As the demand for nonrenewable natural resources, such as aggregate, is increasing worldwide, new production of artificial aggregate should be developed. Artificial lightweight aggregate can bring advantages to the construction field due to its lower density, thus reducing the dead load applied to the structural elements. In addition, application of artificial lightweight aggregate in lightweight concrete will produce lower thermal conductivity. However, the production of artificial lightweight aggregate is still limited. Production of artificial lightweight aggregate incorporating waste materials or pozzolanic materials is advantageous and beneficial in terms of being environmentally friendly, as well as lowering carbon dioxide emissions. Moreover, additives, such as geopolymer, have been introduced as one of the alternative construction materials that have been proven to have excellent properties. Thus, this paper will review the production of artificial lightweight aggregate through various methods, including sintering, cold bonding, and autoclaving. The significant properties of artificial lightweight aggregate, including physical and mechanical properties, such as water absorption, crushing strength, and impact value, are reviewed. The properties of concrete, including thermal properties, that utilized artificial lightweight aggregate were also briefly reviewed to highlight the advantages of artificial lightweight aggregate.

The use of lightweight aggregate can bring advantages to the construction field. Lightweight aggregate has been used due to its lower density and can reduce the dead load applied to the structural elements. Due to the number of natural resources, such as natural aggregate having decreased, producing lightweight aggregate from industrial waste materials can overcome the problem. Different methods produce lightweight aggregates, such as sintering, cold bonding, and autoclaving. From earlier studies, spherical sintered lightweight aggregate can manufacture structural concrete. Using artificial lightweight aggregate in concrete can achieve the minimum strength requirement of structural concrete and has been applied in the construction field. The properties of lightweight aggregate, such as specific gravity, water absorption, crushing strength, and impact value, are reviewed. Besides that, the mechanical and thermal properties review is also important for using lightweight aggregate in concrete. The review also indicates that aggregate produced using the cold bonding method and autoclaving method potential can be used in the concrete.

The effects of supplementary cementitious materials (SCM) on the characteristics and internal structure of synthetic aggregate made from ground granulated blast furnace slag are investigated in this study (GGBS). Due to its high pozzolanic activity, GGBS was shown to be superior to other SCM materials, enhancing both the strength and durability of synthetic aggregate. Because sintering uses a lot of energy and generates a lot of pollutants, using a cold-bonded approach to make low density lightweight aggregates is particularly significant from an economic and environmental standpoint. Thus, the utilisation of ground granulated blast furnace slag (GGBS) as a substitute material in the production of green artificial lightweight aggregate (GLA) using the cold bonding method was discussed in this work. Admixtures of ADVA Cast 203 and Hydrogen Peroxide were utilised to improve the quality of GLA at various molar ratios. The freshly extracted GLA was then evaluated for specific gravity, water absorption, aggregate impact, and aggregate crushing in order to determine the optimal proportion blend. As a result, the overall findings offer great application potential in the development of concrete (GCLA). It has been determined that aggregates with a toughness of 14.6% and a hardness of 15.9% are robust. The compressive strength test found that the GCLA has a high strength lightweight concrete of 37.19 MPa and a density of 1845.74 kg/m3. The porous features developed inside the internal structure of GLA have led to GCLA’s less weight compared to conventional concrete.

Alkali activation for producing alkali-activated materials is noted as a complex due to involving several reactions. Due to complexity of the reactions, various techniques have been applied by past researches on monitoring the evolution of alkali-activated materials. The evolution monitored during alkali activation include internal relative humidity, structural evolution, ultrasonic evolution and heat evolution. All of these techniques provide real-time information which is significant for evaluating the reaction process of alkali activation with respected parameters applied thus will be briefly reviewed in this paper. In addition, among those techniques, due to its reliability, heat evolution is one noted as one of the most common techniques applied to elucidate the alkali activation process. Therefore, the potential of heat evolution will also be significantly highlighted in this study.

This study investigates the nucleation mechanism of slag alkali activation at different solid-to-liquid ratios, focusing on kinetics, including growth rates. Heat evolution during activation was monitored, and calorimetric data were analyzed using the Johnson–Mehl–Avrami–Kolmogorov model. Compressive strength and phase evolution (via wide-angle X-ray scattering) were correlated with heat evolution to enhance understanding of reaction mechanisms in alkali-activated material formation. This is essential for producing alkali-activated slag that meets standard requirements for construction applications. Results showed that the highest heat evolved (–360.60 J/g) did not correlate with the best strength performance (22.69 MPa at 1 day and 25.83 MPa at 3 days), since the lowest cumulative heat (–226.15 J/g) at an S/L ratio of 1.4 yielded the best strength. This was supported by the highest growth rate (0.1172 min–1) at this ratio. JMAK analysis indicated instantaneous nucleation with one-dimensional rod-like growth, driven by increased nucleation site availability. From the results obtained, it can be concluded that an increment in S/L ratio significantly increased nucleation and polymerization of alkali-activated slag, thereby hindering heat flow, as evidenced by the lowest total cumulative heat evolved. In addition, the highest growth rate observed corresponded linearly with the compressive strength, further confirming densification by polymeric gels formed during alkali activation.