Blast Furnace Slag Research Articles

Analysing Sustainable Concrete by Partial Replacement of GGBS and RCA

The report thoroughly explores sustainable M30 concrete options by exploring the utilization of Ground Granulated Blast Furnace Slag (GGBS) and recycled demolition waste. It delves into the environmental and structural advantages of integrating GGBS as a partial substitute for Portland cement and using demolition waste as aggregate. The primary goal of the research is to reduce the environmental impact of concrete production, promote recycling efforts, and elevate the performance of concrete structures. The results of the study suggest that GGBS and demolition waste present significant ecological benefits and enhance the properties of concrete, thus establishing them as feasible alternatives for sustainable construction practices. Index Terms- Recycled coarse aggregate(RCA), Natural coarse aggregate, ground granulated blast furnace slag (GGBS)

Properties and hydration mechanism of slow-setting and expansive cement based on CFB ash and slag

Aiming at the problems of long construction time and easy shrinkage cracking of pavement base, the slow-setting and expansive cement (SEC) was prepared using circulating fluidized bed ash and slag (CFBA and CFBS), S95 ground granulated blast furnace slag (GGBFS), and silica fume (SF) as supplementary cementitious material in this paper. By adjusting the content of supplementary cementitious material, the ratio of ash and slag, the performance of SEC was evaluated by the indexes of water consumption of standard consistency, setting time, flexural and compressive strength. The hydration products of mortar samples and the influence mechanism were studied by means of XRD, TG-DTG, FTIR, and SEM-EDS. The results showed that when the SF content was 6 %, the compressive strength of the mortar specimens reached its maximum (35.19 MPa) at 28 days, which increased by 23.04 % compared to the control group. Meanwhile, the free calcium oxide and gypsum in CFBA reacted under alkaline conditions to form ettringite (AFt) and C-S-H gel, which caused the volume expansion of cement and led to a decrease in shrinkage within the cement system. SEC has higher mechanical properties and much smaller shrinkage cracks than ordinary cement. Therefore, replacing part of the cement by solid waste such as CFBS to prepare SEC to compensate for the shrinkage of the pavement base is an effective way to reduce pavement cracking.

Emerging eco-friendly fiber-reinforced concrete with shaped synthetic aggregates using Taguchi grey relational analysis and utility concept

The present study assessed the applicability of employing Taguchi-based Grey relational analysis (T-GRA) and the Taguchi approach combined with the utility concept (T-UC) for enhancing the mix design parameters of fiber-reinforced synthetic aggregate concrete (FRSAC). Cement was supplemented with binders such as ground granulated blast furnace slag (GGBFS), metakaolin (MK), and lime powder (LP). The optimized mix proportion of FRSAC was determined to enhance the fresh and mechanical performance. Furthermore, this investigation used two weighting approaches: equally weighted and maximum deviation methods. An established L16 (45) Taguchi orthogonal array was used with five different factors, namely, cement replacement (40 %, 50 %, 60 % and 70 %), binder content (B1, B2, B3, B4), water-to-cement ratio (0.31, 0.32, 0.33, 0.34), fiber dosage (0.1 %, 0.2 %, 0.3 % and 0.4 %), and synthetic aggregate replacement (25 %, 50 %, 75 %, and 100 %) were employed to design the experiments. Then, T-GRA and T-UC were used to determine the optimum mix proportions for five response parameters: workability, compressive strength, split tensile strength, elastic modulus, and impact ductility index. Results indicated that the two methods, GRA and UC, can be successfully integrated with the Taguchi method to derive the optimized FRSAC mixture. Confirmation experiments were performed after determining the optimum mix design parameters, including cement replacement of 60 %, binder content of B4, the water-to-cement ratio of 0.34, fiber dosage of 0.1 %, and synthetic aggregate replacement of 75 %. The optimum FRSAC mix was examined for its fresh (workability) and hardened (compressive strength, split tensile strength, elastic modulus, impact ductility index) properties.

Experimental study on CO2 sequestration performance of alkali activated fly ash and ground granulated blast furnace slag based foam concrete

In an effort to reduce the emission level of carbon dioxide (CO2) from metallurgical, thermal, cement burning and other enterprises, an innovative solution is proposed in this study, which aims to sequester CO2 with alkali activated fly ash (FA) and ground granulated blast furnace slag (GGBFS) based foam concrete. The fluidity of alkali activated foam concrete (AAFC) fresh paste, dry density and compressive strength after hardening, micro-pore structure, carbonation products and CO2 sequestration capacity were comprehensively explored. The experimental findings indicated that the fluidity of AAFC slurry was almost unaffected by the content of foaming agent hydrogen peroxide (H2O2). When the H2O2 content ranges between 1 % and 3 %, the dry density of uncarbonated AAFC ranges approximately 752.3–365.2 kg/m3, and the compressive strength of carbonated AAFC ranges about 1.01–0.21 MPa. Accelerated carbonation increased the dry density of uncarbonated AAFC samples. The porous structure of AAFC facilitated CO2 gas penetration into the matrix, leading to rapid carbonation. When the H2O2 content was 1 %, the compressive strength of fully carbonated AAFC was lower than that of non-carbonated AAFC; however, when the H2O2 content exceeded 1.5 %, the trend in compressive strength reversed. The carbonation kinetics of AAFC demonstrated a linear relationship with the square root of carbonation time, and the carbonation coefficient increases proportionally with H2O2 content. The porosity of AAFC increased from 61.05 % to 71.51 % as the H2O2 content increased from 1 % to 2.5 %. The main pore size distribution range of AAFC was 30–400 µm and 5–50 nm. Accelerated carbonation minimally impacted the total porosity of AAFC but transformed certain large pores into capillary pores. Accelerated carbonation would generate calcite, aragonite, vaterite and additional amorphous phases. The maximum carbon sequestration capacity of AAFC, as determined in this study, reached 26.41 kg/m3, indicating significant potential for CO2 sequestration.

Comprehensive evaluation of microstructure and mechanical performance of sustainable ambient-cured alkali-activated composites

Cement is one of the building materials that is most frequently utilized in the construction field. However, the cement industry contributes significantly to the production of greenhouse gases. Therefore, many works have focused on improving sustainable construction materials that could contribute to decreasing greenhouse gas emissions. This study aimed to design a sustainable geopolymer mortar (GPM) made of fly ash (FA) and ground-granulated blast furnace slag (GGBS), which would be suitable for repairing damaged concrete structures. The work focused on investigating the effect of GGBS percentage, alkaline activator ratio, and superplasticizer dosage on the compressive strength, setting time, and workability of an ambient-cured GPM. The results of this research indicated that the compressive strength of GPM improved with the increase in GGBS percentage until a certain limit. However, the workability and setting time deteriorated with the increase in GGBS percentage. Increasing the alkaline activator ratio contributed to improving the compressive strength, workability, and setting time of GPM up to specific levels, but then they started to reduce. Superplasticizer dosage contributed to enhancing the compressive strength, workability, and setting time of GPM. This study found that the optimum FA/GGBS-based GPM that may be used in repair applications contains 50% GGBS, 50% FA, and 5% superplasticizer. The silica sand/binder ratio and alkaline activator ratio were 2.75 and 1.0, respectively. The compressive strength at 1 day, setting time, and workability of the optimum mix were about 12.70 MPa, 20 min, and 138.75 mm, respectively. The XRF, XRD, TGA, and SEM analyses were useful tools used to interpret the effects of the alkaline activator ratio on the fresh and mechanical properties of GPM.

Influence of Ambient Relative Humidity on the Shrinkage Strain of Engineered Geopolymer Composites Based on Orthogonal Experimental Design.

With the aim to systematically analyze the ambient relative humidity on the shrinkage strain of Engineered Geopolymer Composites (EGCs), this paper studied four variables (fly ash to ground granulated blast furnace slag mass ratio, alkali content, water-binder ratio, and fiber volume content) though orthogonal experimental design and three different relative humidity values (30%, 60%, and 100% RH). The results indicated that, for EGC specimens under 30% RH and 60% RH, the decrease in slag content and increase in alkali content both resulted in greater drying shrinkage. The addition of fibers effectively reduced the shrinkage strain, while a minor impact on shrinkage was presented by the W/B ratio. The first and second key factors affecting the drying shrinkage strain were the FA/GGBS ratio and the alkali content. The optimal ratio of FA/GGBS, alkali content, and fiber volume fraction were 0/100, 4%, and 1.5%, respectively. Dring shrinkage strain was decreased with the increase in ambient relative humidity. Compared with the shrinkage strain under 30% RH, the reduction in shrinkage strain under 60% RH and 100%RH was up to 46.1% and 107.5%, respectively. At last, a relationship between shrinkage strain and curing age under 30% and 60% RH was established with a fitting degree from 0.9492 to 0.9987, while no clear relationship was presented under 100% RH. The results in this paper provide a practical method for solving the shrinkage problem of EGCs.

Investigating the potential of electrostatic charging to separate cementitious binder and sand

The environmental footprint of concrete is largely influenced by the binder. It is therefore of high interest to investigate the potential reuse of the binder retrieved by modern separation techniques. However, studies found that the recycled cement fraction (RCF) still contained a certain amount of siliceous concrete aggregates, which forms an obstacle in the upcycling of RCF. In this study, the potential of electrostatic separation as a method to separate cementitious binder (hydrated and unhydrated) and sand (silica) is evaluated. Different cementitious powders and silica (sand) were prepared, resulting in a total of 9 powders and 8 mixtures. The mixtures consisted of a combination of silica and one of the cementitious powders (50/50 wt%) with a particle size of the components <125 μm. The potential of the studied technique was evaluated through charging measurements and x-ray fluorescence (XRF). Silica was assumed to contain no CaO and the detected CaO was therefore assigned to the cementitious powders. Results showed that silica and silica-rich fly ash (FA) particles became negatively charged, blast furnace slag (BFS) particles remained largely charge neutral and all other cementitious particles obtained a positive charge. Through electrostatic separation an enrichment of the cementitious binder fraction for all mixtures was obtained at the negative electrode. FA-Silica achieved the highest enrichment (89.9%), CEM III/B-Silica the lowest (4.7%) and the hydrates were enriched ranging from 28.0 to 31.8%.

The Role of a New Stabilizer in Enhancing the Mechanical Performance of Construction Residue Soils.

Urban construction generates significant amounts of construction residue soil. This paper introduces a novel soil stabilizer based on industrial waste to improve its utilization. This stabilizer is primarily composed of blast furnace slag (BFS), steel slag (SS), phosphogypsum (PG), and other additives, which enhance soil strength through physical and chemical processes. This study investigated the mechanical properties of construction residue soil cured with this stabilizer, focusing on the effects of organic matter content (Oo), stabilizer dosage (Oc), and curing age (T) on unconfined compressive strength (UCS). Additionally, water stability and wet-dry cycle tests of the stabilized soil were conducted to assess long-term performance. According to the findings, the UCS increased with the higher stabilizer dosage and longer curing periods but reduced with the higher organic matter content. A stabilizer content of 15-20% is recommended for optimal stabilization efficacy and cost-efficiency in engineering applications. The samples lost their strength when immersed in water. However, adding more stabilizers to the soil can effectively enhance its water stability. Under wet-dry cycle conditions, the UCS initially increased and then decreased, remaining lower than that of samples cured under standard conditions. The findings can provide valuable data for the practical application in construction residual soil stabilization.

Effect of ground granulated blast-furnace slag (GGBS) and sulphoaluminate cement (SAC) on the strength and microstructure of ordinary Portland cement paste at elevated temperatures

This study explored the potential of GGBS and SAC to enhance the thermal resistance of cement. The research explores changes in compressive strength and pore structure at various temperatures, employing microscopic analysis to elucidate underlying mechanisms. The results indicated that an optimal GGBS content enhanced strength, whereas SAC significantly reduced strength. The strength variation was not correlated with porosity or pore size distribution but rather with the hydration products of the blended cement. GGBS promoted the generation of C-A-S-H gels by introducing Al to replace Si in C-S-H gels, thereby increasing both the quality and quantity of gels. This enhancement suggested that GGBS improved thermal resistance by augmenting hydrate formation. SAC promoted ettringite formation even at high temperatures but reduced the quantity of hydrate gels, illustrating that SAC did not provide Al for the generation of C-A-S-H gels, consequently diminishing strength.

Effect of waste glass powder on the durability and microstructural properties of fly ash-GGBS based alkali activated concrete containing 100 % recycled concrete aggregate

This research investigates the effective utilization of waste glass powder (WGP) in fly ash (FA)-ground granulated blast furnace slag (GGBS) based alkali-activated concrete (AAC) containing 100 % recycled concrete aggregate (RCA) cured at ambient temperature. FA substituted with WGP in the range of 0–25 %, and the percentage of GGBS was kept unaltered at 50 %. The influence of WGP on the strength, durability, and microstructural properties of FA-GGBS based AAC was evaluated. The experimental results showed that the strength and durability were enhanced with the increases of WGP of up to 20 %, and then started to decrease. The highest compressive strength (51.4 MPa) and ultrasonic pulse velosity (UPV) (4.35 km/s) were obtained for F30W20 (FA:GGBS:WGP - 30:50:20). In addition, sorptivity, chloride, and water permeability were reduced by 39.92 %, 56 %, and 64.13 %, respectively for optimized specimens as compared to a control sample (without WGP). Furthermore, the microstructural analysis was carried out to investigate the alteration in the mineralogical and morphology. On the basis of microstructural investigations, WGP notably enhanced the microstructure of FA-GGBS-based AAC by enhancing the formation of reaction products, including C-S-H and C-(N)-A-S-H gel. At last, this study found that CO2 emissions, energy consumption, and cost analysis were lowered by approximately 60 %, 28 %, and 41 % compared to conventional concrete of the same quality.

Nano-silica and Ground Granulated Blast Furnace Slag Blended Concrete: Impact of Temperature on Stress–Strain Constitutive Model

Nano-silica and Ground Granulated Blast Furnace Slag Blended Concrete: Impact of Temperature on Stress–Strain Constitutive Model

Durability Performance of CGF Stone Waste Road Base Materials under Dry-Wet and Freeze-Thaw Cycles.

The disposal of stone waste derived from the stone industry is a worldwide problem. The shortage of landfills, as well as transport costs and environmental pollution, pose a crucial problem. Additionally, as a substitute for cement that has high carbon emissions, energy consumption, and pollution, the disposal of stone wastes by utilizing solid waste-based binders as road base materials can achieve the goal of "waste for waste". However, the mechanical properties and deterioration mechanism of solid waste-based binder solidified stone waste as a road base material under complex environments remains incompletely understood. This paper reveals the durability performance of CGF all-solid waste binder (consisting of calcium carbide residue, ground granulated blast furnace slag, and fly ash) solidified stone waste through the macro and micro properties under dry-wet and freeze-thaw cycling conditions. The results showed that the dry-wet and freeze-thaw cycles have similar patterns of impacts on the CGF and cement stone waste road base materials, i.e., the stress-strain curves and damage forms were similar in exhibiting the strain-softening type, and the unconfined compressive strengths all decreased with the number of cycles and then tended to stabilize. However, the influence of dry-wet and freeze-thaw cycles on the deterioration degree was significantly different; CGF showed excellent resistance to dry-wet cycles, whereas cement was superior in freeze-thaw resistance. The deterioration grade of CGF and cement ranged from 36.15 to 47.72% and 39.38 to 47.64%, respectively, after 12 dry-wet cycles, whereas it ranged from 57.91 to 64.48% and 36.61 to 40.00% after 12 freeze-thaw cycles, respectively. The combined use of MIP and SEM confirmed that the deterioration was due to the increase in the porosity and cracks induced by dry-wet and freeze-thaw cycles, which in turn enhanced the deterioration phenomenon. This can be ascribed to the fact that small pores occupy the largest proportion and contribute to the deterioration process, and the deterioration caused by dry-wet cycles is associated with the formation of large pores through the connection of small pores, while the freeze-thaw damage is due to the increase in medium pores that are more susceptible to water intrusion. The findings provide theoretical instruction and technical support for utilizing solid waste-based binders for solidified stone waste in road base engineering.

Advancing sustainability in concrete construction: enhancing thermal resilience and structural strength with ground granulated blast furnace slag

Advancing sustainability in concrete construction: enhancing thermal resilience and structural strength with ground granulated blast furnace slag

Enhancing acid corrosion resistance in alkaline-activated materials with water treatment residue and blast-furnace slag

This study investigates the acid corrosion resistance of an alkaline-activated material (AAM) composed of ground granulated blast-furnace slag (GGBFS) and water treatment residue (WTR) as precursors. WTR, a byproduct of the drinking water treatment process rich in aluminium and silicon, proves to be a suitable precursor for AAM after cost-effective pre-treatment involving calcination and grinding. As its low-Ca content and aluminosilicate nature of the treated WTR, the AAM incorporating WTR exhibits significant potential for improving acid resistance. This is attributed to the formation of less acid-reactive N-A-S-H gels than C-A-S-H gels in high-Ca AAMs, indicating its applicability in concrete sewage pipes where microbiologically generated acid corrosion is prevalent. In the paper, a comprehensive analysis, including mechanical performance, ion leaching behaviour, and microstructural characteristics, was conducted on mortar samples containing varying WTR/GGBFS ratios before and after exposure to sulfuric acid. Incorporating WTR up to 40 % effectively reduced acid-induced strength loss compared to neat-GGBFS AAM. The obtained results reveal that high-Ca AAMs facilitate gypsum formation during acid attack, leading to mechanical degradation. The inclusion of WTR induces a Si-rich transition layer between the corroded and intact matrix, mitigating sulfate diffusion. The release of aluminium from WTR promotes secondary precipitation of aluminosilicate, beneficially increasing the thickness of the transition layer. This thicker transition layer in the higher WTR samples is advantageous in reducing the likelihood of cracks and reducing the sulfate transportation into the intact matrix.

Effects of Curing Conditions, Age, and Particle Size on CO&lt;sub&gt;2&lt;/sub&gt; Sequestration of Basic Oxygen Furnace Slag Used in Concrete

Mineral sequestration technology is one of the most effective carbon capture and storage techniques. Basic oxygen furnace slag (BOFS), one of the by-products generated during the steelmaking process, has a particularly high potential for mineral sequestration compared to other similar wastes such as blast furnace slag and ladle slag. In the case of BOFS, mineral sequestration not only contributes to carbon uptake but also stabilizes its internal structure. So far, most of the investigations on BOFS mineral sequestration rely on accelerated carbonation involving high pressures and supplying concentrated CO2 in a short period. Although these studies are useful for investigating the overall potential for carbon capture of BOFS, they are less useful for practical applications on a large scale. Moreover, it is hard to draw any conclusions regarding the carbonation reactions lasting for years in stockpiles of BOFS. This research identified the consequences of long-term carbonation on BOFS samples and determined the best conditions for natural mineral sequestration.

Fluid transport in Ordinary Portland cement and slag cement from in-situ positron emission tomography

Fluid transport in cementitious matrices and materials is fundamental for many engineering and environmental applications. However, observing and measuring transport processes inside opaque porous solids, such as cement, is technically challenging. We tested the feasibility of using Positron Emission Tomography (PET) for in-situ tracking of fluid being spontaneously imbibed into cementitious matrices. We found that the 124I radiotracer enables tracking of the 3D spatiotemporal distribution of the fluids moving through the solid phase. Our measurements show a similar transport rate for Ordinary Portland (CEM І) and slag (CEM ІІІ/B) cement pastes. For both cement types, we found that the fluid penetration depth is proportional to t0.25. Such a relationship indicates anomalous transport and agrees with standard imbibition/sorptivity experiments. This result confirms that the method offers a reliable technique to explore transport phenomena in cementitious materials.

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.

Microstructure evolution of cement-based materials under Cl−-SO42- coupling erosion in simulated ocean tidal area

To disclose the corrosion principle of cement-based materials used in ocean tidal surrounding, the effects of chloride ion (Cl−) and sulfate (SO42−) coupling erosion on the microstructure of cement-based materials were mainly investigated. In the presence of Cl− solution at a concentration of 0.6 mol/L, the phase composition, pore structure distribution, and microscopic morphology of the hardened slurry of composite cementitious material containing 30 % fly ash (FA), or 30 % ground granulated blast furnace slag (GGBS), or mixed with 15 % FA and 15 % GGBS with varying concentrations of SO42− were investigated, respectively. The impact of SO42− concentration and mineral admixtures on the chemical binding Cl− and microstructure was examined from the microscopic level. The results showed that adding GGBS or FA can resist Cl− and SO42− erosion; however, GGBS is more effective at chemically solidifying Cl− than that of FA. The erosion of Cl− and SO42− influence each other and contain each other. Furthermore, Friedel salt (FS) transforms into Ettringite (AFt) after the introduction of SO42−, which releases bonded Cl− into the pore solution thereby increasing free Cl− content. In higher concentration (0.8 mol/L) of Na2SO4 solutions, the cement-based material is subjected to the superimposed destruction of physical crystallization and chemical erosion of the salt solution.

Reducing Energy Demand in Concrete Pavements by the Use of Blended Cements

This research explores strategies to minimise energy consumption and enhance environmental sustainability in road construction. Focusing on concrete pavement structures, the study evaluates the impact of substituting Portland cement with environmentally friendly alternatives such as fly ash and blast furnace slag. A comprehensive model is employed to analyse the energy demands of different pavement types, considering various cement replacements over their lifetime, from the initial extraction of materials to the conclusion of construction. Results indicate an energy saving potential of 8.63% by substituting 10% of Portland cement with fly ash, while an impressive reduction of 58.63% in cement production energy is achieved by replacing Portland cement with 80% blast furnace slag. The study underscores the significant role of cement variations in mitigating energy consumption, emphasizes the potential of blast furnace slag as a sustainable alternative as well as highlights the significance of alternative cement types in reducing energy consumption in concrete pavement construction, aligning with environmental sustainability goals and offering insights for more eco-friendly infrastructure development.

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