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

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

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

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

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

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

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]

• 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]

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]

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]

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]

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

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]

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]

Sustainability growth in the infrastructure field demands the need for environmentally friendly construction without compromising its structural properties. In this paper, a durable rubberized geopolymer mortar was developed by using the eggshell catalyzation technique. In order to enhance the interfacial bonding of rubber aggregates with the potassium-based geopolymer mortar, the eggshell catalyst was employed as a natural surface modifier. The developed eggshell catalyzed rubber was used to replace 5% by weight of the fine aggregate system and the sustainability of the rubberized geopolymer mortars was studied by assessing the strength and durability characteristics. From the results, it was inferred that the eggshell catalyst transformed the rubber surface into highly hydrophilic and showed a water contact angle of 10°. The trans-esterification process induced by the eggshell-catalyzed rubber aggregates resulted in 10% improved workability and 98.8% recovery in compressive strength of the rubberized geopolymer mortar. Also, due to the formation of secondary gels around the eggshell-catalyzed rubber, the geopolymer mortar becomes denser which prevents the intrusion of foreign ions and showed a 27.9% change in mass under sulphate attack and 33.86 MPa residual compressive strength after 90 days of acid immersion. This attributed the rubberized geopolymer mortar with eggshell catalyzation process to maintain its structural integrity even in the aggressive chemical environment for the feasible applications of deck slab, piers, underground pipe construction, etc. • Sustainable usage of eggshell catalyst for the reuse of rubber aggregates. • Excellent hydrophilicity from trans-esterification reaction. • Cleaner Production of green mortar with eco-friendly alternative aggregate system. • Efficiency of natural surface modifier through aggressive environmental assessment. • 98.8% recovery in strength and maintains structural integrity at chemical exposure. [ABSTRACT FROM AUTHOR]

Recycled aggregate (RA) is a product of construction and demolition wastes, and RA particle presents low strength and adhesion with asphalt mortar compared with natural aggregate. With the aim of studying fracture characteristics of recycled aggregate asphalt concrete (RAAC), the influence of RA on interfacial zone failure should be evaluated. In this paper, RAAC with different RA percentages and gradations were prepared, and a semi-circular bending test (SCB) was employed to assess the fracture behavior of RAAC specimens. Meanwhile, strain distributions during the fracture process were measured by digital image correlation (DIC). To understand the influence of RA on fracture characteristics of RAAC, the microstructural finite element models (FEM) were established, in which natural aggregate and RA particles were reconstructed, respectively. Zero-thickness cohesive zone elements (CZM) were inserted into continuum elements so that the failure of the interface zone between asphalt mortar with different aggregate particles could be investigated. Results indicate that RA presents a significant impact on the fracture response of the asphalt mixture, and the fracture resistance of RAAC attenuates significantly as the RA percentage exceeds 50%. The aggregate-asphalt mortar interface is the first choice in competing fracture paths inside RAAC. The cement mortar-asphalt mortar interface (CAI) exhibited more significant damage than the bulk fracture within the asphalt mortar (AMI) and natural aggregate-mortar interface (NAI). Also, the damage proportion of CMI increases with RA percentage and the maximum nominal particle size of RAAC. This study shows FEM considering different types of interfacial zone provides an effective method to evaluate the fracture characteristics of RAAC. • Low-temperature fracture performance of asphalt mixture containing recycled aggregates was investigated. • The influence of RA on interfacial damage in RAAC under low-temperature fracture was quantified. • The competition mechanism of crack initiation and developing paths inside RAAC was obtained. [ABSTRACT FROM AUTHOR]

To facilitate the use of geopolymer materials in shotcrete applications, this study presents the development of a geopolymer mortar and explores its flowability and early-stage mechanical properties. Firstly, 15 groups of geopolymer mortar specimens with 3 liquid-binder ratios (0.70, 0.75 and 0.80) and 5 binder-aggregate ratios (0.225, 0.250, 0.275, 0.300 and 0.325) were developed. Secondly, the P-wave velocity, slump, early-age compressive strength and compressive strength were obtained by ultrasonic pulse velocity test, slump test and uniaxial compressive test. Thirdly, discussion on the effect of liquid-binder ratio and binder-aggregate ratio on P-wave velocity, flowability, compressive strength and early-age compressive strength of geopolymer mortar were carried out. Finally, an optimal mix proportions rang of geopolymer mortar materials that meet the requirements of wet shotcrete technology were proposed. The results show that P-wave velocity, slump, early-age compressive strength and compressive strength increase as the increasing of liquid-binder ratio. The slump, compressive strength and P-wave increase as the increasing of binder-aggregate ratio. Moreover, the optimal binder-aggregate ratios were proposed as 0.244 - 0.321, 0.228 - 0.298, and 0.209 - 0.241 for geopolymer mortar with a liquid-binder ratio of 0.70, 0.75 and 0.80, respectively. Geopolymer mortar in these mix proportions achieves compressive strengths ranging from 28.4 MPa to 41.1 MPa after curing for 1 day and 44.2 MPa to 55.4 MPa after curing for 28 days. The mix proportion of geopolymer mortar proposed in this paper can simultaneously meet the standard requirements for mechanical properties and flowability, demonstrating potential for wet shotcrete applications. • A mortar for shotcrete application has been developed using geopolymer as the primary material. • The effects of liquid-binder and binder-aggregate ratios on mortar properties were investigated. • Flowability and early-age mechanical properties of the developed mortar were comprehensively analyzed. • An optimal mix proportion range was proposed for effective use in geopolymer shotcrete applications. [ABSTRACT FROM AUTHOR]

In order to promote the resource utilization of phosphorus tailings and reduce carbon emissions of building materials industry, the effects of four kinds of phosphorus tailings with different fineness on the water requirement of cement standard consistency, setting time, cement mortar consistency, mechanical strength and shrinkage properties were discussed in this paper. The concentration of some ions in the leach solution of phosphorus tailings with different fineness was determined. The effects of phosphorus tailings fineness on the hydration process and hydration products of cement were analyzed by heat of hydration, IMP, XRD and SEM. The results show that with the average particle size of phosphorus tailings increasing from 15 µm to 30 µm, the initial setting time of phosphorus tailings cement composite slurry is shortened by 120 min, the consistency of phosphorus tailings cement composite mortar is reduced by 4 mm, and the 28-day compressive strength is reduced by about 8 MPa. The ion concentrations of Ca2+, Mg2+ and F- in the leaching solution increased with the decrease of the fineness of the phosphorus tailings, but the concentration of PO 4 3- ions changed little. Fine phosphorus tailings increase the total amount of heat release from hydration of cement slurry, and promote the emergence of new phase hydration products hydrotalcite minerals. • The dissolution of Ca, Mg, P, and F increases with the decrease of fineness. • Phosphorus tailings delay the hydration of cement. • Fine particles of phosphorus tailings have filling effects and induce nucleation. • The hydrotalcite appeared in the later hydration stage of composite slurry. [ABSTRACT FROM AUTHOR]

Nanomaterial integration in building materials has become a pivotal approach to provide cementitious composites with dual functionality, namely photocatalytic and antimicrobial attributes, conferring self-cleaning and anti-polluting characteristics to these materials. We conducted a systematic literature review on the photocatalytic and antimicrobial properties of ZnO-NP in construction materials, selecting all articles from the last 5 years. We performed a search on the Web of Science and 25 articles were selected consistent with the study purpose, after the filtration process aligned with PRISMA guidelines. This is the first article on this topic using a methodological review, covering all recent literature and the most cited articles from recent decades. Although the volume of articles is still limited, it was possible to identify the most efficient percentages of ZnO-NP in different construction materials (paint, mortar, concrete, wood, others). The main applications, challenges, and themes for future research are discussed to produce safer and more sustainable materials and with potential to be used in the civil construction industry. [Display omitted] • Application of ZnO-NP in building materials is reviewed. • Antimicrobial and photocatalytic potential was summarized. • ZnO-NP helps to creation of building materials that provide safer environments. • This paper aims to encourage and promote the use of ZnO-NP in building materials. [ABSTRACT FROM AUTHOR]

The geometric tortuosity of pores is a critical parameter for assessing the transport characteristics of eroding agents in concrete. Based on the porous, multiphase, and multiscale features of concrete composite materials, this paper establishes a model for geometric tortuosity of pores in concrete composite materials, correlating it with water-cement ratio, volume fraction and shape factor of aggregates, and quantitative analysis is conducted on the influencing factors of tortuosity. The results demonstrate a close alignment between the developed geometric model and experimental results obtained through Mercury Intrusion Porosimetry (MIP). The quantitative analysis reveals that the geometric tortuosity of pores in concrete composite materials increases with an increase in aggregate shape factor and aggregate volume fraction, while it decreases with an increase in water-cement ratio. For instance, as the aggregate shape factor increases from 1.0 to 3.0, the tortuosity of mortar increases from 8.42 to 25.28, and the tortuosity of concrete rises from 10.41 to 93.69. Similarly, as the water-cement ratio rises from 0.2 to 0.6, the tortuosity of hardened cement paste, mortar, and concrete decreases from 13.68, 18.22, and 29.33 to 7.23, 9.42, and 14.76, respectively. Furthermore, an increase in aggregate volume fraction from 0.1 to 0.5 leads to an increase in the tortuosity of mortar from 12.29 to 13.79 and the tortuosity of concrete from 18.08 to 22.76. • A model proposed for the geometric tortuosity of concrete. • A model reflected the time-varying characteristics of concrete microstructure. • A close alignment between the developed geometric model and MIP test results. [ABSTRACT FROM AUTHOR]

In order to better apply basalt powder to supplement cementitious materials (SCMs), this paper chooses the content of basalt powder, fly ash and slag as the influencing factors, and the early strength (3d, 7d) and long-term strength (28d, 60d) of mortar as the evaluation index of SCMs. Based on the response surface and multi-objective optimization method, the Box-Benken experimental design method was used to study the influence of physical and chemical superposition between various factors on the strength development and optimize the ratio.The low-field nuclear magnetic resonance technique was used to detect the water change and porosity difference between the reference group and the optimization group at each age. The results show that the content of stone powder and fly ash has a significant effect on the early and long-term strength, the slag only has a significant effect on the early strength, the interaction between the three has no significant effect on the early and 60 d strength, and the interaction between stone powder and slag has a significant effect on the 28 d strength. The optimal compatibility of basalt stone powder-assisted cementitious materials is stone powder (10%), fly ash (5%), and slag (25.11%). Under this mix ratio, the strength activity index of mortar at each age meets the requirements. In the early hydration process, the physical filling effect of supplement cementitious materials such as stone powder in the optimization group can better optimize the pore structure inside the slurry, and the strength improvement is slower than that of the reference group. In the later stage of hydration, the number of hydration products in the optimized group increased, and the strength increased significantly, which was closer to the strength of the benchmark group. • Rational use of solid waste; • Reduce the amount of cement. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to design a stone filled with cement stabilized macadam (SFCSM) considering shrinkage resistance and easy construction. The corresponding mix proportion design method for SFCSM was proposed. The skeletal coarse aggregates in SFCSM adopt the particle size frequently applied in engineering practice to facilitate construction. In the mix proportion design, the compressive strength test and compaction test were employed to progressively ascertain the optimal blend ratio of coarse aggregates, cement binder, and cement mortar. The vibratory mixing technology (VMT) was introduced to optimize the production of SFCSM. Further, the strength, modulus and shrinkage properties of SFCSM were also evaluated and validated in comparison with the common CSM. The results of the study illustrate that the skeletal coarse aggregates generate the skeletal structure and the role of the filling fine aggregates enhances the stability of the skeletal structure, thus improving the integrity of the mixer. The bonding effect and hydration level of cement in SFCSM is lower than that of the common CSM. The compressive and tensile strength of SFCSM is lower than that of the common CSM. However, the SFCSM has better resistance to dry shrinkage than CSM. The SFCSM as the base is located between the flexible base and the semi-rigid base in the pavement structure design. In addition, the VMT can improve the mixing uniformity of SFCSM and increase its strength. In summary, this study provides inspiration for the shrinkage resistance and practical engineering application of SFCSM. • The mix design method of SFCSM was proposed considering shrinkage resistance and easy construction. • The vibratory mixing technology (VMT) was introduced to optimize the production of SFCSM. • The material properties of SFCSM were evaluated and validated in comparison with ordinary CSM. • The SFCSM has high compressive strength, excellent shrinkage resistance and easy construction. [ABSTRACT FROM AUTHOR]