Geopolymers, or also known as alkali-activated binders, have recently emerged as a viable alternative to conventional binders (cement) for soil stabilization. Geopolymers employ alkaline activation of industrial waste to create cementitious products inside treated soils, increasing the clayey soils’ mechanical and physical qualities. This paper aims to review the utilization of fly ash and ground granulated blast furnace slag (GGBFS)-based geopolymers for soil stabilization by enhancing strength. Previous research only used one type of precursor: fly ash or GGBFS, but the strength value obtained did not meet the ASTM D 4609 (<0.8 Mpa) standard required for soil-stabilizing criteria of road construction applications. This current research focused on the combination of two types of precursors, which are fly ash and GGBFS. The findings of an unconfined compressive strength (UCS) test on stabilized soil samples were discussed. Finally, the paper concludes that GGBFS and fly-ash-based geo-polymers for soil stabilization techniques can be successfully used as a binder for soil stabilization. However, additional research is required to meet the requirement of ASTM D 4609 standard in road construction applications, particularly in subgrade layers.

This study intended to address the problem of damaged (collapsed, cracked and decreased soil strength) road pavement structure built on clay soil due to clay soil properties such as low shear strength, high soil compressibility, low soil permeability, low soil strength, and high soil plasticity. Previous research reported that ground granulated blast slag (GGBS) and fly ash can be used for clay soil stabilizations, but the results of past research indicate that the road pavement construction standards remained unfulfilled, especially in terms of clay’s subgrade soil. Due to this reason, this study is carried out to further investigate soil stabilization using GGBS and fly ash-based geopolymer processes. This study investigates the effects of GGBS and ratios of fly ash (solid) to alkaline activator (liquid) of 1:1, 1.5:1, 2:1, 2.5:1, and 3:1, cured for 1 and 7 days. The molarity of sodium hydroxide (NaOH) and the ratio of sodium silicate (Na₂SiO₃) to sodium hydroxide (NaOH) was fixed at 10 molar and 2.0 weight ratio. The mechanical properties of the soil stabilization based geopolymer process were tested using an unconfined compression test, while the characterization of soil stabilization was investigated using the plastic limit test, liquid limit test, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The results showed that the highest strength obtained was 3.15 MPA with a GGBS to alkaline activator ratio of 1.5 and Na₂SiO₃ to NaOH ratio of 2.0 at 7 days curing time. These findings are useful in enhancing knowledge in the field of soil stabilization-based geopolymer, especially for applications in pavement construction. In addition, it can be used as a reference for academicians, civil engineers, and geotechnical engineers.

Geopolymers are an inorganic material in an alkaline environment that is synthesized with alumina–silica gel. The structure of geopolymers consists of an inorganic chain of material and a covalent-bound molecular system. Currently, Ordinary Portland Cement (OPC) has caused carbon dioxide (CO₂) emissions which causes greenhouse effects. This analysis investigates the impact on fly ash/dolomite-based-geopolymer with various molarities of sodium hydroxide solutions which are 6 M, 8 M, 10 M, 12 M and 14 M. The samples of fly ash/dolomite-based-geopolymer were prepared with the usage of solid to liquid of 2.0, by mass and alkaline activator ratio of 2.5, by mass. After that, the geopolymer was cast in 50 × 50 × 50 mm molds before testing after 7 days of curing. The samples were tested on compressive strength, density, water absorption, morphology, elemental distributions and phase analysis. From the results, the usage of 8 M of NaOH gave the optimum properties for the fly ash/dolomite-based geopolymer. The elemental distribution analysis exposes the Al, Si, Ca, Fe and Mg chemical distribution of the samples from the selected area. The distribution of the elements is related to the compressive strength and compared with the chemical composition of the fly ash and dolomite.

Globally, there is an increasing need for ceramic materials that have a variety of applications in the environment, for precision tools, and for the biomedical, electronics, and environmental industries. However, in order to obtain remarkable mechanical qualities, ceramics have to be manufactured at a high temperature of up to 1600 °C over a long heating period. Furthermore, the conventional approach presents issues with agglomeration, irregular grain growth, and furnace pollution. Many researchers have developed an interest in using geopolymer to produce ceramic materials, focusing on improving the performances of geopolymer ceramics. In addition to helping to lower the sintering temperature, it also improves the strength and other properties of the ceramics. Geopolymer is a product of polymerization involving aluminosilicate sources such as fly ash, metakaolin, kaolin, and slag through activation using an alkaline solution. The sources of the raw materials, the ratio of the alkaline solution, the sintering time, the calcining temperature, the mixing time, and the curing time may have significant impacts on the qualities. Therefore, this review aims to study the effects of sintering mechanisms on the crystallization of geopolymer ceramics, concerning the strength achieved. A future research opportunity is also presented in this review.

The focus of this study is the fabrication of innovative and sustainable ceramic-based geopolymer with improved low temperatures performances. Kaolin was mixed with liquid sodium silicate (Na₂SiO₃) and 12M of sodium hydroxide (NaOH) solution using alkali activator ratio of 0.24 and solid-to-liquid ratio of 1:1 to synthesize kaolin geopolymer. The effect of the sintering profile on the microstructure, pore evolution and flexural strength were investigated. The heating exposure aided consolidation and created a fairly uniform microstructure, resulting in a smooth surface texture. In comparison to the unheated geopolymer, 3D pore distribution showed a significant increase in the range size of ~30 µm with the appearance of isolated and intergranular pores. The flexural strength at 1200 °C with a heating rate of 5 °C/min and was increased by 146.4% to 85.4 MPa, as compared to the heating rate of 2 °C/min. The sintering process has an impact on the final microstructure formation thus improving the characteristic of geopolymer-based nepheline ceramic.