Papers by Keyword: Metakaolin

Abstract: Metakaolin is in great demand worldwide as a highly active pozzolanic additive to Portland cement. The use of metakaolin helps to increase the density, water resistance, and mechanical strength of Portland cement, which makes it possible to reduce the consumption of clinker – the most energy-intensive and expensive component of cement/concrete. Usually, metakaolin is obtained by thermal processing of kaolin clays at a temperature of 600–850°C. Kaolin clay reserves in the world are strictly limited. Kaolin clays have not been identified in Georgia. However, there are kaolinized clays, which are distinguished by a lower Al₂O₃ content compared to kaolin clays. The purpose of this work is to study the possibility of obtaining a highly active pozzolanic additive – metakaolin based on kaolinized clays of Georgia and regulation of the parameters of their synthesis. It is proved that the addition of fly ash to kaolinized clay allows reducing the temperature of heat treatment and obtaining a highly effective pozzolanic additive to cement.

Abstract: The construction industry is facing increasing pressure to adopt sustainable and eco-friendly practices in response to the growing concerns over environmental degradation and climate change. Among the various innovative materials being explored, geopolymer mud blocks have emerged as a promising alternative to traditional construction materials such as cement and fired clay bricks. These blocks are characterized by their eco-friendly composition, which typically involves the use of industrial by-products like fly ash, metakaolin, and other aluminosilicate materials, activated through an alkaline solution. This process results in a material that not only exhibits superior structural integrity but also significantly reduces the carbon footprint associated with construction.This paper provides a comprehensive review of the material composition of geopolymer mud blocks, detailing the various raw materials used and the chemical reactions that confer strength and durability to the blocks. The review also delves into the structural properties of these blocks, including their compressive strength, thermal insulation capabilities, and resistance to environmental factors such as moisture and temperature fluctuations. Additionally, the paper explores the ecological impacts of geopolymer mud blocks, emphasizing their potential to reduce greenhouse gas emissions, minimize resource depletion, and promote the use of industrial waste, thus contributing to a more circular economy.Finally, the paper looks forward to the future prospects of geopolymer technology in the construction industry, suggesting potential pathways for overcoming the current limitations and further enhancing the sustainability of construction practices. By providing a holistic view of geopolymer mud blocks, this review aims to contribute to the growing body of knowledge on sustainable construction materials and to support the transition towards greener building practices on a global scale.

Abstract: The study investigates the impact of quaternary ammonium and pyridinium salts on the rheological properties of metakaolin-based geopolymer pastes, with a focus on their application in 3D printing technology The experimental results demonstrated that the addition of these salts increased both the plastic viscosity and yield stress of the geopolymer mixtures, with the effect intensifying with higher concentrations and longer aliphatic chains. The coefficient of consistency derived from Herschel-Bulkley model increased from 1.78 up to 3.83 Pa·sⁿ and the yield stress rose from 3.4 up to 31.8 Pa. The study also observed a shift from shear-thickening to shear-thinning behaviour and reduction in thixotropic properties with increased dosages of the admixtures, which is beneficial for 3D printing. The mechanical properties of modified geopolymer mortars were also tested and the results revealed quite negligible effect of admixtures on flexural strength. The compressive strength was slightly reduced by up to 12%. The findings suggest that these admixtures are effective in modifying the rheological properties of geopolymers, making them more suitable for advanced applications like 3D printing.

Abstract: Red mud, a by-product of the aluminum industry, poses a threat to the environment with its high alkalinity and heavy metal content and may seep into the soil and groundwater, endangering ecology and health. Effective utilization of red mud can reduce pollution and achieve resource recycling. In this study, a metakaolin/red mud geopolymer was prepared by phosphoric acid excitation to investigate its adsorption capacity for lead ions. The ratio of metakaolin to red mud and the additions of phosphoric acid and water were optimized, and the optimal formulations were 3/7 mass ratio of metakaolin to red mud, 2.2 molar ratio of H₃PO₄/Al₂O₃, and 0.5 water-solid ratio, which demonstrated good stability and operability.

Abstract: Red mud may cause serious pollution to soil, water, and air. Lead can seriously harm biological and even human health. This chapter summarizes the adsorption properties of metakaolin/red mud base polymer for Pb (Ⅱ). Under optimized conditions, with 0.6g/L adsorbent, pH value of 5, and adsorption time of 120 minutes, the adsorption capacity reached 122.58mg/g, and the removal rate was 73.55%. This will help to mitigate the threat of red mud and lead wastewater to human health and the environment, providing an important reference for water pollution control.

Abstract: The construction industry is crucial for social and economic development, but it faces sustainability challenges. About 40% of global industrial waste comes from construction, and cement contributes approximately 8% of global CO₂ emissions. This study aims to develop more sustainable materials by reusing waste and creating a new environmentally friendly binder, geopolymer, from ignimbrite (IG) from Arequipa, Peru, and metakaolin. Metakaolin from China (MKCh) and locally calcined metakaolin (MK650 and MK750) were used. The materials were characterized by XRD, FTIR, and SEM-EDS. Cylindrical geopolymers were produced with MK and IG ratios of 100/0 and 60/40, using a 9 mol/L NaOH activator solution. Curing was performed at 25 °C for 24 h, followed by 72 h at 50 °C. The results showed that the addition of IG increased the compressive strength, with the best performance observed in the MK-IG-60-40 material, with 52.72 ± 1.02 MPa. Thus, the addition of ignimbrite demonstrated to improve the strength of the geopolymers.

Abstract: For sustainability in the construction field, finding a substitute for cement and recycling the waste in concrete is important. This paper shows the effect of sustainable copper fibres on some properties of perlite structural lightweight concrete containing sustainable materials. Research includes slump, density, compressive strength, flexural strength and thermal conductivity tests. The materials used to cast the specimen are ordinary Portland cement, local ash, metakaolin, combined coarse and fine perlite aggregate, and super-plasticizer. The concrete is reinforced with 1% copper fibres by volume of concrete. The results show that adding sustainable material to the concrete increased compressive strength by a percentage of 2.79% for 28 days and improved flexural and tensile strength by 40% and 8.36%, respectively, at 28 days. The density was within the limits of structural lightweight concrete, while the thermal conductivity was within the limits of insulation concrete, in addition to economic benefits and reducing world waste.

Abstract: In this paper, more than 20 mixtures of metakaolin/blast furnace slag alkali-activated mortar mixtures with a maximum grain size of 2.5 mm are investigated. Parameters varied include mixing procedure, curing conditions of which the most used procedure is sealed curing at 70°C for 7 days, granular skeleton, water-to-solid ratio (0.35 to 0.60), metakaolin content (30 to 100%), and type of alkaline activator (sodium silicate solution or potassium silicate solution). The mix design is based on chemical calculations based on the oxide composition of the precursors and activators. Fresh material properties i.e. initial and final setting time, and workability are measured for part of the mixtures. Mechanical tests have been performed on mortar size prisms in order to determine the compressive and flexural tensile strength of all mixtures. The range of compressive strength varies in between 50 and 142 MPa. Based on the results Feret’s law seems to be valid for alkali-activated materials as well.

Abstract: Recently, research has been devoted to producing a more sustainable and environmentally friendly composite for substituting conventional cement concrete. This supports the global effort toward limiting the environmental impact of cement production. Geopolymer composites or alkali-activated materials have gained more attention within the research community due to the wide availability of waste (e.g., fly ash, slag) or natural (metakaolin, pozzolans) source materials suitable for geopolymer production. The present study investigates the potential of producing metakaolin-based geopolymer mortars with partial substitution of natural sand by recycled plastic fine aggregate (RPFA) to enhance composite sustainability. The primary variables of the experimental program include the percentage replacement of fine natural aggregate by RPFA (0, 10, 20, and 30% by volume). Tests comprising flowability, compressive strength, Flexural strength and unit weight of the various mixes were evaluated. The results indicated that replacing 10%, 20%, and 30% of sand with RPFA caused a reduction in the compressive strength by 10.6%, 21.8%, and 33.9% relative to the control mix. The flexural strength also decreased by 17.5%, 22.4%, and 30.4% compared to the control mix. Although substituting natural aggregate with RPFA reduced the mechanical properties, it improved the mix flowability by up to 20% relative to the control mix. Additionally, a reduction in the unit weight by up to 16.2% relative to the control mix was obtained, which offer a viable mean of producing lightweight mortar.

Abstract: The present study investigates the effect of incorporating metakaolin and silica fumes in the production of high-strength concrete along with partial replacement of coarse granite aggregates in the high-strength concrete. The higher compressive strength, refined microstructure, and decreased permeability of high-strength concrete are some of the properties responsible for its trending use in the modern construction industry. The main purpose of this research is to evaluate the effect of the replacement of coarse granite aggregates with natural aggregates on the mechanical and durability properties of high-strength concrete. For understanding the effect of metakaolin, silica fume, and granite aggregates on the properties of high-strength concrete, various specimens such as cubes, cylinders, and cylindrical discs were cast and tested after 7, 14, and 28 days of curing. Various concrete mixes were prepared by adding silica fume at 5%, 7.5%, and 10% and metakaolin at 5%, 7.5%, 10%, 12.5%, and 15% in concrete production. Furthermore, High-strength concrete mixes were also prepared by replacing natural coarse aggregates with granite coarse aggregates by 25%, 50%, 75%, and 100% to study the effect of replacement percentage on the concrete properties. Test results indicated that the compressive strength and split tensile strength of the concrete mix increased with the increase in the replacement percentage of granite aggregates, with the highest strength seen at complete replacement with granite aggregate due to the enhanced compressive strength of such aggregates in comparison with the natural coarse aggregates. In various mixes cast using metakaolin and silica fume, the highest compressive strength was seen in a mix containing 10% metakaolin and 7.5% silica fume, and results of other mixes indicated that the use of silica fume and metakaolin are viable options for high-strength concrete production in our experimental study.