Supplementary Cementitious Materials In Concrete Research Articles

Embodied carbon saving potential of using recycled materials as cement substitute in Singapore’s buildings

Material production and construction activities are key contributors to global carbon footprints, necessitating sustainable alternatives. This study aims to investigate the potential of integrating recycled materials as Supplementary Cementitious Materials (SCMs) in concrete production to mitigate the substantial carbon emissions of Singapore’s building and construction sector. The research focuses on Ground Granulated Blast-furnace Slag (GGBFS), waste glass powder, and calcined marine clay as alternative SCMs, aiming to reduce environmental impact and waste disposal emissions in Singapore. Employing a cradle-to-gate Life Cycle Assessment (LCA) methodology for 1 m3 of concrete with different grades, this study quantifies embodied carbon savings and assesses the feasibility of substituting these SCMs in concrete. The results reveal that substituting Ordinary Portland Cement (OPC) with GGBFS in concrete offers the most significant reduction, up to 56%, in 1 m3 of concrete. In contrast, the use of calcined marine clay and glass powder in concrete results in reductions of up to 21% and 16%, respectively. Two case studies were used to exemplify the impact of using SCM concrete at the project scale. Results indicate that up to 31% of the total embodied carbon could be saved in the building. Additionally, scenario analysis suggests that the total emissions from cementitious materials in Singapore could decrease by 20% through the incorporation of locally recycled marine clay and glass powder. This reduction could potentially reach 56% if the GGBFS supply is not constrained. To further enhance sustainability in Singapore’s construction sector, the study proposes sourcing GGBFS from neighboring countries to minimize transportation emissions and localizing the production and usage of calcined marine clay and glass powder. These measures can improve material circularity and significantly contribute to achieving carbon reduction targets.

A study of chloride binding capacity of concrete containing supplementary cementitious materials

Chloride-induced steel corrosion is known to be a very common kind of deterioration of reinforced concrete. It is beneficial to bind free chloride ions to reduce the corrosion probability of the reinforcement embedded in the concrete. The binding capacity of the concrete varies according to its cementitious system. This paper investigates the chloride binding capacity of different kinds of supplementary cementitious materials (SCMs): Ground granulated blast furnace slag (GGBFS), Fly ash, and Metakaolin as a partial replacement of Ordinary Portland Cement (OPC). Different properties of concrete after chloride binding are assessed by carrying out the following tests: half-cell potential, accelerated corrosion test, compressive strength, rapid chloride penetration test, sorptivity test, measuring pH value of concrete, and XRD. The results showed that utilizing the SCMs in concrete can enhance the chloride binding capacity, especially those materials that have high quantities of aluminate and calcium in their chemical composition like GGBFS. Based on testing results, it’s recommended that the limit of the chloride content in the different codes should be revised regarding the binding capacity according to the type and quantity of the cementitious materials used.

Early-Age Cracking of Fly Ash and GGBFS Concrete Due to Shrinkage, Creep, and Thermal Effects: A Review.

Supplementary cementitious materials (SCMs) are eco-friendly cementitious materials that can partially replace ordinary Portland cement (OPC). The occurrence of early-age cracking in OPC-SCM blended cement is a significant factor impacting the mechanical properties and durability of the concrete. This article presents a comprehensive review of the existing research on cracking in OPC-SCM concrete mix at early ages. To assess the effects of SCMs on the early-age cracking of concrete, the properties of blended cement-based concrete, in terms of its viscoelastic behavior, evolution of mechanical performance, and factors that affect the risk of cracking in concrete at early ages, are reviewed. The use of SCMs in OPC-SCM concrete mix can be an effective method for mitigating early-age cracking while improving the properties and durability of concrete structures. Previous research showed that the shrinkage and creep of OPC-SCM concrete mix are lower than those of conventional concrete. Moreover, the lower cement content of OPC-SCM concrete mix resulted in a better resistance to thermal cracking. Proper selection, proportioning, and implementation of SCMs in concrete can help to optimize the performance and reduce the environmental impact of OPC-SCM concrete mix.

Characterization and development of alccofine based sustainable concrete – A review

The accelerated rate of industrialization and urbanization in recent decades is producing enormous quantities of waste globally. The per day per capita solid waste of 0.79 kg totalling 2.24 billion tons all over the world in 2020, is estimated to augment by 73% to 3.88 billion tons per annum by 2050. Presently in India, approximately 1 billion ton of solid waste per annum is generated during various processes. On the other hand, high global demand for construction materials (approx. 10 billion tons per annum) is depleting natural resources and disturbing the eco-system. As a result, researchers are switching over from traditional materials to alternative innovative materials by reprocessing diverse wastes and byproducts protecting the environment. Due to this, it has gained popularity and momentum in the production of sustainable concrete by partially replacing or adding Supplementary Cementitious Materials (SCMs) to the conventional binder. The purpose of this work is to review and discuss the mechanical and durability characteristics of alccofine based concrete significantly. Additionally, it aims to provide a better understanding about the mechanism of alccofine-1203 as an SCM in concrete. Due to distinctive chemical composition and ultrafine particles, alccofine-1203 improved pozzolanic reaction, increased pace of hydration process, reduced heat of hydration, reduced permeability to concrete, and reduced segregation and bleeding to produce high strength to concrete at the early curing stages. Considering this, alccofine can be utilized as an SCM due to its ultrafine nature and high concentrations of calcium oxide (CaO) and silica (SiO2), which are advantageous in improving the mechanical and durability qualities of concrete in comparison to other SCMs. A process to use alccofine as a replacement must be developed to produce sustainable concrete. Literature analysis suggests the ideal dosage of alccofine-1203 between 8 and 12% which significantly improved the mechanical and durability qualities of concrete.

Prediction of the compressive strength of nano-titanium based concrete composites using machine learning

Cement manufacturing process is energy-intensive and can release significant volumes of carbon dioxide and other greenhouse pollutants which leads to the severe degradation of the environment. To save the environment, the consumption of the cement must be reduced by replacing it with other materials known as Supplementary Cementitious Materials (SCMs). Utilizing SCMs in concrete can help in lowering the construction industry's overall carbon emissions. SCMs are not only helpful in protecting the environment, but they can also improve the mechanical properties of concrete, mainly when applied in the form of Nano-particles (NPs). When NPs, in particular nano-titanium (nT), are used to replace cement in concrete, it not only improves the concrete's mechanical characteristics but it also improves the durability of concrete. Apart from various advantages of using nT as SCM in the concrete, the most superior advantage is the enhanced compressive strength (CS) which is the far most important mechanical property of concrete. This property of the concrete depends non-linearly with the ingredients required to make it. So, in order to predict the influence of these ingredients on the CS, researchers must either conduct extensive experiments or use soft computing techniques. With the help of these techniques, accurate and trustworthy models were developed to predict the CS of concrete. So, in this study, two machine learning models namely Artificial Neural Network and Gradient Boosting were developed to predict the CS of nT-based concrete composites after 28 days of curing. On comparison between the two developed models, Gradient Boosting model was found to be the most effective for an accurate CS prediction with Correlation coefficient (R2) as 0.992, Mean Absolute Error (MAE) as 1.015 and Root Mean Squared Error (RMSE) as 1.385. Artificial Neural Network was deemed to be inferior with R2 as 0.972, MAE as 1.34 and RMSE as 2.601.

Assessment on Optimal Level of Reactive Biosilica Affected by Incineration Conditions in Perlis Rice Husk Ash as Supplementary Cementitious Materials in Concrete

Rice husk (RH) is an agricultural waste transformed to produce secondary by-products and is widely accepted as a substitution of cement or concrete mixtures. This paper deals with the optimal level of SiO2 content due to various incineration conditions of rice husk grown in Perlis, Malaysia. RH was burnt in a controlled environment with a targeted temperature of 650, 750 and 850 °C at various incineration period between 1 and 6 h. All the ashes were assessed for visual inspection and physiochemical and mineralogical properties using X-ray fluorescence (XRF) and X-ray diffraction (XRD). From the analysis, a significant amount of SiO2 in the range of 89–93 wt % was successfully obtained with the preferable properties of supplementary cementitious materials: amorphous silica with high reactivity, ultrafine size, and large surface area. Contrary, the burning temperature of 850 °C greater than 4 h incineration period is not advisable to be used as it transformed into a crystalline phase. No obvious color changes were observed for the ashes as the amount oxide compound of K2O causes carbon entrapped in surface melting. To sum up, 650 °C incineration for 1 h shows an optimum result, and the RH is bearable to reduce the negative impact on the environment.

Evaluation and beneficiation of high sulfur and high alkali fly ashes for use as supplementary cementitious materials in concrete

Coal-fuel power plants with semi-dry or dry flue gas desulfurization (FGD) systems produce high sulfur and/or high alkali fly ashes due to comingling of fly ash with FGD products. Such fly ashes do not meet the SO3 content limit (5.0% max.) of ASTM C618 or are unable to mitigate the alkali-silica reaction. The mineralogy of the sulfur present in these ashes can vary significantly (e.g., CaSO4, CaSO3, Na2SO4) based on the FGD technology used and this affects the performance of these fly ashes in concrete. Thus, the single SO3% limit of ASTM C618 is unable to capture the complexity and performance of fly ash, and this results in elimination of potentially viable pozzolans for concrete. This study performs a systematic investigation of the effect of SO3 type and content in fly ash on various performance parameters of cement-fly ash pastes and mortars, including workability (flow and flow retention), pore fluid pH, setting time, strength development, and potential for deleterious expansion. To better quantify and understand these effects, the study considers both real and doped fly ashes (i.e., a blend of specification-compliant fly ash with target sulfur compounds). The poor performance observed in the case of setting time and pore fluid pH was successfully mitigated using chemical admixtures.

Rheological properties of cement paste blended with sugarcane bagasse ash and rice straw ash

Rice straw ash and sugarcane bagasse ash are two of the most abundantly available biomass ashes in India and can be used as supplementary cementitious materials in concrete. Unlike rice husk ash which is also a by-product of rice cultivation, the research studies on the use of rice straw ash as a pozzolan are highly limited. This study characterizes the microstructure of the as-received and processed rice straw ash in comparison with sugarcane bagasse ash. Moreover, the influence of these ashes on the rheological properties of cementitious system was investigated. The microstructural characterization reveals that both rice straw ash and sugarcane bagasse ash are constituted of dumbbell shaped silica-storage structures called phytoliths. Rice straw ash is found to be richer in phytoliths compared to sugarcane bagasse ash. However, the prismatic structures as seen in sugarcane bagasse ash is noticeably absent in rice straw ash. The unburnt carbon content is attributed to the fibrous network present in the ashes. The yield stress and viscosity of cement paste are found to increase with the addition of rice straw ash and sugarcane bagasse ash. Cements blended with sugarcane bagasse ash is found to have a significantly greater viscosity than rice straw ash blended cements at all levels of replacement. Mechanical processing of the ashes (sieving and grinding) to remove the coarse fibrous fraction is found to improve the rheological properties of cement blended with rice straw ash and sugarcane bagasse ash. The optimum dosage of superplasticizer required for rice straw ash and sugarcane bagasse ash blended cements were found to be 0.6% and 0.4%, respectively.

Production of concrete using reclaimed water from a ready-mix concrete batching plant: Life cycle assessment (LCA), mechanical and durability properties

This study investigates novel methods and more sustainable techniques that have been developed to minimize the environmental damage of concrete production. The use of reclaimed water and supplementary cementitious materials in concrete can be a solution to the problems of water scarcity and excessive CO2 emissions. In this context LCA, mechanical and durability properties of concrete containing silica fume as a supplementary cementitious material (SCM) and reclaimed water as an alternative source of fresh water are studied. First several properties of concrete such as consistency, compressive strength, electrical resistance, chloride ion penetration and water penetration under pressure were measured. Then, the LCA of concrete using LCA web tool was evaluated and the global warming potential (GWP) emission rates along with air pollutants such as lead, volatile organic compounds, CO, NOX, PM10 and SO2 were determined. The results show that adding a certain level of silica fume is desirable in terms of environmental issues, cost and mechanical and durability properties of concrete. In concrete containing 5, 8 and 11% of silica fume, GWP emissions decreased by 4.9, 8 and 11.2%, respectively. On the other hand, the production of lead, volatile organic compounds (VOCs), CO, NOX and PM10 decreased by 2–12%, while SO2 production increased by 4–10%. According to the obtained results, the manufacture of concrete with the mixing ratios presented in this research in a large-scale ready-mix concrete batching plant that produces 576 tonnes concrete per year (240,000 m3/year) will lead to a reduction of GWP about 3900–8700 tonnes CO2-eq per year.

Rice-Straw Ash as a Potential Supplementary Cementitious Material: Influence of Thermochemical Conversion on Its Properties

AbstractAgro-waste ashes can be used as supplementary cementitious materials in concrete. Although many studies have been reported on the use of rice husk ash as a pozzolan, only limited studies ar...

Alkali-silica reaction: understanding the phenomenon

The alkali-silica reaction in cementitious composites occurs through the chemical association of the solution contained in the matrix pores, which is strongly basic and rich in alkalis, and the reactive phases of some aggregates. For the process to begin, high relative humidity and a high concentration of total alkalis are required. The degradations resulting from this reaction involve expansion, cracking, exudation and decreased mechanical performance of the structure, which can cause it to break depending on the magnitude of the phenomenon. Understanding the reaction development process is necessary to propose measures that can effectively extinguish or mitigate the occurrence. One of the measures widely studied is the incorporation of supplementary cementitious materials in concrete. In Brazil, technical regulations already exist that recommend the use of these cementitious materials. The Northeast region of the country is a major producer of fly ash and granulated blast furnace slag, but not all of this material is destined for other industries. The article in question is a compendium of technical information from relevant research developed about alkali-silica reaction. His contribution is in the didactic approach that allows the understanding of students in the engineering area and professionals who do not have the expertise in the subject in order to stimulate future research on the use of supplementary cementitious materials in Northeast Brazil, mainly.

Effects of Corn Cob Ash as Mineral Admixture on Mechanical and Durability Properties of Concrete – A Review

Concrete is the second most consumed product next to water on earth. Cement is the key ingredient for making concrete. India is the second largest cement producer in the world. The production of cement is emitting an equal amount of CO2 in to the atmosphere and is accounted as about 8% of the world’s total emissions. The addition of mineral additives as supplementary cementitious materials in concrete is one of the solution to avoid such environmental pollution. The natural mineral admixture obtained from the novel agricultural by-product, namely corn cob ash (CCA), is being utilized in cement manufacturing and concrete construction. The similarities in both physical and chemical properties of CCA were established when compared to the decade old agro-based mineral admixtures like rice husk ash (RHA) and sugar cane bagasse ash (BA) through research findings. The results are mentioned that the CCA can be used as chemically active mineral admixture and micro-filler in concrete. With this background, the paper presents a review on the effect of substituting CCA in fresh, mechanical and durability properties of concrete.

Performance of Rice Husk Ash as Supplementary Cementitious Material after Production in the Field and in the Lab.

Supplementary cementitious materials (SCM) can reduce the total amount of Portland cement clinker in concrete production. Rice husk ashes (RHA) can be converted from an agricultural by-product to a high-performance concrete constituent due to a high amount of reactive silica with pozzolanic properties if they are burnt under controlled conditions. The way and duration of combustion, the cooling process as well as the temperature have an effect on the silica form and thus, the chemical and physical performance of the RHA. Various studies on the best combustion technique have been published to investigate the ideal combustion techniques. Yet, the process mostly took place under laboratory conditions. Investigating the difference between the performance of RHA produced in a rural environment and laboratory conditions is useful for the assessment and future enhancement of RHA production, and its application both as building material, for example in rural areas where it is sourced in large quantities, and as additive for high performance concrete. Thus, the paper presents a comparison between RHA produced under rudimentary conditions in a self-made furnace in the rural Bagamoyo, Tanzania and under controlled laboratory conditions at the Technical University of Munich, Germany, with different combustion methods and temperatures. In a second step, RHA was ground to reach particle size distributions comparable to cement. In a third step, cement pastes were prepared with 10%, 20% and 40% of cement replacement, and compared to the performance of plain and fly ash blended cement pastes. The results show that controlled burning conditions around 650 °C lead to high reactivity of silica and, therefore, to good performance as SCM. However, also the RHA burnt under less controlled conditions in the field provided reasonably good properties, if the process took place with proper burning parameters and adequate grinding. The knowledge can be implemented in the field to improve the final RHA performance as SCM in concrete.

Hydration and microstructure of concrete containing high volume lithium slag

Due to requirements for environmental protection, saving of resources and sustainable construction in the future, investigation on the use of high volume mineral admixtures as supplementary cementitious materials in concrete was carried out in this study. The effect of high volume lithium slag (LS) to partially replace cement by weight on compressive strengths of concrete was experimentally investigated, and the hydration of hardened paste was measured by non-evaporable water. Moreover, the microstructure of concrete was determined by mercury intrusion porosimetry and scanning electron microscope methods. Results showed that the use of high volume LS reduced compressive strengths of concrete at early ages, and compressive strengths were remarkably improved at later ages, with concrete containing 40% LS being close to that of the control concrete. Hydration of hardened paste showed similar variation trends with compressive strengths. The highvolume LS degraded concrete microstructure at early ages, and 40% LS improved concrete microstructure at the later ages, due to the filling effect and pozzolanic reaction of LS. However, there still existed defects in microstructure of concrete containing 60% LS, with increased harmful porosity, especially interfacial transition zone.

Feasibility study on the use of shell sunflower ash and shell pumpkin ash as supplementary cementitious materials in concrete

This study proposes that Shell Sunflower Ash (SSA) and Shell Pumpkin Ash (SPA) partially replace cement in concrete as pozzolanic materials. To trace the chemical composition of raw SSA and SPA, X–Ray diffraction (XRD) and scanning electron microscopy (SEM) were utilized. Cement was replaced with 5, 10, 15 and 20% of the SSA and SPA. The slump of fresh concrete, elastic modulus, compressive strength, ultrasonic pulse velocity (UPV) test, SEM, energy dispersive x–ray (EDX), XRD and thermo-gravimetric analysis (TGA) of the sample were studied. Pozzolanic reaction with percentage of SSA and SPA was lower than the control specimen in the early ages. The addition of the SSA to the mix by up to 15% increased the compressive strength of the sample by 27.3% at 28 days. The SEM and EDX results illustrate the replacement of cement with the SSA and the SPA can improve the microstructure of the mixtures at 28 days. The SEM also showed that the addition of 15% the SSA and the SPA decreased the voids in the matrix. XRD and TAG results also demonstrated the effect of SSA and the SPA on reduction of CH content due to pozzolanic reactions. The result show that use of the SSA and SPA as replacement of cement is feasible.

Early and Late Compressive Strengths Behaviour of Concrete with Blended South African Extenders

The use of different supplementary cementitious materials (SCMs) has attracted the interest of researchers for years. These materials have their advantages and dis-advantages. The optimal use of these SCMs in concrete may call for blending them together in concrete instead of using them individually. The blend may increase their quality as one disadvantages may be catered for by another one advantages. The present study focusses on investigating the effect of proportional combination of these SCMs on strength development. Three different South African SCMs (Ground granulated blast-furnace slag, Silica fume and Fly ash) were blended at different proportions and used as replacement of cement in concrete. Compressive strength test based on SANS 5860:2006 standard were adopted. The compressive test was performed on 16 different mixes at 7, 14, 28, 90 and 120 days curing periods. The water/cement ratio for all the mix was maintained at 0.5. The compressive strength results are desirable for each curing age at the 30% replacement of cement in which each SCM contributes 10% to the mix, greater strength value at curing age beyond 120 days compared to control sample was envisaged for this sample.

Green concrete containing diatomaceous earth and limestone: Workability, mechanical properties, and life-cycle assessment

To arrest the growth of global environmental issues, curbing the greenhouse gas emissions and primary energy consumption in concrete production is among the efficacious strategies. Cement production being the most energy- and emission-intensive activity in concrete manufacture, the partial replacement of cement clinker with supplementary cementitious materials (SCMs), which require less intensive processing, is the effective approach. Due to the unbalanced source distribution of commonly-used SCMs, e.g. fly ash (FA) and ground granulated blast furnace slag (GGBFS), this study analyzed the substitution of Portland cement (PC) in mortar and concrete mixes with up to 40% of the highly-reactive pozzolanic diatomaceous earth (DE) with abundant deposit in western United States and many other countries, aiming to provide an alternative SCM with local availability in many regions of limited FA and GGBFS supply. The influence of DE on the density, compressive strength, workability, soundness, and environmental impacts of the production of a mix was studied at different substitution levels in binary, ternary, and quaternary systems. DE-containing mixes showed improved strength development and early properties suitable for general applications. The approach of life-cycle assessment quantified the influence of DE on environmental impacts from material production, processing, and transportation in mortar or concrete manufacture. Substitution of PC with DE at 30 wt% resulted in over ∼30% lower global warming potential and energy use as well as appreciably reduction in air pollutant emissions. The use of DE as SCMs in concrete is promising, worth the consideration regarding availability and cost.

Efficiency Concepts and Models that Evaluates the Strength of Concretes Containing Different Supplementary Cementitious Materials

The usage of Supplementary Cementitious Materials (SCM) is very much acknowledged due to the several improvements possible in the concrete composites, and because of the general economy. Research work till date suggests that utilization of SCMs enhance a significant number of the performance characteristics of the hardened concrete. The idea of efficiency can be utilized for comparing the relative performance of different pozzolans when incorporated into concrete. The efficiency concept, which was initially developed for fly ash, can be effortlessly connected to other advantageous s as well, such as silica fume, slag and natural pozzolans. A quantitative understanding of the efficiency of SCMs as a mineral admixture in concrete is essential for its effective utilization. The paper reviews the literature pertaining to the different efficiency concepts and models present to date that evaluates the strength of concretes containing different SCMs. This short survey demonstrates that there is a need for a superior comprehension of the SCMs in concrete for its powerful usage. Also, it is an effort directed towards a specific understanding of the efficiency of SCMs in concrete.

Extending supplementary cementitious material resources: Reclaimed and remediated fly ash and natural pozzolans

The concrete industry is under increasing pressure to reduce greenhouse gas emissions and energy use in portland cement manufacturing. While there are several possible ways to address this challenge, an immediate solution is to minimize the amount of portland cement used by partially substituting other materials to make concrete binders. Typical supplementary cementitious materials (SCMs) used in concrete are byproducts of other industries, such as fly ash from coal burning power production. However, in some regions, changes in the supply-demand chain for SCMs is limiting the ability of the concrete industry to fully utilize these traditional, byproduct SCMs in concrete. This paper addresses current research on avenues for extending SCM resources, particularly in the context of fly ash shortages in the US, including concrete-grade reclaimed fly ash and natural pozzolans.

MICROSTRUCTURAL CHARACTERIZATION OF RICE HUSK AND RESIDUAL ASH FOR THE PRODUCTION OF SUPERIOR BLENDED CONCRETE

Several industrial by-products such as fly ash, silica fume and slag are widely used as supplementary cementitious materials in concrete. In addition to attain designed characteristic strength of structural concrete, it is very imperative to maintain the strength throughout service life of the structure. Supplementary cementitious materials are commonly used in the modern cement manufacturing process to achieve durable and sustainable concrete. Earlier research studies have clearly reported that higher strength and significant reduction in permeability of concrete containing agricultural waste products such as sugarcane bagasse ash and rice husk ash compared to control concrete. However, utilization of rice husk ash and sugarcane bagasse ash in blended cement production is limited to a greater extend as a consequence of lack of understanding and characterization of these materials. Microstructure of rice husk and silica distribution in the residual ash due to controlled burning is not available in the existing literature. This paper reviews reactive silica formation in the rice husk and its residual ashes based on the microstructure and its influence on the pozzolanic performance. Moreover, rice husk ash was processed based on suitable methodology and compressive strength of mortar was found to be high compared to control specimens.