Ground Granulated Blast Furnace Slag Replacement Research Articles

Laboratory Studies on Strength Properties of Concrete using Fly Ash and GGBS

Abstract: Cement, fine aggregate, coarse aggregate, and water are the basic raw materials used in the manufacture of concrete. The naturally available aggregates are very precious and need to be conserved. Waste materials such as fly ash and Ground Granulated Blast Furnace Slag (GGBS) which cause disposal problems, and environmental problems can be economically used as a partial replacement for both fine and coarse aggregate. The present research focuses on conducting laboratory studies on the properties of M30 grade concrete by replacing fine and coarse aggregate with fly ash and GGBS. The results show that the optimum percentage of partial replacement of fly ash and GGBS is 30% for both fine and coarse aggregate. The compressive strength of concrete increased by 15% and 24%, respectively, and the tensile strength of concrete nearly increased by 20% in both cases. In addition, the use of waste material helps to reduce the cost of construction while simultaneously solving the disposal and environmental pollution problems.

Mechanical, durability and microstructural characterization of cost-effective polyethylene fiber-reinforced geopolymer concrete

Portland cement is widely used in the construction industry. Its production contributes to carbon dioxide emissions, urging the need for sustainable alternatives. The present study aims to evaluate the strength, durability, microstructural properties, and cost-effectivity of geopolymer (GP) concrete containing polyethylene (PE) fibers, with fly ash (FA), ground-granulated blast furnace slag (GGBFS), and calcium magnesium carbonate (CaMg(CO3)2 known as dolomite) as binders. PE fiber used has an ultra-high molecular weight. Six different mixtures were produced with FA, GGBFS, dolomite, and/or PE fiber. The control mix used only FA as a binder without PE fiber. Fresh and mechanical properties, including slump value, compressive strength, and split tensile strength, were determined, and non-destructive tests, such as electrical resistivity and ultrasonic pulse velocity, were conducted. The durability of GP was evaluated through initial surface absorption and capillary suction absorption tests at different curing ages. Microstructural and mineralogical characteristics were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). The results revealed that the addition of PE fibers and CaMg(CO3)2 reduced the workability of GP by 30.22% in comparison with that of PE fiber along with GGBFS. Compared to the reference mix at 28 days, incorporating 20% GGBFS resulted in the highest improvement of 76.89% and 104.86% in compressive and split tensile strength, respectively. GP sample with 20% GGBFS replacement of FA presented the highest reduction of 44.4–41.63% for initial and secondary rate of absorption. SEM analysis showed that the addition of GGBFS and CaMg(CO3)2 to fiber-reinforced FA-based geopolymer mixes developed a denser and more homogenous matrix with improved mechanical behavior due to the co-existence of C−S−H and aluminosilicate gel. PE fibers improve the toughness properties by helping to absorb energy and bridging cracks. The development of a stronger matrix was characterized by C−S−H, calcium aluminate oxide (carbonate) hydroxide (C4AHx) and quartz. A one-way ANOVA analysis and cost analysis demonstrate the cost-effectiveness of partially replacing FA with CaMg(CO3)2 and GGBFS in PE fiber-reinforced GP concrete.

Effect of activator concentration on setting time, workability and compressive strength of sustainable concrete with alkali-activated slag binder

The global need to reduce carbon dioxide (CO2) emissions prompted studies on sustainable alternatives to conventional concrete made with ordinary Portland cement (OPC) binders. Alkali-activated ground granulated blast furnace slag (GGBS) is a promising sustainable to OPC in terms of the impact on the environment and reduction of CO2 emissions. Concretes and mortars made with alkali-activated binders demonstrate promising fresh and mechanical properties. This article presents the findings of an experimental study investigating the fresh and mechanical properties of mortar using alkali-activated GGBS binder. The activators used were sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solution with 6 M, 8 M, 10 M, and 12 M molarities. The study assessed their initial setting time, workability, and 28-day compressive strength. The study evaluated the effect of partial replacement of GGBS with 5 % silica fume. The compressive strength was determined after 28 days of curing in three different environments: 1) ambient air temperature, 2) water submersion, and 3) water immersion for 7 days followed by 21 air curing in ambient temperature. The results showed an increase in compressive strength with higher NaOH concentration but a corresponding decrease in initial setting time and flowability. Depending on the curing method, efflorescence, and blue-green pigmentation were seen during the physical assessment of the samples. The highest 28-day compressive strength was 67.5 MPa when the NaOH activator molarity was 10 mol/L which represents an optimum concentration for strength development. Replacing 5 % of the GGBS binder with silica fume resulted in a decrease in the 28-day compressive strength and workability without affecting the initial setting time.

Cementitious properties of sustainable alkali-activated materials with ground GGBS-based geopolymer waste powder as recycled precursor

Employing ground geopolymer waste powder as a recycled precursor for new alkali-activated materials and geopolymer not only mitigates the amount of geopolymer waste, but also provides a novel alkali-activated binder. This work investigated the repolymerization and cementitious properties of ground granulated blast-furnace slag (GGBS)-based geopolymer blended with geopolymer waste powders as the substitution of GGBS. The geopolymer paste powder (GPP) and geopolymer mortar powder (GMP), both ground from GGBS-based geopolymer waste, contain abundant C-(N)-A-S-H, showing good repolymerization effect and alkali-activated activity. The GPP had better repolymerization effect and alkali-activated activity than GMP. Although replacing GGBS with GPP/GMP negatively impacted the micro-characteristics, 100% GPP/GMP-based geopolymer paste still possessed a relatively dense microstructure. Besides, 100% GPP-based geopolymer paste has finer micro-structure than the 100% GMP-based geopolymer paste. Mixing GPP/GMP as GGBS replacement decreased the autogenous shrinkage, while raised the drying shrinkage of GGBS-based geopolymer mortar. Reusing GPP/GMP as substitutes for GGBS resulted in a reduction of both strength and impermeability of GGBS-based geopolymer mortar, and an obvious decrease in strength and impermeability appeared when GPP/GMP replacement rate was above 90%. Reducing the particle size of GPP/GMP could improve the properties of GPP/GMP blended geopolymer mortar, and GPP-based geopolymer mortar had better properties than GMP-based geopolymer mortar. In particular, the geopolymer mortar made with 100% GPP/GMP still possessed relatively high compressive strength (49.3–64.7 MPa). Utilizing GPP/GMP as recycled precursor for sustainable alkali-activated materials and geopolymer is feasible, and the maximum substitution ratio of GPP/GMP can be up to 100%.

Effects of curing temperature and supplementary cementitious materials on the interfacial transition zone (ITZ) of high-ferrite cement products

This study investigated the changes in three characteristics, including phase compositions, microstructure, and microhardness, in the interfacial transition zone (ITZ) of high-ferrite cement (HFC) products when subjected to different curing systems. In addition, we explored the underlying mechanisms through which supplementary cementitious materials (SCMs) influence the ITZ under steam curing conditions. The characterization was performed through the application of test techniques such as X-ray diffraction analysis, backscattered electron, scanning electron microscopy, energy dispersive X-ray spectrometry, and microhardness. The findings demonstrated that the increase in the curing temperatures promoted the HFC mortar to generate an excellent ITZ performance compared to Portland cement and ground granulated blast furnace slag (GGBFS) showed an improvement in steam-cured HFC-ITZ better than. Specifically, optimal enhancement of the ITZ in steam-cured HFC cement-based materials was achieved through the 40% replacement of GGBFS where the calcium hydroxide (CH) content and orientation growth were reduced while the hydration product formation was increased, resulting in declined porosity. Furthermore, the incorporation of 20% replacement of fly ash (FA) led to the decrease in the CH content and porosity of the ITZ. However, due to the lower reaction activity, unreacted FA persisted in the paste even after 28 days of curing. Additionally, the uneven distribution of hydration products resulted in diminished microhardness. On the other hand, a 40% replacement of FA marginally improved the properties of the ITZ. Finally, the test data and conclusions in the paper can provide some evidence for the application of GGBFS and FA in HFC and HFC-based concrete.

Effect of mineral admixtures on the performance of self-compacting geopolymer concrete

Self-Compacting Geopolymer Concrete (SCGC) emerges as a groundbreaking construction material in the domain of concrete technology. This method integrates supplementary cementitious materials (SCM), alkaline solutions like sodium hydroxide and sodium silicate, and a superplasticizer to form a binder for matrix development and strength enhancement, thereby eliminating the need for compaction.In the present study, fly ash-based Self- Compacting Geopolymer Concrete (SCGC) was substituted with varying proportions of Ground Granulated Blast Furnace Slag (GGBS). Concrete specimens were subjected to curing under both oven and ambient conditions to assess their performance.The investigation unveiled that incorporating GGBS into fly ash-based SCGC resulted in reduced workability alongside improved strength with increasing binder content. Notably, SCGC samples cured at 70°C for 24 hours with a 50% replacement of GGBS emerged as the optimal proportion, meeting the required workability standards. However, surpassing this threshold led to a further enhancement in mechanical properties albeit at the expense of reduced workability.

A novel self-hardening cementitious material by the self-activation of glass powder

The high carbon emissions associated with alkali activators used in ground granulated blastfurnace slag (GGBS) based alkali-activated materials bring a controversy about their sustainability. This study investigated the self-hardening behavior of three glass powders (GPs) in the activator-free self-activating cementitious materials. The mechanisms of the self-activation of the different GPs were revealed. The experimental results showed that the dissolution of the GPs can release Na+ to form an alkaline solution. Due to the self-activation nature of the GPs, the hydration of the paste was promoted with the replacement of GGBS by GPs. As a result, the self-activation of 100% fluorescent lamp GP can achieve a satisfactory compressive strength (30.8 MPa). The main hydration product was N-C-S-H gel, which was similar to that in normal alkali-activated materials. The TGA, FTIR, and NMR results indicated that the GGBS can be activated by the GPs without the addition of external alkalis activators. The dense microstructure contributed to the strength development of the self-hardening cementitious material.

Evaluation of Durability Performance for Chloride Ingress Considering Long-Term Aged GGBFS and FA Concrete and Analysis of the Relationship between Concrete Mixture Characteristic and Passed Charge Using Machine Learning Algorithm

In this study, accelerated chloride diffusion tests are performed on ordinary Portland cement (OPC), ground granulated blast furnace slag (GGBFS), and fly ash (FA) concretes aged 4–6 years. Passed charge is evaluated according to ASTM-C-1202 for 12 mixtures, considering water–binder (W/B) ratios (0.37, 0.42, and 0.47), GGBFS replacement rates (0%, 30%, 50%), and FA replacement rates (0% and 30%). The effects of aged days on passed charge reduction behavior are quantified through repetitive regression analysis. Among existing machine learning (ML) models, linear, lasso, and ridge models are used to analyze the correlation of aged days and mix properties with passed charge. Passed charge analysis considering long-term age shows a significant variability decrease of passed charge by W/B ratio with increasing age and added admixtures (GGBFS and FA). Furthermore, the higher the water–binder ratio in GGBFS and FA concretes, the greater the decrease in passed charge due to aged days. The ML model-based regression analysis shows high correlation when compressive strength and independent variables are considered together. Future work includes a correlational analysis between mixture properties and chloride ingress durability performance using deep learning models based on the time series properties of evaluation data.

An approach for environment protection by regression and cluster analysis of GGBS-based geopolymer composite at different proportion of brick dust

The study focused on the significance of ground granulated blast furnace slag (GGBS) as replacement of brick dust. Compression, tension, rapid chloride permeability test (RCPT) and water absorption test (WA) is analyzed. Study revealed that the produced geopolymer concrete showed better properties over normal concrete. Up to 10% GGBS replacement with calcined clay, exhibits enhanced compressive strength. Chloride ion permeability tests showed that GPC is superior to normal concrete of all ages in its resistance to chloride ion penetration. On increasing brick dust proportion, mass loss minimized due to sulfate attack. Compressive strength has low relationship with water absorption (0.6618).

Characterisation of alkali-activated stainless steel slag and blast-furnace slag cements

Rapid global industrial growth is causing an increase in the generation of large-scale by-products and waste materials, which can be recycled in the construction industry to decrease both the environmental impact of the sector and the impact of these waste materials, to ultimately contribute to the circular economy. In the current study, electric arc furnace stainless steel slag (EAFSS) as a potential precursor in the production of alkali activated materials (AAMs) is investigated, along and alternatively to the use of ground granulated blast-furnace slag (GGBFS). Five blended mixtures with different levels (0, 25, 50, 75 and 100 wt %) of EAFSS to replace GGBFS are activated with an alkaline silicate solution. Partially replacing GGBFS with EAFSS prolongs the dormant period in reaction and reduces the overall heat release of the paste mixtures. This results in a positive effect on fresh-state properties, increasing and prolonging workability and mixture setting times. A general decrease in strength is seen with EAFSS inclusion, although satisfactory compressive and flexural strength values of more than 85 and 9 MPa, respectively, were obtained at 28 days with up to 50% replacement of GGBFS by EAFSS. Most of the crystalline phases present within EAFSS do not participate notably in alkali-activation, other than merwinite which slowly dissolves and reacts to form a weak binder phase. The chromium present in the EAFSS is contained in a stable spinel phase; this element does not appear to be mobile in leaching tests.

The Influence of GGBFS as an Additive Replacement on the Kinetics of Cement Hydration and the Mechanical Properties of Cement Mortars

Granulated blast furnace slag (GBFS) is a byproduct of the iron production process. The objective of this study is to determine the effects of ground granulated blast furnace slag (GGBFS), used as a replacement admixture (0–40 wt.%) for ordinary Portland cement (OPC), on the setting time, the heat of hydration, and the mechanical properties of cement mortar. The influence of GGBFS as a replacement additive on the setting time shows that it has an accelerating effect on cement hydration. Calorimetric measurements were performed on the cement paste system to determine the effects of GGBFS on the hydration of OPC. Calorimetric measurements carried out show that the replacement of GGBFS in an amount up to 40 wt.% reduces the total heat of hydration by up to 26.36% compared to the reference specimen. The kinetic analysis performed on the calorimetric data confirms the role of GGBFS as an accelerator by shortening the time during which the process of nucleation and growth (NG), as the most active part of hydration, is reduced up to 2.5 h. The value of the Avrami–Erofee constant indicates polydispersity and heterogeneous crystallization. Mechanical tests of cement mortars were performed after 3, 7, 14, 28, 70, and 90 days of hydration and showed that replacement addition of GGBFS slightly reduced the mechanical properties in the early phase of hydration, while in the later phase of hydration it contributed to an increase in the mechanical properties.

Influence of GGBFS-based blended precursor on fresh properties of self-compacting geopolymer concrete under ambient temperature

Geopolymer concrete having self-compacting nature is known as self-compacting geopolymer concrete (SCGC) which does not need mechanical compaction to improve the concrete density. The geo-polymerization process primarily depends on aluminosilicate materials and alkaline activator solution (AAS). The type of precursor material greatly affects the hardened concrete properties i.e. both the short-term and long-term concrete characteristics. The present study aims to achieve an optimal blended precursor-based SCGC possing acceptable fresh property characteristics where ground granulated blast furnace slag (GGBFS), the precursor in the control GGBFS-based SCGC is partially replaced by silica fume (SF), and rice husk ash (RHA) with various proportions. Mix proportions with the replacement of GGBFS by SF (10%, 20%, 30%, 40%) and RHA (5%, 10%, 15%, 20%) are prepared along with one control GGBFS-based SCGC. The fresh property of the nine SCGC mixes are interpreted through the filling ability (slump flow, T50cm slump, V-funnel); passing ability (L-box, J-ring), and resistance to segregation (V-funnel at T5minutes) test. All the ambient temperature-cured SCGCs are made with the following mix parameters: 12 M sodium hydroxide molarity, AAS ratio of 2.5, superplasticizer dose of 7%, and extra water of 24%.

An Experimental Study on Partial Replacement of GGBS with Cement and Utilizing Demolished Coarse Aggregate in Concrete

bstract: The majority of municipal solid wastes are made up of debris from construction and demolition projects, including recycled construction aggregate (RCA). This paper presents the findings of an experimental and analytical examination of the creation of environmentally friendly concrete. It is a good idea to replace natural material with aggregate from old, demolished structures to reduce debris and preserve the environment. To reduce consumption, recycled aggregate can be utilized in place of natural aggregate. To address these issues, an attempt is undertaken in the current experimental work to substitute GGBS in varied proportions for cement. The purpose of this research is to demonstrate the findings of an investigation into the applicability of GGBS in the manufacturing of concrete by using construction and demolition debris as a recycled resource. Ground granulated blast furnace slag (GGBS) and recycled concrete aggregates are the recycled materials employed in this study. A concrete mix of grade M25 was created through the mix design process. GGBS was partially replaced with wastedestroyed aggregate in the amounts of 0, 10, 20, 30, and 40% to create the mixes. Cubes of 150x150x150mm3 were poured. The compressive strength of the concrete cube specimens was measured by smashing the cube after 7, 14, 28, 60, and 90 days of curing for various curing intervals. The compression test results on the cubes show that strength increases with the amount of slag added up to the maximum value. Compressive strength was seen to grow when GGBS content increased up to 30%, but after the replacement level was above 30%, strength began to deteriorate. The outcomes of GGBS with conventional concrete and concrete made entirely of demolished aggregate without GGBS are compared to the outcomes of GGBS with concrete containing demolished aggregate

Investigating the retarding effect of CAC in alkali-activated cements

This paper discusses the design of hybrid alkali-activated binders at ambient temperature, specifically the development of mixes based on ground granulated blast-furnace slag (GGBFS) with calcium aluminate cement (CAC) as an additive, aiming to obtain high early strength binders with optimised Al incorporation, increased crosslinking and degree of polymerisation. The effects of 10 wt% CAC replacement of GGBFS, activated with sodium silicate with varying modulus (SiO2/Na2O molar ratio) or with sodium hydroxide, on fresh and hardened properties are investigated. The inclusion of CAC in GGBFS mixtures activated using sodium silicate results in an unexpected retardation of the polycondensation reactions required to form the main calcium aluminosilicate hydrate gel phase. This is due to incomplete dissolution of the GGBFS precursor, inhibited by the rapid formation of additional reaction products (especially cubic aluminate hydrates, C3AH6) resulting in lowered reaction kinetics, and thus delayed setting and hardening times. For sodium silicate activators, this retarding effect appears to be only slightly dependent on the activator solution modulus. When activating with 4 M NaOH, the retarding effect is reduced, along with the incorporation of CAC in the C-A-S-H gel, increasing the amount of reactive aluminium present in the binder to form a more compact gel product. Increasing the molarity of NaOH solutions results in a similar delay in reaction kinetics. The results suggest the existence of only a limited pH range in which the addition of CAC can promote the formation of a binding gel with enhanced mechanical properties, whilst other factors including the effect of sodium silicate inclusion in CAC systems are still unclear. The typical hydration products of CAC were not detected in this study.

Metakaolin cement concrete evaluation using industrial by-products as fine aggregate

Cement, sand, coarse aggregate, and water are the most common ingredients in conventional concrete. During the hydration and manufacturing of cement, a large amount of heat is produced, and the greenhouse gas CO2 is emitted, causing global warming and climate change. Industrial wastes including GGBS (Ground Granulated Blast-furnace Slag), metakaolin, and copper slag may be used to make concrete in major parts without needing cement and sand. In this investigation, seven M30 grade concrete mixes with the designations M1, M2, M3, M4, M5, M6, and M7 are created (along with a control mix). The superplasticizer content in cement is 0.75 percent by weight. The maximum and minimum cement replacement rates for GGBS and Metakaolin are 5% and 10%, respectively. 20%, 40%, and 60% of copper slag are replacement values. The feasibility of a brand-new concrete building has been uncovered. The cured concrete's mechanical characteristics, impact strength, and bond strength are also all tested. The slump data will be used to investigate the workability attribute. The compressive strength is assessed at 14 and 28 days. Throughout the course of 28 days, the split tensile strength, flexural strength, impact strength, and bond strength are assessed. The M5 mixture, which contains 40% copper slag, 10% metakaolin, and 10% GGBS, has the highest compressive and impact strength. Concrete mix M3 with 10% GGBS, 10% metakaolin, and 20% copper slag has higher split tensile strength, flexural strength, and bond strength. The best hardened concrete strength is produced by 10% replacement of GGBS and metakaolin due to their pozzolanic activity and filler.

Development of a novel rapid repairing agent for concrete based on GFRP waste powder/GGBS geopolymer mortars

The use of waste glass fiber-reinforced polymer (GFRP) powder as a binding agent in the synthesis of geopolymers offers an eco-friendly solution for managing GFRP waste. The aluminosilicate present in GFRP powder can be activated by an alkaline solution to produce a sustainable geopolymer. In this study, a novel rapid repairing material was developed from partially-replaced ground granulated blast furnace slag (GGBS) by GFRP waste powder as precursors in geopolymer mortar (GM). The effect of GFRP powder replacement and mix proportions on the fresh and hardened properties of GMs were evaluated. It was found that an increase in GFRP powder replacement led to an increase in the setting time and a decrease in workability. The highest 28-day compressive strength was obtained at a 20% replacement of GGBS with GFRP powder. At this optimal mixture, the GMs achieved a compressive strength of 15.2 MPa after 6 h and 35.7 MPa after 1 day. Results from the slant shear test revealed that the failure pattern of the GM-repaired concrete samples changed from interface failure to monolithic failure and explosive spalling in the concrete substrate (CS), when the test duration increased from 3-days to 7-days and 28-days, respectively. This was attributed to the formation of a compact interfacial zone with prolonged testing duration, leading to increased bond strength. The developed GMs demonstrate a short setting time, excellent flowability, high early mechanical strength and superior bond properties, and thus can be applied as rapid concrete repair materials or as protective coatings for concrete in corrosive environments.

Investigation on the properties of GGBS based geopolymer mortar with the inclusion of calcined clay

ABSTRACT The performances of a geopolymeric binder produced without utilising conventional cement and employing as sources Calcined clay and Ground Granulated Blast Furnace Slag (GGBS) have been examined in this research. The Alkaline liquid-to-binder ratio is considered to be 0.4 and the ratio of Na2SiO3 to NaOH to 2.5. Standard mortar characteristics including setting time, consistency, water absorption and compressive strength were assessed in accordance with the ASTM and Indian standards. The results of the tests demonstrate that the consistency and initial setting time were improved as the increase in the amount of calcined into the paste of geopolymer. The maximum compressive strength (37.1 MPa at 56 days of curing) was obtained at 10% replacement of calcined with GGBS then strength was declined after increasing the proportion of calcined clay and the water absorption (6.5% at 56 days of testing) values were reduced at 10% replacement of GGBS with calcined clay then it was increased as increased the proportion of calcined clay. The cluster and regression analysis were also done in this study.

Effect of copper and stainless steel slags on fresh, mechanical and pore structure properties of alkali activated ground granulated blast furnace slag

Reusing and recycling waste materials in the construction industry can provide a significant contribution in terms of environmental and economical aspects. This article reports a material case study on the combined use of three industrial by-products (metallurgical slags), namely copper slag (CS), stainless steel slag (SS) and ground granulated blast furnace slag (GGBFS) as solid precursors to produce binary blend alkali activated materials (AAMs). A total of seven binary AAMs mixtures with different ratios (0%, 25%, 50%, and 75%) of CS and SS as partial replacement of GGBFS were activated by a combination of sodium hydroxide and sodium silicate as an alkali solution. The behaviour of the mixtures is reported in terms of flow spread and flow curve, compressive and flexural tensile strengths, mercury intrusion porosimetry (MIP) and water absorption by submerging. The flow spread and dynamic yield stress of the mixtures increased and decreased by partially replacing GGBFS with CS or SS, respectively, leading to better workability properties of the fresh mixture. The use of CS or SS up to 50% reduced the compressive and flexural tensile strengths of the specimens between 30‐42% and 14‐46%, respectively. Despite this drop in strength, the 28 days compressive strength of the studied mixtures was always higher than 50 MPa. The capillary porosity of the specimens increased with higher contents of CS or SS. Water absorption results of the specimens appeared highly influenced by the applied drying temperature in the test method. Overall, partial replacement of GGBFS by CS or SS, targeting binary precursor systems, is promising for replacement levels up to 50%.

Investigation of Post Fire Mechanical Performance of Recycled Aggregate Concrete Containing Ground Granulated Blast Furnace Slag

Structures made from recycled aggregate concrete are exposed to high temperatures during fire scenarios which degrade their mechanical properties. Hence, this study investigated the residual mechanical properties of recycled aggregate concrete (RAC) containing ground granulated blast furnace slag (GGBS) after exposure to elevated temperatures. 21 experimental runs for design mix of RAC considering recycled coarse aggregate (RCA) replacement of natural coarse aggregate at 50, 75, and 100%, GGBS replacement of cement at 0, 20, 40, and 60% and water to binder ratio at 0.4 and 0.5 levels were used. The residual mechanical properties of RAC including compressive strength, splitting tensile strength, and elastic modulus were determined through laboratory experimental tests at room temperature (about 25°C) and after exposure to elevated temperatures of 200, 400, 600, and 800°C. Experimental results showed that residual mechanical properties of RAC decreased with increasing temperatures but their resistance to degradation was significantly enhanced with the addition of GGBS at 40% GGBS content. The novel model developed for the prediction of residual compressive strength of RAC has high prediction accuracy based on the performance metrics used to evaluate the model performance. The model has p-values less than 0.0001, a high R² value of 0.9781, a low root mean square error (RMSE) of 1.456 and mean absolute percentage error (MAPE) of 0.2287. Overall, the study contributed immensely to the knowledge of RAC as a sustainable alternative to normal concrete in areas prone to exposure to high temperatures which will significantly aid the effective fire safety design of structural members produced with recycled aggregate concrete.

Innovative use of micronized biomass silica-GGBS as agro-industrial by-products for the production of a sustainable high-strength geopolymer concrete

Micronized biomass silica (MBS) and ground granulated blast furnace slag (GGBS) are agro-industrial byproducts generated by incinerating of rice husk (grinding in jar mill) and blast furnaces that used produce iron, respectively. MBS accounts for 20% of the world's total paddy output of 590 million tons. These by-products (MBS and GGBS) have a high concentration of amorphous silica, which is utilized as a mineral additive in concrete. This amorphous silica interacts with hydration products, resulting in the formation of additional CSH gel. This improves concrete's strength and durability properties. Therefore, it is proven that inclusion of agro-industrial by-products in concrete helps to promote sustainable and greener development, which in turn reduces carbon footprints and waste that must be disposed of in landfills. There have been few investigations on concrete using MBS and demonstrated the great potential of employing MBS as a cement substitute or additive in normal concrete. Also, the utilization of MBS as partial replace to GGBS in geopolymer concrete (GPC) with different molarity is a novel aspect of this study. However, this study has the aim and limit to develop a high-strength eco-friendly GPC with agro-industrial byproducts (MBS and GGBS) for use in sustainable construction. The impact of incorporating MBS as a partial replacement of GGBS on compressive and split tensile strengths, sorptivity, and chloride permeability was tested up to the age of 28 days. MBS was used to replace GGBS in varying percentages in the preparation of concretes. MBS were used in concrete at 0%, 10%, 20%, and 30% replacement by weight. It was discovered that a GPC combination containing MBS 20% and the balance GGBS as the binder had the best performance in terms of its strength and durability. The compressive strengths of all GPC mixtures exceeded the intended design strength. The main findings of this study demonstrated clearly that MBS may be employed as a binder in the production of GPC.