Supplementary Cementitious Materials Research Articles

High-Strength Self-Compacting Concrete Production Incorporating Supplementary Cementitious Materials: Experimental Evaluations and Machine Learning Modelling

AbstractThis study investigates mechanical properties, durability performance, non-destructive testing (NDT) characteristics, environmental impact evaluation, and advanced machine learning (ML) modelling techniques employed in the analysis of high-strength self-compacting concrete (HSSCC) incorporating varying supplementary cementitious materials (SCMs) to develop sustainable building construction. The findings from the fresh characteristics test indicate that mixes’ optimal flowability and passing qualities can be achieved using different concentrations of marble powder (MP) alongside a consistent amount of silica fume (SF) and fly ash (FA). Moreover, the incorporation of 10% MP along with 10% FA and 20% SF in HSSCC significantly improved the compressive strength by 14.68%, while the splitting tensile strength increased by 15.59% compared to the reference mix at 56 days. While random forest (RF), gradient boosting (GB), and their ensemble models exhibit strong coefficient correlation (R2) values, the GB model demonstrates more precision, indicating reliable predicted outcomes of the mechanical properties. Following subsequent testing, it has been demonstrated that incorporating SCMs improves the NDT properties of HSSCC and enhances its durability. The finer MP, SF, and FA particles enhanced microstructural performance by minimizing voids and cracks while improving the C–H–S bond. As noticed by its lower CO2-eq per MPa for SCMs, the HSSCC mix with up to 15% MP inclusion increased mechanical strength while reducing the environmental footprint, making it an eco-friendly concrete alternative.

Investigating the performance and durability of high mechanical milling nano pulverised refused SCMs

This study investigated the performance and durability of high-mechanical-milling nano-pulverized industrial reject supplementary cementitious materials (SCMs). The research utilized industrial reject (IR-1), specifically Ground Blast Furnace Slag (GBFS), as the SCM. As-received IR-1 GBFS was milled for 90 minutes to achieve nano-sized particles, and its properties were compared with the un-milled, or before-milled (BM) material. Three pozzolanicity tests were conducted to compare the before milled (BM) and after-milled (AM) materials. Additionally, M30 grade concrete mixes were developed with cement partially replaced by 30 %, 35 %, and 40 % using both BM and AM IR-1 materials. Mechanical performance, including compressive strength, flexural strength, and split tensile strength, along with durability tests such as water absorption, sorptivity, and rapid chloride penetration, were conducted for the BM and AM IR-1 blended concretes. The results showed that AM IR-1 blended concrete achieved the required design strength at a 30 % cement replacement level. Furthermore, the AM IR-1 blended concrete exhibited 40 % higher compressive strength, 39 % higher flexural strength, and 29 % higher split tensile strength compared to the control concrete. Durability testing also revealed significant improvements in AM IR-1 blended concrete, with reductions of 19.65 % in water absorption, 24.71 % in sorptivity, and 38 % in chloride penetration. This study demonstrates that industrial waste, such as GBFS, can be effectively utilized as a sustainable alternative to traditional materials in the construction industry. Additionally, nano-pulverization treatment significantly enhances the pozzolanicity and overall performance of materials that may not meet the physicochemical standards specified in IS 3812-(Part 1):2017 and ASTM C618–19.

Preparation of aragonite-rich whisker materials from magnesium slag and salt lake bischofite and its effects on cement properties

This study develops an innovative wet carbonation process utilizing Magnesium Slag(MS), Salt Lake Bischofite (SLB), and CO2 to prepare carbonized materials mainly composed of aragonite and active silica gel, all raw materials were solid wastes. Subsequently, it was employed as Supplementary Cementitious Materials (SCMs) additive in cement, with the goal of efficiently capturing carbon dioxide and transforming aragonite whiskers into high-value products. Investigated the parameters influencing the formation of aragonite, including temperature and the concentration of the SLB solution, while exploring the nucleation and growth mechanisms of aragonite. The findings reveal that under 80 °C, the suspension of MS with 0.83 % SLB solution swiftly produces needle-like aragonite whiskers with single crystal lengths ranging from 10-20 μm and diameters of 0.3–0.5 μm. With the increase in SLB concentration, the aspect ratio of aragonite whiskers decreases. Additionally, highly polymerized amorphous silica gel was also detected. Therefore, Carbonated Aragonite-type Magnesium Slag (CAMS) (34.0901 m2/g) exhibits a significantly larger specific surface area compared to MS (0.9877 m2/g), representing an enhancement factor of 34.5 times, which concurrently bolsters its capability to adsorb reactive ions. During the carbonation process, 1 g of MS can sequester and solidify 0.403 g of CO2. Furthermore, incorporating CAMS as SCMs into cement mixtures notably enhances both the compressive and flexural strengths of cement mortar. These findings offer a sustainable approach to the recycling of solid waste, CO2 sequestration, and the improvement of cement-based material properties.

Development of a sustainable stabilized macadam road base using steel slag as supplementary cementitious material

As the main waste product of iron and steel industry, steel slag possesses considerable cementitious activity, making it a promising alternative to cement in Cement Stabilized Macadam (CSM). However, CSM was inevitably exposed to groundwater and rainwater when served as the pavement base course, leading to concerns over poor early strength and potential pollutant leakage, which are the main factors that may hinder the widespread utilization of steel slag in CSM base. To address these issues, this study investigated the feasibility of using steel slag powder to produce CSM. Steel Slag Powder-Cement Stabilized Macadam (SSCSM) samples were prepared and the hydration products, microstructure, mechanical properties, water damage resistance and heavy metal ions leaching behavior were investigated. The results show that the nucleation effect of steel slag powder accelerates the early hydration, but the C-S-H produced by hydration is not sufficient to form a stable hydration product network, so the microstructure of SSCSM is looser than that of CSM. The addition of steel slag powder improved the shrinkage performance of SSCSM, and the mechanical properties and heavy metal ion leaching concentration of SSCSM meet the engineering application requirements when the steel slag powder replacement level does not exceed 30 %. It was also found that the addition of steel slag powder promoted the development of pores in SSCSM samples after dry-wet cycles, resulting in the reduction of water damage resistance. Compared with conventional CSM, the use of SSCSM can not only reduce 4 % of raw material cost and 23.5 % of equivalent CO2 emission, but also mitigate the heavy metal ions leaching risk associated with steel slag, making it an effective and sustainable solution for steel slag recycling.

Chemical shrinkage characteristics and prediction model of desulfurization electrolytic manganese residue-cement composite slurries

To reveal the chemical shrinkage (CS) characteristics of desulphurized electrolytic manganese residue (D-EMR) cement composite slurries, the CS was measured for slurries with different water-cement ratios (0.3 and 0.4) and varying D-EMR content (0 wt%, 5 wt%, 10 %, 15 wt%, 20 wt%, 25 wt%, and 30 wt%) using the expansion method. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and backscattered electron (BSE) image analysis were used to investigate the hydration products and pore porosity at different stages. In addition, the correlation between CS and hydration products was simulated using GEMS thermodynamics. The results indicate that as the water-cement ratio increases, the CS of D-EMR cement composite slurries increases significantly. At a water-cement ratio of 0.4, the CS decreases with increasing D-EMR replacement levels before 1829 h of hydration, but this trend reverses after 1829 h. At 8 days, the CS values for replacement levels of 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, and 30 wt% were 97.2 %, 94.9 %, 87.3 %, 84.4 %, 81.5 %, and 78.6 % of those of the pure cement pastes, respectively. The corresponding limiting chemical shrinkage values were 0.0712 mL/g, 0.0725 mL/g, 0.0742 mL/g, 0.0756 mL/g, 0.0769 mL/g, and 0.0780 mL/g. Finally, the prediction of long-term CS of D-EMR cement composite slurries is well described by both hyperbolic function prediction and thermodynamic simulations. These findings provide valuable theoretical support for the use of D-EMR as a supplementary cementitious material in construction.

Alkali-fusion as an effective method for activating low-reactivity silicate wastes: A comparative study

Silicate wastes are used as supplementary cementitious materials (SCM) in Portland cement production, and as precursors to produce alkali-activated materials such as geopolymers to lower the environmental impact of construction. The high crystallinity of some of these wastes lowers their reactivity and hence the production of cementing hydrates. This paper includes a comparative analysis of the efficiency of alkali-fusion to activate three distinct types of silicate waste sourced from diverse sectors. The paper underscores the robustness of this method and its applicability in a wide composition range. It provides a solid foundation for the application of alkali-fusion across a wide spectrum of industrial waste types. Fly ash (FA), crop bottom ash (CBA) and aluminium processing sludge (APS); were fused with NaOH at 600 °C. XRD and FTIR analyses revealed that alkali-fusion disrupts highly cross-linked Si-O-Si structures transforming them into more reactive phases (sodium aluminosilicate and sodium silicates). Alkali-fusion is efficient even at low NaOH dosage(15 %). 15 % NaOH-fusion increased the mechanical activity index of FA, CBA and APS by 108.19 %, 494.61 % and 27.96 % respectively. The mineral composition of the wastes changed at 50 % alkali content: quartz was largely digested, and sodium silicate emerged as the dominant phase. After alkali-fusion, dense and compact matrices with rich hydrates were found evidencing the enhancement of the pozzolanic reaction. Alkali-fusion at relatively low temperature (600 °C) is successful in activating low-reactivity silicate waste, transforming the waste into valuable SCMs.

Innovative hybrid machine learning models for estimating the compressive strength of copper mine tailings concrete

The growing demand for copper and related materials in various industries is driving increased copper mining globally. This surge presents a substantial challenge in managing and responsibly disposing of large volumes of copper mine tailings (CMT). Incorporating CMT as supplementary cementitious materials (SCMs) in concrete addresses two significant environmental challenges simultaneously: reducing the accumulation of CMT waste in landfills and lowering the carbon footprint by reducing cement usage. The investigation into recycling CMT as a cement substitute involves a thorough assessment of its impact on the compressive strength (CS) of concrete. This research introduces innovative hybrid machine learning (ML) models for estimating the CS of CMT concrete, aiming to streamline strength assessment processes and save valuable resources. The method involves integrating features from large public datasets with the limited available data on the CS of CMT concrete. Support vector regression (SVR) was combined with advanced optimization techniques: firefly algorithm (FFA), grey wolf optimization (GWO) and particle swarm optimization (PSO) to create new hybrid models for forecasting the CS of CMT concrete. Additionally, traditional ML techniques like decision tree (DT) and random forest (RF) were used to compare with these SVR-based hybrids. All three hybrid models demonstrated strong performance, with SVR-FFA emerging as the most effective among them. Notably, SVR-FFA achieved the greatest R² score of 0.96, indicating superior predictive accuracy compared to SVR-PSO (0.92) and SVR-GWO (0.90). Additionally, the DT model attained an R² score of 0.88, while the RF model achieved an R² score of 0.84. Moreover, the SHapley additive exPlanations (SHAP) and partial dependence plots (PDP) analyses underscore the positive effects of curing age, cement, blast furnace slag, and superplasticizer on the CS of CMT concrete. A graphical user interface was developed for predicting the CS of CMT concrete, allowing for instant predictions without the need for conducting experiments.

Life cycle assessment of concrete incorporating all concrete recycling products

This study evaluates the environmental impact of concrete incorporating locally available raw materials through life cycle assessment (LCA). It explores the integration of all concrete recycling products in the concrete mixes, including recycled concrete aggregates (coarse and fine) as alternative aggregates and ternary blended cements made with recycled concrete powder and waste perlite powder. With the declining availability of conventional supplementary cementitious materials like fly ash and blast furnace slag, alternative resources are essential. The developed concrete mixes reduced the climate change impact by up to 12% when ternary blended cements were used instead of ordinary Portland cement with the same aggregate mix. This can be attributed to the utilisation of industrial waste in the binder, which are locally available without any environmental burden other than transportation. The study maintains the same workability class and assesses the competitiveness of the developed mixes across strength classes, with notable environmental benefits recognised for the C50/60 strength class. A comprehensive assessment of the life cycle inventory (LCI) of the raw materials revealed significant variability between different sources for recycled aggregates, demonstrating the necessity for adopting a range of LCI data for alternative raw materials in the absence of specific data. Transparent reporting of production and transportation data is essential to improving LCA accuracy. The study shows the feasibility of developing circular concrete mixes that incorporate all products from the concrete recycling process, highlighting that optimising material performance and reducing reliance on conventional materials are crucial for increasing their attractiveness to the construction industry.

Internal hydrophobic treatment for mortar containing supplementary cementitious materials: thermal analysis of kinetics and products of hydration

AbstractThe presented research investigates the application of the organosilicon admixtures based on triethoxyoctylsilane (OTES) on the hydration of the cement-based material with addition of supplementary cementitious materials (SCM) such as blast furnace slag and microsilica. The influence of silane-based admixtures on the kinetics of hydration was investigated by isothermal calorimetry. The calorimetric results disclosed that applied admixtures affect the hydration process of cement paste with SCM. The DTA/TG analysis provided the information about impact of triethoxyoctylsilane on the composition and formation of the mineral phases. The DTA/TG measurements showed noticeable changes in the thermal decomposition of the tested materials and amount of bounded water. The impact of OTES on the microstructure and pore size distribution of pastes was examined by mercury intrusion porosimetry. The result showed significant changes in the range of pore diameters. The influence of organosilicon admixtures on the compressive strength of mortars after 2, 7, 28, 56 and 90 days was also investigated. The effect depended on the mineral additive used. In case of blast furnace slag, the development of compressive strength was only delayed, however, in the case of microsilica, it was stopped.

Hydration and Mechanical Properties of Cement Kiln Dust-Blended Cement Composite

This study aims to investigate the effects of cement kiln dust (CKD) on the hydration reactions and mechanical properties of cement, and to evaluate its potential for use as a supplementary cementitious material (SCM). The key variables are the CKD type and the replacement ratio. Cement paste and mortar specimens containing CKD were prepared to examine their effects on the cement hydration and mechanical properties. The effect on hydration was assessed using setting time measurements, heat of hydration tests, and thermogravimetric analyses (TG). In addition, compressive strength tests were conducted to evaluate the effect of CKD on the mechanical properties of the cement. The results indicated that CKD promoted early-age cement hydration and enhanced the early-age mechanical properties. However, owing to its lack of pozzolanic reactivity, it did not significantly affect long-term hydration. Given that the effects of CKD vary slightly depending on its chemical composition, careful consideration of CKD’s properties suggests that its potential use as an SCM is promising.

Comparative Study of Mechanical Properties of Self Compacting Concrete Using Binary Pozzolanic Materials

Abstract: The study examined the viability of using waste supplementary cementing materials (SCMs), such as fly ash (FA) and silica fume (SF), as partial replacement of Ordinary Portland cement. The way SCC's fresh properties and hardened were impacted by FA and SF. The study examined the fresh characteristics and hardened characteristics of various distinct SCC mixes using SCC with partial replacement of Ordinary Portland Cement with FA (class F) and SF. First, the cement was replaced by percentages in the mixes 0%, 10%, 15%, 20%, 25%, and 30% by FA and constant replacement of 10% by SF. Then cement was replaced by percentages in the mix with 25% FA constant and 4%, 6%, 8%, 10%, and 12% by SF. For every combination, the water/binder (w/b) ratio was set at 0.43. The EFNARC (Specification and Guidelines for Self-Compacting Concrete) standards were met by the slump flow, T50, and viscosity of the SCC. After 28 days of curing, the blend consisting of 65% PC, 25% FA, and 10% SF had a maximum compressive strength of 41.22 MPa which is 12.07% greater than the compressive strength of the control specimen which is 36.78 MPa. The Split Tensile Strength of the same blend is 4.37% is greater than the control specimen. Non-destructive tests were also performed after 28 days of curing and the regression equations give the excellent relationship between Rebound Number, Ultrasonic Pulse Velocity, and Compressive Strength. This is due to the formation of the proper matrix as the particle size of SF and FA is less than that of cement and the free lime of cement reacts with FA and SF to form C-S-H gel which provides strength.

Comparative study on the chemical and physical filling effects of binder materials in Green Ultra‐High Performance Concrete and Ultra‐High Performance Concrete

The development of Green Ultra-High Performance Concrete (GUHPC) is one of the primary approaches to combat global warming in the construction industry and has received widespread attention. Accurately quantifying the physical and chemical filling effects of binder materials can aid in the development of more efficient design methods for GUHPC. The hydration and microstructure development of GUHPC were investigated by a combination of the isothermal calorimetry, mercury intrusion porosimetry (MIP), thermogravimetry (TG), X-ray diffraction (XRD) and backscattered electron microscopy (BSEM). The physical and chemical filling effects of each binder material on the porosity of paste were quantified. The results indicated that both the physical and chemical filling effects of the binder materials made essential contributions to the porosity. Compared with in UHPC, supplementary cementitious materials (SCMs) play a better chemical and physical filling role in GUHPC. More attention needs to be paid to the chemical filling effect of mineral admixtures in the design of GUHPC. Reasons for limiting the ability of binder materials in GUHPC to achieve better chemical filling effects were discussed.

Geological evaluation of black shale as a suitable Supplementary Cementitious Material (SCM) to optimize the use of clinker in cement production

Faced with challenges like resource depletion and climate change, the cement industry needs sustainable solutions. This study explores the potential of geologically-delinaeated black shale from Apersua, Ghana, as a supplementary cementitious material (SCM) to reduce reliance on traditional methods. The researchers analysed the shale's chemical composition and mineralogy, then created laboratory cement formulations with varying black shale content. These were compared to standard formulations without shale. The results show cement with black shale has comparable compressive strength, meeting standard requirements. Even a formulation with only black shale (excluding limestone, a common ingredient) passed strength tests. Overall, the black shale demonstrated good potential as a SCM based on strength, chemical makeup, setting time, and its possible contribution to durability. This research suggests that black shales from Apersua are worth exploring further as a sustainable and potentially cost-effective alternative in cement production.

Feasibility study on the preparation of ternary blended cements with low-kaolinite calcined coal gangue and limestone

This paper presents a feasibility study on the production of ternary blended cements with low-kaolinite calcined coal gangue (CCG) and limestone, considering kaolinite contents varying from 11.7 % to 40.6 % in coal gangue (CG). The ternary systems were designed with 15 %, 30 %, 45 % and 60 % by mass of cement replaced by CCG and limestone with a fixed mass ratio of 2:1. The fluidity and compressive strength of the mortars were measured, followed by the strength efficiency analysis combined with CO2 emission. The potential hydration mechanism was revealed by analysing the hydration kinetics, hydrates and microstructural evolution of these ternary pastes. The results showed that it is possible to use low-kaolinite CCG and limestone to prepare ternary blended cements with adequate mechanical strength that can fulfill the 28-day strength requirement of 32.5 or 42.5 grade cement. In addition, Increasing the kaolinite content in CG can increase the substitution of cement up to 60 %. Microstructural studies indicated that the compressive strength of these ternary mortars at 3 and 7 days was mainly dominated by cement hydration and the pozzolanic reaction between CCG and portlandite (CH), respectively. The precipitation of carboaluminates from the synergy of CCG and limestone significantly reduced critical pore size and increased the volume fraction of fine capillary pores from 7 days, well supporting the strength development of the ternary mortar. The findings of this work underscores the potential of using low-kaolinite CCG as a supplementary cementitious material (SCM) to reduce carbon footprint in the field of construction, and also in contributing to a high-value green utilization of solid waste.

Rapid Assessment of Sulfate Resistance in Mortar and Concrete.

Extensive research has been conducted on the sulfate attack of concrete structures; however, the need to adopt the use of more sustainable materials is driving a need for a quicker test method to assess sulfate resistance. This work presents accelerated methods that can reduce the time required for assessing the sulfate resistance of mixtures by 70%. Class F fly ash has historically been used in concrete mixtures to improve sulfate resistance. However, environmental considerations and the evolving energy industry have decreased its availability, requiring the identification of economically viable and environmentally friendly alternatives to fly ash. Another challenge in addressing sulfate attack durability issues in concrete is that the standard sulfate attack test (ASTM C1012) is time-consuming and designed for only standard mortars (not concrete mixtures). To expedite the testing process, accelerated testing methods for both mortar and concrete mixtures were adopted from previous work to further the development of the accelerated tests and to assess the feasibility of testing the sulfate resistance of mortar and concrete mixtures rapidly. This study also established criteria for interpreting sulfate resistance for each of the test methods used in this work. A total of 14 mortar mixtures and four concrete mixtures using two types of Portland cement (Type I and Type I/II) and various supplementary cementitious materials (SCMs) were evaluated in this study. The accelerated testing methods significantly reduced the evaluation time from 12 months to 21 days for mortar mixtures and from 6 months to 56 days for concrete mixtures. The proposed interpretation method for mortar accelerated test results showed acceptable consistency with the ACI 318-19 interpretations for ASTM C1012 results. The interpretation methods proposed for the two concrete sulfate attack tests demonstrated excellent consistency with the ASTM C1012 results from mortar mixtures with the same cementitious materials combinations. Metakaolin was shown to improve sulfate resistance for both mortar and concrete mixtures, while silica fume and natural pozzolan had a limited impact. Using 15% metakaolin in mortar or concrete mixtures with Type I/II cement provided the best sulfate resistance.

A Lab-Scale Evaluation of Parameters Influencing the Mechanical Activation of Kaolin Using the Design of Experiments.

This research investigates the mechanical activation of kaolin as a supplementary cementitious material at the laboratory scale, aiming to optimize milling parameters using the response surface methodology. The study evaluated the effects of rotation speed and milling time on the amorphous phase content, the reduction in crystalline kaolinite, and impurity incorporation into the activated clay through the Rietveld method. The results demonstrated that adjusting milling parameters effectively enhanced clay activation, which is crucial for its use in low-carbon cements. High rotation speeds (300/350 rpm) and prolonged grinding times (90/120 min) in a planetary ball mill increased the pozzolanic activity by boosting the formation of amorphous phases from kaolinite and illite and reducing the particle size. However, the results evidenced that intermediate milling parameters are sufficient for reaching substantial degrees of amorphization and pozzolanic activity, avoiding the need for intensive grinding. Exceedingly aggressive milling introduced impurities like ZrO2 from the milling equipment wear, underscoring the need for a balanced approach to optimizing reactivity while minimizing impurities, energy consumption, and equipment wear. Achieving this balance is essential for efficient mechanical activation, ensuring the prepared clay's suitability as supplementary cementitious materials without excessive costs or compromised equipment integrity.

A Review On Air Pollution Reduction Properties Of Concrete By Using Supplementary Cementitious Materials

A Review On Air Pollution Reduction Properties Of Concrete By Using Supplementary Cementitious Materials

Feasibility of upcycling red mud for low-CO2 cement via calcination: A comparative study with FA and GGBFS based in China

This study examines the feasibility of developing low-CO2 cement using calcined red mud (RM) and explores positive scenarios that simultaneously attain technical, environmental, and economic benefits in reference to conventional fly ash (FA) and ground granulated blast furnace slag (GGBFS) cements. Based on the variables of RM's content and calcination temperature, we investigated the fresh properties (paste rheology and mortar flowability), strength development, microstructure, embodied CO2 emissions, and cost of the RM-blended cement. The results show that there was an optimal range of RM's calcination temperature (400–600 °C) that improved the cement paste viscosity while attaining a higher strength than that of FA cement. Considering the cradle-to-gate CO2 emissions and cost of cement production, the optimal cement composition is comprised of up to 30% RM calcined at 600 °C, where the cement cost is lowered by 19.3% compared to the FA reference having a comparable CO2 footprint. According to the geographical analysis, the calcined RM shows minimal advantages over GGBFS but could substitute FA as a cleaner, cheaper, and more reactive supplementary cementitious material in regions where electricity grid is dominated by clean energy. Therefore, RM offers a plausible solution to future low-CO2 cement in light of the increasing shortage of FA led by the declining use of coal-powered electricity.

Comparing durability and compressive strength predictions of hyperoptimized random forests and artificial neural networks on a small dataset of concrete containing nano SiO2 and RHA

Through the increasing use of supplementary cementitious materials, the properties of concrete have taken on increased significance in a design code. Using reliable prediction models based on a small data set for the mechanical properties and durability of concrete can reduce the number of trial batches and experiments needed to produce useful design data in the laboratory, reducing time as well as resources. In this study, we investigate how the properties of water penetration, chlorine resistance, and compressive strength can be predicted by polynomial regression (PR), random forest (RF) regression, and artificial neural networks (ANNs) based on the input values of density, workability, and the constituent amount of rice husk ash, cement, and nano SiO 2 . We vary the training data used and test the coefficient of determination ( R 2 score) on the remaining data as a test set to measure predictive capability. We show that RFs and ANNs outperform PR in all settings and have unambiguously extrapolating properties when hyperparameter optimization is designed for this purpose. Remarkably, we obtain R 2 scores on the test data of 0.858 − 0.990 for RFs and 0.825 − 0.985 for ANNs.

Mechanical properties and microscopic characterization of waste perlite powder as supplementary cementitious material

In this study, we conducted a comprehensive investigation on the influence of waste perlite powder (WPP) on the various properties of mortar and paste, including slurry performance, mechanical strength, hydration products, and microstructure. Additionally, we also aimed to uncover the underlying mechanism behind these effects. It was found that WPP reduced the workability and facilitated the setting process of cement-WPP pastes. WPP decreased the mechanical strength of mortar, but it exhibited significant strength enhancement during the subsequent stages. The incorporation of WPP worsened the water absorption behavior; however, this negative effect was mitigated as the curing age of the mortar was prolonged. The drying shrinkage cement-WPP binary system was significantly improved, with the prolongation of curing age. Moreover, WPP reduced the early heat release of the binary system, which may be beneficial for reducing the temperature gradient in mass concrete. It was confirmed that WPP accelerated the transformation from AFt to AFm, promoted the formation of C-A-S-H and optimized the pore structure of the system. It was confirmed that WPP was involved in the hydration reaction, which accelerated the transformation from AFt to AFm and promoted the formation of C-A-S-H. Such results suggested that the reuse of WPP in concrete production was technically feasible owing to its high pozzolanic reactivity.