Supplementary Cementitious Materials Research Articles

Optimizing recycled aggregate concrete performance with chemically and mechanically activated fly ash in combination with coconut fiber

As a matter of fact, although RCA is inferior to that of NA (natural aggregate) in terms of performance, RCA is currently being used extensively in concrete production as a sustainable solution due to global increasing construction waste. To overcome these limitations, several mechanisms and supplementary cementitious materials (SCMs) have been investigated in the recent past. This study investigates the combined effect of natural fiber coconut (0%, 0.5%,1%,1.5% and 2%) and activated fly ash (mechanically and chemically) on performance of recycled concrete aggregate (RCA). Four concrete compositions were studied: a control group with varying RCA percentages and no fly ash, second group with 30% inactive fly ash, third group with 30% mechanically activated fly ash, and a fourth group with 30% chemically activated fly ash. The findings revealed that the addition of 30% chemically activated fly ash with 1.5% CF increased compressive strength by 25%, tensile strength by 17% for 100% RCA mix, While strength losses for the same mix are 7.18% after one month and 22.14% after three months of acid exposure. Scanning electron microscopy further validates the enhanced packing density and effective crack filling in the optimized mixes, highlighting their superior performance. This approach holds significant potential for advancing sustainable development pathways in high-performance structural concrete, particularly in regions prioritizing green building solutions.

Data driven design of ultra high performance concrete prospects and application

Ultra-high performance concrete (UHPC) is a specialized class of cementitious composites that is increasingly used in various applications, including bridge decks, connections between precast components, piers, columns, overlays, and the repair and strengthening of bridge elements. The mechanical and durability properties of UHPC are significantly influenced by factors such as low water-to-binder ratios, the inclusion of supplementary cementitious materials (SCMs), and fiber reinforcement. Machine learning (ML) has been employed to predict the performance of UHPC and optimize its mixture designs by using various raw materials. This study first provides a comprehensive review of ML applications in UHPC, focusing on predicting workability, mechanical, and thermal properties. The use of data crossing, generative AI, physics-guided ML models, and field-applicable software are explored as practical directions for future research. This study also develops ML models to predict the compressive strength of UHPC by using a database containing 1300 data-records. The influence of various input variables is evaluated using SHapley Additive exPlanations (SHAP), revealing that chemical compositions have relatively minor impacts, given the material types used. By excluding insignificant variables, the models enhance both efficiency and accuracy in predicting strength. This advancement facilitates optimized material design and performance prediction while reducing the experimental workload required to inform ML models. Adding more diverse data to the database could further enhance the prediction performance and generalizability of the proposed ML models.

Improving the Shear Strength and Compressibility of Sandy Soil by Utilizing Calcined Shale and Cement

Abstract Sandy soil is one of the problematic soils due to the uniform distribution of the particles and the rounded shape of particles. These properties of soils lead to low shear strength, high compressibility, high collapsibility potential, and hard compaction. For that, Soil stabilization is mandatory for these kinds of soils. Calcium-based stabilizers have been used widely to stabilize these kinds of soils. Despite that, these materials have some challenges regarding environmental matter and possess numerous shortcomings, leading to the exploration of more effective stabilizers. Calcined shale has been used for concrete modification as a supplementary cementitious materials SCMs but never been used for soil stabilization. This study uses calcined shale as a partial replacement for cement to stabilize sandy soil. This research consists of two parts; the first part evaluates the optimum percentage of cement to stabilize the sandy soil used in this study. The second part is determining the optimum amount of calcined shale used to partially replace cement. The results revealed that 10% is the optimum dose of cement and 30% of CS is the best percentage to partially replace cement. 10% of cement reduced the consolidation by 98%. Using 30% of calcined shale as a partial replacement for cement increased the consolidation by 29% at a curing time of 7 days and reduced it by 9.2% when cured for 28 days.

Innovative Approaches to Sustainable Concrete Design: Exploring Green Materials For Enhanced Durability In Civil Engineering Structures

The urgent global demand for sustainable infrastructure has propelled civil engineering towards adopting environmentally conscious practices. Concrete, as the backbone of modern construction, presents significant challenges due to its substantial carbon footprint and reliance on non-renewable resources. This research explores innovative approaches to sustainable concrete design, focusing on integrating green materials and advanced technologies to enhance durability and reduce environmental impact. The study systematically evaluates alternative cementitious materials, recycled aggregates, and bio-based admixtures as viable replacements for traditional concrete components. By examining their physical, chemical, and mechanical properties, the research highlights their potential to mitigate carbon emissions and improve long-term structural performance. Central to this investigation is the role of supplementary cementitious materials (SCMs), such as fly ash, slag, and silica fume, which are incorporated to replace a portion of Portland cement. These materials not only enhance the durability of concrete by improving its resistance to chemical attacks and reducing permeability but also contribute to waste utilization and resource conservation. Furthermore, the inclusion of recycled aggregates derived from construction and demolition waste is examined for their ability to preserve natural resources while maintaining satisfactory structural properties. The study also delves into the potential of bio-based materials, such as bacterial concrete and algae-based additives, to promote self-healing properties and improve crack resistance, further extending the service life of concrete structures. To address durability challenges in extreme environmental conditions, the research integrates nanotechnology and polymer-based solutions. The application of nano-silica, graphene, and other nanomaterials is explored for their ability to enhance the microstructure of concrete, leading to improved compressive strength and reduced porosity. Additionally, the use of polymer-modified concrete is investigated for its exceptional resistance to moisture ingress and chemical degradation, making it suitable for marine and industrial applications. The environmental and economic implications of these innovative approaches are critically assessed using life-cycle analysis (LCA) and cost-benefit evaluations. These analyses provide insights into the feasibility of adopting green concrete solutions at scale, highlighting their ability to align with sustainable development goals while meeting industry demands for high-performance materials. Case studies of implemented projects are presented to illustrate the practical application and real-world performance of sustainable concrete designs. This research underscores the importance of a multidisciplinary approach to advancing sustainable concrete technology, involving material scientists, engineers, and policymakers. By embracing innovative materials and construction techniques, the civil engineering industry can significantly reduce its ecological footprint while delivering durable and resilient infrastructure. The findings contribute to a growing body of knowledge on sustainable construction and pave the way for future research and development in green concrete design.

Rice straw ash as supplementary cementitious materials for concrete: optimizing water soaking duration of rice straw to remove alkalis

In 2016, global cement consumption reached 4.65 billion tonnes, accounting for 8% of the world’s carbon dioxide emissions. Reducing the reliance on cement is an effective strategy for mitigating cement’s climate impacts. This study investigates rice straw ash (RSA) as a supplementary cementitious material (SCM) for concrete. To enable large-scale RSA production via rice straw combustion at bioenergy plants, the effect of varying water-soaking durations (3, 6, 24, and 72 h) on the leaching of salts and heavy metals from rice straw was assessed. The resulting leachate was treated by reverse osmosis, producing clean water for irrigation and a potassium-rich fertilizer concentrate. The soaked rice straw was combusted to produce RSA samples (RSA 0 for unsoaked straw, and RSA 3, RSA 6, RSA 24, and RSA 72 for soaked durations) for evaluation as SCM based on physicochemical properties, pozzolanic reactivity and strength activity index (SAI), available alkalis, and alkali-silica reactivity (ASR) mitigation.Results revealed that a soaking duration of just 3 h was effective at removing harmful compounds detrimental to combustion systems. All RSA samples exhibited high pozzolanic reactivity (heat release > 335 J/g and calcium hydroxide consumption > 130 g/100 g RSA) and SAI exceeding 120%. Furthermore, soaking was effective in enhancing ASR mitigation, achieving an 85% expansion reduction with RSA 3. This study demonstrates the potential of rice straw as bioenergy feedstock and its ash as a viable SCM for concrete, offering a pathway to reducing cement consumption while creating value-added uses for agricultural residues.

Reliability-based durability requirements for RC structures made of low-carbon concretes in climate change conditions

ABSTRACT Concretes with high contents of supplementary cementitious materials (SCMs) such as fly ash and ground granulated blast-furnace slag, typically exhibit reduced resistance to carbonation compared to conventional Portland cement concrete. The current study examines what durability requirements should be applied to reinforced concrete (RC) structures made from such low-carbon concretes to prevent unacceptable damage caused by carbonation-induced corrosion throughout their design service life. The requirements are determined based on two durability limit states – depassivation of reinforcing steel and excessive concrete cover cracking due to corrosion. The evaluation is carried out in a probabilistic format for RC components of a road bridge with a design service life of 100 years. For such a long lifespan, the effects of climate change on carbonation and the resulting corrosion need to be considered. This is done for three different types of concrete – ordinary concrete and two low-carbon concretes, two IPCC emission scenarios – SSP2-4.5 and SSP3-7.0, and three representative locations with very different climates – Dubai, Dublin and Seoul. The study's results show that accounting for the corrosion propagation stage, which follows the depassivation of reinforcing steel, is essential for establishing efficient durability requirements for RC structures made from low-carbon concretes in XC3/XC4 environments.

Flash Calcination of Kaolinite Clay in a Pilot Reactor: Evaluation of Clay Color Change in Oxidizing, Inert and Reducing Atmospheres

Cement production, while essential for global infrastructure, contributes significantly to carbon dioxide emissions, accounting for approximately 7% of total emissions. To mitigate these environmental impacts, flash calcination of kaolinitic clays has been investigated as a sustainable alternative. This technique involves the rapid heating of clays, enabling their use as supplementary cementitious materials. The primary objective of this study was to modify the color of calcined clay in various atmospheres (oxidizing, inert, and reducing) to achieve a grayish tone similar to commercial cement while preserving its reactive properties. The experimental procedure employed a tubular reactor with precise control of gas flows (atmospheric air, nitrogen, and a carbon monoxide–nitrogen mixture). Physicochemical characterization of the raw clay was conducted before calcination, with analyses repeated on the calcined clays following experimentation. Results indicated that clay calcined in an oxidizing atmosphere acquired a reddish hue, attributed to the oxidation of iron in hematite. The Clay exhibited a pinkish tone in an inert atmosphere, while calcination in a reducing atmosphere yielded the desired grayish color. Regarding pozzolanic activity, clays calcined in oxidizing and inert atmospheres displayed robust strength, ranging from 82% to 87%. Calcination in a reducing atmosphere resulted in slightly lower strength, around 74%, likely due to the clay’s chemical composition and the calcination process, which affects compound formation and material reactivity.

Waste Glass as Partial Cement Replacement in Sustainable Concrete: Mechanical and Fresh Properties Review

The significant anthropogenic carbon dioxide (CO2) emissions from cement production and the disposal of the majority of post-consumer waste glass into landfill sites have increased environmental pollution. In order to reduce the environmental impact, ground glass pozzolan (GGP) as a partial cement replacement has drawn interest from the concrete industry. This review examines the potential of GGP as a supplementary cementitious material (SCM), exploring the chemical composition of pozzolans, the different types of glass used for GGP, and the impact of glass color on pozzolanic reactivity. In addition, this study gathers the most recent research articles on the fresh and mechanical properties of concrete incorporating GGP. Key findings show that the incorporation of GGP in concrete improves the modulus of elasticity and the compressive, tensile, flexural, and punching strengths due to the pozzolanic reactions. The results indicate that GGP, made from waste glass, has pozzolanic properties that form additional strength-enhancing calcium silicate hydrate (C-S-H) gel and densify the concrete matrix. Additionally, the life cycle assessments of GGP-incorporated concrete demonstrate reductions in energy consumption and CO2 emissions compared to conventional concrete, supporting a circular economy and sustainable construction practices.

Long‐term mechanical properties of hybrid fiber‐reinforced engineered cementitious composite

AbstractHybrid fiber‐reinforced engineered cementitious composites (hybrid ECC) employing short straight polyethylene (PE) and steel fibers have attracted growing interest in engineering applications due to their superior strength and ductility. In most studies, the mechanical properties of hybrid ECC were determined based on samples cured for 28 days, while their long‐term mechanical properties are seldom studied. Since hybrid ECCs often incorporate supplementary cementitious materials that alter the hydration process over time, relying solely on the 28‐day strength of samples may lead to inaccurate structural designs. To better understand the long‐term mechanical properties of hybrid ECC, this work presents an experimental investigation of hybrid PE‐steel fiber‐reinforced ECC samples cured under standard conditions for up to 3 years. Uniaxial compressive tests, direct tensile tests, and four‐point bending tests were conducted with samples cured at standard conditions for 28 days, 1 year, and 3 years. It was found that the compressive and tensile strengths of hybrid ECC increased with age. However, as the age increased to 3 years, the ultimate tensile strain and flexural ductility decreased significantly by 54% and 35%, respectively, compared to their 28‐day values. Furthermore, most changes occurred within 1 year. It was also found that the main damage pattern of the PE fibers was transformed from pull‐out to rupture failure as the curing age increased. Thermal‐gravity analysis revealed that the hydration process of hybrid ECC may last for up to 3 years, which explains their changes in mechanical properties and PE fiber failure mode.

The mechanical properties of cement mortar reinforced with silica fume subjected to sulfate and chloride environment

The mechanical properties of cement mortar reinforced with silica fume subjected to sulfate and chloride environment

Flowability and compressive strength of ternary blended cement mortar of coal bottom ash and ground cockle shell ash

Flourishing cement industry to meet the demand of construction industry has negative impact to the global environment owing to the carbon emission during calcination of cement. At the same time, the disposal of coal bottom ash and cockle shell from coal power plant and cockle trade which pollutes the environment also need to be resolved. In view of circular economy, the present research aims to produce ternary blended cement consisting of coal bottom ash (CBA) and cockle shell ash (CSA) for sustainable mortar production. The research was conducted to determine the effect of CBA as partial cement replacement on flowability and compressive strength of CSA blended cement mortar. Seven mortar mixes consisting of CBA as supplementary cementitious material ranging from 0% to 60% by weight of cement were prepared. All specimens were water cured up to 56 days. The flowability test was conducted to assess the properties of the fresh state, while hardened properties were evaluated through compressive strength test at 1, 3, 7, 28, and 56 days. The results showed flowability decreased by 5% to 31% with increasing CBA content compared to the control mix. The use finer sized CBA forms a slightly stickier mortar mix with lower flowability. A combination 10% to 20% CBA is the best percentage to use for formation of CSA mortar with enhanced strength. However, a maximum strength of 23 MPa was achieved at 56 days with an optimal CBA replacement of 10%. This research demonstrates the potential by transforming industrial waste for low-carbon cement production to save the use of landfills for waste disposal and optimize consumption of non-renewable resources.

Ratio of water to cement and supplementary cementitious materials on mechanical and impact resistance properties of reactive powder concrete

Reactive powder concrete (RPC) is a novel high-performance building material widely used in large-scale engineering structures due to its superior mechanical properties and durability. However, structural failure can still occur under dynamic load impacts. Therefore, optimizing the mechanical properties and impact resistance of RPC remains a critical issue for enhancing its engineering applications. In this study, the mechanical properties and impact resistance of RPC were investigated by adjusting the water-cement ratio and incorporating supplementary cementitious materials (SCMs), such as fly ash microspheres (FAM) and silica fume (SF). The effects of these adjustments on water absorption, strength, and impact resistance were assessed. Three water-cement ratios (0.16, 0.18, and 0.20) and various proportions of FAM and SF were selected to evaluate water absorption, compressive strength, bending strength, and impact resistance. The results indicated that reducing the water-cement ratio enhanced the densification of the concrete, reduced water absorption, and improved both compressive and bending strength. Specifically, when the water-cement ratio was 0.16 and FAM and SF were synergistically incorporated, the compressive strength reached 134.4 MPa, the bending strength reached 16.86 MPa, and the impact resistance was 22,838.4 J. Impact test results revealed that combining a low water-cement ratio with an appropriate amount of SCMs effectively increased energy absorption capacity and significantly slowed crack propagation. Analysis based on the Weibull distribution model demonstrated a more pronounced probability distribution of the number of impacts, suggesting that the optimization measures improved the impact resistance of RPC.

Application of Phosphogypsum in Ultra-High-Performance Concrete (UHPC) Matrix for Strength Enhancement and Shrinkage Reduction.

Ultra-high-performance concrete is a high-strength and durable material widely used in infrastructure, but its high cement content raises environmental concerns, particularly in terms of CO₂ emissions and resource consumption. Phosphogypsum, an industrial by-product of phosphoric acid production, presents a sustainable alternative by partially replacing cement, thereby reducing cement demand and addressing solid waste disposal issues. This study investigates the effects of PG incorporation (0-40%) on hydration kinetics, mechanical properties, and volume stability in UHPC. The results indicate that increasing PG content delays hydration, affecting the induction period and peak hydration time. XRD and TG analysis confirm that PG modifies hydration product formation, influencing the development of key hydration phases. Strength tests reveal that moderate PG replacement (10-20%) maintains or improves long-term mechanical performance, while excessive PG replacement negatively impacts strength development. Additionally, PG effectively reduces autogenous shrinkage, improving the volume stability of UHPC. These findings highlight that PG can serve as a viable supplementary cementitious material in UHPC, contributing to both environmental sustainability and enhanced material performance.

Comparative analysis of chloride and acid resistance in one-part geopolymer and low carbon concrete

A comparative analysis of the chloride and acid resistance of one-part geopolymer and low carbon dioxide concretes is presented, with a focus on their potential to replace traditional systems based on ordinary Portland cement (OPC) in construction. The performance of geopolymer concretes (GPCs) was compared with concretes made with OPC and OPC blended with supplementary cementitious materials (fly ash and slag) under aggressive environmental conditions. The findings revealed that, while GPCs exhibit superior resistance to acid attack, their chloride resistance is highly dependent on the specific precursor materials used. The study also highlights the limitations of using rapid chloride permeability tests at standard voltages for GPCs, suggesting that lower voltage tests at 30 V may offer a more accurate assessment. Overall, the results underscore the need for optimised precursor selection in GPCs to enhance durability and advocate for further research into testing methodologies tailored to these innovative materials.

Supply Chain (Re)Design and Pricing for Biomass Ash Valorization as Supplementary Cementitious Materials

Biomass ash is a byproduct of renewable energy generation that can be used in the cement and concrete industries as a supplementary cementitious material (SCM) to reduce their environmental impact. However, using biomass ashes as an SCM presents challenges, such as the distant location of crops and processing plants from cement and concrete plants, the absence of a supply chain to connect the biomass ash and cement/concrete producers, and the lack of a mechanism to set the price of the ash. We adopted a supply chain perspective to evaluate the environmental and economic impact of incorporating biomass ashes as an SCM in the cement and concrete industries. We developed a bilevel optimization model considering the strategic behavior of the two stakeholders of the supply chain: the biomass ash generator, which maximizes its profits by setting the price of the ash, and the cement/concrete manufacturer and minimizes its total operating costs, including the processes necessary to adapt its supply chain for the use of new raw material. We validated the model using data from the Colombian context at a nationwide industrial level. Our results indicate that introducing SCMs can potentially reduce CO2 emissions without increasing the cost of the supply chain.

Development of OptiCon: A Mathematical Model with a Graphical User Interface for Designing Sustainable Portland Cement Concrete Mixes with Budget Constraint

The production of Portland Cement Concrete (PCC) generates significant environmental impacts that increase climate change and decrease people’s quality of life. Recent studies highlight the potential to reduce these environmental burdens by partially replacing Portland cement with Supplementary Cementitious Materials (SCMs) and coarse aggregates with Recycled Concrete Aggregate (RCA). However, designing PCCs with simultaneous contents of SCMs and RCA is not easily manageable because current design procedures fail to adjust all of the variables involved. In order to overcome these limitations, this research introduces a novel mathematical model designed to develop operationally efficient PCC mixes that are both environmentally sustainable and cost-effective. The proposed model, denominated OptiCon, employs the Life-Cycle Assessment and Life-Cycle Costs Analysis methodologies to evaluate the incorporation of three different SCMs (i.e., fly ash, silica fume, and steel slag) and RCA into PCC mixes. OptiCon is also integrated within a graphical user interface in order to make its implementation straightforward for potential users. Thus, OptiCon is operationalized through an algorithm, offering a replicable approach that can be adapted to various contexts, providing both a theoretical framework and a practical tool for state agencies, engineers, suppliers, and other stakeholders to adopt more environmentally friendly practices in concrete production. Furthermore, a case study from northern Colombia analyzed thirty mix design scenarios with varying supplier conditions (foreign, local, or mixed), calculating costs and CO2 emissions for a fixed concrete volume of 1 m3. The findings demonstrated that utilizing OptiCon can achieve substantial reductions in both CO2 emissions and production costs, underscoring the model’s efficiency and practical impact.

Experimental investigation and comparison of soak and flash calcined kaolinite and montmorillonite

Calcined clay holds great potential as a Supplementary Cementitious Material (SCM). Despite ample literature on using calcined clays as SCMs, there is a shortage of studies comparing clay calcination methods, especially on 2:1 clays. This research aims to address this gap by evaluating the properties of laboratory-grade kaolinite and montmorillonite under different calcination processes and conditions at laboratory-scale, specifically: a) a rotary kiln for soak and b) an entrained flow reactor for flash calcination. The results show that soak and flash calcination deliver similar pozzolanic reactivity when compared at equivalent dehydroxylation, with flash calcination requiring slightly higher temperatures, with minimal mineralogical differences. Additionally, flash calcination influenced the structural and morphological properties of the clay particles, with kaolinite exhibiting significant agglomeration and formation of pseudo-hexagonal plates, while montmorillonite had reduced surface area and led to deposit formations, which mainly consisted of mullite and quartz. This study was conducted in laboratory-scale conditions and did not account for heat-transfer limitations present in industrial systems. However, it aims to provide a solid foundation for future studies to expand to an industrial scale, potentially leading to a more substantial impact of the calcination method on clay properties. Moreover, the choice of materials in this study represents pure clays. Although this creates a fundamental background, it does not directly apply to the complexity of natural clays. As such, this work purposely serves as an initial step toward upcoming studies that compare natural clays with various compositions to further evaluate the observations.

Carbonation models using mix-design parameters for concretes with supplementary cementitious materials

Carbonation models using mix-design parameters for concretes with supplementary cementitious materials

Explainable artificial intelligence-based compressive strength optimization and Life-Cycle Assessment of eco-friendly sugarcane bagasse ash concrete.

Investigations on the potential use of sustainable sugarcane bagasse ash (SCBA) as a supplementary cementitious material (SCM) in concrete production have been carried out. The paper employs model agnostic eXplainable Artificial Intelligence (XAI) to develop interpretable models for the compressive strength of SCBA concrete. A dataset of SCBA concrete, comprising of 2616 data points, was first established. Then, black box machine learning models were employed for predicting compressive strength of SCBA concrete. White box modelling using model agnostic XAI explanations for the influence of different input parameters on the compressive strength of SCBA concrete was then used for the local and global interpretations of influencing parameters. Based on the relative influence of features on the compressive strength of SCBA concrete, a nonlinear model equation was thus developed. Optimization of SCBA concrete mixes was done and it was found that a compressive strength of 40MPa could be achieved for water to binder content ranging from 0.42 to 0.48 with low cement content. Additionally, the Life-Cycle Assessment (LCA) was carried out, and finally, it was proposed that SCBA concrete has potential for becoming an alternate eco-friendly building material.

Water quenching and grinding of ladle furnace slag for use as supplementary cementitious material in cemented mine backfills.

Water quenching and grinding of ladle furnace slag for use as supplementary cementitious material in cemented mine backfills.