Strength and durability study on alccofine based geo-polymer concrete

A study on development of pavement quality geopolymer concrete for low volume roads

Awareness of environmental sustainability is driving the shift from conventional Portland cement, a major contributor to carbon dioxide emissions, to more sustainable alternatives. This study focuses on developing a geopolymer concrete by optimizing geopolymer concrete mixtures with various ratios of Ground Granulated Blast Furnace Slag (GGBS) and pulverized fly ash (PFA) as precursors, aiming to find a mix that maximizes strength while minimizing environmental impacts. The precursor was activated using a laboratory-synthesized silica fume (SF)-derived sodium silicate solution in combination with NaOH at a molarity of 10M. This study aims to find the optimal geopolymer concrete mix with a 0.55 water-to-binder ratio, a 0.40 alkali-to-precursor ratio, and a 1:1 sodium silicate to sodium hydroxide ratio. Ordinary Portland cement was used as the control mix binder (C), while the geopolymer mixes included varying GGBS-PFA compositions [CL0 (50% GGBS-50% PFA), CL1 (60% GGBS-40% PFA), CL2 (70% GGBS-30% PFA), CL3 (80% GGBS-20% PFA), and CL4 (90% GGBS-10% PFA)]. The engineering performance of the mixtures was assessed using slump, unconfined compressive strength, split tensile, and flexural strength tests in accordance with their relevant standards. Observations showed that GPC specimens exhibited similar or slightly higher strength values than conventional concrete using PC. In addition to strength, geopolymers have a smaller environmental footprint, consuming less energy and reducing greenhouse gas emissions. These qualities make geopolymer concrete a sustainable construction option that aligns with global efforts to reduce carbon emissions and conserve resources.

Ambient- and oven-cured geopolymer concretes under active confinement

Expanding the world’s infrastructure drives up demand for building materials, particularly ordinary Portland cement (OPC) concrete, whose high carbon dioxide (CO2) emissions have a detrimental effect on the environment. To address this issue, researchers looked into employing alternative supplementary cementitious materials (SCMs), including metakaolin (MK), which is derived from calcined kaolin clay with pozzolanic properties, to partially or completely replace OPC in concrete. This review article examines the MK’s application in alkali-activated materials (AAMs) and OPC-based concrete. By interacting with calcium hydroxide, MK functions as a pozzolanic additive for OPC concrete, enhancing its mechanical qualities and durability. The use of MK as a source material in AAMs, a newly developed class of sustainable binders, is also covered in this article. The effects of different combinations of MK with additional SCMs, including fly ash (FA), ground granulated blast furnace slag (GGBFS), silica fume, and rice husk ash, on the characteristics of alkali-activated concrete both in its fresh and hardened states, are compiled. The majority of the articles considered in this study are from the past decade, while some relevant articles from 2014 and earlier are also taken into account. The results showed that adding MK to concrete in combination with FA or GGBFS has excellent synergistic effects on microstructural development, pozzolanic activity, and strength increases. In particular, the MK–FA mix demonstrated the most encouraging performance gains. Because of its large surface area, the use of nano-MK helped achieve a denser geopolymer structure and improve mechanical properties. The best curing temperatures for MK-based geopolymers to gain strength were found to be between 40 and 80°C for a total of 28 days. The review also pointed out that the compressive strength and geopolymerization process of MK-based geopolymers were enhanced by increasing the mass ratio of Na2SiO3 to NaOH and NaOH concentration. Nevertheless, geopolymerization was hampered by unnecessarily high alkali concentrations. Moreover, the compressive strength was increased by partially replacing MK with TiO2 or GGBFS. The synergistic effects of combining MK with other SCMs to improve concrete performance highlight the potential of MK-based solutions in lowering the environmental footprint of concrete buildings.

This study, third in the series, following from ground limestone and Class F fly ash, evaluates, as a cement constituent, the effect of using ground granulated blast furnace slag (GGBS) on the strength development of concrete, and consequently its embodied carbon dioxide (CO2e). The paper has been built from systematically analysing, evaluating and modelling the extensive data-matrix developed, having 85,099 data points, from the information sourced from 663 studies published in English, during 1974 to 2020, by 1,672 authors, working in 718 institutions in 49 countries, globally. It is shown that, at a given water/cement ratio, in comparison to Portland cement (PC), the use of GGBS results in a reduction in 28-day concrete strength, which increases with GGBS content, at a rate determined by the strength of concrete, GGBS fineness, and curing of concrete. It is also shown that, as to achieve a 28-day design strength, a lower water/cement ratio is required with a PC/GGBS blended cement than PC, this will reduce the actual CO2e savings that can be realised with the use of GGBS as cement constituent in manufacturing concrete. Finally, it is shown that GGBS is more effective in lowering CO2e of concrete than FA and GLS.

The utilization of steel slag (SS) in construction materials represents an effective approach to improving its overall recycling efficiency. This study incorporates SS into a conventional ground granulated blast-furnace slag (GGBS)–fly ash (FA)-based binder system to develop a ternary system comprising SS, GGBS, and FA, and investigates how this system influences the static mechanical properties of ultra-high-performance geopolymer concrete (UHPGC). An axial point augmented simplex centroid design method was employed to systematically explore the influence and underlying mechanisms of different binder ratios on the workability, axial compressive strength, and flexural performance of UHPGC, and to determine the optimal compositional range. The results indicate that steel slag has a certain negative effect on the flowability of UHPGC paste; however, with an appropriate proportion of composite binder materials, the mixture can still exhibit satisfactory flowability. The compressive performance of UHPGC is primarily governed by the proportion of GGBS in the ternary binder system; an appropriate GGBS content can provide enhanced compressive strength and elastic modulus. UHPGC exhibits ductile behavior under flexural loading; however, replacing GGBS with SS significantly reduces its flexural strength and energy absorption capacity. The optimal static mechanical performance is achieved when the mass proportions of SS, GGBS, and FA are within the ranges of 9.3–13.8%, 66.2–70.7%, and 20.0–22.9%, respectively. This study provides a scientific approach for the valorization of SS through construction material applications and offers a theoretical and data-driven basis for the mix design of ultra-high-performance building materials derived from industrial solid wastes.

Optimum mix design of geopolymer pastes and concretes cured in ambient condition based on compressive strength, setting time and workability

Ultra-high-performance geopolymer concrete is a low-carbon and environmentally friendly cementitious composite formed through alkali activation of industrial by-products and incorporation of ultrafine fillers and fiber reinforcement, exhibiting high compressive strength and excellent durability. In this study, ultra-high-strength geopolymer concretes (UHSGM) were prepared using ground granulated blast furnace slag (GGBFS), fly ash (FA), and silica fume (SF) as binders. Three GGBFS-to-FA mass ratios, namely 4:1, 1:1, and 1:4, were adopted. The SF content was varied at 0%, 5%, 10%, 20%, and 30% by mass of the precursor. In addition, three types of steel fiber were incorporated at a constant volume fraction of 2%. Two curing conditions, namely standard curing and steam curing, were adopted. The influences of mixture proportions, with or without silica fume and steel fiber, on the flowability, compressive strength, and flexural performance of UHSGM were systematically evaluated. The results indicated that an increase in GGBFS content led to a reduction in flowability but an enhancement in the compressive strength of UHSGM. The influence of SF on flowability and compressive strength was strongly dependent on the GGBFS-to-FA ratio. The highest compressive strength of the geopolymer reached 157.0 MPa at a GGBFS-to-FA ratio of 4:1 with 5% SF, which is comparable to that of ultra-high-performance concrete. An increase in GGBFS content and the incorporation of steel fibers enhanced the flexural strength of UHSGM, whereas high-temperature curing led to a reduction in flexural strength. An increase in SF had a negative effect on the deflection capacity and toughness of UHSGM, regardless of curing conditions. Further investigation is required to optimize the overall performance of UHSGM.

Environmental impact assessment of fly ash and silica fume based geopolymer concrete

In the current situation, to overcome the difficulties of feasible construction, concrete made with various mixtures of Ordinary Portland Cement (OPC) and diverse mineral admixtures, is the wise choice for engineering construction. Mineral admixtures viz. Ground Granulated Blast Furnace Slag (GGBS), Meta kaolin (MK), Fly Ash (FA) and Silica Fume (SF) etc. are used as Supplementary Cementitious Materials (SCM) in binary and ternary blend cement system to enhance the mechanical and durability properties. Investigation on the effect of different replacement levels of OPC in M25 grade with FA + SF in ternary cement blend on the strength characteristics and beam behavior was studied. The OPC was partially replaced (by weight) with different combinations of SF (5%, 10%, 15%, 20% and 25%) and FA as 50% (High Volume Fly Ash - HVFA). The amount of FA addition is kept constant at 50% for all combinations. The compressive strength and tensile strength tests on cube and cylinder specimens, at 7 and 28 days were carried out. Based on the compressive strength results, optimum mix proportion was found out and flexural behaviour was studied for the optimum mix. It was found that all the mixes (FA + SF) showed improvement in compressive strength over that of the control mix and the mix with 50% FA + 10% SF has 20% increase over the control mix. The tensile strength was also increased over the control mix. Flexural behaviour also showed a significant improvement in the mix with FA and SF over the control mix.

The use of high-volume industrial by-products in high-performance concrete (HPC) production offers a promising and sustainable strategy for reducing ordinary Portland cement (OPC) consumption. However, each pozzolanic material has a unique chemical composition and physical characteristics, making ternary and quaternary binder systems an effective approach for optimizing performance. In this study, quaternary binders comprising OPC partially replaced with Class F fly ash (FA), ground granulated blast-furnace slag (GGBFS), and silica fume (SF) were designed using the Taguchi method, and the mechanical and durability properties of fine-grained HPC were evaluated. Sixteen concrete mixtures were developed considering three factors—FA, GGBFS, and SF replacement levels—each at four dosage levels. The results show that incorporating SF significantly enhanced both mechanical performance and durability. An optimal blend containing 60% OPC, 30% GGBFS, and 10% SF exhibited superior performance compared with the 100% OPC control mix. Additionally, a mixture of 40% OPC, 40% GGBFS, 10% Class F FA, and 10% SF achieved comparable compressive strength to the control, exceeding 100 MPa at 28 days. SEM observations confirmed the dense microstructure of this HPC mix. ANOVA analysis indicated that FA and SF had a significantly greater influence on HPC strength development than GGBFS. Overall, these findings demonstrate the potential of high-volume industrial by-products to produce fine-grained HPC, providing a high-performance and environmentally friendly alternative to conventional OPC-based concrete.

Influence of superplasticizer on the properties of geopolymer concrete using industrial wastes

Performance of sustainable concretes containing very high volume Class-F fly ash and ground granulated blast furnace slag

Geopolymer concrete is a new and alternative to cement concrete, thus decreasing greenhouse emissions and leading to better construction practices. This can be produced by complete replacement of cement with pozzolanic materials such as Fly Ash (FA), Ground Granulated Blast Furnace Slag (GGBS) and activation through alkaline activator solution. The present study aims to investigate the effect of 8M sodium hydroxide solution for the chemical ratios of Na2SiO3 to NaOH are 1.5, 2.0, 2.5, and 3 with different combinations of fly ash and GGBS. The cast specimens were outdoor cured and tested at the age of 1, 3, 7, and 28 days for compressive strength, followed by XRD analysis to identify the mineralogical variations with a change in parameters. The obtained results concluded that GGBS content with 8M concentration of sodium hydroxide in the mix increases the compressive strength of geopolymer mortar. The optimum dosage of Na2SiO3/NaOH was 2.5 based on the compressive strength of mortar. The compounds responsible for strength were identified through XRD analysis as N-A-S-H gel and C-A-S-H gel in mixes with fly ash and GGBS as binders.

The construction industry contributes significant greenhouse gases to the climate by consuming vast amounts of cement. Researchers are looking at alternative cement methods to decrease the adverse effects, one of which is Geopolymer Concrete (GPC). The GPC is made from industrial waste materials high in silica and activated with sodium hydroxides (NaOH) to form sodium silicate (Na2SiO3) because Geo polymer is a material that is just two decades old and is an area of extensive research. To study the effect of the addition of cement to GPC’s mechanical properties by replacing up to 50% of the ground granulated blast furnace slag (GGBFS) and fly ash with ten per cent increments. The outcomes are contrasted with the Geo Polymer Concrete control mix. For this study, an analysis of activators to fly ash at 0.35, NaOH to Na2SiO3 at 2.5, and the molarity of sodium hydroxide was set at 8M. At different ages, the compressive strength of cubes was calculated, as well as their split and flexural strengths following a 28-day curing period. The findings revealed that adding cement to the mix improves the mechanical properties. The best results are obtained at 40% cement, fly ash, and GGBFS at 60%.