Granulated Blast Furnace Slag Research Articles

Fresh, hardened properties and microstructural analysis on the effect of NaOH molarities of industrial by-products based self-compacting geopolymer concrete

AbstractThe sodium hydroxide (NaOH) molarity in Self-compacting geopolymer concrete (SCGC) is essential for activating the precursor and aggregate to develop strength, workability, and microstructure. In this study, SCGC mixes prepared with 50% fly ash (FA) and 50% ground granulated blast furnace slag (GGBS) to investigate fresh and hardened properties with NaOH molarities (M) ranges from 8 to 16, the ratio of Na2SiO3 to NaOH kept constant at 2.5 and ratio of alkaline solution to the binder at 0.45 with 2% SP for the polymerization process. SCGC workability studies indicate the NaOH concentration increased, the slump flow decreased, and 14 M was the optimum molarity. The compressive, split tensile, and flexural strength results showed 39.4 MPa, 4.72 MPa, and 5.91 MPa at 28 days. The C–S–H gel enhanced the strength qualities studied from Fourier transform infrared spectroscopy. The scanning electron microscope showed microstructural densification of the entire system, which improved with the NaOH concentration, and the strength increased with the degree of polymerization and polycondensation. Hence, based on workability, the optimized NaOH concentration is 14 M with binder contents of FA (50%) and GGBS (50%). This study helps to improve the microstructure and strength properties with potential cost implications of SCGC.

Fluidized solidified soil using construction slurry improved by fly ash and slag: preparation, mechanical property, and microstructure

Abstract Fluidized solidified soil (FSS) is a cement-based engineering matergood working performance and mechanical properties. Based on fixed cement and desulphurisation gypsum (DG), fly ash (FA) and ground granulated blast furnace slag (GGBS) were added as admixtures to the construction slurry to prepare three types of FSS: namely cement-GGBS-DG FSS (CGD-FSS), cement-FA-GGBS-DG FSS (CFGD-FSS), and cement-FA-DG FSS (CFD-FSS). Considering 7 d, 14 d, and 28 d three curing times, compressive, flexural, scanning electron microscopy (SEM), and x-ray diffraction (XRD) analyses were conducted to explore the time-dependent mechanical properties and microscopic characterisation of FSS. The mechanical test showed that CFGD-FSS doped with FA and GGBS had better fluidity, compressive strength, and flexural strength than CGD-FSS doped with FA alone and CFD-FSS doped with GGBS. The CFGD-FSS specimen with a cement:FA:GGBS:DG ratio of 30: 10: 40: 20 in the curing agent had the best mechanical properties, i.e., the CFGD01 specimens. It has fluidity of 189 mm, compressive strength of 671 kPa, and flexural strength of 221 kPa with a 28d curing time, which can meet the working requirements of FSS for filling narrow engineering spaces. And compared with other specimens, it has the shortest setting time, which can effectively shorten the construction period. Microscopic analysis showed that a large number of hydration products, such as calcium silicate hydrate, calcium aluminate hydrate, and ettringite (Aft), were well-formed in the FSS, resulting in good mechanical properties, especially for the CFGD-01 specimens. Finally, two empirical models were established to describe the compressive strength–porosity and flexural strength–porosity relationships. Moreover, the investigated data agreed well with the modelling results.

Prediction of the R3 Test-Based Reactivity of Supplementary Cementitious Materials: A Machine Learning Approach Utilizing Physical and Chemical Properties

This study utilized machine learning (ML) models to investigate the effect of physical and chemical properties on the reactivity of various supplementary cementitious materials (SCMs). Six SCMs, including ground granulated blast furnace slag (GGBFS), pulverized coal fly ash (FA), and ground bottom ash (BA), underwent thorough material characterization and reactivity tests, incorporating the modified strength activity index (ASTM C311) and the R3 (ASTM C1897) tests. A data set comprising 46 entries, derived from both experimental results and literature sources, was employed to train ML models, specifically artificial neural network (ANN), support vector machine (SVM), and random forest (RF). The results demonstrated the robustness of the ANN model, achieving superior prediction accuracy with a testing mean absolute error (MAE) of 9.6%, outperforming SVM and RF models. The study classified SCMs into reactivity classes based on correlation analysis, establishes a comprehensive database linking material properties to reactivity, and identifies key input parameters for predictive modeling. While most SCMs exhibited consistent predictions across types, GGBFS displayed significant variations, prompting a recommendation for the inclusion of additional input parameters, such as fineness, to enhance predictive accuracy. This research provided valuable insights into predicting SCM reactivity, emphasizing the potential of ML models for informed material selection and optimization in concrete applications.

Functionalizing heavy metal contained incinerated sewage sludge ash in recycled glass-based alkali-activated materials for sewer environment

This study evaluates the performance of alkali-activated cement (AAC) mortars in an artificial sewage environment. The mortars, initially prepared with waste glass powder (GP) and ground granulated blast furnace slag (GGBS) in a 50:50 mass ratio, were modified by replacing 10 wt% of GGBS with incinerated sewage sludge ash (ISSA) with the goal of offering a biocidal effect. Comparisons were made with calcium aluminate cement (CAC), metakaolin (MK), and MK combined with zinc ferrite nanoparticles, each at a similar GGBS replacement level. The results showed that only incorporating CAC improved the strength development, achieving compressive and flexural strengths of 62.7 MPa and 7.4 MPa, respectively, at 28 days, while introducing ISSA or MK reduced the compressive strength to 47 MPa and flexural strength to 4.5 MPa. Although heavy metal ions from ISSA or zinc ferrite nanoparticles minimized biofilm thickness, they could not compensate for the reduced strength and increased alkalis leaching. Among all the tested mixtures, the 50GP40GGBS10CAC mixture exhibited superior biogenic acid resistance, possibly due to its Al-rich C-N-A-S-H gel phases (Ca/Si = 0.4, Na/Al = 0.8, Si/Al = 3.4) and refined pore structure (porosity = 3.4 %), making it the most microbial acid-resistant option for sewer rehabilitation.

Exploring effects of supplementary cementitious materials on setting time, strength, and microscale properties of mortar

The concept of sustainability has become a crucial concern for safeguarding the planet. The current research has focused on developing affordable and eco-friendly mortar by using industrial wastes. This study explores the use of fly ash (FA) and ground granulated blast furnace slag (GGBFS), byproducts of steelmaking and coal burning, in mortar production. It examines their impacts on the compressive strength and setting times, when utilizing varying proportions of the materials. The study also evaluates water requirements for the workability, thus demonstrating the sustainability of these waste products in construction. The cementitious materials were employed in finely ground form and were replaced with further tertiary mixes including both supplements at 10%, 30%, and 50% of each. The mixtures were allowed to cure for 7, 14, and 28 days by immersion in water. The results showed improvements in the compressive strength of mortar samples incorporating FA and GGBFS at various curing ages. However, the water requirement and workability of mortar samples were altered as a result of utilizing these supplementary cementitious materials (SCMs). These findings will serve as a standard for environmentally responsible mortar using GGBFS and/or FA as SCMs.

Utilization of Granulated Blast Furnace Slag in Cement Mortar: Performance Analysis Against M-Sand

This study aims to explore the feasibility of incorporating Granulated Blast Furnace Slag (GBFS) as a sustainable alternative to manufactured sand (M-Sand) in cement mortar, to enhance both environmental sustainability and mechanical performance. The research involves a systematic investigation where M-Sand is progressively replaced by GBFS at varying levels of 10%, 20%, 30%, 40%, and 50%. The effects of these replacements are evaluated through a series of tests that focus on the mortar's physical properties, as well as its compressive and tensile strengths. Experimental results reveal that replacing 30% of M-Sand with GBFS produces the most favorable outcomes, with the compressive strength of the mortar exceeding that of the control mix by 12% after 28 days. The tensile strength also showed marked improvements at this replacement level. However, when the replacement level exceeds 30%, both compressive and tensile strengths begin to diminish, indicating that excessive substitution may adversely affect the mortar's structural integrity. The findings of this study provide valuable insights into the optimal use of GBFS in cement mortar, demonstrating that a 30% substitution not only enhances strength characteristics but also contributes to more sustainable construction practices by reducing reliance on natural sand resources. This research supports the potential of GBFS as a viable material for improving the environmental profile and durability of cement-based materials.

A Novel Landfill Liner Material for Solidified Lake Sediment Based on Industrial By-Product and Construction Waste: Engineering Behavior and Cr(VI) Breakdown Characteristics

Engineering sludge, industrial waste, and construction waste are marked by high production volumes, substantial accumulation, and significant pollution. The resource utilization of these solid wastes is low, and the co-disposal of multiple solid wastes remains unfeasible. This study aimed to develop an effective impermeable liner material for landfills, utilizing industrial slag (e.g., granulated blast furnace slag, desulfurized gypsum, fly ash) and construction waste to consolidate lake sediment. To assess the engineering performance of the liner material based on solidified lake sediment presented in landfill leachate, macro-engineering characteristic parameters (unconfined compressive strength, hydraulic conductivity) were measured using unconfined compression and flexible wall penetration tests. Simultaneously, the mineral composition, functional groups, and microscopic morphology of the solidified lake sediment were analyzed using microscopic techniques (X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy + energy dispersive spectroscopy). The corrosion mechanism of landfill leachate on the solidified sediment liner material was investigated. Additionally, the breakdown behavior of heavy metal Cr(VI) within the solidified sediment liner barrier was investigated via soil column model experiments. The dispersion coefficient was computed based on the migration data of Cr(VI). Simultaneously, the detection of Cr(VI) concentration in pore water indicated that the solidified sediment liner could effectively impede the breakdown process of Cr(VI). The dispersion coefficient of Cr(VI) in solidified sediments is 5.5 × 10−6 cm2/s–9.5 × 10−6 cm2/s, which is comparable to the dispersion coefficient of heavy metal ions in compacted clay. The unconfined compressive strength and hydraulic conductivity of the solidified sediment ranged from 4.90 to 5.93 MPa and 9.41 × 10−8 to 4.13 × 10−7 cm/s, respectively. This study proposes a novel approach for the co-disposal and resource utilization of various solid wastes, potentially providing an alternative to clay liner materials for landfills.

Review of Recent Developments in Tensile Properties of Engineered Geopolymer Composites

Engineered Cementitious Composite (ECC) is a type of highly ductile cementitious material. However, due to its characteristics of high energy consumption and high carbon emissions, it is necessary to seek a new type of low-carbon and environmentally friendly substitute. Engineered Geopolymer Composite (EGC), as a promising construction material for replacing ECC, has broad application prospects. Through visual analysis of the relevant literature in Web of Science, it was discovered that the research on EGC mainly concentrates on aspects such as the types of precursors, the chemical composition of the alkali-activated solution, and the related parameters of fibers. This paper mainly combines the relevant experimental research data on the tensile properties of EGC conducted by scholars at home and abroad, and focuses on analyzing the influence of precursor types, the chemical composition of the alkaline activator, and fibers on the tensile properties of EGC. The statistical results indicate that fly ash and ground granulated blast-furnace slag (GGBFS) are the most commonly used precursor materials. Replacing an appropriate amount of fly ash in the precursor with GGBFS can significantly enhance the tensile strength of EGC. The type of alkaline activator and its molarity have a relatively obvious influence on the tensile properties of EGC. An increase in the molarity of NaOH within a certain range can enhance the tensile strength of EGC. Furthermore, the incorporation of fibers, especially synthetic fibers such as polypropylene (PP) and polyvinyl alcohol (PVA) fibers, as well as inorganic fibers such as glass fibers (GF) and carbon fibers (CF), can effectively enhance the tensile strength and tensile strain capacity of EGC. The use of hybrid fibers may further improve the tensile properties.

Mechanical Properties and Microstructure of Alkali-Activated Cements with Granulated Blast Furnace Slag, Fly Ash and Desert Sand

In this study, desert sand was used as supplementary materials in alkali-activated cements (AAC) with granulated blast furnace slag (GBFS) and fly ash (FA). For the first time, a systematic investigation was conducted on the effects of various treatment methods and contents of desert sand on the strength and microstructure of AAC. This study also analyzed the X-ray diffractometer (XRD), Scanning Electron Microscopy-Energy Dispersive X-ray Microanalysis (SEM-EDX), Mercury Intrusion Porosimetry (MIP), pH values, and Fourier-transform infrared spectroscopy (FT-IR) properties of AAC pastes containing differently treated desert sand to uncover the mechanisms by which these treatments and dosages influence mechanical properties of AAC. Untreated desert sand (DS), temperature-treated desert sand (DS-T), and ground desert sand for two different durations (20 mins and 30 mins) all exhibited some pozzolanic activity but primarily acted as fillers in the AAC pastes. Among the samples, DS-T demonstrated the highest pozzolanic activity, though it was still less than that of fly ash (FA). The optimal dosage for the modified desert sands was determined to be 10%. However, The optimal dosage of different modified desert sands is 10%. The flexural strength of DS-G30-10 reaches 6.62 MPa and the compressive strength reaches 72.3 MPa, showing the best comprehensive mechanical properties.

Performance of Pervious Concrete with Ground Granulated Blast Furnace Slag (GGBS) as Partial Replacement for Cement

Performance of Pervious Concrete with Ground Granulated Blast Furnace Slag (GGBS) as Partial Replacement for Cement

Advancements in Lightweight Artificial Aggregates: Typologies, Compositions, Applications, and Prospects for the Future

Currently, the environment and its natural resources face many issues related to the depletion of natural resources, in addition to the increase in environmental pollution resulting from uncontrolled waste disposal. Therefore, it is crucial to identify practical and effective ways to utilize these wastes, such as transforming them into environmentally friendly concrete. Artificial lightweight aggregates (ALWAs) are gaining interest because of their shift in focus from natural aggregates. Researchers have developed numerous ALWAs to eliminate the need for natural aggregates. This article explores the diverse applications of ALWAs across different industries. ALWAs are currently in the research phase due to various limitations compared to the availability of the various natural aggregates that form more durable solutions. However, researchers have discovered that certain artificial aggregates prioritize weight over strength, allowing for the effective use of ALWAs in applications like pavements. We thoroughly studied the various ALWAs discussed in this article and found that fly ash and construction waste are the most diverse sources of primary material for ALWAs. However, the production of these aggregates also presents challenges in terms of processing and optimization. This article’s case study reveals that ALWAs, consisting of 80% fly ash, 5% blast-furnace slag, and only 15% cement, can yield a sustainable solution. In the single- and double-step palletization, the aggregate proved to be less environmentally harmful. Additionally, the production of ALWAs has a reduced carbon footprint due to the recycling of various waste materials, including aggregates derived from fly ash, marble sludge, and ground granulated blast-furnace slag. Despite their limited mechanical strength, the aggregates exhibit superior performance, making them suitable for use in high-rise buildings and landscapes. Researchers have found that composition plays a key role in determining the application-based properties of aggregates. This article also discusses environmental and sustainability considerations, as well as future trends in the LWA field. Simultaneously, recycling ALWAs can reduce waste and promote sustainable construction. However, this article discusses and researches the challenges associated with the production and processing of ALWAs.

Mechanical properties and chemical microscopic characteristics of all-solid-waste composite cementitious materials prepared from phosphogypsum and granulated blast furnace slag

Industrial wastes, such as phosphogypsum, are characterized by high production and accumulation volumes, and significant pollution. A high-performance, all-solid waste, phosphogypsum-based composite cementitious material (PCCM) was developed by using a hybrid ball milling method and thermal activation to stimulate various industrial wastes. Optimization of rationing was analyzed using extreme variance, standard variance, and multiple regression models. The macro-engineering parameters of PCCM were evaluated through flexural and compressive tests. The mineralogical composition, functional groups, micro-morphology, and molecular structure of PCCM were examined through micro-testing. When the mass ratio of Ball milled calcined phosphogypsum (BCPG) to granulated blast furnace slag (GGBS) is 1.2:1, with a 4 % addition of calcium oxide and a water-cement ratio of 0.4, the 28-day flexural and compressive strengths, as well as the softening coefficients, of PCCM can reach 7.27 MPa, 40.1 MPa, and 0.922, respectively, closely matching the performance of C42.5 cement. Under the synergistic effects of the hydration reaction and an alkaline environment, the CaSO4 in the PCCM system hydrated and crystallized to produce gypsum-phase crystals, enhancing early strength properties by 60–174 %. As hydration continued, SO42- reacted with silicon and aluminum oxides, prompting secondary hydration of GGBS, and increasing AFt and C-(A)-S-H in the system. This research offers a new approach for the co-disposal and resource utilization of various solid wastes while identifying a cementitious material that can replace traditional cement in practical engineering applications.

Physical, Mechanical and Durability Properties of Eco-Friendly Engineered Geopolymer Composites

Engineered geopolymer composite (EGC) is a high-performance material with enhanced mechanical and durability capabilities. Ground granulated blast furnace slag (GGBFS) and silica fume (SF) are common binder materials in producing EGC. However, due to the scarcity and high cost of these materials in some countries, sustainable alternatives are needed. This research focused on producing eco-friendly EGC made of cheaper and more common pozzolanic waste materials that are rich in aluminum and silicon. Rice husk ash (RHA), granite waste powder (GWP), and volcanic pumice powder (VPP) were used as partial substitutions (10–50%) of GGBFS in EGC. The effects of these wastes on workability, unit weight, compressive strength, tensile strength, flexural strength, water absorption, and porosity of EGC were examined. The residual compressive strength of the proposed EGC mixtures at high elevated temperatures (200, 400, and 600 °C) was also evaluated. Additionally, scanning electron microscope (SEM) was employed to analyze the EGC microstructure characteristics. The experimental results demonstrated that replacing GGBFS with RHA and GWP at high replacement ratios decreased EGC workability by up to 23.1% and 30.8%, respectively, while 50% VPP improved EGC workability by up to 38.5%. EGC mixtures made with 30% RHA, 20% GWP, or 10% VPP showed the optimal results in which they exhibited the highest compressive, tensile, and flexural strengths, as well as the highest residual compressive strength when exposed to high elevated temperatures. The water absorption and porosity increased by up to 106.1% and 75.1%, respectively, when using RHA; increased by up to 23.2% and 18.6%, respectively, when using GWP; and decreased by up to 24.7% and 22.6%, respectively, when using VPP in EGC.

Study of silicon dioxide nanoparticles on the rheological and mechanical behaviors of self-compacting geopolymer concrete

AbstractGeopolymer concrete (GPC) is a rising eco-conscious substitute for traditional cement-based concrete, bringing the construction industry closer to sustainability. Self-compacting geopolymer concrete (SCGC) enhances the concrete flowability and fills the congested reinforced areas without vibrators in concrete structures such as bridges, tunnels and canals. This study aims to analyze the impact of silicon dioxide nanoparticles (NS) on the rheological and mechanical properties of SCGC to optimize the dosage of NS in SCGC. For this purpose, NS (0–6%) blended in partially distributed binders of fly ash and ground granulated blast furnace slag (50:50) with 0.5 alkaline binder ratio, 2% superplasticizers (9 kg m−3) (MasterGlenium SKY 8233) and 12% extra water (54 kg m−3). Sodium silicate solution and sodium hydroxide ratio of 2.5 was used for this study. It is observed that SCGC with 3% NS replacement complied with the guidelines of EFNARC. According to the T50cm slump flow test, V-funnel test, and L-box test results meet the guidelines of up to 4% NS replacement, and 3% NS addition offers excellent mechanical properties in SCGC. This study concluded that the replacement of 3% of NS improved the fresh and hardened properties of SCGC, which can apply to construction.

Utilization of pretreated green liquor dregs as an activator for blast furnace slag: Effect on hydration, phase assemblage, and rheology

This study explores the utilization of calcium- and magnesium-rich pulp mill residues, i.e., green liquor dregs (GLDs), as an activator for ground granulated blast furnace slag (BFS). The aim of this study is to examine the potential of this unutilized residue when used as a part of alkali-activated materials (AAMs) and in this way enhance the exploitation of GLD. This study focuses on the fresh- and hardened-state properties of the produced paste and mortar samples, where 70% of BFS and 30% of GLD have been incorporated. Two different-sourced and thermally pretreated (105 °C, 300 °C, and 525 °C) GLDs have been used. The effect of thermal treatment on the utilization possibility of GLDs with respect to viscosity, setting times, reactivity, mineralogy, and microstructure is analyzed using the paste samples, while its effect on workability, and strength gain is measured using the mortar samples. Results show that both GLDs enhance the hydration of BFS and that the early-age hydration and strength increase when the GLDs have undergone pretreatment at the highest temperature (525 °C). However, at the later age (28 days), the samples activated with the GLDs treated at 300 °C achieve the highest strength. The addition of both GLDs treated at any temperature increases the viscosity of the composite samples and reduces their workability; however, it should be noted that optimization of water to binder ratio was not the objective of this study. The results of this study show that GLD, previously considered unreactive, can potentially become a reactive component of AAMs.

Study on the Properties of All-Solid Waste Fluidized Filling Materials Applied to Mine Void Area Filling Engineering

The extraction of mining resources, as well as processing processes such as ore beneficiation and smelting, generate large amounts of tailings that are difficult to directly utilize. Meanwhile, substantial filling materials are required for the voids formed after mining operations, and the environmental issues and safety hazards brought on by massive solid waste disposal cannot be ignored. By utilizing solid waste with alkaline and pozzolanic activity as the binder component and gold tailings as filler aggregate to prepare filler material to fill up the void areas, the purpose of waste treatment can be achieved. In this study, salt sludge, steel slag, ground granulated blast furnace slag, and gold tailings were used to prepare all-solid waste fluidized filling material for filling mine void areas, which not only solves the engineering safety problem of easy collapse of the mine airspace in the mining process but also ensures a backfill effect with high strength, which continuously guarantees the uninterrupted progress of the mining project. At the same time, the preparation of fluidized materials can consume a large amount of tailings and other solid waste, solving the problem of their stockpiling. The components of the solid wastes used are all general industrial solid wastes, so the preparation of the fluidized materials will not have an impact on the surrounding environment. The effects of binder ratios on the workability of the filling materials were investigated by means of the slump and slump flow tests. Combined with the unconfined compressive strength test, the change in backfill material strength with curing age and the water–binder ratio was studied. The experimental results showed that the slump and slump flow value of the filling material were positively correlated with the water–binder ratio. The water–binder ratio range satisfying a slump value of 180~260 mm and a slump flow value not less than 400 mm was 0.95~1.106. However, the strength decreased with the increase in the water–binder ratio, conforming to a hyperbolic relationship. The all-solid waste fluidized filling material had strengths not less than 0.22, 1.09, and 1.95 MPa at 3, 7, and 28 d, respectively, meeting the workability requirements. Finally, a method for determining the optimal range of water–binder ratio considering both workability performance and strength is proposed based on the relationship between slump value, slump flow value, unconfined compressive strength, and the water–binder ratio.

Durability Evaluation of GGBS-RHA-Based Geopolymer Concrete Along with Lightweight Expanded Clay Aggregate Using SEM Images and EDAX Analysis

The durability of geopolymer concrete containing Ground Granulated Blast Furnace Slag (GGBS) and Rice Husk Ash (RHA), along with Lightweight Expanded Clay Aggregate (LECA), was investigated. Six different LWGPC mixtures were made with NaOH molarities of 8, 10, and 12M. For each molarity, two combinations of source materials were selected: 100% GGBS (G) and 80% GGBS with 20% RHA (RG). In all the mixtures, coarse aggregate was substituted with 35% LECA. LWGPC mixtures were exposed to 3% HCl, 5% MgSO4, and 3.5% NaCl for studying the durability properties. The test results demonstrate that 100% GGBS with 12M NaOH (12G) outperformed all other mixtures. The residual compressive strength of 12G mix LWGPC specimens after six months of exposure was found to be 86.4% in an acid environment, 90.6% in a sulfate environment, and 91.4% in a salt environment. The elemental composition analyzed using EDAX reveals that silica, alumina, calcium, and sodium are the predominant elements that form a dense microstructure with N-A-S-H, C-A-S-H, and C-S-H. Further, the inner properties of the specimens exposed to chemicals were examined using MATLAB R2023b and ImageJ 1.54f based on SEM images. The SEM image showed that the porosity of LWGPC specimens ranged from 0.5194 to 0.6748 µm, signifying an enhanced durability performance. The experimental results and microstructural analysis show that the LWGPC incorporating RHA and GGBS with LECA offers a superior performance, making it a promising solution for sustainable and durable construction.

The effect of copper slag as a precursor on the mechanical properties, shrinkage and pore structure of alkali-activated slag-copper slag mortar

Copper slag, an industrial by-product produced in large quantities during copper smelting and refining, has the potential to be used as an alternative precursor for alkali-activated materials. This approach not only reduces the environmental impact of copper slag but also addresses the growing scarcity of conventional precursors, such as ground granulated blast furnace slag. In this research, copper slag was used as an alternative precursor for alkali-activated slag-copper slag mortars. Sodium hydroxide and water glass served as the activators. The workability, mechanical properties, autogenous shrinkage and drying shrinkage were investigated to evaluate the influence of copper slag content. Furthermore, the reaction products and pore structure of hardened mortar were analysed to gain deeper insights into its performance. The results show that the incorporation of copper slag effectively prolongs the setting time and increases the fluidity. Copper slag reduces the autogenous shrinkage, but it also results in an undesirable increase in drying shrinkage. While copper slag delays strength development and reduces the strength, incorporating copper slag at a 50 % ratio still results in strength comparable to that of mortars utilizing 100 % ground granulated blast furnace slag as the precursor. The incorporation of copper slag alters the composition of calcium aluminosilicate hydrate and promotes the formation of ferro-silicate. Although it reduces the proportion of macropores in the total pore volume, it simultaneously increases the amount of capillary pores. Copper slag alters pore solution, and although heavy metal leaching remains minimal, risks in complex environments require further study.

Fracture toughness of alkali-activated concrete subjected to aggressive environment

This study investigates the fracture toughness of alkali-activated granulated blast-furnace slag (GBFS)-based geopolymer concrete (GPC), non-activated slag cement concrete, and ordinary Portland cement (OPC) concrete in acidic, alkaline, and chloride solutions over six months. A total of 580 centrally straight-notched Brazilian disc (CSNBD) specimens were cast to assess pure mode-I (0°), pure mode-II (28.7°), and mixed-mode (15° and 45°) fractures under these conditions. Microstructural analyses (SEM) were performed to evaluate microstructural changes after six months of exposure. Results showed that GPC exhibited the lowest initial fracture toughness but the smallest reduction (7 %-11 % depending on the mode) across all environments, with slag cement concrete and OPC experiencing reductions of 11 %-14 % and 14 %-21 %, respectively, in acidic conditions. In alkaline environments, GPC showed a 3 %-6 % decrease in fracture toughness, while OPC and slag cement concrete showed reductions of 6 %-13 %. The gradient boosting regressor accurately predicted the failure load of CSNBD specimens, achieving an R² score of 0.948. Finally, SHAP sensitivity analysis identified concrete type, exposure time, and environment as critical input features, consistent with experimental results.

Production and recycling of blast furnace slag: A life cycle assessment approach in India

AbstractThis article investigated the cradle‐to‐gate environmental impact of granulated blast furnace slag (GBFS) produced in the steel industry and replacement of blast furnace (BF) slag (50%) in place of clinker in Portland slag cement using GaBi software (Indian extension database). In case of GBFS production, maximum burden on the environment is due to BF slag production and the amount of electricity consumed (161 MJ/ton) during the granulation process. The influence of electricity sources on GBFS production was studied via scenario analysis. For investigation, solar and thermal electricity mixes were considered in 50:50 and 75:25 ratios. For the 75:25 ratios, the abiotic depletion potential (fossil), acidification, eutrophication, global warming, and human toxicity potential show a decreasing trend of approximately 45%, 49%, 48%, 46%, and 41%, respectively. The scenario analysis of BF slag transportation (from 100 to 750 km) demonstrates a negative impact due to fuel. The results quantitatively confirm that the addition of GBFS can lower the overall impact for construction and steel industries.