Aggregates can be categorized into natural and artificial aggregates. Preserving natural resources is crucial to ensuring the constant supply of natural aggregates. In order to preserve these natural resources, the production of artificial aggregates is beginning to gain the attention of researchers worldwide. One of the methods involves using geopolymer technology. On this basis, this current research focuses on the inter-particle effect on the properties of fly ash geopolymer aggregates with different molarities of sodium hydroxide (NaOH). The effects of synthesis parameters (6, 8, 10, 12, and 14 M) on the mechanical and microstructural properties of the fly ash geopolymer aggregate were studied. The fly ash geopolymer aggregate was palletized manually by using a hand to form a sphere-shaped aggregate where the ratio of NaOH/Na₂SiO₃ used was constant at 2.5. The results indicated that the NaOH molarity has a significant effect on the impact strength of a fly ash geopolymer aggregate. The highest aggregate impact value (AIV) was obtained for samples with 6 M NaOH molarity (26.95%), indicating the lowest strength among other molarities studied and the lowest density of 2150 kg/m³. The low concentration of sodium hydroxide in the alkali activator solution resulted in the dissolution of fly ash being limited; thus, the inter-particle volume cannot be fully filled by the precipitated gels.

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.

This paper elucidates the mechanical performance, microstructure, and porosity evolution of fly ash geopolymer after 10 years of curing age. Given their wide range of applications, understanding the microstructure of geopolymers is critical for their long-term use. The outcome of fly ash geopolymer on mechanical performance and microstructural characteristics was compared between 28 days of curing (FA28D) and after 10 years of curing age (FA10Y) at similar mixing designs. The results of this work reveal that the FA10Y has a beneficial effect on strength development and denser microstructure compared to FA28D. The total porosity of FA10Y was also lower than FA28D due to the anorthite formation resulting in the compacted matrix. After 10 years of curing age, the 3D pore distribution showed a considerable decrease in the range of 5–30 µm with the formation of isolated and intergranular holes.

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.

This research was conducted to study the mechanical and morphology of fly ash based geopolymer as artificial aggregate at different sintering temperature. The raw material that are used is fly ash, sodium hydroxide, sodium silicate, geopolymer artificial aggregate, Ordinary Portland Cement (OPC), coarse aggregate and fine aggregate. The research starts with the preparation of geopolymer artificial aggregate. Then, geopolymer artificial aggregate will be sintered at six difference temperature that is 400°C, 500°C, 600°C, 700°C, 800°C and 900°C to known at which temperature the geopolymer artificial aggregate will become a lightweight aggregate. In order to characterize the geopolymer artificial aggregate the X-ray Diffraction (XRD) and X-Ray Fluorescence (XRF) was done. The testing and analyses involve for the artificial aggregate is aggregate impact test, specific gravity test and Scanning Electron Microscopy (SEM). After that the process will proceed to produce concrete with two type of different aggregate that is course aggregate and geopolymer artificial aggregate. The testing for concrete is compressive strength test, water absorption test and density test. The result obtained will be compared and analyse.