulted in higher heating and cooling rates. [ABSTRACT FROM AUTHOR]