Ground Granular Blast Furnace Slag Research Articles

Feasibility of using three solid wastes/byproducts to produce pumpable materials for land reclamation

Land reclamation is important for land-scarce countries and it requires a huge volume of filling materials. This study intended to reuse three solid wastes/byproducts, namely excavated marine clay (MC), incineration bottom ash (IBA), and ground granular blast-furnace slag (GGBS) to produce pumpable filling materials for land reclamation. Ordinary Portland cement (OPC) was utilized as a reference binder for comparison with GGBS. To this end, the workability (flowability and bleeding), appearance, unconfined compressive strength (UCS), mineralogy and microstructure, and heavy metal leaching of the proposed materials were investigated. Considering the seawater exposure at land reclamation sites, the stability of materials in water environments was examined. The results highlighted that for air-cured specimens, to achieve a target UCS of 100-200 kPa, the binder usage of IBA-MC-GGBS could be only half that of IBA-MC-OPC. In water environments, IBA-MC and IBA-MC-OPC generated cracks or were dismantled, especially when soaked in seawater, posing a significant concern for land reclamation. However, IBA-MC-GGBS showed much higher resistance against seawater than IBA-MC and IBA-MC-OPC. The formation and growth of ettringite was the primary cause of the instability of IBA-MC and IBA-MC-OPC. The hydration of GGBS in IBA-MC-GGBS consumed alkaline minerals, which in turn suppressed the formation of ettringite.

Evaluating Techno-Eco-Efficiency of Waste Clay Brick Powder (WCBP) in Geopolymer Binders

The global focus on geopolymer binder production has increased due to the adoption of waste materials and industrial byproducts. Given the gradual decline in the availability of fly ash and ground granular blast furnace slag (GGBFS) resulting from the decarbonization process in electricity and steel production, waste clay brick powder (WCBP) could be a viable substitute for these pozzolanic by-products. This study presents the economic and environmental benefits of the use of WCBP as a replacement for conventional pozzolanic by-products in geopolymer binder production by assessing its techno-eco-efficiency, environmental impact, and cost-effectiveness performances. The favorable mechanical characteristics exhibited by the fly ash–GGBFS–WCBP-based geopolymer binder emphasize the importance of assessing its sustainability alongside its technical viability. The study employed life cycle analysis (LCA), following ISO framework, and using the Simapro software 9.2, to evaluate the environmental implications of the use of WCBP-based geopolymer mixtures. Human toxicity emerged as the primary impact. Moreover, the analysis of life cycle costs highlighted key financial factors, with around 65–70% attributed to alkaline activators of the total cost. The production of alkaline activators was identified as a critical point for both environmental impact and economic considerations due to energy consumption. While WCBP-rich samples exhibit a 1.7–0.7% higher environmental impact compared to the control mix (CM), their high mechanical strength and cost-effectiveness make them technologically and economically efficient geopolymer mixes. In conclusion, the portfolio analysis for techno-eco-efficiency affirms that mixes containing 40%, 30%, and 20% WCBP are more efficient than those using 10% and 0% WCBP, respectively.

Enhancement of ductility characteristics of fiber-reinforced ternary geopolymer mortar

There is a need for ambient-cured geopolymer as a potential replacement for conventional ordinary Portland cement (OPC) based concrete. But geopolymers, that belong to the ceramic family, behave in a brittle manner and hence this research focusses on the enhancement of ductility using fibers. Thus, this experimental work was conducted to investigate the performance of polypropylene (PP) and micro steel fiber (MS) of fiber-reinforced geopolymer mortar (FRGM) on the hardened properties. The volume fractions of fiber used were 0%, 0.5%, 1%, and 1.5%. The ternary blended geopolymer mortar consisted of fly ash (FA), ground granular blast furnace slag (GGBS), and palm oil fuel ash (POFA). The hardened properties investigated are compressive strength, splitting tensile strength, modulus of elasticity (MoE), and ultrasonic pulse velocity (UPV). Furthermore, the load-deflection response was investigated in terms of deflection, load, flexural, and toughening mechanisms. The morphology of matrix mortar with the bonding of the fibers was examined through field emission scanning electron microscope (FESEM). The results revealed that the splitting tensile strength was enhanced with the inclusion of 0.5% of PP fibers and up to 1.5% of MS fibers by 27% and 177%, respectively. The enhancements in the ultimate flexural strength with 1.5% fiber were found 173% and 33% higher for MS and PP fibers, respectively compared to the control mixes. The inclusion of both MS and PP fibers showed a significant enhancement in the post-cracking flexural and toughness energy measured at L/150 mm. Furthermore, the addition of fiber volume of 0.5–1.5% enhanced the toughness by 33% (T600), 62% (T150), and 28% (T600), 46% (T150) for MS and PP mixes, respectively.

Mineral Additives in Concrete Durability: A Comprehensive Review

The body of literature on concrete using mineral admixtures covers a number of review studies on the durability characteristics of various materials used in concrete, such as fly ash (FA), rice husk ash (RHA), ground granular blast furnace slag (GGBS), fly ash (SF), and met kaolin (MK) are reviewed in this work. The features that are related to durability have been evaluated, and they include permeability, resistance to chloride ion penetrations, abrasion, fire resistance efflorescence. Incorporating mineral admixtures in concrete affects various properties. Concrete's permeability decreases and its ability to resist chloride ion penetration rises when admixtures containing a greater alumina content are used. Use of mineral admixtures enhances compressive strength and enhancing abrasion resistance. Moreover, highly reactive mineral admixtures mitigate efflorescence. Notably, while heating PFA concrete improves fire resistance, it reduces overall durability. SF concrete, on the other hand, behaves similarly to standard concrete but can be more brittle. MK concrete exhibits increased strength at 200°C, but its durability and strength decline at higher temperatures compared to other concrete types.RHA pozzolans can replace OPC up to 15% by weight after curing for up to 200 days without lowering the concrete's compressive strength.

Enhancing the properties of geopolymer concrete using nano-silica and microstructure assessment: a sustainable approach

Nowadays low calcium fly ash-based geopolymer concrete can be replaced with cement-based concrete to avoid the adverse effect of manufacturing cement on the environment. Utilization of geopolymer concrete instead of traditional concrete using low calcium fly ash and nano silica reduces a significant amount of CO­2 emission towards the atmosphere. However, the performance of geopolymer concrete is less than that of Portland cement concrete. To improve the performance of geopolymer concrete nano silica was used in the present study. In this work, geopolymer concrete was made utilizing fly ash, ground granular blast furnace slag (GGBS), and sugarcane bagasse ash. In the first instance, binary combinations i.e. fly ash and GGBS were employed as cementitious materials for the production of geopolymer concrete. In the second instance, a ternary mixture of pozzolanic material was prepared by taking 25% GGBS, 65% Fly ash, and 10% bagasse ash. In the third instance, varying percentages of nanoparticles were used for the above ternary mixture. The mechanical and durability properties of the geopolymer composite that was made earlier were tested. The compressive strength and split tensile strength of geopolymer composites were assessed for mechanical properties and a rapid chloride permeability test, water absorption test, and acid attack test were done to know about the porosity of concrete. Results showed that, with a dose of 4% nanoparticles, the durability and strength properties of the concrete had improved the most. The GCBA-N4 mixture had the highest split tensile and compressive strength was measured to be 2.91 MPa and 41.33 MPa and the rapid chloride permeability test, water absorption rate, and percentage of mass loss due to sulfate attack were found as a minimum for GCBA-N4 specimen.

Mechanical properties, flexural behaviour, and ductility characteristics of fibre-reinforced geopolymer mortar

This study aims to explore the potential of ambient-cured geopolymer as a substitute for ordinary Portland cement (OPC)-based mortar. However, due to their brittle nature, geopolymer materials require reinforcement to enhance ductility. To address this, an experimental program was conducted to investigate the effects of adding polypropylene (PP) and micro steel (MS) fibers to fiber-reinforced geopolymer mortar (FRGM) at volume fractions of 0%, 0.5%, 1%, and 1.5%. The ternary blended geopolymer mortar consisting of fly ash (FA), and ground granular blast furnace slag (GGBS), along with a novel pozzolan called eco-processed pozzolan (EPP) was investigated. The present study assessed the hardened properties of the FRGM, including compressive strength, splitting tensile strength, modulus of elasticity (MoE), ultrasonic pulse velocity (UPV), and the compressive strength of the material when exposed to elevated temperatures. The aim of this study was also to investigate the load–deflection response in terms of deflection, load, flexural strength, and toughening mechanisms; and also, the bonding between the fibers and the mortar matrix was examined using field emission scanning electron microscopy (FESEM). The results indicated that including 0.5% PP fibers and up to 1.5% MS fibers marginally improved compressive strength and MoE. The corresponding increments in splitting tensile strengths were 5% and 134%, respectively. The addition of fibers improved the fracture parameters of the FRGM. The inclusion of both MS and PP fibers significantly enhanced post-cracking flexural and toughness energy. At deflection L/150, MS fiber mixes exhibited 4–5 times higher toughness energy than PP fiber mixes, and also its evidently observed in the FESEM micrographs. The incorporation of 1.5% fiber volume to non-fibrous mix resulted in an improvement of 43.2 N.m. and 10.1 N.m. in toughness (T150) for MS and PP mixes, respectively. At an elevated temperature of 600 °C, the FRGM specimens gained a massive reduction in compressive strength, with the maximum result being at 87% for 1.5PP and 71% for 0.5MS. Overall, the MS fiber-reinforced geopolymer mixes exhibited superior performance as compared to PP fibers.

Utilization of agricultural, industrial waste and nanosilica as replacement for cementitious material and natural aggregates – Mechanical, microstructural and durability characteristics assessment

This study examines the effect of rice husk ash (RHA) and nanosilica, and ground granular blast furnace slag (GGBS) on concrete mechanical and durability properties. The cement had been partially replaced with nanosilica and RHA having substitution percentages up to 6% and 10% respectively whereas the sand had been partially replaced by GGBS at 20% for all mixes. A water-to-cementitious materials ratio of 0.38 and a sand-to-cementitious materials ratio of 2.04 were used to cast eight different concrete mixes. The nanosilica used in the present research possessed some favorable effects such as rich fineness, higher surface area and greater reactivity which signified one of the best cement replacement materials. Both the durability and strength of concrete specimens possessing nanosilica, RHA and GGBS was evaluated using in-elastic neutron scattering, SEM image, piezoresistive test, split tensile strength, flexural strength and compressive strength test. Concrete specimens were also subjected to chloride penetration and water absorption to examine the impact of replacement materials on the concrete's durability attributes. Concrete performance was increased by the ternary blending of concrete because of the active participation of nanosilica in durability and strength at early ages, both RHA and GGBS played an important role in improving packing density. It was found that as the percentage of cement replaced with nanosilica increases, the durability of concrete also significantly increases. But the optimum strength parameter was found when 4% of cement was replaced by the nanosilica effectively. The proposed ternary mix may be eco-friendly by saving cement and enhancing strength and durability effectively.

Effect of nano titanium di oxide on mechanical properties of fly ash and ground granulated blast furnace slag based geopolymer concrete

In current scenario, new innovative recyclable materials are scientifically tried to be a part of concrete for improving the properties and reducing the cost. The aim of the present study, is to evaluate the mechanical properties of Fly ash Ground Granular Blast Furnace Slag based Geopolymer Concrete (FGGPC), with partial replacement of fly ash by various percentage of Titanium di oxide (TiO2). In this study, mechanical properties like strength (compressive and split tensile strength) and elasticity properties (modulus of elasticity and modulus of rupture) are assessed, which is basic requirement study for any type of concrete. It is found that, up-to 3% partial replacement of fly ash by TiO2 result in enhanced mechanical properties of FGGPC. Models based on mechanical properties of conventional concrete are available in literatures and standards. Dependency of these models are checked using statistical method and interval concepts. Reliability of the relationships between conventional and FGGPC is validated by Integral Absolute Error (IAE), Mean Absolute Error (MAE), Root Mean Square Error (RMSE), prediction and confidence intervals concepts.

Air Content in Fresh Air-Entraining Cement Mortars

The durability of a cement composite is the most important criterion for assessing this material. However, due to the durability of the cement composite, its frost resistance is an important property. In order to ensure concrete frost resistance, the European standard PN-EN 206-1: 2013 requires its aeration at the level of 4 - 7%. The Committee 201 of the American Concrete Institute (ACI) also requires the use of an air-entraining admixture in concretes exposed to frost damage. The amount of air-entraining admixture is significantly influenced by the composition of the cement used. In order to minimize the problems with obtaining frostresistant concrete, an attempt was made to create air-entraining cements. This article presents the effect of the amount and type of dosing of air-entraining admixtures (natural and synthetic) on the air content in fresh air-entraining cement mortars. The test cements used also differed in the production method: joint mixing of components and joint grinding of components. Based on the research, a lot of valuable information was obtained related to the influence of the preparation of air-entraining cements on the air content in the mortar, e.g. mortars with mixed cement with natural air-entraining admixture have a higher air content. The air content is higher in the cement co-ground with natural air-entraining admixture. A synthetic air entraining admixture added separately to mixed cements with silica fly ash and ground granulated blast furnace slag increases air entrainment in mortars. The synthetic air-entraining admixture added separately to co-milled cements causes an increase in air entrainment in the mortars, except for those containing cement with ground granular blast furnace slag.

Self-Immobilizing Metals Binder for Construction Made of Activated Metallurgical Slag, Slag from Lignite Coal Combustion and Ash from Biomass Combustion.

Research on the effective use of secondary products is gaining more and more importance in Poland due to the intensively implementing idea of the circular economy. The solution used in this work are one of many tests useful in construction. The subject of this work was therefore the formation and testing of a new ecological construction binder, in particular for mortars or prefabricated elements working in the environment with high humidity. The binder was made of alkaline activated ground granular blast furnace slag (AAS), fly ash from biomass combustion (BFA) and furnace slag from brown coal combustion (LFS). The mixture was modified by introducing the zeolite to check the degree of metals immobilization contained in the ingredients of the mixture. A series of three mixtures were prepared: without and with zeolite soaked in distilled water or calcium nitrate. The strength of binders in time in dry and wet curing were tested and compared with the microstructure. The maximum compressive strength values at the eighth week were about 30 MPa. The strength values after 4 weeks of dry and wet curing were also compared. It was shown that 28-day wet curing increased the bending strength of the beams more than twice, but slightly decreased the compressive strength. The microstructure of the mixture with the highest values of compressive strength was the densest and the one with the lowest values of compressive strength, the most loosened with the most differentiated topographically fracture. The impregnation of zeolite with calcium nitrate decreased the compressive strength of the binder significantly. The bending strength of samples curing in dry conditions decreased during hardening. The results of the metals leaching test showed that the mixtures were safe for the environment, and due to the impregnation of zeolite with calcium nitrate, the binding effect of copper and zinc in the first weeks was greater than in the other mixtures.

LIME CALCINED CLAY CEMENT (LC3): A Review

Discovery of alternative to the pozzolanic materials generated from industrial wastes was needed because of its unavailability when the industries was shutdown permanently. Consumption of pozzolanic materials in concrete will be a safer solution for this problem. Numerous studies were presented for utilization of fly ash, Ground Granular Blast Furnace Slag (GGBS), Metakaolin and silica fume as a pozzolanic material in concrete. LC3 is a type of cement by mixing of limestone, calcined clay and gypsum, a few literatures were available on LC3. This paper presents the overview of research work presented on physical, chemical, performance in cement mortars like consistency, setting times & compressive strength, properties of fresh & hardened concrete like workability, compressive strength, split tensile strength, flexure strength made LC3.

Micro-level studies of fly ash and GGBS—based geopolymer concrete using SEM and XRD

In order to recognize the features contributing to strength (geo polymerization) for higher grade of geopolymer concrete, characterization of concrete specimens is needed. Fly Ash (FA) and Ground Granular Blast Furnace Slag (GGBFS) based geopolymer concrete is tested for 28 days’ compressive strength. And the mixes were characterized by adopting various physical-chemical methods such as X-Ray Diffraction analysis (XRD), Scanning Electron Microscope (SEM) This information helps to recognize the contribution of ingredients of mix to strength and resultant properties from the mix in a better way.

Micro-level studies of fly ash and GGBS –based geopolymer concrete using Fourier transform Infra-Red

In order to understand the factors contributing to strength (geopolymerization) for higher grade of geopolymer concrete, characterization of concrete specimens is needed. Fly Ash (FA) and Ground Granular Blast Furnace Slag (GGBS) based geopolymer concrete is tested for 28 days’ compressive strength. And the mixes were characterized by adopting various physical-chemical method Fourier Transform Infra-Red (FTIR) spectroscopy. This knowledge helps to understand the contribution of ingredients of mix to strength and derived properties from the mix in a better way.These short-term micro analyses of FTIR were then compared to that of M45 grade of conventional concrete (CC). The molar ratio of hydroxide solution considered in the investigation is 10 M.

STUDY OF BENTONITE USAGE IN ENVIRONMENTALLY FRIENDLY CONCRETE

Production of cement generates a huge amount of carbon dioxide emissions into the environment, utilization of pozzolanic materials in concrete is a better solution for this environmental problem. Several studies are conducted for using of pozzolanic materials such as fly ash, ground granular blast furnace slag, and silica fume as a pozzolanic material in concrete. A few studies were available on using bentonite in concrete. Bentonite is mainly clay contains rich amount of silicain which obeys the pozzolanic properties. The objective of present study is to find out the effectiveness of using bentonite and waste rubber crumb in the design mix of concrete. An experimental investigation is performed on concrete mixtures to study the effect of using bentonite as a partial replacement of cement and conducting an environmentally friendly concrete using crumb rubber in the concrete mixtures as a partial replacement of fine aggregates. Cement is partially replaced by volume (2%, 5%, 10%, 15%, 20%) with Bentonite and fine aggregate is partially replaced (5%, 20%, 25%, 30%, 40%) with crumb rubber. Slump tests were conducted to evaluate the workability of fresh concrete. Compressive strength of cubes at 7days and 28 days, splitting strength and abrasion strength at 28 days are studied and compared with conventional concrete. A part of research work addresses the effect of using bentonite and waste rubber crumb on durability of concrete. For this purpose, specimens were submerged in solution containing 50 g/l of NaOH and H2SO4. Based on the test results, the ideal percentage of mix which shows maximum compressive strength is identified. The results showed that the compressive strength of the concrete was generally increases when bentonite replaced a part of the cement and decreases with the replacement of fine aggregates by the waste crumb rubber. Although the using of bentonite and crumb rubber decreases the compressive strength. The optimal mixture from the laboratory experimental investigation is 5% reduction of cement content and 20% of fine aggregates replacement that exhibited a compressive strength of 30 MPa at 28 days. The test results substantiate the feasibility to develop environmentally friendly concrete using bentonite and crumb rubber in the concrete mixtures. فى هذا البحث ،تم دراسة استخدام البنتونیت کبدیل جزئی للأسمنت ومخلفات المطاط کبدیل جزئى للرکام الناعم فى الخرسانة الصدیقة للبیئة، تم مقارنة نتائج إختبارات قابلیة التشغیل ومقاومة الضغط و مقاومة الشد الغیر مباشر (الانفلاق) ومقاومة البرى والإستدامة بالخرسانة التقلیدیة.أوصت الدراسة بإمکانیة إستخدام البنتونیت حتى 5% کبدیل للأسمنت وإستخدام مخلفات المطاط حتى 20% کبدیل للرکام الناعم فى الخلطات الخرسانیة.

Development of geopolymer cement concrete for highway infrastructure applications

Purpose The purpose of this work is to study the in-situ performance of ternary geopolymer concrete in road repair work. Geopolymer cement concrete is an attractive alternative to Portland cement concrete owing to environmental, economic and performance benefits. Industrial wastes, such as fly ash (FA) and ground granular blast furnace slag (GGBS), have been extensively used to manufacture unitary and binary geopolymer concrete with heat activation (at different temperature); however, it has indicated a limitation for its application in precast industry only. Design/methodology/approach In the present study, efforts have been made to produce a ternary geopolymer concrete mix, using GGBS, FA and Silica fumes (SF) in varied proportion mixed with 8 M sodium hydroxide (NaOH) as alkali activator and cured at ambient temperature. Total ten geopolymer concrete mixes have been prepared and tested for strength and durability properties and compared with control mix of ordinary Portland cement (OPC). Based on the mechanical properties of various mixes, an optimum geopolymer concrete mix has been identified. The control mix and optimum geopolymer have been studied for microstructural properties through scanning electron microscopy. Findings The in situ performance of the optimum mix has been assessed when used as a road repair material on a stretch of road. The ternary geopolymer concrete mixes (a) 65% GGBS + 25% FA + 10% SF, (b) 70% GGBS + 20% FA + 10% SF, and (c) 75% GGBS + 15% FA + 10% SF have resulted in good strength at ambient temperature and the mix 75% GGBS + 15% FA + 10% SF have shown good in situ performance when tested for road repair work. Originality/value Geopolymer concrete is gaining interest in many fields as an alternative to conventional concrete, as it not only reduces carbon footprint due to huge cement production but also provides a sustainable disposal method for many industrial wastes. This paper focuses on finding some alternative of OPC concrete to reduce dependency on the OPC.

Migration of Chromium Through Black Cotton Soil Amended with Ground Granular Blast Furnace Slag

The aim of this work is to assess the suitability the locally available black cotton soil amended with industrial waste material such as blast furnace slag in the context of using them as liner materials. The black cotton soil (BCS) and Ground Granulated Blast furnace Slag (GGBS) are mixed in three ratios, 90:10, 80:20 and 70:30 and hydraulic conductivity of these mixtures have been tested using falling head method. The hydraulic conductivity of soil with 30% GGBS is the lowest and satisfies the hydraulic conductivity criteria of 10-7 cm/s or less for liner application. Soil column tests are conducted to determine the transport parameters of chromium through the optimized soil mixture. The transport parameters of chromium through optimized mixture was found to be diffusion coefficient D = 3.9x10-6 cm2/s and retardation factor R = 4.964. BCS with 30% GGBS mixture with a hydraulic gradient of 0.3 and can be used as liner to contain chromium ion as it gives a breakthrough time of more than 100 years for a liner thickness of 1m.

Removal of metals from wastewaters by mineral and biomass-based sorbents applied in continuous-flow continuous stirred tank reactors followed by sedimentation

Numerous studies have examined the performance of mineral and biomass-based sorbents for metal removal under laboratory conditions, but few pilot-scale tests have been performed on possible water purification systems in which these sorbents can be used. This study addressed this issue by evaluating the suitability of selected sorbents for use in continuous-flow continuous stirred tank reactors (CSTR) followed by sedimentation in laboratory and in situ pilot-scale experiments. Acid (HCl)-modified peat (M-Peat), a commercially available mineral sorbent containing mainly magnesium (Mg) carbonates, Mg oxides and Mg silicates (Mineral-P) and a calcium-rich ground granular blast furnace slag (by-product of stainless steel production (Slag) were tested for treatment of metallurgical industry wastewater (laboratory, pilot). Overall, higher metal removal was achieved from samples with higher initial metal concentrations. M-Peat achieved good removal of Zn (50–70%) and Ni (30–50%) in laboratory and pilot experiments. However, the poor settling characteristics of M-Peat can restrict its application in systems where sedimentation is the solid-liquid separation process applied. Mineral-P showed good performance in removing 65–85% of Zn present in the water and it performed similarly in laboratory and pilot tests. However, low concentrations of As and Ni leached from Mineral-P in all tests. Slag achieved good performance in treatment of the industrial wastewater, removing 65–80% of Zn and 60–80% of Pb during pilot tests. However, low concentrations of Cr and Cu were leached from Slag in a few tests. As a by-product of the same (metallurgical) industry, ground granular blast furnace slag is an excellent candidate for reducing Zn concentrations from industrial wastewater flows.

Experimental Study on the Compressive Strength and Permeable Properties of GGBS Based Geopolymer Pervious Concrete

This paper deals with the experimental investigation on the mechanical, thermal and moisture properties of Ground Granular Blast Furnace Slag (GGBS) based Geopolymer Pervious Concrete (GGPC) with different size of aggregates. The concentration of NaOH is maintained as 12 M throughout the study. Fine aggregate is completely eliminated in the mix proportion to maintain the pervious nature. Coarse aggregate size is varied in three sizes such as 6mm, 12mm, and 20mm to study the effect of aggregate on the properties of GGPC. The ratio between sodium silicate and sodium hydroxide is maintained as 2.5 throughout the study, and the liquid to solid ratio is maintained as 0.45. The results from the experiments revealed that the compressive strength is higher for the aggregate size 12 mm at the end of 28 days compared to other mixes. The Co-efficient of Permeability (k) is increased with respect to the increase in the aggregate size from 6 to 20 mm.

Green Concrete: By-Products Utilization and Advanced Approaches

The popularity of concrete has been accompanied with dreadful consumptions that have led to huge carbon footprint in our environment. The exhaustion of natural resources is not yet the problem, but also the energy that is needed for the fabrication of the natural materials, in which this process releases significant amount of carbon dioxide (CO2) emissions into the air. Ordinary Portland Cement (OPC) and natural aggregates, which are the key constituents of concrete, are suggested to be recycled or substituted in order to address the sustainability concern. Here, by-products have been targeted to reduce the carbon footprint, including, but not limited to, fly ash, rice husk ash, silica fume, recycled coarse aggregates, ground granular blast-furnace slag, waste glass, and plastic. Moreover, advanced approaches with an emphasis on sustainability are highlighted, which include the enhancement of the hydration process in cement (calcium-silicate hydrate) and the development of new materials that can be used in concrete (e.g., carbon nanotube). This review paper provides a comprehensive discussion upon the utilization of the reviewed materials, as well as the challenges and the knowledge gaps in producing green and sustainable concrete.

Investigation of geopolymers containing fly ash and ground-granulated blast-furnace slag blended by amorphous ratios

A new amorphous phase mix design framework had been successfully developed in consideration of calcium content through the combination of ground-granular blast-furnace slag (GGBFS) in fly ash (FA) blended geopolymers. The new framework has been developed considering the amorphous silicon, aluminium, sodium and calcium containing phases of the aluminosilicate sources to increase geopolymerisation reactivity and compressive strength. By utilising this new framework, this study found that the optimal amorphous Si/Al ratio of FA- and GGBFS-blended geopolymers are between 2.3 and 3.1. At 40–50% of FA replacement with GGBFS, it had been observed that blended geopolymers are able to achieve the majority of its 28 days compressive strength at 7 days. To account for the effect of calcium content, a new amorphous ratio, (Na + 2Ca)/Al, is proposed, with an optimal ratio of between 3.2 and 3.4.