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Toward expanding the application of fly ash in cement‐based materials, this study proposes a comprehensive study on predicting the elastic properties of low‐volume fly ash concrete, with the replacement levels limited to 30% or less. Unlike conventional ordinary Portland cement concrete, the inclusion of fly ash in concrete brings alterations in properties from both chemical and physical perspectives: (1) the presence of fly ash liberates the alkaline solution that consumes calcium hydroxide to generate secondary calcium silicate hydrate gels; (2) unreacted fly ash particles exhibits a refinement effect on the micropore structure and contributes to forming a denser solid matrix. In order to characterize these effects on the mechanical properties of fly ash concrete, this paper conducts qualitative assessment of hydration reactions and quantitative calculations of volumetric compounds in the material. Utilizing the Mori‒Tanaka scheme, a predictive model is then developed to integrate the hierarchical effects of constituents at multiple scales on the modulus of elasticity of low‐volume fly ash concrete. The reliability of the proposed model is validated through a series of mechanical tests involving various mix designs, as well as comparison with other published test data. [ABSTRACT FROM AUTHOR]

In recent years, individuals have begun to pay more attention to non-traditional stabilizers due to the problems connected with traditional stabilizers. Traditional stabilizers have undergone extensive investigation, and the mechanisms by which they act are well understood. This paper presents findings of the effect of sugarcane vinasse wastewater (VI) and sodium alginate (SA) polymer on the compressibility behavior, and microstructural evolution of clay soil using mixing method. The premise of this paper is to eliminate waste material from nature and compare the performance of this material against the use of polymers that have recently been used in improvement. The additives were dissolved in water and then introduced to the dried stratified soil to produce improved soil samples using the mixing technique. Transported unconfined compressive strength (UCS) was examined for 1, 14, and 28 days of treatments with additive ranges of 3–15% for VI and 0.25–1.25% for SA. In clay with high plasticity, the findings show that VI significantly influences increasing the UCS. With the addition of 9% vinasse to the soil at the age of 28 days, the UCS has increased by 78.8%. Additionally, the introduction of 1.25% SA to the soil has increased by 261.9% for the 28-day treatment efficiency significantly. Microstructural and chemical examination revealed that the mineralogical and morphological contents of the stabilized soil were influenced due to the pozzolanic reaction. The results showed that waste by-product liquid was able to significantly increase the strength and compressibility of the clay soil. Using a large volume of waste by-product liquid to stabilize soil, the researchers discovered a straightforward application method. [ABSTRACT FROM AUTHOR]

This research is focused on the development of an eco-friendly low-cost concrete using fly ash (FA) and marble powder waste (MPW) as partial replacements for cement and fine aggregate respectively. The substantial use of cement in concrete makes it expensive and contributes to global warming due to high carbon emissions. Thus, using such waste materials can help reduce the overall carbon footprint. For this purpose, various mix designs of concrete were developed by varying the percentages of FA and MPW. The concrete's fresh and hardened properties were experimentally determined for those mixes. The test results revealed that MPW as a sand substitute increases strength up to 40% and gradually decreases beyond that, but a 60% replacement still has more strength than the control specimen. Similarly, using FA as a cement replacement was found to reduce the strength, but the reduction was not very significant up to 20%. A mixed blend of FA and MPW showed superior results and maximum strength was obtained at F10M40. The optimal mix, with 10% FA and 40% MPW (F10M40), achieved a compressive strength of 4493.46 psi, a 16.21% improvement compared to the control mix proportion. Furthermore, the microstructure of the cementitious material was improved due to the pozzolanic reaction that led to a denser microstructure, as supported by the permeability test and SEM analysis. [ABSTRACT FROM AUTHOR]

Thermoactivated recycled cement (RC) is a growing area of research and development in the cement industry. The approach represents a reversible process of cement hydration in which dehydrated compounds with similar characteristics to cement are obtained by means of thermal activation. To avoid CO2 emissions during the production of such RC, this study assesses the possibility of replacing ordinary Portland cement (OPC) with hardened cement powder (HCP) prepared with different proportions of hydrated lime (HL), relying on a second pozzolanic reaction, and compares it with RC mortars. Due to the thermal activation of HCP, the compressive strength increases by 11.5%. The addition of 8% HL produced an important increase in strength from 28 days to 90 days by 12.8%, although without surpassing the strength values of mortar produced only with HCP or with RC. The compressive strength results suggest the existence of a secondary pozzolanic reaction when using HCP from a cement paste source, but such a pozzolanic reaction was fully perceived in XRD patterns when using concrete as parent material, unlike cement paste, possibly due to large crystalline sand peaks that could have hindered the effective identification of smaller crystalline peaks. [ABSTRACT FROM AUTHOR]

Mining and industrial operations are often associated with metalloid and heavy metal contamination of terrestrial and aquatic ecosystems. Heavy metals can weaken the soil's purification ability to remediate and can accumulate in the human body through crops grown in contaminated soil. In this study, a stabilization method was applied for the remediation of arsenic (As) and heavy metal (Pb and Zn) contaminated soil. Scallop shells (SLS) and starfish (Asterias amurensis, ASF), commonly regarded as waste resource materials, are selected as stabilizers. Proper recycling/reuse measures are required to limit uncontrolled disposal of SLS and ASF, prevent environmental degradation of coastal areas, and take advantage of their high calcium carbonate contents. The stabilizers were processed through −#10 mesh (0.2 mm) and −#20 mesh (0.85 mm) sieves. In addition, calcined stabilizers were produced by calcining SLS and ASF at 900 °C to compare stabilization efficiency based on the presence/absence of high-temperature heat treatment. Each of the three types of processed stabilizers was added to contaminated soil at 2 to 10 wt.%, and the mixtures were subjected to wet curing for 28 days. Extraction with 0.1 N HCl was applied for stabilization efficiency assessment. Crops were cultivated in the stabilized soil to evaluate As and heavy metal immobilization capacity. Analysis by X-ray diffraction (XRD) established that calcite (CaCO3) was observed in the natural materials and quicklime (CaO) in the calcined materials. The stabilization efficiency assessment results showed that treatment with SLS and ASF effectively reduced the elution of Pb and Zn. SLS was effective in immobilizing As, but the application of natural ASF increased the leachability of As due to the presence of organic matter. However, applying calcined ASF effectively immobilized As because the organic matter was removed at high temperatures. When the transition of As and heavy metals to crops was evaluated, Pb concentrations that exceeded the criterion for leafy vegetables were detected in the lettuce grown in contaminated soil. However, Pb was not detected in the lettuce grown in SLS- and ASF-treated soil, confirming the stability of heavy metal immobilization. Scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM-EDX) analysis showed that the pozzolanic reaction is related to heavy metal immobilization, and Ca–As precipitation is related to the immobilization of As. The results of this study verified that SLS and ASF effectively immobilize As and heavy metals (Pb and Zn) around mines and that they can be used safely in agricultural soil. [ABSTRACT FROM AUTHOR]

Biomass fly ash is a sustainable, eco-friendly cement substitute with economic and performance benefits, being renewable compared to coal fly ash. This study examines using biomass fly ash (BFA) as a sustainable cement substitute, comparing it with Class F fly ash (CFA). With a water–binder ratio of 0.5 and replacement rates of 10%, 15%, 20%, 25%, and 30% (by mass), the research highlights BFA's promising applications. BFA and CFA were mixed into cement paste/mortar to analyze their reactivity and properties, with hydration products CH and C-S-H evaluated at 7, 28, and 91 days. Compressive strength, micro-pore structure, and drying shrinkage (assessed from 7 to 182 days) were tested. Results showed BFA had similar pozzolanic reactions to CFA at later stages. While compressive strength decreased with higher BFA replacement rates, early-stage performance matched CFA; growth was CFA-10 (18 MPa) and BFA-10 (17.6 MPa). BFA mortars exhibited slightly better deformation properties. BFA-30 cement had superior performance, with a lower drying shrinkage rate of 65.7% from 14 to 56 days compared to CFA-10's 73.4% and a more stable shrinkage growth rate decrease to 8.4% versus CFA-10's 6.4% after 56 days. This study concluded that BFA, usable without preprocessing, performed best at a 10–15% replacement rate. [ABSTRACT FROM AUTHOR]

Nano-SiO2, a highly acclaimed nanomaterial for enhancing cemented soil, has shown remarkable improvements in the physical properties and microstructure of cemented soil. The organic matter content in soil plays a crucial role in determining the engineering quality of cemented soil, regardless of whether it is in a freshwater or seawater environment. Therefore, when employing Nano-SiO2 as an amendment for cemented soil, it is crucial to consider the influence of different soil types and environmental conditions on the effectiveness of the enhancement. This study presents a scientific approach for enhancing the consolidation of cemented soil by incorporating Nano-SiO2 as an additive in both freshwater and seawater environments. To ensure consistency with practical construction practices, the experiments were divided into freshwater preparation and curing groups, as well as seawater preparation and curing groups. In soils with distinct characteristics, we utilized five different gradient levels of Nano-SiO2 additives and subjected the cemented soil specimens to a 60-day immersion curing process. Subsequently, unconfined compressive strength (UCS) tests were performed on samples that had reached the specified curing age to investigate the alterations in the mechanical properties of cemented soil caused by Nano-SiO2. The internal microstructure and chemical composition of the cemented soil were analyzed utilizing scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The UCS and deformation modulus of cement soil composed of silty clay A and silty clay D with low organic matter content in fresh water environment increased by 109%, 24.7% and 117%, 43% respectively after adding 3.2% Nano-SiO2; In freshwater environments, the cemented soil composed of high-organic-matter content mucky silty clay B, muddy soil C, and dredged silt E experienced respective increases of 16% and − 27%, 2% and 42%, 6% and − 6% in UCS and deformation modulus after adding 3.2% Nano-SiO2; The UCS and deformation modulus of cemented soil with high organic matter content in seawater and freshwater environment increased by 3% and 6% (Soil B), 12% and 67% (Soil C), 23% and 27% (Soil E), respectively, after adding 3.2% Nano-SiO2; The increase of UCS and deformation modulus of cement soil by adding Nano-SiO2 is negatively correlated with the content of organic matter. in the case of cemented soil with high organic matter content in a seawater environment, the specific type of soil not only impacts UCS and deformation modulus of the soil but also influences the effectiveness of enhancement. Due to the organic matter, the rate of hydration reaction in cemented soil is reduced, resulting in a decrease in the formation of pozzolanic reaction products with SiO2. As a result, the improvement in Nano-SiO2 effectiveness is diminished. [ABSTRACT FROM AUTHOR]

This work studied the thickening progression mechanism of the silica fume - oil well cement composite system at high temperatures (110-180 °C) in order to provide a theoretical guidance for the rational application of silica fume in the cementing engineering. Results showed that silica fume seldom affected the thickening progression of oil well cement slurry at 110-120 °C, but when temperature reached above 130 C, it would aggravate the bulging degree of thickening curves and significantly extend the thickening time, meanwhile causing the abnormal “temperature-based thickening time reversal” and “dosage-based thickening time reversal” phenomena in the range of 130e160 °C and 170-180 C respectively. At 130-160 °C, the thickening time of oil well cement slurry was mainly associated with the generation rate of calcium hydroxide (CH) crystal. The introduced silica fume would be attracted to the cement minerals’ surface that were hydrating to produce CH and agglomerate together to form an “adsorptive barrier” to hinder further hydration of the inner cement minerals. This “adsorptive barrier” effect strengthened with the rising temperature which extended the thickening time and caused the occurrence of the “temperature-based thickening time reversal” phenomenon. At 170-180 °C, the pozzolanic activity of silica fume significantly enhanced and considerable amount of C-S-H was generated, thus the “temperature-based thickening time reversal” vanished and the “dosage-based thickening time reversal” was presented. [ABSTRACT FROM AUTHOR]

Slag nikel is a by-product of nickel ore smelting through the pyrometallurgical process, which contains silica (> 50 %). This suggests that nickel slag, possessing pozzolanic properties, which potentially to be used as a binding material in construction projects dealing with low soil bearing capacity, such as soil improvement for road foundation. Pozzolanic reactions are greatly influenced by the chemical bonds formed between the binding material and the soil, causing mechanical characteristic changes in the soil. This study aims to examine the effect of adding nickel slag to soft soil based on changes in its physical, mechanical and chemical properties. Physical and mechanical property tests were conducted according to ASTM standards, while the changes in chemical structure in the soil were analyzed based on X-Ray Diffraction (XRD) test results. In this study, nickel slag percentages of 3, 6, 9 and 12 % were used based on the weight ratio of clay soil, at optimum water content (wopt). Furthermore, the test specimens were cured for 14, 28 and 56 days to observe the effect of time on the increase of crystal phases in each variation. The results showed that the presence of nickel slag in the soil can affect its physical and mechanical properties. The nickel slag content in the soil of 3, 6, 9 and 12 % reduces the plasticity index by 16.69, 12.02, 8.86 and 6.38 %, respectively. Meanwhile, the density values increased by 10.97, 11.27, 11.68 and 12.01 kN/m³, respectively. The changes in physical and mechanical properties can be explained by the XRD analysis results, showing changes in the spectrum curve and peak intensity of X-Ray Diffraction in the soil with the addition of nickel slag. This explanation clarifies the transformation of the soil's atomic structure from an amorphous state to a crystalline form, which is stabilized by nickel slag. [ABSTRACT FROM AUTHOR]

The problem of loss of strength caused by the conversion reaction with calcium aluminate cements (CAC) is well known. It has been shown that the addition of ground granulated blast furnace slag (GGBS) to CAC inhibits the conversion process. Different slags can have a different chemical and mineralogical composition depending on their origin and production process, which can significantly influence their reactivity. This work investigated the extent to which the R3 test, developed for Portland cement and based on isothermal calorimetry and/or bound water, was used to predict the reactivity of ground granulated blast furnace slag in a CAC. Mortars and cement pastes with a 30% replacement of slag were tested to evaluate their compressive strength and microstructure. The results show that slags with higher reactivity due to their hydraulic properties lead to a lower compressive strength loss within the first 6 h, a higher strength loss after 24 h due to stratlingite formation and a lower strength loss after 28 days due to pozzolanic reaction and stratlingite formation. The results also confirm that the R3 test was used as a rapid method to predict the effects of slag on the compressive strength of CAC. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effect of calcined clay as supplementary cementitious material on thermogravimetric analysis and compressive strength. Thai iron-rich Lopburi calcined clay was used as Portland cement replacement in the study at 5%, 10%, 15% and 20% by mass. Mortar and paste samples were water cured for 3, 7 and 28 days. The results showed that compressive strength increased when replacement level of Portland cement with calcined clay increased. The change in compressive strength with calcined clay content is discussed in relation to the acceleration in Portland cement hydration and pozzolanic reaction. Thermogravimetric analysis detected many phases such as calcium silicate hydrate (C–S–H), calcium aluminum silicate hydrate (C–A–S–H), monocarboaluminate and hemicarboaluminate hydrate, calcium hydroxide (Ca(OH)2) and calcium carbonate (CaCO3). In addition, thermogravimetric analysis showed the most hydration products which enhance the compressive strength such as C–S–H and C2ASH8 were found in the 20% calcined clay mix. [ABSTRACT FROM AUTHOR]

Nanopore-rich high porosity aerated cement (NHPAC) was prepared by introducing nanomontmorillonite slurry (NMS) into aerated cement paste, and the rheology of slurry, pore structure (air voids and microscopic pores), performance of NHPAC, and related mechanisms were investigated. The results indicated that NMS can generate rich microscopic pores in NHPAC and successfully achieve the part replacement of air void, increasing 0% to 30% of NMS rose microscopic pore porosity from 40.4% to 57.2% and from 40.5% to 54.9% for density grade of 250 and 400 kg/m3 , respectively. In addition, the content of air voids below 0.5 mm increased with increasing NMS. Due to the creation of small air voids, the replacement of air voids by microscopic pores, the pozzolanic reaction of nanomontmorillonite, and the performance of NHPACs were enhanced. 20% of NMS improved 56-day compressive strength by 34.8% and 10.9%, and reduced thermal conductivity by 15.3% and 9.3% for density grades of 250 kg/m3 and 400 kg/m3 , respectively. This development might allow for the use of high porosity aerated cement. [ABSTRACT FROM AUTHOR]

Ceramic-added air lime mortars have been used since ancient times owing to the pozzolanic effect provided by crushed ceramic particles that impart hydraulic properties. This work reviews the historical use, composition, reaction mechanisms, characterization techniques, and performance properties of ceramic-added air lime mortars. The fine ceramic powder composed of silica and alumina phases reacts with calcium hydroxide released during lime hydration to form calcium silicate hydrates (CSH) and calcium aluminate hydrates (CAH) via pozzolanic reaction. This provides hydraulicity and reduces setting time compared to pure air lime mortars. The coarser ceramic particles also serve as aggregate and refine the microstructure as filler. The reactivity depends on the ceramic composition, amorphous phase content, particle size distribution, and firing temperature. Optimal proportioning of the fine ceramic powder and coarse ceramic aggregate is necessary to achieve desired properties. Ceramic addition enhances the durability of air lime mortars against weathering while maintaining compatibility with lime-based masonry structures. Key novelties of this review include: (i) in-depth analysis of the influence of ceramic characteristics (mineralogy, particle size, pozzolanicity) and processing on reaction kinetics and phase evolution; (ii) systematic assessment of mechanical, physical and durability properties in comparison to conventional air lime mortars and cement-based grouts; (iii) elucidation of microstructural mechanisms governing performance using advanced characterization techniques; (iv) critical appraisal of test methods and standards for evaluation; and (v) rigorous discussion on potential applications in construction, conservation and repair, with case studies. [ABSTRACT FROM AUTHOR]

With the order of better understanding the early hydration process and reaction mechanism of CaO-MgO combined expansion agent-involved cement-based systems (CMEA-CBS), CMEA dosage, CaO to MgO ratio (Ca/Mg), MgO activity, hydration temperature, and water-binder ratios (w/b) were chosen as the influencing factor. Accordingly, isothermal calorimetry was implemented to analyze the hydration heat release law, and the Krstulovic–Dabic model was applied to investigate the hydration kinetic. Moreover, the activation energy of CMEA-CBS was calculated. The findings of this study are as follows. The incorporation of CMEA can accelerate the hydration of cementitious systems. Hydration temperature increase markedly promote the hydration reaction of CMEA-CBS. The hydration reaction of CMEA-CBS is a complex associated reaction process dominated by multiple reaction mechanisms in sequence. At both 20 °C and 45 °C, the hydration process of CMEA-involved cement-based systems experienced three stages of crystallization nucleation and crystal growth (NG), phase boundary reaction (I), and diffusion (D), and the hydration mechanism was NG → I → D. However, the hydration of CMEA-CBS at 65 °C switched from the NG stage to the D stage directly. The hydration promotion effect of increasing temperature on I and D process of CMEA-CBS is less than I and D process of pure cement. Compared to the other groups, the temperature increase had the least effect on the early hydration process of 10%-C1M1-M-0.4 with the lowest apparent activation energy. [ABSTRACT FROM AUTHOR]

This paper presents the characterization of a binary mixture of construction and demolition waste (CDW) and bamboo leaf ash (BLAsh) calcined at 600 °C (novel mixture) and the study of its pozzolanic behavior. Different dosages in a pozzolan/Ca(OH)2 system were employed. The aim is the valorization of fine-fraction CDW that achieves a more reactive binary mixture and allows an adequate use of CDW as waste, as CDW is a material of limited use due to its low pozzolanic activity. The pozzolanic behavior of the mixture was analyzed using the conductometric method, which measures the electrical conductivity in the CDW + BLAsh/CH solution versus reaction time. With the application of a kinetic–diffusive mathematical model, the kinetic parameters of the pozzolanic reaction were quantified. This allowed a quantitative evaluation of the pozzolanic activity based on the values of these parameters. To validate these results, other experimental techniques were used: X-ray diffraction, thermogravimetry and scanning electron microscopy. Also, mechanical compressive strength assays were carried out. The results show an increase in the pozzolanic activity of binary mixes of CDW + BLAsh for all the dosages used in comparison to the pozzolanic activity of CDW alone. The quantitative assessment (kinetic parameters) shows that the binary mixture CDW50 + BLAsh50 is the most reactive (reaction rate constant of 7.88 × 10−1 h−1) and is superior to the mixtures CDW60 + BLAsh40 and CDW70 + BLAs30. Compressive strength tests show higher strength values for the ternary mixes (OPC + CDW + BLAsh) compared to the binary mixes (OPC + CDW). In view of the results, the binary blend of pozzolans CDW + BLAsh is suitable for the manufacture of future low-carbon ternary cements. [ABSTRACT FROM AUTHOR]

In this study, the effect of curing humidity on mechanical performance, hydration as well as microstructure for cement paste containing metakaolin (MK) and limestone powder (LP) with various water to binder (w/b) ratios, such as 0.24, 0.36, and 0.48, were investigated. A total of 18 types of slurries were prepared and cured under three levels of humidity [55% relative humidity (RH), 95% RH, and water curing at 20°C] for 28 days. The compressive and flexural strengths were measured to evaluate the influence of humidity on the strength performances of pastes. The MK reaction degree of pastes was tested using the method of selective dissolution in hydrochloric acid. X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM) tests were employed to evaluate the hydration and microstructure of paste. Research results demonstrated that the strengths of pastes generally decreased with curing humidity. Curing at 55% RH can obviously degrade the flexural strength of pastes compared with curing at 95% RH and water curing. The influence of humidity on the compressive strength of MK-containing pastes decreased with the decrease of w/b. The compressive strength of 0.24 w/b pastes containing MK at various humidities were similar. Increasing humidity can enhance the MK reaction degree of pastes with different w/b ratios, which is responsible for the enhanced strength tendency of pastes with humidity. Similar to the compressive strength tendency, humidity had insignificant effects on the MK pozzolanic reaction of pastes with a low w/b ratio. XRD results demonstrated that raising humidity can further increase the synergistic effect of MK and LP. The quantities of monocarboaluminate (Mc) and hemicarboaluminate (Hc) in paste with a high w/b under water curing were greater than those in pastes cured at 55% RH. The microstructures of pastes investigated using MIP and SEM tests also corresponded well to the results of mechanical performances. The findings of this study can provide some guidance for manufacturing normal concrete (NC), high-performance concrete (HPC) and ultrahigh-performance concrete (UHPC) incorporating MK and LP under different levels of humidity. [ABSTRACT FROM AUTHOR]

Traditional wood protection methods involving fire retardants and preservative paints have limitations, requiring periodic renewal during a building's lifecycle and generating hazardous waste post-use. This study aims to achieve a multifaceted solution, simultaneously enhancing wood's resistance to fire, fungi, and insects using natural and/or recycled mineral waste components containing lime that react with pozzolanic additives. Additionally, organic humates provide protection against pests (fungi and insects). Following the crystallization processes within the wood's structure, it exhibits increased resistance to fire, as demonstrated by tests involving seven species. The study also describes wood tolerance tests against termites (Reticulitermes flavipes) that yielded promising results, indicating that the treated wood is an unsuitable habitat for these pests. An additional advantage for the timber industry is that the crystallized composite filling the wood's pores minimizes wood stitching and reduces internal stresses during the drying process. This property enhances the utility of timber in frame structures and carpentry joints, which are less susceptible to moisture-induced movements. The timber impregnated by our method can also be repurposed or disposed of as non-hazardous waste. This research thus offers an eco-friendly and effective approach to wood protection. [ABSTRACT FROM AUTHOR]

In order to improve the applicability of pervious concrete in the seasonal frozen region, and exploit the utilization value of sustainable materials, orthogonal design was used to explore the strength and freeze-thaw damage of glass rubber composite permeable pavement. The results show that the high-quality mix proportion based on lightweight permeable concrete pavement is porosity of 20%, water cement ratio of 0. 26, rubber particles of 6%, and glass powder of 20%. The freeze-thaw durability test conducted on different permeable concrete samples show that the permeable concrete with composite doping of glass powder and rubber particles had an average increase of 13. 93% and 38. 82% in frost resistance compared to the single-doped rubber particle and control groups. The modified compound pervious concrete can combine permeability and strength performance to meet the mechanical performance and durability requirements while achieving the goal of reducing ecological pressure and production costs, which has important application value in the field of road construction and sustainable development. [ABSTRACT FROM AUTHOR]

This study investigates the potential of incorporating recycled fine aggregates (RFA) into sustainable concrete. In this research, a conventional compaction technique is utilized to establish the order of compressive strength and, consequently, to assess particle packing density in terms of weight within a specific cylindrical volume and evaluate workability, compressive and flexural strengths, splitting tensile strength, elasticity modulus, and microstructural properties (analyzed through XRD, SEM, and EDAX). The study found that RFA can improve concrete properties, hardened characteristics, and microstructure up to an optimum 25 % RFA replacement threshold (RFA 25). Beyond this value, concrete strength and microstructure deteriorate. RFA 25 exhibits significantly higher compressive (14.75 %), flexural (6.61 %), and splitting tensile (13.14 %) strengths compared with the reference concrete, along with a 5.71 % decrease in the modulus of elasticity. Lower replacement levels promoted pozzolanic reactions, enhancing strength through additional hydration products, whereas higher replacements reduced strength. [ABSTRACT FROM AUTHOR]

The inferior mechanical performance and freeze–thaw (FT) resistance of recycled concrete are mostly due to the significant water absorption and porosity of recycled coarse particles. In this study, different dosages of zeolite powder were used in recycled concrete. A series of macroscopic tests were used to evaluate the workability and FT durability of zeolite powder-modified recycled concrete (ZPRC). X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to reveal the micro-mechanisms of FT resistance in ZPRC. The results show that the increase in zeolite powder content leads to a decrease in the slump and water absorption of ZPRC. Additionally, ZPRC with 10% zeolite powder has superior mechanical characteristics and tolerance to FT conditions. The higher strength and FT resistance of the ZPRC can be attributed to the particle-filling effect, water storage function, and pozzolanic reaction of zeolite powder, which results in a denser microstructure. The particle-filling effect of zeolite powder promotes the reduction of surface pores in recycled coarse aggregates (RCAs). The water storage function of zeolite powder can provide water for the secondary hydration of cement particles while reducing the free water content in ZPRC. The pozzolanic reaction of zeolite powder can also promote the generation of hydrated calcium silicate and anorthite, thereby making the microstructure of ZPRC more compact. These results provide theoretical guidance for the engineering application of recycled concrete in cold regions. [ABSTRACT FROM AUTHOR]

Soil-improvement techniques with binders are used in several geotechnical engineering applications as a sustainable solution for the reuse of waste soils. Due to their inherent complexity and their mechanical behaviour, pyroclastic soils are generally considered waste geomaterials in their natural state. Lime treatment of pyroclastic soils can be considered a viable solution for their reuse in geotechnical applications. In this paper, some peculiar features of the chemo-physical evolution and mechanical behaviour of lime-treated pyroclastic soils are evidenced through a multi-scale experimental investigation. While, for clayey soils, the fine fraction is mainly responsible for ion exchange and pozzolanic reactions induced by lime, for pyroclastic soils, pozzolanic reactions are dominant processes due to the low quantity of clay minerals along with the abundance of aluminates and silicates as the main constituents of their amorphous phase. The link between the phenomena detected at the microscale level, the mineralogical composition, and the macroscopic behaviour of two lime treated pyroclastic soils of different origin is explored through a multiscale approach. [ABSTRACT FROM AUTHOR]

To enhance the application of coal series kaolinite clay in the cement industry, the properties and hydration of ternary system based on calcined coal series metakaolin (CMK), limestone (LS), and Portland cement were investigated in this work. The results showed that the kaolinite phase transformed into an amorphous phase for coal series kaolinite clay calcined over a wide temperature range. The negative effects of the CMK on the early (3 and 7d) compressive strength of mortars and of LS on the later (28 and 90 d) compressive strength of mortars could be offset by using a combination of LS and the CMK. The combined incorporation of the CMK and LS promoted the hydration of cement at an early hydration age, and the pozzolanic reaction of the CMK generated additional hydration products. In the ternary system, the use of LS weakened the influence of the calcination temperature of the CMK on the early hydration of cement; similar heat release and strength development can be observed for all CMK-LS content blends. At a late hydration age, the incorporation of LS resulted in the formation of carboaluminate instead of monosulfoaluminate, and the CMK enhanced this reaction. As a result, the hydration of Portland cement, CMK, and LS was improved due to the synergistic effect of the CMK and LS, and the mixture of CMK and LS is expected to be a promising supplementary material. [ABSTRACT FROM AUTHOR]

Ceramisite lightweight concrete has excellent performance and relatively light self-weight characteristics. At the same time, the recent development of green high-performance concrete and prefabricated components has also brought the abundant utilization of these mineral mixture. An interfacial transition zone exists between the hardened cement paste and the aggregate, which is the weakest part of the concrete, characterized by high porosity and low strength. In order to study the effect of slag content on the interfacial transition zone in lightweight high-strength concrete, experiments were designed to replace cement with slag at different contents (0%, 5%, 10%, 15%). A series of studies was conducted on its macro-strength, microstructure, and composition. The results indicated that the addition of slag improved the porosity and width of the interfacial transition zone. Adding slag did not reduce the thickness of the concrete interfacial transition zone significantly at 3 d, but it led to significant improvement in the thickness of the interfacial transition zone at 28 d, and the thickness of the interfacial zone at 28 d was reduced from 19 μm to 8.5 μm, a reduction of 55%. The minimum value of microhardness in the slurry region of the interfacial specimens also increased from 19 MPa to 26 MPa, an increase of 36%. In addition, the structural density of the interfacial region was further increased, resulting in varying degrees of improvement in the macroscopic anti-splitting strength. One of the important reasons for this phenomenon is that the addition of slag optimizes the chemical composition of the interface and promotes the continuation of the pozzolanic reactivity, which further enhances the hydration at the interface edge. [ABSTRACT FROM AUTHOR]

In order to enhance the utilisation efficiency of lithium slag (LS) in cement-based materials, calcification and thermal activation of LS were conducted, and the activation mechanism was analysed. Results showed that gypsum and spodumene in LS decomposed at high temperature by way of calcification and thermal activation, and spodumene as well as limestone calcination decomposed at high temperature, to generate more CS, CA and other mineral phases. Calcification and thermal activation could enhance the activity of LS to participate in pozzolanic reaction, and generate the formation of more hydration products. After calcification and thermal activation of LS, the hydration exothermic peak, the total amount of hydration heat and the hydration production of LS composite binder were significantly increased. The hardened matrix was more compact with less porosity. Compared with cement mortar incorporating raw LS, the incorporation of calcified and thermally activated LS enhanced the compressive strength of cement mortar at 3, 7 and 28 days by 25.8, 13.4 and 20.5%, respectively. [ABSTRACT FROM AUTHOR]

Metakaolin-based geopolymers have substantial potential as replacements for cement, but their relatively inferior mechanical properties restrict their application. This paper aims to enhance the mechanical properties of metakaolin-based geopolymers by incorporating appropriate amounts of calcium sources. CaCO3, Ca(OH)2, and CaSO4 are three types of calcium sources commonly found in nature and are widely present in various industrial wastes. Thus, the effects of these three calcium sources on the performance of metakaolin-based geopolymers were studied. Through the analysis of the mechanical properties, heat-release behavior during hydration, hydration products, and microstructure of geopolymers, the effectiveness of the aforementioned calcium sources in improving the performance of metakaolin-based geopolymer was evaluated, and the mechanisms of action were elucidated. The results indicate that the pozzolanic reaction between CH and MK could promote MK hydration and increase the proportion of CASH gel in the hydration products, thereby facilitating the setting of the geopolymer and enhancing its strength. CS could react with the active aluminates in MK to form ettringite, thus forming a higher early strength. CC had a lower reactivity with MK and does not improve the performance of MK-based geopolymers. [ABSTRACT FROM AUTHOR]

Xinjiang has a temperature difference of 20°C between day and night, interannual temperature difference of 50°C, the control of the temperature cracks in mass concrete becomes difficult. Although low-heat portland (P·LH) cement concrete containing fly ash (FA) can reduce hydration heat, the mismatch between its mechanical and thermal properties is still not fully resolved. An attempt to explore the effect of FA on the competitive hydration reaction of C3A and C3S at super-early ages, and how this effect changes the physical and chemical properties of hardened cement pastes by electrical resistivity and zeta potential and common microstructure test methods, and to provide a theoretical basis for optimization of mechanical and thermal properties of P·LH cement concrete with FA. Results showed that in the fast dissolution stage, a numerous {Ca6[Al(OH)6]224H2O}6+ ions and a very small amount of H3SiO4−/H2SiO42− ions were formed, and incorporating 20%, 30%, 40% FA primarily inhibited the Al(OH)63− hydration and the {Ca6[Al(OH)6]224H2O}6+ generation, resulting in the generation time of AFt in comparison with pure cement, respectively, delayed by 44%, 140%, and 524%. This phenomenon decreased the nucleation and crystallization growth rate of AFt and Ca(OH)2 in the induction stage, and reduced the consumption of gypsum in the acceleration stage. Hence, monosulfoaluminate did not exist for pastes with more than 30% FA, and the number of particles involved in the reaction for the P·LH cement stone with 20%, 30%, and 40% FA decreased by 4.0%, 46.5%, and 52.0% in the deceleration stage compared with the pure cement. The research results can provide a theoretical reference for modifying chemical properties of FA to meet the matching of mechanical strength and thermal of P·LH cement. [ABSTRACT FROM AUTHOR]

This research investigated the synergistic adoption of sodium silicate (SS) and the synthetic calcium silicate hydrates (C-S-Hs)/polycarboxylate (PCE) nanocomposites on the hydration behavior of portland cement containing 20% by weight of lithium slag (LS). Effects of SS and C-S-Hs-PCE on rheological performance, mechanical strength development, and hydration process were evaluated. Results showed that C-S-Hs-PCE was advantageous for modifying the rheological performance of fresh LS-cement binder, while SS increased the rheology and yield stress and shortened setting time of the LS-cement binder. C-S-Hs-PCE promoted the hydration of silicates to form abundant CH, and SS generated the dissolution of metallic ions from LS. The hastened dissolution of LS accelerated the formation of ettringite (AFt) as well as C-S-H gel. Because the hydration of cement and pozzolanic reaction of LS were both promoted, the hydration products of hardened matrix were increased, and the interlaced combination structure of hydrates in the matrix was greatly improved, which was favorable for the development of mechanical strength. The findings provide theoretical guidelines for modifying the properties of blended cements by uniting nanoparticles and chemicals. [ABSTRACT FROM AUTHOR]

This study evaluates the potential to use shrinkage-reducing admixture (SRA) and pre-saturated lightweight sand (LWS) to shorten the external moist-curing requirement of ultra-high-performance concrete (UHPC), which is critical in some applications where continuous moist-curing is challenging. Key characteristics of UHPC prepared with and without SRA and LWS and under 3 days, 7 days, and continuous moist curing were investigated. Results indicate that the combined incorporation of 1% SRA and 17% LWS can shorten the required moist-curing duration because such a mixture under 3 days of moist curing exhibited low total shrinkage of 360 µε and compressive strength of 135 MPa (19,580 psi) at 56 days, and flexural strength of 18 MPa (2610 psi) at 28 days. This mixture subjected to 3 days of moist curing had a similar hydration degree and 25% lower capillary porosity in paste compared to the Reference UHPC prepared without any SRA and LWS and under continuous moist curing. The incorporation of 17% LWS promoted cement hydration and silica fume pozzolanic reaction to a degree similar to extending the moist-curing duration from 3 to 28 days and offsetting the impact of SRA on reducing cement hydration. The lower capillary porosity in the paste compensated for the porosity induced by porous LWS to secure an acceptable level of total porosity of UHPC. [ABSTRACT FROM AUTHOR]

The present paper discusses experimental results obtained on several mortars prepared using a commercial type1 OPC cement, a commercial limestone aggregate with maximum particles dimension below 5 mm, superplasticizer and water. Different amounts of a waste silica sand, in form of loose powder, derived from the industrial production of refractory blocks, were added to the above basic components. Several additional samples were also prepared using same basic commercial components added by different amounts of a fine limestone filler. This latter set of compositions was used to prepare samples to be used as reference materials. Waste silica sand and fine limestone filler were used as received from their producer. During preparation, pastes containing silica sand showed better workability compared to all the other blended components. All hydrated materials displayed fair compressive strength and low water absorption after curing, but those containing silica sand showed the best mechanical performances due to their low residual porosity and to the pozzolanic reaction which could enable application for the production of structures in direct contact with water or aggressive environments such as sewers or tanks suitable for the containment of organic substances. [ABSTRACT FROM AUTHOR]

This study investigated the effects of lithium slag and iron tailings on the hydration mechanism of Basic Oxygen Furnace (BOF) slag cement paste with the addition of 0.06% diethanol-isopropanolamine (DEIPA). This study examined the fluidity, compressive strength, pore solution pH, and hydration products of BOF slag-based composite cementitious materials. The results showed that DEIPA facilitated the conversion from ettringite (AFt) to monosulphate (AFm) and improved the early compressive strength of the BOF slag–cement mortar. Incorporating lithium slag into the DEIPA-containing BOF slag–cement system promoted AFt formation, increased calcium-silicate-hydrate production, and enhanced the microstructure. BOF slag, lithium slag, and iron tailings exhibit synergistic effects in cement pastes. BOF slag and lithium slag provided the reactive components SiO2 and Al2O3. In the early hydration stages, the iron tailings primarily served as fillers, accelerating the system's reactions. [ABSTRACT FROM AUTHOR]

This study contributes to the quantitative understanding of kaolinite reactions with lime over two years. Unconfined Compressive Strength (UCS) increased linearly with time, doubling within one year, followed by a 14% decrease. Spectroscopic analysis of the system was performed at ten curing times (0, 7, 28, 90, 120, 180, 270, 360, 540 and 720 days) using Thermogravimetric Analysis (TGA), X-Ray Diffraction (XRD) and 2Nuclear Magnetic Resonance (NMR). Both TGA and XRD showed decrease of portlandite up to 180 days; complete consumption appears to have occurred by 270 days. TGA curves indicated an increase in hydration products in the first 360 days which followed a linear trend with UCS increase. No hydration products were observable by either XRD or NMR during that timeframe and no detectable changes in the kaolinite content either. After 360 days, growth in the hydrates in TGA slowed, and XRD, NMR showed a rapid increase of stratlingite (Ca2Al2SiO7∙8H2O) up to 720 days along with a decrease in the kaolinite signal. Collectively, these results point to two phases in kaolinite dissolution: the first phase, up to about 360 days, is incongruent, characterized by preferential release of Si or Al and portlandite consumption, leading to amorphous Calcium Silicate Hydrate (CSH) or an Afm phase, calcium monosulphoaluminate hydrate (CAH) formation. The second phase involves congruent dissolution and formation of Calcium Alumino Silicate Hydrate (CASH). It is hypothesized that CSH or CAH to CASH transformation occurs in the second stage, causing a disturbance in the cementitious matrix and loss in strength. [ABSTRACT FROM AUTHOR]

Solar energy production was initiated in the 1990s following by rapid increase of the use of photovoltaic (PV) technology. Most of older solar panels in the Czech Republic were installed between 2000 and 2006 and a global installed capacity of 222GW was reached by the end of 2015. With the growing global PV market, a large amount of waste is expected to accumulate after 2030 which is associated with the new industry to process this waste, based on reduce, reuse, and recycle. This article summarizes findings and research conclusions regarding local issues collected by experts from the Czech Republic. Previous research showed that waste glass from photovoltaic panels can be used as a pozzolanic material in high-performance concrete, improving its properties. Further research on the use of waste from photovoltaic panels has been conducted in the Czech Republic since 2019 and the conclusions from various research confirm the suitability of using PV panel glass. [ABSTRACT FROM AUTHOR]

Reducing cement usage and replacing it with solid waste in high volume is one of the most important ways for the sustainable development of the cement industry. In the present work, sustainable foamed concrete with a high content of phosphogypsum (PG) was prepared through the combination activation and synergistic strengthening of waterglass, ground blast furnace slag (GBFS), and cement. The fluidity, mechanical properties, volume stability, and durability of this sustainable foamed concrete were studied and its reaction mechanisms were also investigated using hydration calorimetry, X-ray diffraction (XRD), and scanning electron microscopy (SEM) techniques. The results show that the early age cohesive strength for this foamed concrete is mainly derived from ettringite formation, which is a product of the pozzolanic reaction of GBFS in the presence of sulfate ions. Cement in this sustainable foamed concrete is presented as an alkali activator. Too small addition of cement would weaken its activation effect and reduce the hydration product formation, which delays the strength development of the foam concrete. High cement content would provide sufficient Ca2+ ions, which can also retard the GBFS hydration. The unreacted PG particles are covered by ettringite and other hydration products during the reaction process to prevent its dissolution in a moist environment and help improve the water resistance and durability of foamed concrete. The sustainable foamed concrete prepared with 15% of cement and more than 50% of PG has 7 and 28 days compressive strengths of 2.86 and 3.36 MPa, respectively. In addition, it has a water-softening coefficient of 0.81 and a volume microexpansion feature in a moist environment, which is suitable for subgrade or underground filling. [ABSTRACT FROM AUTHOR]

The use of raw materials from the recovery of construction waste is frequent. In this study, the waste is obtained from degraded railway ballast, made up of siliceous minerals. This material is added directly to the mixtures to replace part of the cement, forming a good quality cementitious product. The pozzolanic reaction is studied within the waste/lime system in a solid phase and water system for one year. Reaction products such as stratlingite, layered double hydroxide-type compounds, hydrated tetracalcic aluminate, and gels appear. The formation of stratlingite and gels was favored throughout the reaction. The reaction was monitored, calculating the saturation index. [ABSTRACT FROM AUTHOR]

The growing construction industry and global population have led to increased demand for concrete, resulting in increased waste production. Recycling construction and demolition (C&D) waste as recycled fine aggregates (RFA) in concrete could help reduce waste and conserve natural resources. This research delves into the meticulous examination of particle packing density within specific cylindrical volumes under standard compacting efforts, elucidating an order of compressive strength. The study comprehensively explores various concrete properties, including workability, compressive strength, flexural strength, split tensile strength, drying shrinkage, electrical resistivity, rapid chloride penetration, and microstructural characteristics (analyzed through XRD, SEM, and EDAX). RFA particles, ranging from 0.15 to 4.75 mm, were employed as partial replacements for fine aggregates, with replacement percentages varying from 0% to 100% in increments of 25%. The empirical findings underscore that the incorporation of RFA significantly enhances concrete properties. However, it was observed that surpassing the optimum replacement percentage of 25% (RFA 25) adversely impacts the concrete's strength and microstructure. Specifically, RFA 25 exhibited remarkable improvements, with a 14.75% increase in compressive strength, a 6.61% boost in flexural strength, and a 13.14% enhancement in split tensile strength compared to conventional concrete (RC). Furthermore, RFA 25 demonstrated a 4.16% increment in drying shrinkage, 17.65% higher electrical resistivity, and an 18.83% superior resistance to chloride penetration compared to RC. The analysis of XRD, SEM, and EDAX results elucidated that at lower replacement percentages, the pozzolanic reaction enhances strength by forming additional hydration products. Conversely, at higher replacement levels, strength diminishes. [ABSTRACT FROM AUTHOR]

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This investigation elucidates the development of an innovative, sustainable binder derived from calcium carbide residue and silica fume, aimed at enhancing soft clay stabilization with minimal environmental impact. Various mixtures were examined, focusing on the CaO to SiO2 molar ratio (Ca/Si), which varied from 1.85 to 0.65. Comprehensive analyses of the raw materials and pastes, including chemical composition, phase evolution, and microstructure, were conducted using techniques like Energy dispersive X-ray fluorescence, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. Results indicate a significant impact of raw material fractions on the compressive strength and cementitious properties. The mixture with a Ca/Si of 1.55 demonstrated the highest long-term strength, attributed to increased C–S–H content. A mixture of 30 wt% calcium carbide residue and silica fume was found to improve the unconfined compressive strength of soft Bangkok clay by 84% compared to 10 wt% ordinary Portland cement, demonstrating its efficacy and potential for widespread application in green construction initiatives. This research not only promotes the recycling of industrial by-products, reducing environmental impact, but also represents a significant advancement in sustainable construction materials.

Due to the high embodied carbon of cement and limited availability of conventional supplementary cementitious materials (SCMs), calcined clay has gained numerous attentions worldwide as an alternative SCM. This study explores the potential of four kaolinic clay-rich soils from waste streams in Victoria, Australia, as SCMs. The clays are compared to three commercial calcined clay products from different countries after undergoing grinding and calcination processes. The research assesses physical, chemical, and mineralogical characteristics, as well as pozzolanic activity in ternary cement systems. Results highlight the importance of fineness and calcined kaolinite content in influencing performance. Overall, the study demonstrates the feasibility of Victorian clays as SCM, even from waste streams, with suitable calcination procedures, contributing to sustainable alternatives in cement production.

Abstract To reveal the mechanism of the influence of the curing temperature on the strength of lime activated fly ash-GGBS cured silt soil, the curing of dredged silt was carried out by using fly ash and GGBS as the curing agent and lime as the activator. Unconfined compressive strength (UCS) experiments were carried out, and the micro-analysis of the cured silt was carried out by experimental methods including scanning electron microscope (SEM) tests, X-ray diffraction (XRD), etc. to reveal the mechanism of the curing temperature on the dredged silt. According to the test results, the hydration reaction and pozzolanic reaction between lime-fly ash-GGBS and silt soil were promoted with the increase of the curing temperature. when the curing temperature of the sample reached 40 ℃, a large amount of gel products such as hydrated calcium aluminate (C–A–H) and hydrated calcium silicate (C–S–H) were generated, which enhanced the bonding force between soil particles and filled up the inter-particle pore space, thereby improving the UCS of the sample. The results of SEM confirmed that C–A–H and C–S–H were the main substances for the construction of cured silt skeleton. C–S–H and C–A–H were detected by XRD. The results of the study fill the gap in the effect of curing temperature on the direction of lime-activated fly ash-GGBS cured silt soil.

To reveal the mechanism of the influence of the curing temperature on the strength of lime activated fly ash-GGBS cured silt soil, the curing of dredged silt was carried out by using fly ash and GGBS as the curing agent and lime as the activator. Unconfined compressive strength (UCS) experiments were carried out, and the micro-analysis of the cured silt was carried out by experimental methods including scanning electron microscope (SEM) tests, X-ray diffraction (XRD), etc. to reveal the mechanism of the curing temperature on the dredged silt. According to the test results, the hydration reaction and pozzolanic reaction between lime-fly ash-GGBS and silt soil were promoted with the increase of the curing temperature. when the curing temperature of the sample reached 40 ℃, a large amount of gel products such as hydrated calcium aluminate (C–A–H) and hydrated calcium silicate (C–S–H) were generated, which enhanced the bonding force between soil particles and filled up the inter-particle pore space, thereby improving the UCS of the sample. The results of SEM confirmed that C–A–H and C–S–H were the main substances for the construction of cured silt skeleton. C–S–H and C–A–H were detected by XRD. The results of the study fill the gap in the effect of curing temperature on the direction of lime-activated fly ash-GGBS cured silt soil. [ABSTRACT FROM AUTHOR]

The use of a modified lime mortar as a binder for the stabilization/solidification of mine tailings presents a promising and sustainable solution for immobilizing potentially toxic elements found in these waste materials compared to cement mortars. The effectiveness of this modified lime mortar in avoiding the mobility of toxic elements, namely lead (Pb) and arsenic (As), in mine tailings has been thus studied. Encapsulating matrices of 1:1 and 2:1 tailings waste/air lime ratios were prepared. Due to the content of potentially pozzolanic compounds in the mine tailings, mainly some silicate phases, 1:1 matrices showed better mechanical strength than 2:1 samples, ascribed to a more intense pozzolanic reaction. SEM observations identified needle-shaped C-S-H structures. The hardened materials showed good endurance against freeze–thaw cycles. The semi-dynamic tank test demonstrated the effective encapsulation of the toxic components due to the use of lime mortars, yielding values of released Pb and As below the detection limit in all instances. Considering the cost-effectiveness, widespread availability, and ease of use, the use of modified lime mortar for the treatment of mine tailings can be recommended to mitigate the environmental impacts of mining activities. [ABSTRACT FROM AUTHOR]

Agro industries have produced huge amounts of waste, influencing the environment. Palm oil clinker (POC), routinely dumped from Malaysian palm oil mills, is one of these waste products. This research investigates the feasibility of using it as a filler substitute in hot mix asphalt (HMA) as an alternative avenue to utilize this waste. The waste POC powder (POCP) is comparable to the properties of the traditional fillers used-granite stone dust (GSD), according to physiochemical analysis. The POCP passes through 75 µm sieve, and 6% (w/w) of the filler was substituted by 0%, 20%, 40%, 60%, 80%, and 100% (w/w) of the GSD. HMA mixes were prepared for various percentages using the Marshall mix design to evaluate their respective optimum bitumen contents (OBC). Subsequently, at OBC, the influence of POCP on the HMA volumetric, Marshall properties, Cantabro test resilient modulus, and moisture damage tests was investigated. The study revealed that all POCP mixtures improve performance in terms of stability, stiffness, and higher resistances against moisture damage than the control mixture. The improvement could be attributed to the synergistic influence of POCP pozzolanic reaction and fineness, resulting in a thicker refined mastic between POCP and bitumen, producing more durable HMA. However, based on the study findings, 80% of POCP filler for HMA mixes can be considered the optimal content to improve its properties. In conclusion, the study depicts the viability of utilizing POCP as a replacement for conventional filler to promote sustainability and provides a proper channel for its disposal. [ABSTRACT FROM AUTHOR]

Nanosilica and diatomite are pozzolanic resources rich in SiO2. In this study, the purpose of this study was to improve the moisture resistance of the specimen by producing a mixed material using pozzolanic materials and calcium stearate and adding it to cement mortar while stirring. The results showed that the hydration reaction was not activated when calcium stearate adhered to the fine particles of nanosilica; it existed simply in the form of a filler inside the specimen. Diatomite, due to its atypical particles and porosity, may have greater water tightness than nanosilica because of the pozzolanic reaction in particles to which calcium stearate is not attached. [ABSTRACT FROM AUTHOR]

To promote resourceful utilization of argon oxygen decarburization (AOD) slag, this research developed a new three-ash stabilized recycled aggregate with AOD slag, cement, fly ash (FA), and recycled aggregate (RA) as raw materials. The AOD slag was adopted as an equal mass replacement for fly ash. The application of this aggregate in a road base layer was investigated in terms of its mechanical properties and mechanistic analysis. First, based on a cement: FA ratio of 1:4, 20 sets of mixed proportion schemes were designed for four kinds of cement dosage and AOD slag replacement rates (R/%). Through compaction tests and the 7-day unconfined compressive strength test, it was found that a 3% cement dosage met the engineering requirements. Then, the unconfined compressive strength test, indirect tensile strength test, compressive rebound modulus test, and expansion rate test were carried out at different age thresholds. The results showed that the mixture's strength, modulus, and expansion rate increased initially and then stabilized with age, while the strength and modulus initially increased and then decreased with increasing R. Secondly, based on X-ray diffraction (XRD) and scanning electron microscopy (SEM) used to analyze the mechanism, it was found that the strength, modulus, and expansion rate of the new material can be promoted by blending AOD slag, due to its ability to fully stimulate the hydration reaction and pozzolanic reaction of the binder. Finally, based on the strength and modulus results, R = 3% was identified as the optimal ratio, which provides a reference point for the effective application of AOD slag and RA in road base materials. [ABSTRACT FROM AUTHOR]

The present work analyzes the behavior in terms of corrosion resistance of three reinforced concrete formulations over a period of 1 year. The samples were subject to a monitoring methodology using the Electrochemical Impedance Spectroscopy (EIE) technique, working only with the real component over time. Three mixtures were used, one conventional without pozzolanic addition (REF) and two others with pozzolanic additions, rice husk ash (RHA) and metakaolin (MK). Prototypes were created and exposed to the action of a 165 g/L NaCl sodium chloride solution. The characterization of the materials was carried out by determining the chloride diffusion profile (ASTM 1556), analyzing images using tomography and with the support of analytical techniques such as X-ray fluorescence and X-ray diffraction. The monitoring methodology using EIE demonstrated the positive effect of the insertion of pozzolans, rice husk ash (RHA) and metakaolin (MK) in delaying the process of chloride diffusion in the concrete, resulting in greater resistance to corrosion. The EIE also showed that the active mineral addition in concrete, resulting in aluminum-silicic composition (MK), had a predominant protective effect on the steel/concrete interface against the attack of chloride ions. [ABSTRACT FROM AUTHOR]

Large quantities of abandoned marine soft soil are generated from coastal engineering which cannot be directly utilized for construction without modification. The utilization of traditional binders to modify abandoned marine soft soil yields materials with favorable mechanical properties and cost efficiency. However, the production of traditional binders like cement leads to environmental pollution. This study uses a CGF all-solid-waste binder (abbreviated as CGF) composed of industrial solid waste materials such as calcium carbide residue (CCR), ground granulated blast furnace slag (GGBS), and fly ash (FA), developed by our research team, for the modification of abandoned marine soft soil (referred to as modified soil). It is noteworthy that the marine soft soil utilized in this study was obtained from the coastal area of Jiaozhou Bay, Qingdao, China. Physical property tests, compaction tests, and unconfined compressive strength (UCS) tests were conducted on the modified soil. The investigation analyzed the effects of binder content, compaction delay time, and curing time on the physical, compaction, and mechanical properties of CGF-modified soil and cement-modified soil. Additionally, microscopic experimental results were integrated to elucidate the mechanical improvement mechanisms of CGF on abandoned marine soft soil. The results show that after modification with binders, the water content of abandoned marine soft soil significantly decreases due to both physical mixing and chemical reactions. With an increase in compaction delay time, the impact of chemical reactions on reducing water content gradually surpasses that of physical mixing, and the plasticity of the modified soil notably modifies. The addition of binders results in an increase in the optimum moisture content and a decrease in the maximum dry density of CGF-modified soil, while the optimum moisture content decreases and the maximum dry density increases for cement-modified soil. Moreover, with an increase in binder content, the compaction curve of CGF-modified soil gradually shifts downward and to the right, while for cement-modified soil, it shifts upward and to the left. Additionally, the maximum dry density of both CGF-modified and cement-modified soils shows a declining trend with the increase in compaction delay time, while the optimum moisture content of CGF-modified soil increases and that of cement-modified soil exhibits a slight decrease. The strength of compacted modified soil is determined by the initial moisture ratio, binder content, compaction delay time, and curing time. The process of CGF modification of marine soft soil in Jiaozhou Bay can be delineated into stages of modified soil formation, formation of compacted modified soil, and curing of compacted modified soil. The modification mechanisms primarily involve the alkali excitation reaction of CGF itself, pozzolanic reaction, ion-exchange reaction, and carbonization reaction. Through quantitative calculations, the carbon footprint and unit strength cost of CGF are both significantly lower than those of cement. [ABSTRACT FROM AUTHOR]

The utilization of recycled rubber tires as a partial substitution of the natural aggregate in concrete is the solution for safe disposal of it. Since that rubber affects the mechanical characteristics of concrete negatively due to the rubber and cement mortar low cohesion, it was necessary to improve these properties by adding pozzolanic additives such as fly ash. The objective of this paper is to study the effect of treated crumb rubber and fly ash on the performance of concrete. The crumb rubber (CR) has been treated with benzene. CR particles were added as a partial substitution of sand by 5%, 10%, 15%, and 20% of its weight, and the cement was replaced with fly ash by 15% of its weight. Many tests were carried out to evaluate mechanical characteristics of hardened concrete such as compressive strength, splitting tensile strength, water absorption, density, and modulus of elasticity. The slump test was conducted to assess the consistency of the concrete. The results showed that the compressive strength of CR mixes decreased by 7.14%, 18.36%, 26.5%, and 35.7% compared with that of the control mix. The tensile strength of CR mixes reduced by 6.5%, 10.8%, 18.9%, and 35.13% than that of the reference mix at the age of 28 days. With an increasing rubber content, the modulus of elasticity reduced, and the water absorption rate of CR mixes increased compared with that of the control mix. The mixture containing 5% CR achieved the highest value of compressive, flexural, and indirect tensile strength, and the lowest water absorption rate in comparison to the other mixtures including CR particles. [ABSTRACT FROM AUTHOR]

Supplementary cementitious materials (SCMs) are partial substitutes for ordinary Portland cement (OPC) to reduce cost, the production of carbon dioxide (CO2), and fossil fuel consumption. Recent studies illustrated the effectiveness of calcined kaolinite clay as a proper partial replacement for OPC. Hence, schist‐type materials containing sufficient clay contents are regarded as promising candidates for OPC replacement. This study focuses on the possible use of activated calcium carbonates (CaCO3) to augment pozzolanic reactions of schists as a substitute for OPC. The use of activated calcium carbonates proved to be successful in expediting pozzolanic reactions and facilitating the formation of additional calcium aluminosilicate hydrate (C‐A‐S‐H). In this study, the optimal strength performance for blended cement was achieved by adjusting the total carbonate content to 30 wt.% of the schist. The decision to introduce carbonate to the schist was guided by calculations determining the need for an excess of calcium ions to fully harness the potential for C‐A‐S‐H formation. Virgin and augmented schists were activated by up to 80% of their respective potentials by heat treatment. Phase content and decomposition behavior of the active components were investigated by thermogravimetric analysis (TGA), x‐ray diffraction (XRD), and scanning electron microscopy (SEM). Cement paste samples incorporating 30 wt.% replacement of OPC with activated schist SCMs were prepared. The phase distribution and compressive strengths of these samples were assessed at hydration intervals of 2, 7, 28, 50, and 90 days. Cement formulations with activated calcium‐augmented SCMs exhibited compressive strength values at 109%, 101%, 96%, 95%, and 94% compared to pure cement paste at 2, 7, 28, 50, and 90 days, respectively. These values surpassed 90% of the compressive strength of pure OPC at equivalent hydration time points. [ABSTRACT FROM AUTHOR]

This study attempts to comprehend mechanisms that enhance the photocatalytic properties of autoclaved cementitious pastes. The photocatalytic self-cleaning performance, phase composition, microstructure, optical properties, and silicate chain properties are characterized and analyzed. The results indicate that the silica source and alumina play significant roles in the evolution of phase composition and microstructure, which consequently affects the photocatalytic self-cleaning performance. The impacts of in - situ generated cement hydrates on the photocatalytic performance of cementitious materials are discussed for the first time, as well as the mechanisms governing the different morphologies of C–S–H crystals with the addition of different oxides. For the first time, the role of aluminum incorporation in the C–S–H network and major factors at different stages on the photocatalytic performance of cementitious materials are discussed. Finally, a systematic understanding of the photocatalytic properties of autoclaved cementitious materials is established. These results provide insights into the development of photocatalytic cementitious materials with tailored performances. [ABSTRACT FROM AUTHOR]

Over the past two decades, extensive research has been conducted to explore alternative supplementary cementitious materials (SCMs) in order to address the environmental concerns associated with the cement industry. Bricks, which are frequently preferred in the construction sector, generate a lot of waste during the production and demolition of existing buildings, requiring environmentally sustainable recycling practices. Therefore, many studies have been carried out in recent years on the use of brick waste as supplementary cementitious materials (SCMs) in cement mortar and concrete production. This critical review evaluates the impact of waste brick powder (WBP) on the mechanical and durability properties of mortar and concrete when used as a partial replacement for cement. It was observed that the properties of WBP-blended cement mortar or concrete depend on several factors, including WBP particle size, replacement ratio, pozzolanic activity, and mineralogical structure. The findings indicate that WBP with a particle size range of 100 µm to 25 µm, with a maximum cement replacement level of 10–20%, exhibits a positive impact on the compressive strength of both mortars and concretes. However, it is crucial to emphasize that a minimum curing duration of 28 days is imperative to facilitate the development of a pozzolanic reaction. This temporal requirement plays a vital role in realizing the optimal benefits of utilizing waste brick powder as a supplementary cementitious material in mortars and concretes. [ABSTRACT FROM AUTHOR]