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This study focuses on improving the mechanical properties and microstructure of cement-based materials, which are crucial for the durability and safety of construction projects. Conventional cement, although commonly used, has certain limitations in terms of its mechanical strength and durability. Therefore, there is a requirement for innovative methods to enhance these properties. This study investigates the potential of nano-TiO2 (titanium dioxide) as an additive to overcome these limitations. The objective of this research is to perform a thorough experimental analysis to examine how different concentrations of nano-TiO2 impact the mechanical performance and microstructural changes in cement paste and mortar. The study examines the influence of nano-TiO2 on the compressive and flexural strengths of cementitious materials. It also explores how nano-TiO2 modifies the microstructure to enhance compactness and resilience. The results suggest that incorporating nano-TiO2 into cement leads to a substantial improvement in both compressive and flexural strengths. This enhancement is particularly notable when the nano-TiO2 concentration is at an optimal level of 1.0% by weight. The SEM and XRD analyses demonstrate that this concentration enhances the microstructure by decreasing voids and facilitating the development of C-S-H crystals. However, excessive concentration may have negative consequences, such as the creation of extra empty spaces. The results indicate that nano-TiO2 has considerable promise in enhancing cement-based materials, thereby aiding the advancement of construction materials that are more long-lasting and effective. This study contributes to the knowledge of how nano-TiO2 improves cement and emphasizes its potential uses in the construction sector. [ABSTRACT FROM AUTHOR]

Machine learning (ML) methods have become increasingly prominent for predicting material and structural performance in civil engineering. However, these methods often require repetitive iterations and optimizations by professionals to obtain an optimal model, which are time‐consuming and challenging for nonexpert users. In this paper, we propose an automated ML (Auto‐ML) model using the tree‐based pipeline optimization tool (TPOT) to address these limitations and streamline the performance prediction process. TPOT leverages genetic programming to optimize various ML models, including DT, RF, GBDT, LightGBM, and XGBoost, and to search possible models that fits a particular dataset, which cuts the most tedious parts of ML. To demonstrate the effectiveness of TPOT‐based Auto‐ML, two case studies are presented by using TPOT‐based Auto‐ML algorithms to construct prediction models for compressive strength of recycled micropowder mortar, and punching shear bearing capacity/failure mode of RC slab‐column joints. To explain the "black box" of Auto‐ML, Shapley Additive Explanation (SHAP) is introduced to interpret the best predictive models and rank the importance of influencing factors, providing a basis for material and structural design. Finally, a user interface (UI) for engineering applications is developed which enables end‐to‐end automation from data preprocessing to predictive results presentation. [ABSTRACT FROM AUTHOR]

AbstractThe objective of this study is to investigate the potential of combined pond fly ash (PFA) and flue gas desulfurization gypsum (FGDG) as a partial replacement for cement by mixing them with fine river sand for green mortar development. We studied the physical, mechanical, and microstructural properties of mortars by using techniques such as scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM-EDXS) and X-ray diffraction (XRD) for chemical component identification of the hydrated phase. These experimental results show that mortar containing pond fly ash, FGDG, and cement concentrations of 5 wt%, 5 wt%, and 90 wt% yields the maximum compressive strength (8.9 MPa) and flexural strength (3.4 MPa) after 28 days. This mortar has 12.6% higher compressive strength and 48% lower shrinkage in comparison with control specimens. A reduction in shrinkage is attributed to the denser structure of the mortar, as the calcium silicate hydrate (C–S–H) gel is found to exist in the SEM image and also identified through XRD studies. It is also concluded that excessive ettringite formation causes expansion in the volume of mortar, voids formation, and results in the reduction of strength. The application of this mortar can be in the internal plaster, bricks, and masonry. [ABSTRACT FROM AUTHOR]

The integration of organic wastes into cement-based materials shows promise as a solution to mitigate environmental pollutants. It achieves this by minimizing waste sent to landfills and in some conditions decreasing Portland cement use. One of these organic wastes that produces positive effects when used in cement products is olive seed. In this study, the effect of a new generation bio-polymeric admixture on the physical and mechanical properties of cement mortars is examined in detail. The bio-polymeric admixture is prepared by grinding olive seeds in 0/125 μm sizes. The olive seeds have been used as bio-polymeric admixture in cement mortars at different rates, i.e., 0, 0.2, 0.35, 0.5, 1 and 1.5% of total weight. The olive seed is characterized by XRD, FT-IR analysis and by determining extracts, pectin, cellulose, hemicellulose and lignin content. The characteristics of hydration products were analyzed by SEM/EDS and XRD investigations. Effect of bio-polymeric admixture addition on the unit weight, flowability, setting time, compressive and flexural strength and capillary water absorption was analyzed. The results suggested that the bio-polymeric admixture hindered the cement hydration at low usage rates but promoted at high usage rates. Accordingly, 28 days compressive and flexural strength of test samples decreased. However, 1.5 wt% bio-polymeric admixture was associated with a slight increase of 150-days compressive strength. Bio-polymeric admixture improves the hydrophobicity property of the hardened mortar samples by declining effect on the water absorption. Another important effect of the bio-polymeric admixture contribution was also observed on the flowability property of the cement mortars. As the bio-polymeric admixture increased, the flow diameter values of the mortar were also significantly increased. The research outcomes suggested for the first time the beneficial effect of bio-polymeric admixture as a natural and bio-degradable alternative of chemical admixtures on especially flowability, set retarder and hydrophobicity of cement mortars with comparable mechanical properties. [ABSTRACT FROM AUTHOR]

This paper evaluates the flowability and strength properties of alkali-activated mortar produced using silicomanganese fume (SiMnF) as the sole binder, combined with alkaline activators and sand, cured at room temperature (23 ± 1 °C). A total of 18 mixes were prepared by varying binder content (370, 470, and 570 kg/m3), alkaline activator content (33, 43, and 53% of binder by weight), and NaOH concentration (8 M and 12 M). The SiMnF-based alkali-activated pastes were characterized using SEM, XRD, and FTIR techniques to study morphology, mineral composition, and functional groups, respectively. Statistical modeling, including analysis of variance (ANOVA) and response surface method (RSM), was performed to optimize the mixes, and a life cycle assessment was conducted to evaluate the environmental impact of the developed SiMnF-based alkali-activated mortars (SiMnF-AAM). The experimental results showed that an optimal mix design with 470 kg/m3 SiMnF, 43% alkaline activator content, and NaOH concentrations of 8 M and 12 M achieved the best balance of flow and strength. XRD and FTIR analyses confirmed that Nchwaningite was the primary reaction product, with secondary phases including magnetite, manganese ferrite, and potassium feldspar, influenced by alkali concentration. The SiMnF-based mixtures had a significantly lower CO₂ footprint (0.08 kg CO₂/kg) compared to the cement-based mix, with alkali activators being the primary contributors to emissions. The developed SiMnF-AAM mixes, cured at room temperature, exhibited improved workability, mechanical properties, and reduced environmental impact, making them adaptive to real-life applications. [ABSTRACT FROM AUTHOR]

AbstractAs the global population has continued to grow, the costs and environmental issues associated with traditional construction materials like cement and river sand have become increasingly problematic. This study explores the innovative enhancement of early-age mechanical properties of 3D-printable mortar through the incorporation of Styrene-Butadiene Rubber (SBR) latex and kaolin. Various sands (Lawrencepur, Chenab, and Ravi) were tested at 120 min for compressive stress, direct shear strength, Young’s Modulus, and Shear Modulus. Lawrencepur Sand exhibited the highest compressive stress (206.75 kPa) and shear strength (74.60 kPa), followed by Chenab Sand and Ravi Sand. Young’s Modulus values were highest in Lawrencepur Sand (7.93 MPa), indicating superior stiffness, while Shear Modulus was highest in Chenab Sand (3.79 MPa). Ravi Sand, despite lower mechanical strengths, was found optimal for printable mortar due to its fine particle size and desirable texture. The incorporation of SBR latex and kaolin resulted in reduced maximum deflection and enhanced load-bearing capacity over time, with Lawrencepur Sand containing 99.64% sand particles and minimal silt bearing the ultimate load effectively. This study highlights the potential of SBR latex and kaolin in improving the early-age mechanical properties and suitability of sands for 3D-printable mortar, providing a balance between mechanical performance and printability. [ABSTRACT FROM AUTHOR]

The last decade was dominated by a serious problem that now affects all the planet's natural ecosystems: the increasing growth of plastics and microplastics that are difficult to dispose of. One strategy to mitigate this problem is to close the life cycle of one of them—polyethylene terephthalate (PET)—by reusing it within the most common building materials, such as mortars and concretes. The reuse of PET waste as aggregates also allows us to limit the CO2 emissions released during the production of natural aggregates. This paper analyzes the outcomes of many studies carried out on the characteristics of cementitious mixtures reinforced with waste PET material. Many researchers have demonstrated how PET used as reinforcement of mortars and concretes can produce an increase in the mechanical strengths of the corresponding cementitious mixtures without PET. The tensile strength of this resin is higher than that of concrete; so, by combining the two materials it is possible to obtain a mixture with an overall higher tensile strength, resulting in increased flexural strength and reduced cracking. Using an effective size of PET fibers, it is possible to achieve an increase in the ductility and toughness of the cementitious mixture. Several studies reveal that PET reinforcement reduces the density with a consequent decrease in weight and structural loads, while the workability increases using spherical and smoother PET aggregates. [ABSTRACT FROM AUTHOR]

One of the key trends affecting the future of the construction industry is the issue of ecology; therefore, current activities in construction aim to reduce the use of raw materials, which is made possible by including recycled materials in composites, among other methods. This article describes the results of tests conducted using four types of epoxy composites, i.e., composites modified with waste rubber (WR), composites modified with waste polyethylene (PE) agglomerate, glycolysate obtained using polyethylene terephthalate (PET) waste, and control unmodified mortars (CUM). Selected properties of the mortars were monitored during their maturation under laboratory conditions, as well as after post-curing at elevated temperatures in the range of 60 °C–180 °C. With the increase in the reheating temperature, an increase in the flexural strength of all types of mortars was noted, with the highest more than twofold stronger than the unmodified composites. The compressive strength increased up to a temperature of 140 °C, and then decreased slightly. The highest value of 139.8 MPa was obtained using PET mortars. Post-curing also led to a slight loss of mass of all samples in the range of 0 to 0.06%. Statistical methods were employed, which made it possible to determine the post-curing temperature and composite composition for which the determined properties are simultaneously the most beneficial, especially for the prefabricated elements. [ABSTRACT FROM AUTHOR]

This paper investigates the effects of the partial replacement of natural hydraulic lime (NHL) with waste glass powder (GP) on the physical, mechanical, and microstructural properties of NHL mortars. In the experimental study, five mixtures containing up to 50% GP were prepared to evaluate its effect on the flow, carbonation, unit weight, water absorption, porosity, ultrasonic pulse velocity, capillary water absorption, compressive strength, and microstructure of NHL mortars. The experimental results suggest that the partial replacement of NHL with GP significantly affects the properties of NHL mortars. A reduction in compressive strength was observed with increasing GP content in mortars at both early and later stages. Nevertheless, the compressive strength difference between samples containing 50% GP and the reference was found to be relatively minor at 91 days, implying an enhanced pozzolanic reaction over time. The incorporation of GP improved the consistency and capillary water absorption of mortars, while the opposite was observed for ultrasonic pulse velocity, porosity, and water absorption. The microstructural analysis revealed distinct changes in the structure of samples incorporating GP. The partial substitution of hydraulic lime with GP could be beneficial in reducing the CO2 emissions of NHL mortars. [ABSTRACT FROM AUTHOR]

Reducing energy consumption in the building sector has driven the search for more sustainable construction methods. This study explores the potential of cork-modified mortars reinforced with basalt fabric, focusing on optimizing both mechanical and hygroscopic properties. Six mortar mixtures were produced using a breathable structural mortar made from pure natural hydraulic lime, incorporating varying percentages (0–3%) of cork granules (Quercus suber) as lightweight aggregates. Micro-computed tomography was first used to assess the homogeneity of the mixtures, followed by flow tests to evaluate workability. The mixtures were then tested for water absorption, compressive strength, and adhesion to tuff and clay brick surfaces. Adhesion was measured through pull-off tests, to evaluate internal bonding strength. Additionally, this study examined the relationship between surface roughness and bond strength in FRLM composites, revealing that rougher surfaces significantly improved adhesion to clay and tuff bricks. These findings suggest that cork-reinforced mortars offer promising potential for sustainable construction, achieving improved hygroscopic performance, sufficient mechanical strength, internal bonding, and optimized surface adhesion. [ABSTRACT FROM AUTHOR]

The widespread adoption of geopolymer concretes in the industry has been slow, mainly due to concerns over their long-term performance and durability. One of the main causes of concrete structures' deterioration is chloride-induced corrosion of the reinforcement. The reinforcement corrosion process in concrete is composed of two main stages: the initiation phase, which is the amount of time required for chloride ions to reach the reinforcement, and the propagation phase, which is the active phase of corrosion. The inherent complexities associated with the properties of precursors and type of activators, and with the multi-physics processes, in which different transfer mechanisms (moisture, chloride, oxygen, and charge transfer) are involved and interact with each other, have been a major obstacle to predicting the durability of reinforced alkali-activated concretes in chloride environments. Alternatively, the durability of alkali-activated concretes can be assessed through testing. However, the performance-based tests that are currently available, such as the rapid chloride permeability test, the migration test or the bulk diffusion test, are only focusing on the initiation phase of the corrosion process. As a result, existing testing protocols do not capture every aspect of the material performance, which could potentially lead to misleading conclusions, particularly when involving an electrical potential to reduce the testing time. In this paper, a new performance-based test is proposed for assessing the performance of alkali-activated concretes in chloride environments, accounting for both the initiation and propagation phases of the corrosion process. The test is designed to be simple and to be completed within a reasonable time without involving any electrical potential. [ABSTRACT FROM AUTHOR]

In the construction area, as well as in the restoration of old and historical buildings, different metallic materials are frequently in contact with gypsum plaster. Due to the high porosity of gypsum plaster, and particularly in high relative humidity environments, the risk of corrosion exists. In the present work, carbon, galvanized and stainless steel, as well as copper, were embedded in gypsum plaster (with varying water/gypsum ratios) and exposed to different environmental conditions, and the corrosion rate was assessed by electrochemical techniques. Stainless steel showed very low corrosion rates, carbon and galvanized steel showed considerable corrosion rates, and copper showed moderate corrosion rates. The higher the humidity, the higher the corrosion rate, independently of the water/gypsum ratio. A comparison with results obtained for the same materials embedded in mortar was performed. Except for stainless steel, the corrosion rates obtained in gypsum are higher than those obtained in mortar, being this difference up to two orders of magnitude. The differences in the pH of both matrices explained the lower corrosion rates measured in mortar. [ABSTRACT FROM AUTHOR]

Ground granulated blast-furnace slag (GGBFS) is well known to be capable of improving the performance of cement-based materials, but few studies focus on the impact of its large dosage on concrete containing basalt powder. In this study, the compressive strength and chloride permeability of cement-based materials with compound mineral admixtures (CMAs) containing high-volume GGBFS, basalt powder and desulfurisation gypsum were investigated. The results showed that the mortar strengths at 3, 7 and 28 days decreased with increasing GGBFS content, but that at 56 and 84 days increased with the addition of 45 wt% GGBFS. This is because the activity of GGBFS at an early stage has not been stimulated and the pozzolanic effect is exerted at a later stage. Moreover, cement replacement with up to 55 wt% GGBFS caused a significant decrease in the chloride diffusion coefficient of the mortar and concrete. Furthermore, the incorporation of GGBFS led to a remarkable refinement in pore structure of the hardened paste due to pozzolanic and filler effects. Therefore, the partial replacement of cement with high CMA contents (≥70 wt%) in concrete is desirable for ocean projects requiring low chloride permeability, and significantly reduces carbon dioxide emissions. [ABSTRACT FROM AUTHOR]

The characteristics of shotcrete can lead to significant shrinkage deformation, presenting potential threats to tunnel structure safety. To research this concern, in this study the effects of three accelerators on the volume stability of cement paste, cement mortar and concrete were investigated. The correlation equations of the shrinkage deformation of cement paste, cement mortar and concrete were established, and the drying shrinkage prediction model of cement mortar with accelerator was constructed by combining the ACI 209 model and the GL2000 model. Findings from this study show that the liquid alkali accelerator AR had the greatest autogenous shrinkage and drying shrinkage, with the highest mass loss under drying conditions. The study demonstrated that there exists a good linear relationship between the shrinkage deformation of cement paste, cement mortar and concrete with accelerator. Finally, the proposed prediction model for drying shrinkage of cement mortar exhibits strong predictive capabilities. [ABSTRACT FROM AUTHOR]

Cracks in concrete structures are generally initiated due to the shrinkage i.e. the volume change characteristics of the concrete structures. In this experimental study, effects of the mix parameters related to alkaline liquid (AL) and recycled fine aggregate (RFA) on the shrinkage behaviour of environment-friendly mortar mixes produced with fly ash (FA)-based geopolymer binder and RFA were investigated and reported. To find out the effects of AL, concentration of liquid sodium hydroxide (LSH) was varied from 6M to 16M, ratio of liquid sodium silicate (LSS) to LSH in AL was varied from 1.0 to 2.5 and AL/FA ratio was considered as 0.4 and 0.6. Different fly ash-based geopolymer mortar mix were produced depending on above-said combinations of mix parameters along with the RFA content (by weight) of 10%, 20%, 30%, 40% and 50% in lieu of natural fine aggregate. Prismatic specimens (25 mm × 25 mm × 285 mm) were cast and cured at ambient air temperature to determine the shrinkage behaviour. Higher RFA content in mix, higher LSS/LSH ratio in AL and higher AL/FA ratio resulted in higher shrinkage value. But, lesser shrinkage value was noticed for those specimens of mortar mix with the consideration of higher concentration of LSH in AL with varying RFA content. [ABSTRACT FROM AUTHOR]

In the frame of the Venezia2021 project the private 'Byzantine house' designed by Giuseppe Torres in 1905 was chosen as the emblematic architectural site which marks Venice's transition towards modernity, requiring study of its conservation in the lagoon environment of the city of Venice. In conjunction with the definition of a specific Path of Knowledge of the ground floor, a series of stone and lithoid materials as well as their related deterioration products from the interior rooms were sampled for analysis. The investigations covered a wide range of materials (plasters, mortars, natural and artificial stones, bricks, glass and finishings). They were carried out by means of a multi-analytical approach comprising SEM-EDX and optical microscopy; XRPD; XRF, ion chromatography; and Raman and infrared (FTIR) spectroscopies. The stones identified are linked to the Venetian architectural tradition (Euganean trachyte and Istrian stone). The sands in the mortars are mainly of regional origin and the glass is compatible with traditional Venetian (Murano) recipes. Of particular interest is the presence of an intonachino charged with ground fluorite. The deterioration products are linked to the extensive and intense phenomenon of capillary rising damp and efflorescence deposition induced by the lagoon environment. [ABSTRACT FROM AUTHOR]

The influence mechanism of waste rubber particles (WRPs) on the workability, mechanical properties, and sound insulation performance of recycled aggregate sound insulation mortar (RCM) were investigated. According to the principle of volume fraction replacement of recycled fine aggregate by 0 to 50%, WRPs with a particle size of 1–4 mm were incorporated in various mixtures of RCM. Each RCM mixture was tested for workability, mechanical, and sound insulation performance. Mercury intrusion porosimetry was used to analyze the distribution of pores and their sizes inside the material, and X-ray diffraction and scanning electron microscopy were used to analyze the characteristics of the interfacial transition zones (ITZs) between the rubber particles and the cement paste. The results showed that, owing to the hydrophobicity of WRPs, greater WRPs content led to greater fluidity of the mortar mix and a smaller water retention rate. Notably, the rubber in the mortar did not contribute to the hydration reactivity of the cement paste, but it changed the crystal morphology and pore structure of ITZ hydration products. The RCM incorporating 3–10% WRPs produced the optimal pore structure through the aggregate effect, which increased its overall compactness and mechanical performance. Further increase of WRP content significantly improved the sound insulation performance while significantly reducing the strength. Moreover, there was a clear logarithmic relationship between the strength and impact sound level index. This new knowledge can be used to prepare RCM that meets the actual strength and sound insulation requirements of the floor. Thus, the resource utilization of solid waste can be expanded. [ABSTRACT FROM AUTHOR]

In this study, geopolymers (GMs) were produced using basalt fiber, polyamide fiber, and polypropylene fiber-reinforced and ground blast furnace slag (GBFS) waste ceramic powder (WCP). In the initial phase of the study, the optimal ingredient proportions were identified, and an ideal geopolymer was selected based on its highest compressive strength. Subsequently, at the second stage of the study, various fibers with differing proportions were incorporated into the ideal geopolymer, and the resulting properties were evaluated through laboratory testing. In the third stage, the optimal GMs were determined through a holistic approach, employing a multi-criteria decision-making method. A total of ten mixtures, comprising 23 properties (230 parameters in total), were subjected to a multi-criteria decision support method (TOPSIS). The optimal GM mixture with the proportions and suitable components was identified. The findings indicated that a 20% substitution of WCP with GBFS resulted in an optimal and cost-effective mixture in a 10 M NaOH solution, serving as a reference point or ideal unreinforced mixture in this research. With regard to the addition of fibers, all three types of fibers were observed to enhance the compressive, flexural, and splitting tensile strength of the WCP–GBFS-based GM. Maximum compressive strength was observed to be 60.15 MPa, while the flexural strength was 12.98 MPa and the splitting tensile strength was 3.45 MPa for the polyamide fiber (PA)-reinforced GM. Furthermore, all reinforced GMs exhibited enhanced abrasion resistance, with the inclusion of polypropylene fibers yielding the best results. Additionally, these fiber-reinforced GMs demonstrated significant resistance to high temperatures, even as temperatures increased. The TOPSIS results indicated that PA0.8 was the optimal GM, and its components with suitable components were recommended as a sustainable net zero/low CO2 emission building material. [ABSTRACT FROM AUTHOR]

With the continuous advancement of marine engineering and coral reef construction, the construction process of using coral reefs and sand as aggregate to make concrete or mortar came into being. Therefore, this study delves into the impact of aggregate type, water–cement ratio (W/C), and sand–cement ratio (S/C) on the workability, shrinkage, and mechanical properties of mortar. Simultaneously, it uses microscopic techniques to elucidate the mechanisms underlying the impact of aggregate type, W/C , and S/C on mortar performance. The results demonstrate that the S/C of coral mortar should be controlled at 1.5–2. The self-shrinkage and drying shrinkage values of coral mortar decrease progressively with higher S/C and increase with increasing W/C. Coral mortar exhibits a smaller self-shrinkage than ordinary mortar. Unlike self-shrinkage, the early drying shrinkage of coral mortar is less than that of ordinary mortar. However, as time progresses, the drying shrinkage of coral mortar becomes notably greater than that of ordinary mortar. The flexural and compressive strengths of coral mortar are inferior to those of ordinary mortar. Coral mortar experiences transcrystalline fracture, in contrast to the intergranular failure observed in ordinary mortar. Moreover, strength exhibits a quadratic power function correlation with the S/C and a negative linear correlation with the W/C. In addition, the construction technology for coral mortar differs from that of ordinary mortar. [ABSTRACT FROM AUTHOR]

This research conducted a comprehensive assessment of how aging processes and the powder to binder ratio (P/B ratio) influence asphalt mortar's performance. Analysis demonstrated that all tested performance metrics significantly differed (P<0.05), signifying a notable effect of the aging process, particularly long-term thermal oxidation aging, on key properties such as ductility and the complex shear modulus (G*). Adjusting the P/B ratio enables precise control over the rate of aging and the asphalt mixture's functional characteristics. The optimal P/B ratio, found to be between 0.8 and 1.0, effectively balances aging properties with mechanical strength. Moreover, a detailed analysis of the four main asphalt components shed light on aging's effects on both the composition and functionality of asphalt, highlighting the critical role of component dynamics in designing and assessing asphalt mixtures. Additionally, the study introduces a predictive model that uses linear regression to compute five parameters (β0 to β4), forming equations for various performance metrics. This facilitates optimized selection and combination of asphalt components at the design stage. [ABSTRACT FROM AUTHOR]

This study investigated the potential of incorporating crushed brick powders (CBPs) and hydrated lime (HL) as additives in concrete production. Various tests were conducted on mortar, paste, and concrete samples to evaluate the performance of different blend types. The results reveal that among 3%, 6%, 9%, and 12% HL additive in the cement-CBP blend, 6% HL addition yields a significant increase in compressive strength of up to 16% compared to the control mortar. X-ray diffraction (XRD) and thermogravimetric analysis (TGA) indicate improved hydration and reduced calcium hydroxide content in CBP-blended pastes, particularly in the blend with 6% HL. The concrete blend incorporating crushed bricks (C-CB) with 6% HL (C-CB-6HL) demonstrates superior early strength gain, surpassing the control blend by approximately 2.1% at 28 days and exhibiting the highest compressive strength at 90 days. It also shows enhanced moisture resistance, with a reduction in water absorption percentage of up to 10.6% compared to the control blend, reduced water permeability, improved resistance against chloride permeability, and better durability against acid attack compared to other blends. Overall, the C-CB-6HL blend shows the most promising durability characteristics, highlighting the potential for sustainable concrete production. Its outcomes have implications for shaping technical standards and promoting sustainable practices in the construction industry, aligning with environmental conservation goals. [ABSTRACT FROM AUTHOR]

This paper investigates the impact of chitosan addition on mortar performance during sulfuric acid attack. Twenty-four mortars were prepared using Brazilian portland cements, varying traces, and chitosan dosages ranging from 0% to 3%. Mortar expansion tests were performed to evaluate sulfuric acid attack resistance. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) were performed to evaluate the morphology, XDR was performed to confirm the FTIR results. Chemical structure and bending (3 points) and compressive tests were conducted to evaluate mechanical properties. The study demonstrated that mechanical properties as well the sulfuric acid-attack resistance are sensitive to the biopolymer incorporation, with noticeable effects even at low concentrations, 1% chitosan improves bending strength for CP V-ARI and CP V-ARI-RS in trace A, but decreases it for all cements in trace B, an outcome reflected in SEM images. FTIR results reveal lower levels of gypsum and ettringite formation in mortars with added biopolymer, except for CP V-ARI-RS. Tests on mortar expansion demonstrate that chitosan enhances sulfuric acid attack resistance by reducing mortar expansion by up to 60%. Practical Applications: The degradation of cement-based materials due to sulfuric acid-attack is a significant issue, as it leads to the formation of expansive products that progressively weaken concrete structures and increase its vulnerability to penetration by other substances. This research aims to investigate the impact of incorporating chitosan, a biopolymer, into mortar prisms in terms of sulfuric acid resistance. The study examines changes in mechanical properties, alterations in material structure, and the performance of mortars with and without chitosan when exposed to sulfuric acid attack. Findings indicate that both mechanical properties and resistance against sulfuric acid deterioration are influenced by the addition of biopolymer and chitosan enhances protection from sulfuric acid attack by reducing mortar expansion. This research has application on concrete structures subject to sulfate attacks present on soil and water. So, reservoirs, sewage treatment plants and pipes are some of the practical applications of this study. [ABSTRACT FROM AUTHOR]

This study synthesized a biobased hydrogel from local and renewable raw materials to improve the freeze–thaw resistance of hardened cementitious matrices. A biobased hydrogel was produced by thermal gelatinization process with different cornstarch contents ranging from 1% to 3% of mortar mixing water. The effectiveness of cornstarch hydrogel was gauged by comparing its void structure with those of two commercially available super absorbent polymers (used at 0.2% of cement weight) and an air-entraining agent (0.49% of total mortar weight). The resulting void structures were analyzed by evaluating porosity, void-size distribution, spacing factor, and shape of voids using microcomputed tomography scanning with a sensitivity of 10 μm. The 3% cornstarch hydrogel produced a robust void structure with high porosity and relatively large number of smaller voids. The high porosity was achieved without a significant reduction in compression strength. Furthermore, chemical analysis revealed that the 3% cornstarch hydrogel had a positive influence on the hydration of cement compared with the commercial air-entrainment agent. Overall, the 3% cornstarch hydrogel can be a sustainable biodegradable replacement for traditional and commercial surfactants for air entrainment, and has an additional internal curing advantage. [ABSTRACT FROM AUTHOR]

Inspired by the hierarchical structures and flexible interface of natural nacre, a "fiber-metal-polymer" composed "brick-mortar" structural biomimetic materials with different layout modes and interface characteristics was designed. It shows that, compared with the continuous or random arranged short carbon-fiber reinforced composites, the discontinuous short carbon fiber reinforced nacre-like "brick-mortar" ordered structural composites can improve the stress distribution, failure modes and energy dissipation of the materials by optimizing the topological characteristics of "brick" (e.g. length and lap ratio), introducing flexible interfaces, thus realize the optimal combination of strength and toughness. [ABSTRACT FROM AUTHOR]

This investigation was aimed at finding the optimum replacement level of waste brick powder (WBP) as a partial replacement of cement. For this purpose, three groups of tests are made: fresh, mechanical, and permeation properties. Eight mixes with different percentages of replacing ratios are as follows: 10, 15, 20, 25, 30, 35, 40, and 50%. In addition to the reference mix without powder replacements, the experimental programs include three groups of tests: fresh properties (flow test and fresh density), mechanical properties (dry density, compressive strength, and flexural strength), and transport properties (water absorption ratio, rate of water absorption, i.e., sorptivity, and permeable void ratio). Also, an ultrasonic velocity impulse test was made. The flowability and density of fresh mixes are decreased linearly as the amount of WBP increases for the constant water/binder ratio. However, the density of the in-hardened state was found to be slightly higher than the reference mix for mixes with a brick powder content of up to 20%. Results indicate that strengths for mixes containing WBP are higher than those for the control mix. The highest strength was examined in the mix with 15% WBP for both compressive and tensile strengths of specimens. Generally, the brick powder reduced the ability of mortar to transfer liquid, as was clear from the results of the permeability test results. Empirical relations were proposed according to experimental results. [ABSTRACT FROM AUTHOR]

The American Water Works Association (AWWA) has developed a new standard (ANSI/AWWA C607) for concrete pressure pipe (CPP) installation, expected to be published in early 2025. The standard aims to reduce installation defects and increase the reliability and sustainability of pipelines, covering various CPP materials. Users are responsible for determining if the minimum requirements of the standard are suitable for their specific projects and should provide comprehensive project requirements. The standard also addresses best practices for delivery, handling, trench construction, pipe joint installation, embedment and backfill, corrosion testing, and verification testing to prevent pipeline failures. [Extracted from the article]

The use of seashells as a partial substitute for cement in construction not only offers an innovative solution for marine waste management but also contributes to reducing the carbon footprint of the cement industry, decreasing the CO2 emissions associated with cement production and promoting more sustainable construction practices. This study addresses the mechanical behavior of mortar specimens with partial cement replacement using crushed Biobío region clam shells, both calcined and uncalcined, at substitution rates of 5% and 10%. This approach allows the analysis of their effect on the mechanical strength and properties of the mortar, which has not been widely investigated in the Chilean context or with this particular species of shell. For the mechanical characterization of the specimens, tensile flexural tests and compressive tests were were conducted at ages of 3, 7, 14, and 28 days. The compressive strengths of the samples that incorporated calcined residue with partial cement replacements of 5% and 10% were 83.69% and 78.27%, respectively, of the average strength of 20.97 MPa reached by the standard sample. In terms of their tensile flexural strength, these samples reached average strengths of 104.31% and 104.04% of the strength of 12.12 MPa obtained by the standard sample. In the case of the uncalcined samples, the 5% and 10% replacements reached 103.55% and 102.64% of the tensile strength of 15.54 MPa obtained by the standard sample, while they reached 92.32% and 80.07% of the compressive strength of 27.81 MPa achieved by the standard sample. From these results, it is determined that the calcined shells did not improve the mechanical resistance of the mortar, suggesting that the calcination process must be studied in depth. [ABSTRACT FROM AUTHOR]

The concept of sustainability has become a crucial concern for safeguarding the planet. The current research has focused on developing affordable and eco-friendly mortar by using industrial wastes. This study explores the use of fly ash (FA) and ground granulated blast furnace slag (GGBFS), byproducts of steelmaking and coal burning, in mortar production. It examines their impacts on the compressive strength and setting times, when utilizing varying proportions of the materials. The study also evaluates water requirements for the workability, thus demonstrating the sustainability of these waste products in construction. The cementitious materials were employed in finely ground form and were replaced with further tertiary mixes including both supplements at 10%, 30%, and 50% of each. The mixtures were allowed to cure for 7, 14, and 28 days by immersion in water. The results showed improvements in the compressive strength of mortar samples incorporating FA and GGBFS at various curing ages. However, the water requirement and workability of mortar samples were altered as a result of utilizing these supplementary cementitious materials (SCMs). These findings will serve as a standard for environmentally responsible mortar using GGBFS and/or FA as SCMs. [ABSTRACT FROM AUTHOR]

In the current study, the high-volume replacement of river sand (20%, 30%, 40%, 50%, 60%, 80%, and 100%) by pond ash in cement mortar was considered using a 1∶3 volumetric mix proportion to evaluate the engineering properties, sustainability aspects, and cost of mortar mixes. The compressive strength, tensile bond strength, and adhesive strength increased by 30%, 21%, and 24%, respectively, at 30% replacement and were in line up to 60% replacement as compared with the reference mix. However, the drying shrinkage was observed to increase with volume replacement of river sand. The life-cycle assessment of mixes containing pond ash showed reductions in the environmental impacts. Four different scenarios were considered on the basis of the preference advantage of the indicators. Considering the engineering properties, sustainability aspects, and cost as the primary indicators, the gray clustering analysis showed that the mix with 60% volume replacement exhibited the best performance among the mixes under Scenario S-1, while TOPSIS and VIKOR showed that the mix with 50% volume replacement exhibited best performance under Scenario S-1. Overall, the comparison of all scenarios showed that the mix of 60% pond ash had the best performance followed by the mix with 50% pond ash, irrespective of the multicriteria decision-making techniques and preference advantages. [ABSTRACT FROM AUTHOR]

This paper presents the results of experimental testing of block masonry prisms and wallettes under uniaxial compression. The compressive load was applied in a direction perpendicular or parallel to the bed joints. Masonry prisms and wallettes were tested in the former direction, whereas only wallettes were tested in the latter direction. No influence of mortar strength or block thickness was observed on the cracking and failure patterns of specimens of similar type, although material crushing and spalling was marginally influenced by block strength. The cracking load for the assemblages tested normal to the bed joint was nearly 90% of the peak load capacity and higher as compared to 70% of the peak load capacity for the wallettes tested parallel to the bed joints. Similar load capacity and elastic modulus were observed for the prisms and wallettes tested normal to the bed joints. Whereas the strength for the wallettes tested parallel to the bed joints was 49%–83% less compared to those tested normal to the bed joints, their elastic modulus was nearly 25% higher. The experimental strength and strain values were compared with the existing analytical methods, which correlated well. [ABSTRACT FROM AUTHOR]

In this study, the bulk modification method via incorporating two different types of waterproof admixtures was adopted to make natural hydraulic lime-based mortars more durable. The influence of two admixtures and their dosages on the hydration, physical, mechanical, and aggressive environment resistance properties were evaluated. The correlations between pore and water absorption characteristics, between hydration, pore characteristics, and mechanical strength were interpreted. Results showed that two waterproof admixtures changed the microscopic reaction between different components as well as internal structure of NHL-based mortar. Introduction of silane impregnant improved the workability of natural hydraulic lime-based mortars, and the appropriate dosage of silane impregnant facilitated hydration and improved mechanical strength at 28 and 90 days. Silane impregnant modified mortars were no more hydrophilic, acid resistance was improved while water absorption characteristics were not obviously improved even resulting in degraded freeze-thaw cycle resistance. Introduction of silicon-acrylic latex deteriorated the workability and retarded hydration of natural hydraulic lime-based mortars, regardless of dosage, leading to the degradation of mechanical strength. However, water absorption characteristics and freeze-thaw cycle and acid resistance can get a noticeable improvement when appropriate dosage was adopted. [ABSTRACT FROM AUTHOR]

AbstractThis study comprehensively investigates the literature on using bacteria to confer self-repair abilities on concrete and mortar. Although crack-healing is the main objective, calcite-precipitating bacteria affect concrete’s durability and mechanical properties. This article reviews the research on bacteria-based self-healing concrete and its developments from 1984 to 2023. This systematic review was developed by adhering to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. R studio and Vosviewer were used to perform bibliometric analysis and visualization of the 295 documents by 874 authors affiliated with 97 sources acquired from Scopus (NY). It is vital to emphasise that the document selection was carried out by two impartial reviewers to prevent any bias. In addition to repairing cracks in the material, the data indicate that applying various self-healing bacteria improves concrete’s mechanical and durability properties. A meta-analysis evaluated the summary effect size of the most cited articles. It was concluded with the statistical evidence from the meta-analysis that bacteria incorporated concrete, which shows self-healing efficiency of 5.07 and 7.29 times than that of control concrete. [ABSTRACT FROM AUTHOR]

ABSTRACT Throughout history, architectural heritage has been constructed using masonry, clay or stone elements, and lime‐based mortars. Over time, old buildings are subjected to different degrees of movement and degradation, leading to the formation of microcracks. Water dissolves and transports lime in mortar, but when the water evaporates, the lime is deposited and heals cracks in a process known as autogenous healing. Lime‐based mortars can regain some mechanical properties due to their healing capacity, given certain conditions. In the present work, a constitutive formulation has been developed to simulate cracking and healing in lime‐based mortars. The proposed model captures the residual displacements within cracks, associated with interacting crack surface asperities, as well as the healing effect on mechanical properties. A new approach is described which expresses these mechanisms mathematically within a micromechanical formulation. The proposed model was validated by comparing the outputs with experimental data. The results show that the new continuum micromechanical damage‐healing model could capture the damage‐healing cycle with good accuracy. [ABSTRACT FROM AUTHOR]

A rigid block model with elasto‐plastic softening interfaces is developed for nonlinear static analysis of masonry structures subject to monotonic loading. Cracking, crushing, and shear failures are taken into account at interfaces, following a simple micro‐modeling approach. An optimization‐based formulation is used for the solution of the equation systems governing the behavior of the rigid block assemblage. A simple incremental solution procedure is implemented to take into account the material softening behavior and the effects of large displacements on equilibrium conditions. The interface models are validated against tension and shear tests on bi‐block prisms from the literature. Applications to numerical and experimental out‐of‐plane loaded masonry walls as well as to circular arches with mortar joints are presented to evaluate the effects of tensile strength and the accuracy of the developed model against responses involving P‐Δ effects. Comparisons with experimental tests on shear walls also involving cracking of the units in the failure mechanisms are finally reported to discuss the potentialities and limitations of the proposed modeling approach. [ABSTRACT FROM AUTHOR]

The performance of cement-based materials depends on the characteristics of solid particles at the nano-scale or nanometer porosities in the interfacial transition zone between cement particles and aggregate. Heat significantly affects the properties of these particles and the connection between them. Accordingly, the present study seeks to investigate the effect of nano-silica on the strength parameters of sand–cement mortar at high temperatures. In this regard, the sand–cement mortar was prepared by replacing 5, 10, and 15 percent of cement with nano-silica. The specimens were subjected to temperatures of 25, 100, 200, 400, 600, and 800 °C after curing at the ages of 3, 28, and 90 days. The effect of high temperatures on the physical and mechanical properties of sand–cement mortar was analyzed using macro-structural tests of compressive strength, loss in weight, and water absorption, and microstructural tests of X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results revealed that the macro-structural behavior of sand–cement mortar highly depends on the microstructure and changes in cement nanostructures during heat treatment. Primary portlandite and C–S–H nanostructure were destroyed at 600 °C, and alite, belite, and β-wollastonite were formed at 800 °C. Adding nano-silica improved the strength properties of sand–cement mortar against heat, so the compressive strength of 28-day specimens containing 15% nano-silica increased from 13.9 to 19.2 MPa at a temperature of 800 °C. [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic has led to a surge in medical waste generation, posing hazards to both the environment and global health. The impacts of the COVID-19 pandemic's medical waste hazard may persist long after the pandemic itself subsides. Improper disposal of medical waste can contaminate environment, posing risks to ecosystems and public health. Discarded medical rubber gloves, for example, can become a source of infection, improper disposal of these gloves can escalate the spread of infectious diseases and increase the risk of transmission of the virus to the general public. This study proposes an innovative and sustainable method to reinforce cement mortar by adding recycled glove rubber as an additive to cement mortar to increase its resistance to impact loads. This study conducted uniaxial compression tests, separating hopkinson pressure bar (SHPB) experiments and SEM observations to evaluate the quasi-static compressive strength and dynamic stress of recycled rubber fiber mortar (RRFM) with varying recycled rubber fiber (RRF) contents (0, 1%, 2%, 3%). Strain curves, dynamic increase factor (DIF), energy absorption rules, failure modes, and microstructure of RRFM mixtures. The experimental results demonstrate that with the addition of RRF, the dynamic stress-strain curve flattens and the peak strain gradually increases. The RRFM sample shows stronger toughness. In comparison to regular cement mortar (NM), RRFM has a higher DIF and specific absorbed energy, a faster increase in dynamic compressive strength, and the ability to absorb more energy per unit volume. Under the same impact load, RRFM has fewer and smaller cracks than NM. Scanning electron microscopy (SEM) testing also observed that RRF formed a strong connection pattern with the cement mortar matrix. [ABSTRACT FROM AUTHOR]

Soft computing techniques have become popular for solving complex engineering problems and developing models for evaluating structural material properties. There are limitations to the available methods, including semi-empirical equations, such as overestimating or underestimating outputs, and, more importantly, they do not provide predictive mathematical equations. Using gene expression programming (GEP) and artificial neural networks (ANNs), this study proposes models for estimating recycled aggregate concrete (RAC) properties. An experimental database compiled from parallel studies, and a large amount of literature was used to develop the models. For compressive strength prediction, GEP yielded a coefficient of determination (R²) value of 0.95, while ANN achieved an R² value of 0.93, demonstrating high reliability. The proposed predictive models are both simple and robust, enhancing the accuracy of RAC property estimation and offering a valuable tool for sustainable construction. [ABSTRACT FROM AUTHOR]

This article aims to investigate the mechanical properties and substrate adhesion of the pull-off method in polymer mortars modified with styrene-butadiene resin polymer (SBR) containing glass powder and composite fiber-reinforced slag. Different mix designs were investigated with and without SBR, taking into account different amounts of glass powder and slag separately and in combination, along with the effect of glass, polypropylene, and steel fibers alone and in combination. The flexural performance and energy absorption of beams retrieved with these layers were also assessed. The results revealed significant differences and increases in the substrate adhesion of the restored modified polymer layers containing SBR compared to the polymer-free repair overlays. Furthermore, an improvement was observed in the adhesion performance of the repair overlay using a combination of slag and glass powder and the glass and polypropylene fiber composite. The highest adhesion was related to the modified polymer mortar design containing composite fibers of glass, polypropylene, and steel with 25% replacement of SBR polymer for 10% glass powder, 10% slag, and 5% slag with 5% glass powder. The adhesion was increased by about 3.74, 3.72, and 3.78 times compared to the repair overlay of the control design. Modified polymer mortars had a higher T 150 D toughness. Moreover, the energy absorption was significantly improved by the presence of SBR polymer. The highest toughness values were found in the beams restored with modified polymer mortars containing polypropylene, glass, and steel composite fibers with an increase of 48.51%-66.42% compared to the samples without polymer as a result of the pozzolans used in this mix. [ABSTRACT FROM AUTHOR]

Microbially Induced Calcite Precipitation (MICP) has emerged as a promising technique for bio-cementation, soil improvement, and heavy metal remediation. This study explores the potential of Bhargavaea beijingensis, a urease-producing bacterium, for these applications. Six ureolytic bacteria were isolated from calcareous bricks mine soil and screened for urease and calcite production. B. beijingensis exhibited the highest urease activity and calcite precipitation. Urease activity, calcite precipitation, sand solidification, heavy metal removal efficiency, and compressive strength were evaluated. It showed significant heavy metal removal efficiency, particularly highest for HgCl2. Mortar blocks treated with B. beijingensis or its crude enzyme exhibited improved compressive strength, suggesting its potential for bio-cementation. Crack remediation tests demonstrated successful crack healing in mortar blocks using the bacterium or its enzyme. This study identifies B. beijingensis as a novel and promising MICP agent with potential applications in bio-cementation, soil improvement, and heavy metal remediation. Hence, B. beijingensis diversified abilities prove superior performance compared to commonly used strains like Bacillus subtilis and Shewanella putrefaciens in bio-cementation applications. Its high urease activity, calcite precipitation, and heavy metal removal abilities make it a valuable candidate for sustainable and eco-friendly solutions in various fields. [ABSTRACT FROM AUTHOR]

To counteract the contribution of CO2 emissions by cement production and utilization, biochar is being harnessed as a carbon-negative additive in concrete. Increasing the cement replacement and biochar dosage will increase the carbon offset, but there is large variability in methods being used and many researchers report strength decreases at cement replacements beyond 5%. This work presents a reliable method to replace 10% of the cement mass with a vast selection of biochars without decreasing ultimate compressive strength, and in many cases significantly improving it. By carefully quantifying the physical and chemical properties of each biochar used, machine learning algorithms were used to elucidate the three most influential biochar characteristics that control mortar strength: initial saturation percentage, oxygen-to-carbon ratio, and soluble silicon. These results provide additional research avenues for utilizing several potential biomass waste streams to increase the biochar dosage in cement mixes without decreasing mechanical properties. Highlights: A broad selection of biochars were used to replace 10 wt.% cement in mortars, resulting in similar or improved strength. Biochar moisture saturation percentage, O/C, and soluble silicon are the most important predictors of mortar strength. The data support the hypothesis that biochar improves strength via internal curing, found to be the most important mechanism. [ABSTRACT FROM AUTHOR]

With growing environmental concerns due to the excessive use of natural river sand in construction, finding sustainable alternatives is crucial. This study explores the potential of basalt waste dust, a by‐product of basalt rock crushing, as a replacement for river sand in one‐part geopolymer mortar. The experimental program is segmented into three series: replacing river sand with basalt waste dust at 25%, 50%, 75%, and 100%; adjusting the activator‐to‐binder ratio as 0.12, 0.15, 0.18, and 0.21; and modifying the aggregate‐to‐binder ratios (1, 1.4, 1.8, and 2.2). Results are discussed using various test results such as fresh property, hardened property, and microstructural property to provide a detailed analysis of mixture properties. Findings in series 1 reveal that replacing 50% of river sand with basalt waste dust optimally enhances the fresh and hardened properties of geopolymer mortar. In series 2, the varying activator‐to‐binder ratio with optimum replacement from series 1, activator‐to‐binder ratio 0.15, was found to be optimal, improving hardened properties. Further opting for this ratio in series 3 and increasing the aggregate‐to‐binder ratio to 2.2 was found to positively impact both the hardened and microstructural properties of one‐part geopolymer mortar. This study demonstrated that basalt waste dust plays a crucial role in these improvements and emphasizes the necessity of optimizing mix proportions to achieve superior performance, establishing basalt waste dust as a viable and sustainable alternative to river sand. [ABSTRACT FROM AUTHOR]

The current framework for managing construction waste, guided by European Union regulations, calls for an integrated waste management system. However, the reuse of old plaster waste, particularly from deteriorated facades, remains underexplored. This study investigates the potential of repurposing old plaster waste as a substitute for aggregates and cement in mortars, with the aim of promoting environmental sustainability and resource efficiency. Three mortar mixes were analyzed: a control mix, a mix with 45% waste replacing aggregates, and a mix with 10% waste replacing cement. Results show that replacing 45% of aggregates with plaster waste led to a 30% reduction in flexural strength, while the 10% cement replacement increased flexural strength by 6%. Compressive strength dropped by 27% and 38% for cement and aggregate replacements, respectively. Despite these reductions, the waste replacement remained within acceptable limits for structural integrity. Further microscopic analysis revealed that the incomplete integration of portlandite particles from the waste contributed to non-uniform bonding and crystal formation, weakening the mortar's structure. This research demonstrates the feasibility of reusing old plaster waste, offering a novel approach to reducing construction waste and promoting a circular economy. It contributes to filling the knowledge gap on the reuse of plaster mortars while aligning with sustainable construction goals. [ABSTRACT FROM AUTHOR]

The use of membrane-forming curing compounds on fresh concrete has been widely adopted by many States' Departments of Transportation as it is feasible where there is a deficiency of water, on sloping surfaces where curing with water is challenging, and in cases where large areas like pavement have to be cured. However, the evaluation of the curing compound application effectiveness is difficult because most of the evaluation test methods are not performed during the early age of the concrete. Moreover, the ASTM C156 standards test of water retention for the qualification of curing compounds has met criticism as the moisture retention is performed only on the mortar specimens, with a fixed application rate and curing condition. Therefore, in this study, the embedded resistance technique was used as a test replacement for the moisture retention test to assess concrete curing. The findings from this study showed that a correlation can be found between the moisture retention test and the embedded resistance test. Based on the findings, the embedded resistance test could be a suitable replacement for the moisture loss test, because the test is much simpler and quicker to be performed both in the lab and in the field. [ABSTRACT FROM AUTHOR]

This review presents the scope of current efforts to utilize recycled construction and demolition waste in mortars for masonry. More than 100 articles are divided into groups pertaining to the type of mortar, different binder systems, the type of construction and demolition waste (CDW), and its utilization specifics. Cement-based mortars dominate this research domain, whereas recycled concrete is the main material employed to replace virgin aggregates, followed by recycled masonry and recycled mixed waste aggregates. Such application in cement-based mortars could increase water demand by 20–34% and reduce strength by 11–50%, with recycled concrete aggregates being the most favorable. Natural aggregate substitution is disadvantageous in strong mortars, whereas weaker ones, such as lime-based mortars, could benefit from this incorporation. The extent of this topic also suggests possibilities for different recycled material use cases in mortars for masonry, although the available literature is largely insufficient to infer meaningful trends. Nonetheless, the most relevant knowledge synthesized in this review offers promising and environment-conscious utilization pathways for recycled concrete and other construction and demolition waste, which brings opportunities for further research on their use in mortars for masonry and industrial-scale applications. [ABSTRACT FROM AUTHOR]

The chloride–sulfate corrosion environment of concrete is a significant engineering problem. This paper investigates the effect of the complete/semi–immersion mode on the durability of concrete in a chloride–sulfate environment by using different granulated blast furnace slag (GBFS) dosage rates (10–50%) of a metakaolin (MK)-based geopolymer mortar. The chloride–sulfate corrosion environment is discussed by analyzing the apparent morphology, mass change, and mechanical property change in specimens at the age of 120 d of erosion combined with XRD and SEM. The high Ca content in GBFS has an important effect on the strength and erosion resistance of the metakaolin geopolymer (MGP) group mortar; an increase in the GBFS dosage makes the MGP group mortar denser, and the initial strength of the MGP group mortar is positively correlated with the dosage of GBFS. After 120 d of erosion, the GBFS dosage is negatively correlated with erosion resistance, with the high GBFS dosage groups showing more severe damage. Semi-immersion resulted in more severe deterioration at the immersion–evaporation interface zone due to the difference in the ionic concentration and the 'wick effect' at the immersion–evaporation interface zone. Compared with the commonly used OPC mortar, the M40 and M50 groups have improved strength and corrosion resistance and are suitable for engineering environments in highly erosive areas. [ABSTRACT FROM AUTHOR]

Structural lightweight concrete (SLWC) is crucial for reducing building weight, reducing structural loads, and enhancing energy efficiency through lower thermal conductivity. This study explores the effects of incorporating silica fume (SF), micro-polypropylene (micro-PP), and macro-PP fibers on the workability, thermal properties, and strength of SLWC. SF was added to all mixtures, substituting 10% of the Portland cement (PC), except for the control mixture. Macro-PP fibers were introduced alone or in combination with micro-PP fibers at volumetric ratios of 0.3% and 0.6%. The study evaluated various parameters, including slump, Vebe time, density, water absorption (WA), ultrasonic pulse velocity (UPV), thermal conductivity coefficients (k), compressive strength (CS), and splitting tensile strength (STS) across six different SLWC formulations. The results indicate that while SF negatively impacted the workability of SLWC mortars, it improved CS and STS due to the formation of calcium silicate hydrate (C-S-H) gels from SF's high pozzolanic activity. Additionally, using micro-PP fibers in combination with macro-PP fibers rather than solely macro-PP fibers enhanced the workability, CS, and STS of the SLWC samples. Although SF had a minor effect on reducing thermal conductivity, the use of macro-PP fibers alone was more effective for improving thermal properties by creating a more porous structure compared to the hybrid use of micro-PP fibers. Moreover, increasing the ratio of micro- and macro-PP fibers from 0.3% to 0.6% resulted in lower CS values but a significant increase in STS values. [ABSTRACT FROM AUTHOR]

Materials for the conservation of cultural heritage must meet specific demands, such as high durability, service life, and compatibility with other materials used in the original building structures. Due to their low permeability to water and water vapor and their high rigidity, the use of Portland cement (PC) mortars, despite their high mechanical resistance and durability, does not represent an appropriate solution for the repair of historic masonry and structures. Their incompatibility with the original materials used in the past, often on a lime basis, is therefore a serious deficiency for their application. On the other hand, lime-based mortars, compared to PC-based materials, are more susceptible to mechanical stress, but they possess high porosity, a high water vapor transmission rate, and moderate liquid water transport. This study aims at the development of two types of lime-based mortars, calcium lime (CL) and hydraulic lime (HL). The modification of mortars was conducted with a carbon-based nanoadditive and graphene nanoplatelets (GNs) in three dosages: 0.1%, 0.3%, and 0.5% of the binder weight. The enhancement of CL mortars by GNs greatly increased mechanical strength and affected heat transport characteristics, while other characteristics such as porosity, water absorption, and drying rate remained almost similar. The application of GNs to HL not only enhanced the strength of mortars but also decreased their porosity, influenced pore size distribution, and other dependent characteristics. It can be concluded that the use of graphene nanoplatelets as an additive of lime-based composites can be considered a promising method to reinforce and functionalize these composite materials. The improved mechanical resistance while maintaining other properties may be favorable in view of the increasing requirements of building materials and may prolong the life span of building constructions. [ABSTRACT FROM AUTHOR]

The use of construction waste in creating concrete and mortar is an important process that not only offers economic benefits but also helps protect the environment by reducing waste in rural and urban areas. This experimental study aims to investigate the effect of adding crushed ceramic waste (CCW) and crushed brick waste (CBW) on the bulk density, workability, compressive and flexural strengths, water absorption and microstructural properties of dune sand mortar. To determine changes in porosity, the study uses the mercury intrusion porosimetry technique to measure porosity and pore size distribution. Scanning electron microscopy and energy-dispersive X-ray spectroscopy analyses are conducted to examine the microstructure and size of the voids using an electron microscope, and photographs of voids in the mortar matrix are taken. By replacing 15% of the sand with CCW and CBW, the compactness and mechanical strength of the dune sand mortar are enhanced, increasing the dynamic modulus of elasticity by around 29 and 26%, respectively. This is due to the pozzolanic activity of these residues, which mainly occur in the form of medium and small capillaries in all the mortars studied, reducing the diameter of the pores. [ABSTRACT FROM AUTHOR]

In this study, the chloride ion (Cl−) binding rate of sulfoaluminate cement (SAC) mortars containing different mineral admixtures was investigated. This is essential to improve the durability of concrete structures in high Cl− environments, especially where they are susceptible to Cl− attack such as coastlines and marine structures. The effects of Cl− concentration, curing age, and the type and amount of mineral admixture on the Cl− binding rate of SAC mortars were analyzed. It was found that the content of water-soluble Cl− in SAC mortars decreased with the increase of curing age, while the Cl− binding ratio increased accordingly, indicating that its resistance to internal Cl− permeation increased. The addition of fly ash (FA) and ground granulated blast furnace slag (GGBS) can significantly improve the Cl− binding rate of SAC mortars, and the Cl− binding rate increases to 46.6% with 20% of FA and 38.7% with 40% of GGBS. The effects of mineral admixtures on the microstructure and phase composition of SAC mortars were further investigated by X-ray diffraction (XRD) analysis. The results showed that the addition of FA and GGBS promoted the formation of C-S-H (calcium silicate hydrate) gels and improved the resistance of SAC mortars to Cl− penetration. On the other hand, the excessive addition of silica fume (SF) decreased the Cl− binding rate, whereas a moderate amount of limestone powder (LP) improved the Cl− binding rate. The study of the Cl− binding rate of SAC mortars can help to evaluate their resistance to Cl− erosion in real projects, thus guiding the optimization of concrete formulations and the improvement of durability. [ABSTRACT FROM AUTHOR]

Cement plays a crucial role in mortar composition, and its particles exhibit a strong tendency to flocculate when mixed with water. This flocculation necessitates the addition of substantial water to improve the workability of mortar or concrete. However, this extra water does not contribute to the hydration reaction, potentially weakening the mechanical properties of the mortar. The introduction of superplasticizers has addressed this issue by reducing the water demand. Nevertheless, a common practice in construction is to use a standard dosage of superplasticizers for the same type of cement, even when sourced from different cement factories, which may affect material performance. This study investigated the influence of varying superplasticizer dosages on Portland pozzolana cement from different Ethiopian cement factories, examining the morphological characteristics of masonry mortar. Specifically, it evaluated the impact on cracks, porosity, and surface structure across different curing ages, as well as assessed the mortar's physical and mechanical properties. Mortar samples prepared using cement from three factories, labeled A, B, and C, with constant cement‐to‐sand ratios of 1:3 and water‐to‐cement ratios of 0.5. Superplasticizer added in varying amounts 0%, 0.6%, 0.8%, and 1%. The morphological analysis conducted using a 3D optical surface profiler microscope at 1, 7, 21, and 28 days. Besides these standard physical and mechanical tests also performed on all samples. The results demonstrated that addition of superplasticizers significantly influenced the surface morphology of mortar samples. Mortars A and B exhibited denser structures with superplasticizer dosages 0.8% and 1%, respectively, whereas mortar C displayed a denser structure in its control state (without superplasticizer). The flexural and compressive strength tests also revealed notable differences. Sample A2 (0.8%) from group A, sample B3 (1%) from group B, and sample C0 (0%) from group C achieved the highest strength within their respective groups at 28 days. The findings suggest that it is essential to evaluate the specific properties of cement before applying a standardized superplasticizer dosage, as variations in cement production can significantly influence the performance of the mortar. [ABSTRACT FROM AUTHOR]