Supplementary Cementitious Materials Research Articles

Assessment of the Mechanical and Microstructural Performance of Waste Kraft Fibre Reinforced Cement Composite Incorporating Sustainable Eco-Friendly Additives

This study investigates the influence of limestone powder and metakaolin as sustainable eco-friendly additives on the properties and behavior of cementitious composite boards, with a focus on mechanical strength, physical properties, and microstructural characteristics. The experimental investigation begins with the characterization of the raw materials, including limestone powder, and metakaolin, to assess their particle sizes, elemental composition, and microstructural features. Cement composite boards were fabricated using an innovatively developed lab-simulated vacuum dewatering process, by varying the proportions of limestone powder and metakaolin as partial replacements for cement, along with waste kraft fibres as reinforcement. Mechanical testing was conducted to evaluate the flexural strength and behaviour of the composite boards according to standardized procedures. A microstructural analysis was performed using scanning electron microscopy (SEM) to examine the effect of additives on the cementitious matrix, fibrematrix interaction, and hydration products. The findings from the experimental study reveal insights into the influence of limestone powder and metakaolin on the mechanical properties and microstructure of waste kraft fibre-reinforced cement composite boards. Our analysis of the results shows that adding 9% limestone powder as partial cement replacement produces a 24% and 50% enhancement in flexural strength at 7 and 28 days of hydration, while that of metakaolin as partial cement replacement was optimum at 6% with an enhancement of 4% and 36%, respectively, at 7 and 28 days of hydration. The implications of these findings for the development of sustainable cementitious composite are discussed, including the potential benefits of using limestone powder and metakaolin as supplementary cementitious materials in waste kraft fibre-reinforced cement composite boards. Finally, recommendations for optimizing additive proportions are also provided to enhance the understanding and application of these materials in the construction and building industries.

Pozzolanic Potential of Calcined Clays at Medium Temperature as Supplementary Cementitious Material

Pozzolanic Potential of Calcined Clays at Medium Temperature as Supplementary Cementitious Material

Life Cycle Analysis Comparison of Stabilizing Materials for Expansive Soils

Expansive soils present significant challenges to infrastructure stability, necessitating the use of stabilizing materials. This study conducts a comprehensive life cycle analysis (LCA) research design to evaluate the environmental sustainability of various stabilizing materials for expansive soil. The study uses a quantitative analysis assessing materials, including cement, limestone, natural pozzolana, iron ore tailings, and geopolymers (especially alkali-activated slag cement). The method involves a comprehensive LCA, considering phases from raw material extraction through production, use, and disposal. The analysis reveals distinct differences in environmental impact. Cement and lime, common stabilizers, show a high carbon footprint. Natural pozzolana and iron ore tailings exhibit potential as supplementary cementitious materials with reduced environmental impact. Geopolymers, particularly alkali-activated slag cement, offer promising alternatives with lower carbon emissions. This research contributes insights into sustainable geotechnical practices, guiding material selection aligned with environmental goals for effective expansive soil stabilization.

Performance assessment of pervious concrete incorporated with calcium silicate hydrates (C-S-H) cultivated on rice husk ash substrates – A trend surface analysis interpretation

Pervious concrete is a special type of concrete designed to allow water to pass through by omitting fine aggregates from the mix, or by using special techniques to create interconnected voids within the concrete. The current study investigates a novel method of cultivating calcium silicate hydrate (CSH) precipitates on a supplementary cementitious material (SCM), Rice husk ash (RHA), substrate and integrating the RHA substrate into pervious concrete to improve mechanical and durability properties. Scanning electron microscopy (SEM) images indicates the formation of precipitates of calcium silicate hydrates on the surface of RHA particles. The silica to RHA (Si/RHA) ratio and curing age of pervious concrete specimens serve as focal points for assessing the mechanical characteristics. Trend surface analysis is utilized to analyse the results, using a polynomial equation to identify underlying trends or patterns within the dataset. The analysis reveals that the Si/RHA ratio and curing days have minimal impact on permeability, while an increase in RHA substrate volume reduces permeability, indicating microstructure densification rather than macro void filling. For compressive strength, the results show that higher Si/RHA ratios and longer curing times positively correlate with strength, with accelerated hydration suggested by the quadratic coefficients of curing age. In terms of split tensile strength, increasing substrate volume enhances strength, while linear terms of Si/RHA ratio and curing age also exhibit positive correlations, although quadratic terms indicate minimal change in strength gain rates. Flexural strength correlates positively with both Si/RHA ratio and curing age, while abrasion resistance negatively correlates with Si/RHA ratio and substrate volume, suggesting enhanced resistance with increased values. CSH seeds grown on RHA enhances the microstructure of concrete, resulting in a denser material facilitating rapid strength development and improved durability.

Mechanical properties of geopolymer concrete incorporating supplementary cementitious materials as binding agents

This research investigates the environmental impact of cement production by exploring eco-friendly geopolymer binders as alternatives. Geopolymer concrete, developed using silica and alumina-rich precursors such as pozzolanic materials, achieves high compressive strength, up to 43.6 N/mm2 with a 16 M concentration and integrated steel fibers. Utilizing manual mixing and industrial by-products, the study pioneers cast-in-situ geopolymers with innovative curing techniques. The paper presents experimental results on the engineering properties of geopolymer concretes of 40 MPa, cured at 100 °C and 60 °C. The study systematically varies binder content, examining proportions of fly ash, GGBS, metakaolin, and silica fume, along with different mix ratios and molar concentrations. Key findings include increased compressive strength with higher NaOH concentration, peaking at 35.2 N/mm2 and 34.22 N/mm2 for 14 M mixes at 7 and 28 days, and 40.29 N/mm2 for 16 M mixes at 7 days. Optimal results were observed at higher curing temperatures, especially with 14 M and 16 M compositions at 100 °C. The study recommends mechanized mixing for efficiency and calls for further investigation into the microstructure and chemistry of geopolymers to advance sustainable construction practices. This research represents a significant step towards eco-conscious building materials, reducing the environmental impact of the construction industry.

Mineralogical Characterization and Geochemical Signatures of Supergene Kaolinitic Clay Deposits: Insight of Ropp Complex Kaolins, Northcentral Nigeria

This study presents the chemical and mineralogical composition of clay deposits and associated rock types within the Ropp Complex in order to assess the influence of parent lithology on the kaolinization, genesis, and utility of the deposit. Representative kaolin samples from E horizons of the weathering profiles and their bedrocks were collected from six sites in the Ropp Complex. Clay mineralogy was determined via the XRD technique, while a geochemical analysis was conducted using XRF, SEM coupled with EDS, and ICP-MS. The results showed that all kaolins dominantly contain kaolinite with a content of 77%–98% except for the AS1 kaolin with only minor kaolinite (20%) but mainly illite (65%). The notably lower crystallinity of kaolinite (HI value of 0.53–1.1) as well as its markedly small grain size is consistent with the formation of kaolinite from intensive chemical weathering of igneous rocks. The AS1 kaolin was probably formed from hydrothermal alteration in the burial stage due to the heating of groundwater by the late volcanism. Mobile trace elements (Sr, Ba, and Eu) exhibited a depletion trend, while immobile elements (Hf, Ta, Th) showed enrichment. The relatively more zirconium in kaolins implies the formation of low-temperature kaolinization. The notably high kaolinite content, accompanied by reasonable levels of Fe2O3 and TiO2, signifies a medium-grade quality. Furthermore, chondrite-normalized rare earth element (REE) patterns exhibit congruent trends in rocks and kaolin samples, indicating a relative enrichment in light rare earth elements (LREEs) alongside a discernible negative Eu anomaly. The abundant kaolinite and silicon–aluminum composition make the kaolins suitable for refractories, pharmaceutics, cosmetics, and supplementary cementitious material (SCM).

Assessment of Properties of Green SCC with and without Novel Additive

Concrete is the most widely used construction material in civil engineering industry because of its proved structural strength and stability when made properly. The concrete industry is constantly trying to evolve to make concrete more sustainable replacing a part of full cement with additives and Supplementary Cementitious Materials (SCMs). Each tonne of cement production releases one tonne of CO2 into the atmosphere and hence to greenhouse effect and global warming. A cost effective, alternative and innovative materials called novel additive is taken up for present study to reduce the cement consumption per m3 of concrete/SCC without reduction in strength of required grade. In this project an effort is made replacing cement content of SCC partially with Fly Ash, Ground Granulated Blast Furnace Slag (GGBS) in combination of novel additive. The study focused at studying the properties of fresh SCC and hardened SCC. The design mix proportion of 1: 2.63: 1.86 with a W/B ratio of 0.36 is taken up and 4 different mixes with different combinations of varied percentage replacement materials with 2% by weight of cement of novel additive. The properties of green SCC showed that fresh properties get enhanced through usage of mineral admixtures including a novel additive and hence, the addition of mineral admixture improve the flowability or rheology of SCC mixes. The strength of SCC achieved is ranging from 32- 46 N/mm2 for a cementitious content of 400 kg/m3 , highest being with lowest cement content with novel additive. Keywords: Rheology of SCC, Mineral Admixtures, Novel Additive, Sustainability

Production of amorphous aluminosilicate and vaterite from acid leaching of hydrated cement paste

Acetic acid has been used to leach Portland cement paste, and the effect of acid concentration, liquid/solid ratio, temperature, and time on leaching of Ca, Al, Fe and Si is reported. The silica-rich solid residue (SR) remaining after leaching was washed, dried, and ground. This amorphous aluminosilicate has comparable pozzolanic reactivity to commercial supplementary cementitious materials (SCM) such as coal fly ash. The 28-day compressive strength of 0.5 w/b mortar containing 20% CEM 1 replaced with SR extracted from cement paste (63.6 MPa) was higher than the reference (51.2 MPa). The leachate from acid leaching contains high levels of Ca2+ ions, and these can sequester CO2 under controlled conditions to form vaterite, a spherical polymorph of CaCO3. Cement paste present in waste concrete can therefore be used to form a reactive silica-rich SCM in a process that sequesters carbon. The research has implications for the development of circular concrete.

Carbonated Concrete Slurry Waste as Supplementary Cementitious Material

Carbonated Concrete Slurry Waste as Supplementary Cementitious Material

Current and potential materials for the low-carbon cement production: Life cycle assessment perspective

Given the carbon-intensive nature of cement production, conducting a comprehensive environmental evaluation using life cycle assessment (LCA) modeling is paramount to achieving eco-friendly cement standards. This study meticulously compiles and evaluates LCA findings from diverse analyses of current and potential supplementary cementitious materials (SCMs) within the blended cement sector. It underscores the impact of the functional unit (FU) within the LCA approach, supply chain considerations, and technical and regulatory factors on the sustainability of blended cement mixtures. Most of LCAs studied herein show that integrating SCMs into the cement matrix typically reduces land use, energy consumption, and greenhouse gas (GHG) emissions, thereby lowering the global warming potential (GWP) of ordinary portland cement (OPC) samples from 831 to 980 kg of CO2-eq to 768-481 kg of CO2-eq per ton of cement. However, in some instances, environmental indicators like abiotic depletion potential-elements (ADP-E) and human toxicity potential (HTP) rise due to increased mining, electricity, and transportation demand for SCMs. Regarding the environmental potential of alkali-activated cementitious materials and low-carbon clinker formulations, we found that limitations arise in fully replacing OPC due to global raw material availability constraints, rendering them economically unfavorable and impeding their widespread adoption. Among the SCMs examined in this study, clays, which are more widely available compared to industrially sourced materials like fly ash, slag, and silica fume, exhibited a more favorable environmental profile when evaluated using a mass-based FU. Incorporating compressive strength into the FU resulted in greater environmental benefits from high-strength blendedcement composites. However, this approach might lead to inaccurate results because higher strength does not always correspond to a lower environmental impact. Thus, establishing a FU that accurately reflects the environmental impact of blended cement and its composites (e.g., concrete and mortar) is crucial. Despite the potential of various pozzolanic materials to reduce clinker content in cement mixtures, their wide utilization remains restricted due to the absence of widescale market-based initiatives, green procurement strategies, and effective policy measures, which hampers their industrial and public acceptance. Consequently, governmental support is essential for developing and integrating sustainable cement solutions.

A digital workflow for assessing lifespan, carbonation, and embodied carbon of reusing concrete in buildings

Concrete is the most used construction material, accounting for 8 % of global CO2 emissions. Various strategies aim to reduce concrete's embodied carbon, such as using supplementary cementitious materials, utilizing cleaner energy, and carbonation. However, a large potential lies in reusing concrete for new buildings in a Circular Economy, thereby closing material loops and avoiding CO2 emissions. This study focuses on the reuse of precast concrete elements. We present a digital workflow for assessing reuse by predicting the remaining service life, estimating CO2 uptake by natural carbonation, and calculating the embodied carbon savings of concrete reuse. Both carbonation rates from EN 16757 and our investigation were applied to a case study building. While EN 16757 rates suggest that most precast elements have reached the end of their service life, our assessment shows that these elements have a sufficient lifespan for reuse. Plaster and coverings significantly delay carbonation and extend service life. During the first service life following EN 16757, carbonation was 19,2 kg CO2/m3, whereas our prediction was 5,4 kg CO2/m3. Moreover, CO2 uptake during service life, including reuse, was less than 6 % of the embodied carbon. The climate benefits of reuse greatly exceeded those of carbonation. Furthermore, carbonation did not have a decisive influence when applying Cut-Off, Distributed, and End-of-Life allocations for assessing embodied carbon of re-used elements in subsequent life cycles. The digital workflow is useful in quickly assessing lifespan, carbonation, and embodied carbon of concrete. It can be leveraged as a decision-making tool when designing for reuse.

Sustainable Solutions: Exploring Supplementary Cementitious Materials in Construction

Sustainable Solutions: Exploring Supplementary Cementitious Materials in Construction

Multifractal of acoustic emission for the multi-scale fracture behavior of diatomite modified concrete

It has been attempted to determine how supplemental cementitious materials (SCMs) affects concrete's resistance to fracture. Nevertheless, acoustic emission (AE) has not been used to investigate the impact of diatomite, an SCMs, on the fracture characteristics of concrete. In this investigation, the aim was to assess the fracture behavior of concrete with variable loadings of diatomite (0 %, 1 %, 2 %, 3 %). Three-point bending is performed along with continuous AE monitoring for concrete with various contents of diatomite to obtain AE information. The fracture behavior (fracture parameters, fracture mode, multi-scale fracture and damage) is determined by analyzing AE parameters and corresponding statistical indicators such as Multifractal Detrended Fluctuation Analysis(MF-DFA) and Weibull theory. The results show that the addition of diatomite enhances the fracture property of concrete especially the optimal 2 % content. Then, the high RA value and tensile crack ratio suggest the improvement of the tensile resistance of diatomite. Moreover, a novel quantitative index called multifractal parameter is proposed to evaluate the multi-scale fracture. The finding contributes to a novel method for quantifying multi-scale cracking. The low multifractal parameter in diatomite modified concrete implies a small cracking scale in comparison with the ordinary concrete. Finally, the presence of diatomite slowed down the development of fracture damage in concrete.

Novel low-carbon eco-concrete filled-FRP tubes under axial compression: Experimental behavior and analytical model

Concrete is essential in global construction but significantly contributes to carbon emissions, primarily due to cement production. The cement industry is adopting low-carbon practices, such as using supplementary cementitious materials (SCMs) to reduce emissions. Concrete prepared with calcined clay can achieve a carbon reduction effect of approximately 30 % compared to ordinary cement. Current studies highlight the reuse of kaolin clay, the predominant constituent of engineering sediment in Shenzhen, China, providing raw materials for sustainable low-carbon and eco-friendly concrete. However, high substitution rates of calcined clay can compromise concrete strength, posing a challenge for the application in load-bearing structures. This study proposed a novel low-carbon eco-friendly concrete (i.e., using calcined clay as supplementary cementitious materials) filled into FRP tubes (i.e., Low-Carbon Eco-Concrete-Filled FRP Tubes, termed LCE-CFFTs) aiming to enhance substitution rates of calcined clay and to improve compressive strength and ductility. This paper provides a detailed description of the preparation method, chemical reaction process, chemical composition, and microstructure of calcined clay. Experimental tests investigated the axial compressive performance of LCE-CFFTs, considering calcined clay substitution rates and FRP thickness as key parameters. The experimental work and theoretical analysis indicated that: the inclusion of 10 % and 40 % calcined clay led to a reduction in carbon emissions, resulting in a decrement of 5.8 % and 23.3 %, respectively; confinement provided by FRP tubes mitigated the reduction in axial compressive strength resulting from calcined clay inclusion, particularly evident at higher substitution rates (40 %); the effect of FRP tube confinement in improving peak stress and axial performance of LCE-CFFTs became more pronounced with higher calcined clay substitution rates; to more accurately predict the axial compressive behavior of LCE-CFFTs of this study, it is essential to consider the biaxial stress-strain state of filament-wound FRP tubes.

Utilization of Sintered Sludge Ash with Different Mechanical-Thermal Activation Parameters as a Supplementary Cementitious Material: Mechanical Properties and Life Cycle Assessment of Cement-Based Paste.

The proposal of sintered sludge cement (SSC) paste aligns with the low-carbon development goals of building materials. However, there is a lack of scientific guidance for the preparation of sintered sludge ash (SSA). Herein, this study systematically investigates the influence mechanism of mechanical-thermal activation parameters of SSA on the mechanical properties and life cycle assessment (LCA) of SSC paste, and conducts a comprehensive evaluation using a radar chart and the TOPSIS method. The results show that with the increase in calcination temperature and duration, the compressive and flexural strengths of the SSC paste are improved, especially at 600 °C and above, increasing by 57.92% and 62.52%, respectively. The longer calcination time at 1000 °C results in a decrease in its mechanical properties. The addition of SSA significantly reduces the LCA indicators of cement paste. Specifically, 30% SSA only contributes 8.1% to the global warming potential. Compared to calcination, the LCA indicators have less sensitivity to ball milling, and prolonging the time hardly increases them. Based on performance and environmental impact, the optimal SSA is obtained by calcining at 800 °C for 2 h and ball milling for 10 min. This study can provide theoretical guidance for efficient building material utilization of dredged sludge.

The Steelmaking Transformation Process and Its Consequences for Slag Utilization

The main challenge of the European steel industry for the next decade is the steel production transformation process. Many steel producers aim to avoid their CO2 emissions by substituting the CO2‐intensive blast furnace/basic oxygen furnace route by a gas‐based direct reduced iron (DRI) process combined with an electric smelting process. Thus, the well‐known latent hydraulic granulated blast furnace slag (GBS) will vanish step by step. For more than 140 years, this slag has been used as a supplementary cementitious material due to its clinker reduction potential and from there its CO2 reduction potential for the cement and concrete production. Moreover, slag cements offer some special technical advantages. Whereas the solid‐state DRI process itself does not generate any slag, the different electric smelting processes will produce liquid steel or “electric” pig iron, respectively, together with very different types of slags. However, specific slag/metal ratios, resulting slag volumes, chemical and mineralogical composition, and physical properties of the new slags are yet unknown. Therefore, their cementitious and environmental properties are also still unknown. Different current and scheduled projects aim mainly to enable the different types of new slags to substitute GBS to continue the successful cross‐industrial cooperation between steel and cement industry.

A study on the synthesis and performance evaluation of fly ash and alccofine as sustainable cementitious materials

Construction and global infrastructure depend on cement production. It is one of the biggest carbon emitters, making it an aspect of environmental sustainability and climate change mitigation. Each stage of cement production releases CO2 and other greenhouse gasses. About 8% of worldwide CO2 emissions come from the cement sector, making it a major contributor. Different supplementary cementitious materials (SCMs) like fly ash (FA), silica fume (SF), and slag are used to partially replace traditional raw materials like limestone, reducing the environmental impact. This study investigated the use of supplementary cementitious materials, specifically FA and alccofine (AF), as partial replacements for cement in concrete to reduce environmental impact. The study first identified an optimal replacement percentage for FA (20%, 30%, and 40%) by weight of cement. Subsequently, using the optimal FA percentage, AF was added at varying percentages (5%, 10%, and 15%) by weight of cement. The study evaluated the mechanical properties of the concrete mixtures, including workability, compressive strength, split tensile strength, and flexural strength. Durability, measured by water sorptivity and rapid chloride penetrability tests, was also assessed. The microstructural properties of the concrete were analyzed to understand their influence on performance. As a result of the significant environmental implications of producing and using concrete for all activities, an in-depth life cycle assessment (LCA) was conducted. Additionally, artificial neural networks were employed to predict the compressive strength of the concrete. The study concluded that incorporating FA and AF in concrete mixtures is a promising approach to producing more environmentally friendly concrete.

A preliminary exploration of waste red-bed as a supplementary cementitious material

A red-bed is a type of continental clastic sedimentary stratum, with red serving as the main color. This type of stratum accounts for 20% of the land area in China. In the process of infrastructure construction, a large amount of waste red-bed is generated. Waste red-bed exacerbates the shortage of land resources and is a misuse of resources. In this study, a preliminary exploration of the recycling of waste red-bed in central Yunnan Province was conducted. The studied red-bed contains approximately 30% clay minerals and was used as supplementary cementitious material (SCM) instead of clay after calcination. Through laboratory characterization, environmental impact assessment, and cost analyses, the feasibility of using the red-bed as a type of SCM was demonstrated. The results show that the dehydroxylation reaction of clay minerals in the red-bed was almost complete after calcination at 800 °C. A pozzolanic reaction occurred, and additional heat was released after the addition of the calcined red-bed (CRB) to the cement mortar. When the cement replacement ratio increased from 10% to 30%, the strength activity index decreased from 98.2% to 82.2%, which met the relevant requirements. However, compared with the control samples, the samples with replacement ratios of 40% and 50% had lower mortar fluidities by 57.3% and 75.5% and higher porosities by 33.3% and 20.0%, respectively. Owing to the dilution effect of the cement and the decrease in the mortar fluidity, the internal structure of the sample porosity increased, and the strength decreased dramatically. In addition, the environmental impacts, energy consumption, and cost of using waste red-bed as a SCM were quantitatively analyzed via a carbon emission index and a cost index.

Dynamic material flow analysis of construction materials in Saudi Arabia: Strategies for sustainability of residential buildings

Globally, the expansion of building infrastructure has serious environmental implications due to emissions from cement and steel. The construction industry uses the vast majority of cement and steel produced globally and locally. Consequently, this paper proposes a model to estimate and mitigate future material flow emissions into residential buildings in Saudi Arabia. First, a dynamic material flow model is used to quantify material flows and stock in residential buildings. The evolution of Saudi housing stock and related steel and cement are simulated from 1950 to 2100. Second, various strategies such as material efficiency improvement, lifetime extension, and reducing production emissions are simulated to reduce emissions caused by cement and steel. The findings indicate that implementing substantial material efficiency improvements can result in 33 %–46 % reductions of cumulative steel and cement emissions from 2023 to 2100, respectively. Furthermore, improving material efficiency measures could result in over 80 % reductions in emissions for steel over the same period. Reducing the ratio of clinker to supplementary cementitious materials in cement to 75 % could reduce cumulative cement emissions by 129 million tCO2e (17 %). Adoption of high material efficiency practices in cement use, low clinker cement, and waste as fuel can reduce emissions by 70 %. The findings of this study contribute to a better understanding of future emissions from building materials used in residential buildings, as well as the impact of emission mitigation strategies on future emissions, which will help decision-makers and researchers develop policies and research.

Effect of low carbon marble dust powder, silica fume, and rice husk ash as tertiary cementitious material on the mechanical properties and embodied carbon of concrete

The recent decade has seen a surge in study towards cost-effective, ecologically benign, as well as socially advantageous cement replacements. Alternatives include industrial and agricultural waste, which can be recycled, repurposed, as well as renewed. However, using these wastes as supplementary cementitious materials (SCM) saves energy as well as reduces cement use, which helps reduce CO2 emission. Therefore, this research investigation is to use the silica fume (SF), rice husk ash (RHA), as well as marble dust powder (MDP) individually as SCM and combine as tertiary cementitious materials (TCM) for determining the fresh (workability), hardened (dry density, splitting tensile and compressive strength) and durability (carbonation depth, and water absorption) properties of concrete. In this regard, 345 concrete samples were made with 1:1.5:3 mix ratio and cured for 28 days. The outcome has been demonstrated that the workability, dry density, water absorption and carbonation depth of concrete is getting reduced with growing the SF, RHA and MDP as SCM and TCM in concrete. Besides, the compressive and split tensile strength are increased by 10.44% and 9.544% respectively at 9% of SF, RHA and MDP as TCM for 28 days. Besides, the embodied carbon of concrete is decreasing while amount of SF, RHA and MDP as SCM and TCM is increasing. It has been observed that the use of 9% TCM is offering good results for construction sector and reduce the consumption of cement in concrete which helps to decrease the carbon emission in the environment.