Cement-based Construction Materials Research Articles

New Methodology for Evaluating Strength Degradation from Temperature Increase in Concrete Hydration under Adiabatic Conditions

Cement-based construction materials, commonly known as “cement concrete”, result from the hydration reaction of cement, which releases heat. Numerous studies have examined the heat of cement hydration and other thermal properties of these materials. However, a significant gap in the literature is the assessment of the impact of the hydration temperature on the material’s strength, particularly compressive strength. This work presents an experimental methodology that consistently estimates the temperature evolution of a mixture used to manufacture concrete or mortar during the first hours of Portland cement hydration. The methodology aims to ensure results that correspond to an infinite medium (adiabatic conditions), where there are no heat losses to the surroundings. Results obtained under adiabatic conditions (simulating an infinite medium) indicate that a ready-made mortar (Portland cement: sand: water; 1:2.5:0.5) can reach temperatures of approximately 100 °C after 48 h of hydration. Under these conditions, compressive strength decreases by up to 20%.

Optimizing alkali-activated clay with rubber waste for sustainable earthen bricks: A comprehensive study

This study explores the potential of optimizing alkali-activated clay with rubber waste to create sustainable earthen bricks. The research addresses the environmental challenges associated with traditional cement-based construction materials by incorporating locally sourced calcined clay and recycled rubber tire waste. The experimental program involves testing different proportions of sand with calcined clay, varying sodium hydroxide (NaOH) concentrations, and integrating rubber content. The aim is to develop a material that balances environmental sustainability with improved mechanical and durability properties. The mechanical and microstructural properties of the resulting materials were evaluated through compressive and flexural strength tests, wetting and drying cycles, and advanced analysis techniques such as X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicate that while the inclusion of rubber enhances certain properties such as reducing the unit weight and Structural Integrity During Wet-Dry Cycles, it adversely affects compressive and flexural strengths. This study highlights the importance of optimizing the balance between durability and mechanical strength to develop effective and sustainable construction materials.

Flexural and fracture characterization of UHPGC notched beam with various glass sand replacement ratios and steel fiber contents

The preparation process of quartz sand (QS) can cause serious environmental pollution, which is particularly important to find a new replacement material for QS in cement-based construction materials. In this study, an economical and environmentally friendly ultra-high performance glass sand concrete (UHPGC) was prepared by partially replacing QS in conventional ultra-high performance concrete (UHPC) with glass sand (GS) ground from waste glass. The effects of material composition characteristics including water-binder ratio (W/B), GS replacement ratio, and steel fiber content on the flexural and fracture characteristics of UHPGC notched beams were investigated based on response surface method (RSM) and acoustic emission (AE) monitoring. The results indicate that the GS replacement rate presents almost no effect on the tensile strength and flexural toughness of the specimens while reducing the water-binder ratio or increasing the steel fiber content can significantly improve the flexural tensile strength of UHPGC notched beams. UHPGC notched beams show the best performance when the W/B is 0.17, the steel fiber content is 3 %, and the GS replacement rate is 50 %. By analyzing and comparing the AE parameters and fracture modes, the discrepancies in flexural and fracture properties of UHPGC notched beams with variable material composition characteristics can be elucidated. Among them, the low water-binder ratio or high steel fiber content has a significant effect on the fracture characteristics and fracture process of the specimens, while the GS replacement rate exhibits negligible effect.

Effect of expanded perlite aggregates and temperature on the strength and dynamic elastic properties of cement mortar

The residential market consumes nearly half of the world’s concrete production, and it is anticipated that 68 % of the global population will reside in urban areas by 2050. Researchers have focused their efforts on exploring alternative options to natural aggregates in concrete and mortar. In line with the principles of circular economy, construction and demolition waste has been repurposed for the manufacture of cement-based materials. Volcanic products, which are abundant but underutilized, have been identified as an alternative to recycled aggregates. They offer several advantages over natural river aggregates, including reduced weight, enhanced thermal and acoustic insulation, improved fire resistance and pozzolanic characteristics. While there has been a significant amount of research on the use of expanded perlite as a supplementary cementitious material, studies involving the use of expanded perlite aggregates (EPA) in cement-based construction materials are relatively limited. This paper seeks to address this knowledge gap by investigating the use of EPA in cement-based mortar at both room and elevated temperatures. The study examines the impact of varying replacement percentages (10 %, 20 % and 30 % - by volume) of natural sand with EPA having a maximum grain size of 4 mm, and the exposure temperature of mortar prisms at the age of 28 days. Specifically, temperatures of 100ºC, 150ºC and 200ºC were selected for analysis. The impact of these parameters on the flexural and compressive strength of mortar, as well as its dynamic elastic properties, was experimentally determined. The findings indicate that, at room temperature, higher replacement percentages of natural sand by EPA result in decreased flexural and compressive strengths, by as much as 50 % and 30.71 %, respectively. However, the dynamic moduli values for replacement percentages up to 20 % are similar to those of the reference mix. Conversely, when subjected to temperatures up to 200ºC, significant improvements were observed in the flexural strength values, e.g. over 20 % for temperatures of 150°C and 200°C, with only marginal improvements in compressive strength, 3 % ÷ 20 % for temperatures of 150°C and 200°C, compared to values obtained at room temperature.

Circular Economy Approach: Recycling Toner Waste in Cement-Based Construction Materials

Based on a waste generated survey by companies in the area of the city of Bahia Blanca (Argentina), the possibility of incorporating part of them in a Portland cement matrix was examined. Among the waste is toner (TW), which is obtained from cartridges used in photocopiers, laser printers, and faxes. This paper aims to analyze the physical and mechanical properties of cement pastes and mortars using toner as a Portland cement replacement compared to a reference sample without toner. The mixes were made with 2.5, 5, 10, and 15 wt.% replacement of cement by toner, and it was measured the flow, normal consistency, setting time, calorimetry, and Frattini test in pastes and mechanical strengths in mortars employing standardized tests. Also, an analysis of the leachate in the curing water was carried out after 56 days to look for contaminating materials. The replacement of up to 5% cement with toner did not produce substantial alterations in the final setting time or mechanical properties. No heavy metals were found in the leachate, so TW can be immobilized in a cementitious matrix as it does not cause leaching above the established limits. Therefore, TW from a local industry can be used in construction materials and could contribute to a reduction of up to 14% of CO2 emissions with a cement replacement of 15% in cement-based materials.

Self-sensing properties of cementless ultra-high performance concrete (UHPC) with slag aggregates

This research addresses the environmental impact of traditional cement-based construction materials and explores sustainable alternatives. The study aims to explore the mechanical properties, flowability, setting time, and self-sensing performance of cementless ultra-high performance concrete (UHPC) by utilizing the electrical properties of electric arc furnace slag (EAF slag) as a replacement for natural aggregates, along with alkali-activated slag as the binding material. Comparative analyses are conducted between cementless UHPC with EAF slag and silica sands, as well as the impact of incorporating carbon fiber. The study reveals that cementless UHPC with EAF slag exhibits improved fluidity and slightly increased setting time compared to UHPC with silica sands, attributed to the spherical shape and ball bearing effect of EAF slag. While the compressive and tensile strength of cementless UHPC with EAF slag is slightly lower than that of UHPC with silica sands, it still meets UHPC standards with strengths of 150 MPa and 8 MPa, respectively. Nonlinear curve fitting accurately quantifies the self-sensing performance, yielding precise simulation results. Importantly, EAF slag-based UHPC exhibits superior self-sensing capabilities, outperforming carbon fiber incorporation. Unlike UHPC with silica sands, which generates substantial noise even with carbon fiber, EAF slag-based UHPC demonstrates effective self-sensing with minimal noise, even in the absence of carbon fiber. This study expands the understanding of self-sensing performance in cementless UHPC by effectively utilizing EAF slag as a replacement for natural aggregates. The results suggest that the valorization of EAF slag has the potential to enhance sustainability and the self-sensing capabilities of cementless UHPC.

Novel application of sustainable coal-derived char in cement soil stabilization

Cement soil stabilization is a commonly used method to improve in-situ soil properties catering to different geotechnical applications. However, cement manufacturing is typically associated with high CO2 emissions and energy consumption. Coal char is a sustainable and environmentally friendly material derived from the coal pyrolysis process. Traditionally used for combustion and gasification, recent research has revealed its potential to improve the engineering performance of cement-based construction and building materials. This study explores the innovative use of coal char in cement soil stabilization. Examining various cement contents (5%, 10%, and 20%) and char contents (10%, 20%, and 30%), the properties of char-cement stabilized soils, including mineralogy, density, water content, thermal conductivity, unconfined compressive strength (UCS), and mechanical properties under triaxial compression, are comprehensively investigated and compared with cement stabilized soil. It is found that char promotes both cement hydration and reaction between soil minerals and cement. The thermal conductivity and UCS of char-cement stabilized soil are 0–9% lower and 8–16% higher, respectively than that of cement stabilized soil. Under triaxial compression, the addition of char in stabilized soil leads to 23.7% increase in shear strength, 17.7% increase in cohesion, and 16.7% increase in the angle of internal friction. In conclusion, the introduction of coal char into traditional cement soil stabilization demonstrates a novel approach to achieving sustainability and enhancing engineering performance in relevant geotechnical applications.

The Use of Natural Zeolites in Cement-Based Construction Materials—A State of the Art Review

Natural zeolite is a honeycomb-structured aluminosilicate mineral with an open crystalline structure which makes it suitable for a variety of applications. Given the beneficial effects of zeolites on the properties of cementitious materials, the present paper aims to summarize the recent findings reported in the scientific literature on the use of zeolites in cement-based construction materials. This paper limits the analysis to natural zeolites. The influence of natural zeolites on the workability and setting time of cement-based construction materials revealed that increasing the zeolite content led to a reduction in workability compared to the control mixes. At the same time, the initial and final setting times of cement pastes showed a decreasing trend with an increase in the replacement percentage. The slow pozzolanic reaction of clinoptilolite zeolite results in lower flexural strength and compressive strength values of mortars at the age of 28 days. Blending zeolites with other supplementary cementitious materials resulted in improved values of the mechanical properties of mortar and concrete. The findings regarding the impact of zeolite on the durability of concrete suggest that zeolite shows promise as a viable alternative to cement, with positive effects on various aspects of durability. The majority of the durability factors are interconnected. The presence of conflicting findings is particularly significant in this context, highlighting the need for a comprehensive approach to address these challenges in the future.

Optimization of additives in cement mortar using Taguchi method

Recent emerging developments in construction works have introduced many enormous and wonderful construction materials. But till now, cement based construction materials are being used in various activities e.g., masonry, lining, grouting etc. Cement, a key ingredient for various construction materials, needs to be replaced by another natural or artificial inert, due to its perilous effects in ecology. The present study has been conducted to evaluate the compressive strength, electrical resistivity, cost analysis and environment assessment of cement mortar after replacing the cement with various proportions of Kota stone powder. Calcium nitrate and triethanolamine were also added to the mortar mixes to control the parametric behaviours of the mixes. The Taguchi technique has been used to curtail the number of mix proportions for effort saving practices. Taguchi technique produces a data set of lesser experimental runs than a full factorial approach. Therefore, Taguchi method could be used to optimize the number of combinations to make the project cost-effective. The purpose of this study is to evaluate the performance of cement mortar containing calcium nitrate, triethanolamine, and Kota stone powder in various proportions with respect to various attributes. An L9 (3^3) orthogonal array containing nine mortar blends was analyzed to optimize the process parameters on the basis of the laboratory responses. Results of the study positively affirmed that the efficacy of the incorporation of Kota stone powder in mortar has yielded as economic and ecological construction material over other additives.

Impact of Eggshell Powder on the Mechanical and Thermal Properties of Lightweight Geopolymer

Adopting proper waste management technology in the place of the construction industry to the extent possible to lower the production of new materials and intern reduces the environmental impact pertaining to the industry. In this work, eggshell powder (ESP; waste from the poultry industry) and fly ash (FA; waste from combustion of coal) were utilized as precursors for producing geopolymer and to substitute conventional cement-based construction materials. Three different weight percentage ratios of precursors, namely, 90FA:10ESP, 80FA:20ESP, and 70FA:30ESP were reinforced with two different weight percentages, namely, 15 and 30 wt% of paddy straw in the presence of suitable combinations of sodium silicate and sodium hydroxide to obtain lightweight geopolymer panels. Results received from different analytical tests, namely, density, water absorption, compressive strength, and flexural strength infer that the incorporation of ESP enhances the performance of the geopolymer products to a considerable extent. The specimen sample made using 70FA:30ESP in the absence of paddy straw reinforcement possesses a compressive strength value of 15.64 MPa, which is higher than that of paddy straw reinforced panels. It was observed that there was a reverse trend noticed in the case of flexural behavior on reinforcement of paddy straw, namely, 15 wt% possesses a higher value than that of the panel (70FA:30ESP) made using in the absence of reinforcement. The lowest thermal conductivity value was observed at 0.0633 W/m·K for the sample 90FA:10ESP reinforced with 30% paddy straw. Data from different studies infer that using ESP and paddy straw reinforcement influences strength properties and thermal conductivity. The present study indicates valid information related to the using biowastes for the production of insulation materials and environmental preservation and energy conservation.

ENCAPSULATION OF GROUND BOTTOM ASH AS SUPPLEMENTARY CEMENTITIOUS MATERIALS FOR CEMENT MORTAR

Excessive carbon dioxide (CO2) emissions due to the Portland cement manufacturing process have encouraged the industry to look for more sustainable alternatives to cement. Supplementary cementitious material (SCM) has been widely used to improve concrete performance through considerable research. By-product waste, such as fly ash, has been utilized in many construction projects. It is an effective solution to solve long-term environmental pollution. As one of the coal industry by-products, bottom ash has similar chemical properties compared to fly ash, but it is rarely used as SCM because of its size. Therefore, this research aims to modify the regular bottom ash and observe the strength development of cement mortar incorporating bottom ash as SCM. The pre-treatment process of bottom ash was performed by 4 hours of milling to produce micro-size particles. The chemical and physical properties of modified bottom ash were evaluated before being cast into cement mortar specimens. Various percentages of cement replacement using modified bottom ash were used in this research. The evaluations include X-ray fluorescence (XRF) analysis, specific gravity, particle size analysis, scanning electron microscope-energy dispersive X-ray (SEM-EDX), normal consistency, and setting time. The compressive strength and strength activity index were evaluated to obtain the strength development and optimum composition of cement mortar incorporating bottom ash, caused by pozzolanic activity. The results indicate that bottom ash positively affects the strength development of cement mortar, and it can be used as SCM to produce more sustainable cement-based construction materials.

Sequestration and utilization of carbon dioxide to improve engineering properties of cement-based construction materials with recycled brick powder: a pathway for cleaner construction

The research explores the possibility of utilizing carbon dioxide to modify the properties of recycled brick powder (RBP) and enhance the engineering performances of RBP-mortar. The RBP, crushed to the size range of 0.075 to 4 mm, is carbonated by exposing to 5% CO2 for 4 h and characterized for phase composition, porosity and micro-structure. The non-carbonated RBP (RBP) and pre-carbonated RBP (Carb-RBP) are applied to replace 25% and 75% of manufactured sand (M-sand) in cement mortars maintained at similar flow level (110 – 113%), which are then cured under three conditions - (i) ambient condition (N), (ii) 4 h of steam curing followed by moist and dry curing (STC), and (iii) accelerated CO2 curing (5% CO2 of 99% purity) for 4 h followed by moist curing and dry curing (CC). Physico-chemical characterizations suggest that Carb-RBP has higher micro-pore volume and surface area contributed by pores in the size range of 1 nm to 3 nm than RBP. After carbonation, the reactivity of RBP in alkaline environment is increased due to CO2-induced breakdown of calcium and alumino-silicate minerals into calcium carbonate and silica gel. Due to addition of 25% and 75% RBP and Carb-RBP, hydration kinetics is accelerated by 4 – 4.50 h compared to control due to nucleation of hydration products on the surfaces of RBP. Faster precipitation of hydration products, more micro-pore sites in RBP and higher porosity due to increased water demand enhance the carbon sequestration in RBP-mortars and Carb-RBP mortars by 30–82% compared to control (0% RBP). Use of Carb-RBP to replace 25% of M-sand offer similar compressive strength as control and 19 – 21% higher strength than mortars with RBP (non-carbonated). CO2 curing also reduces the total shrinkage of mortars with recycled brick powder by 12 – 17% compared to ambient curing and steam curing due to densification by calcium carbonate crystals. The findings from this research strongly suggests a significant reduction in embodied carbon of Portland cement-based construction materials by utilizing a combined approach of carbon sequestration and replacement of fine aggregates by recycled brick powder.

Flexural Performance of RC Beam with the Partial Replacement of Cement with EggshellPowder(ESP)

Abstract: It's a renowned fact that concrete used around the globe is second only to water. The cement industries have been categorized as highly polluting industries by the Central Pollution Control Board (CPCB). The production of ordinary Portland cement contributes 5-7% of total greenhouse gas emission and also consumes large amount of energy, hence it is crucial to discover substitute to cement. Eggshell is a waste material that can be obtained from restaurants, bakeries and households. Eggshell powder (ESP) has high amounts of calcium and can be combined with pozzolanic materials, such as fly ash, which have low calcium content. If effective uses for eggshell can be found, it would create an opportunity for a sustainable solution. Eggshell waste is among the most abundant agro-waste material discharged from food processing industries. Despite the exceptional properties and several applications, eggshell is castoff in huge quantity without any further use. This review paper focuses on appraising the potential uses of eggshell waste as a feedstock for production of sustainable construction materials. The emphasis is on the need to exploit extensively eggshell waste as a partial cement replacement material in cement-based construction materials. This study focuses on the viability of using calcined eggshells (CES) as a partial replacement of cement by analysing early age performance. Compressive, Flexural and Split Tensile Strength of concrete with 10%, 15%, 20% cement replacement with eggshell powder. The utilization of PES which offers a low-cost and energy-efficient resource for construction.

Use of Clay and Titanium Dioxide Nanoparticles in Mortar and Concrete—A State-of-the-Art Analysis

In the past decades, nanomaterials have become one of the focal points in civil engineering research. When added to cement-based construction materials (e.g., concrete), it results in significant improvements in their strength and other important properties. However, the final mix characteristics depend on many variables that must be taken into account. As such, there is no general consensus regarding the influence upon the original material of certain nano-sized additives, the optimum dosage or the synergistic effect of two or more nano-materials. This is also the case for titanium dioxide (TiO2) and nanoclay (NC). The paper focuses on reporting the existing research data on the use of the above-mentioned materials when added to mortar and concrete. The collected data is summarized and presented in terms of strength and durability properties of cement mortar and concrete containing either TiO2 or NC. Both nano-materials have been proven, by various studies, to increase the strength of the composite, at both room and elevated temperature, when added by themselves in 0.5%~12% for TiO2 and 0.25%~6% for NC. It can be inferred that a combination of the two with the cementitious matrix can be beneficial and may lead to obtaining a new material with improved strength, elastic and durability properties that can be applied in the construction industry, with implications at the economic, social and environmental levels.

Innovative approach for the protection of recycled concrete by biogenic silica biodeposition

Over the past few years, the construction industry has sought to be more sustainable through use of more economically responsible materials and the use of environmentally friendly techniques such as bio-remediation. One promising area in this regard is that of surface treatments, particularly bio-repair techniques, to reduce the deterioration suffered by cement-based materials as a result of environmental conditions. This study presents original work on the use of silicaceous biodeposition by diatoms as a waterproofing surface treatment for recycled concrete. A recycled concrete mix containing a 50% substitution of recycled aggregates (RA) was used as a test substrate and the effectiveness of the bio-treatment was assessed using four different tests: capillary absorption, high-pressure water penetration, low-pressure water absorption and also characterised the biodeposited layer using SEM. Results demonstrate reductions of up to 33% in the capillary absorption test, while high-pressure water penetration decreased by 54.7%, compared to controls. In addition, Karsten tube tests showed low-pressure water absorption was delayed by up to 436 times relative to control samples. In combination these tests confirm the efficacy of diatom biodeposition as a protective surface treatment for cement-based construction materials.

Cementitious nanocomposites engineered with high-oxidized graphene oxide: Spotting the nano to macro correlation

There has been increasing interest in using nanosized fillers in cement-based construction materials to upgrade mechanical properties, durability, and multi-functionality. In this context, graphene oxide (GO) is proved to be an effective candidate, and its interaction with cement can lead to remarkable enhancement in its macro-properties. To guarantee reproducibility and to maximize environmental and health safety, a GO water suspension ( GONan, Nanesa, Italy ) was selected from the market-available products. A complete morphological, microstructural and chemical characterization was performed by Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS), Raman Spectroscopy, Infra-Red Spectroscopy (FTIR-ATR), X-ray Diffraction (XRD), and Thermogravimetric Analysis. The aggregation test of GONan in saturated Ca(OH) 2 water solution was also performed, and results were obtained by UV-VIS spectroscopy and Scanning Electron Microscopy (SEM). Different dosages (0.01%, 0.1%, and 0.2% by weight of cement) of GONan were added to a commercial M5 mortar. Fresh properties were determined by rheology measurements and flowability and workability tests. Samples were hardened in water at room temperature (RT) for 7, 14, and 28 days. The compressive and bending strength of all samples were evaluated following the standards. The microstructural features of nanocomposites hardened at 28 days were investigated by SEM. Results clearly evidenced that the extra-low GONan dosage (0.01%) was the most promising formulation. Despite the worsening of fresh properties (i.e., increase of plastic viscosity and decrease of flowability and workability by 150%, 50%, and 100%, respectively, compared to the control sample), the mechanical properties of such an extra-low dosage nanocomposite at 14 days showed a notable increase of 20% and 40% for bending and compressive strength, respectively.

A bio-inspired, plant-derived admixture for metakaolin blended cement mortars

Partially replacing ordinary Portland cement (OPC) with metakaolin (MK) can refine the pore structure, improve mechanical properties, and enhance the durability of concretes. However, MK tends to agglomerate due to its high surface area and high concentration of hydroxyl groups. To overcome this problem, this study exploits a plant-derived polyphenol, tannic acid (TA), as an eco-friendly admixture to disperse MK. Due to its similar chemical functional groups as the adhesive protein in the mussel byssus, TA can adhere to various surfaces like the mussel’s adhesive protein. An experimental program was carried out to characterize the TA treated MK and investigate the effects of the proposed method on the properties of the cement paste and mortar. After mixing with the MK, TA can be adsorbed on the surface of MK particles, achieving deflocculation and dispersion of mineral grains by electrostatic repulsion forces and steric effect, significantly improving the workability of the mortar. Pore structure analysis suggests that TA dispersion densifies the hydration products, as revealed by the much-reduced gel and interhydrate pores. The nanoindentation results indicated that all low-density calcium hydrate silicate (CSH) was converted to high density by the TA dispersion, leading to a drastic improvement in the compressive strength of the produced mortars. As a result, the 28 days compressive strength of cement mortar prepared with TA dispersed MK was enhanced by up to 97 % compared with the one prepared without MK substitution, which exhibits great potential in reducing the carbon footprint of cement-based construction materials.

A multi-method investigation into rheological properties, hydration, and early-age strength of cement composites with admixtures recovered from inorganic and bio-based waste streams

• Influence of supplementary admixtures on fresh properties, hydration and strength are compared. • Silica fume substantially increases yield stress, while glass powder reduces yield stress. • Final setting time is reduced in biochar-cement, while fly ash and glass powder delays the setting. • Biochar has the highest accelerating effect on hydration kinetics due to higher surface area for nucleation. • Silica fume and biochar offer 14% higher strength than control at 28-day mark. The selection of mineral admixtures to develop low-carbon cement composites must be diversified to balance the increasing demand and low supply of certain widely used admixtures. The research aims to advance scientific knowledge into the comparative influence of several admixtures recovered from different waste streams including silica fume (SF), fly ash (FA), pulverized glass powder (PGP), biochar (BC), and high-performance ash (HPA) on static yield stress, dynamic yield stress, plastic viscosity, setting, micro-structural build-up, degree of hydration and compressive strength of cementitious paste. Experimental findings show that adding 10 wt% silica fume results in a 300% increase in yield stress (under static and dynamic shear rate) and plastic viscosity than control, attributed to its fine particle size and higher gelling rate during early hydration. HPA leads to an 83% increase in static yield stress compared to control at 70 mins, but the application of a high shear rate leads to a marginal increase (18%) in yield stress than control. PGP leads to improvement in workability by reducing the dynamic and static yield stress by 50 – 55% than the control without significant change in plastic viscosity. Comparing the influence of BC, FA, and PGP, which have comparable particle size distribution in this research, the addition of biochar accelerates micro-structural build-up and final setting, evident from higher ultrasonic pulse velocity and faster hydration kinetics by 1.20 h. Cement pastes with FA, PGP and HPA demonstrate significantly lower compressive strength at 3-day and 7-day age than control but offer similar 28-day strength. The addition of SF and BC do not compromise 3-day and 7-day strength while offering 16% enhancement in 28-day strength than control attributed to a higher degree of hydration due to pozzolanic and filler effects respectively. The findings suggest that PGP, BC, and HPA could be potential alternatives to more widely used FA and SF as supplementary mineral admixtures in cement-based construction materials.

Investigation of different paper mill ashes as potential supplementary cementitious materials

Integrating supplementary cementitious materials (SCMs) in cement-based construction materials is a key strategy for reducing environmental burdens and the greenhouse gas emissions related to cement production. Supplies of commonly applied SCMs such as fly ash and blast furnace slag are becoming limited, and therefore the search for alternative SCMs is of high significance. The present research investigates the viability of four paper mill ashes collected at different stages from the same incineration process as SCMs at different cement substitution rates (5–30 wt%). The ashes were first classified depending on their mineralogical and chemical composition, and their contribution to strength development of the prepared mortars is examined. Furthermore, the effects of the ashes on the hydration kinetics and the fresh and hardened properties of the prepared mortars were studied. The obtained results showed that a high level of SCM replacement accelerates the early hydration reactions and decreases the setting time. In addition, the incorporation of paper mill ashes increased the bound water depending on the ash type and resulted in strength development of the mortars at low replacement percentages (5–10 wt%). This study shows that the ashes belonging to type C medium acid based on bio ash classification could be incorporated as SCMs at a maximum level of 10 wt%, while those corresponding to type C low acid could be used up to 20–30 wt%. • Four paper mill ashes were characterized and classified based on the chemical and mineralogical composition then used as SCM. • Paper mill ashes corresponding to type C low acid based on bioash classification could be used as SCMs up to 20–30 wt%. • The addition rate of paper mill ashes controls the fresh properties and strength development of the mortars.

Microstructural integrity characterization of cement-based construction materials

In this paper, a new micromechanical framework to characterize the microstructural integrity and predict the effective properties of multi-phase particulate composites is presented. Within the framework, a new scalar micromechanical parameter is identified and used to derive new expressions for the effective elastic properties of particulate composites using the mean-field homogenization technique. The derived equations are then generalized for composites with multiple phase constituents. The generality of the proposed framework is demonstrated by combining the derived equations with the existing homogenization techniques such as the Mori–Tanaka method and the Generalized Maxwell’s Approach (GMA). The results show that the theory delivers consistent estimates of the effective properties of two-phase elastic composite materials. The new scalar micromechanical parameter is also used to characterize the microstructural integrity of both asphalt mixtures and Portland cement concrete. The results show that the new scalar micromechanical parameter correlates well with multiple key fundamental properties of asphalt concrete mixture, including the creep rate, the fracture energy density, the endurance limit, and the damage rate parameters. The results also show that the new micromechanical framework can be used to accurately predict the effective modulus properties of Portland cement concrete mixtures.