In this paper, we report the results of our investigation on the possibility of producing foam concrete by using a geopolymer system. Class C fly ash was mixed with an alkaline activator solution (a mixture of sodium silicate and NaOH), and foam was added to the geopolymeric mixture to produce lightweight concrete. The NaOH solution was prepared by dilute NaOH pellets with distilled water. The reactives were mixed to produce a homogeneous mixture, which was placed into a 50 mm mold and cured at two different curing temperatures (60 °C and room temperature), for 24 hours. After the curing process, the strengths of the samples were tested on days 1, 7, and 28. The water absorption, porosity, chemical composition, microstructure, XRD and FTIR analyses were studied. The results showed that the sample which was cured at 60 °C (LW2) produced the maximum compressive strength for all tests, (11.03 MPa, 17.59 MPa, and 18.19 MPa) for days 1, 7, and 28, respectively. Also, the water absorption and porosity of LW2 were reduced by 6.78% and 1.22% after 28 days, respectively. The SEM showed that the LW2 sample had a denser matrix than LW1. This was because LW2 was heat cured, which caused the geopolymerization rate to increase, producing a denser matrix. However for LW1, microcracks were present on the surface, which reduced the compressive strength and increased water absorption and porosity.

Fly ash–based geopolymers required heat to increase the geopolymerization process in order to obtain higher compressive strength. As such, geopolymer samples were prepared using different curing temperatures (room temperature, 50°C, 60°C, 70°C, 80°C), in which sodium silicate and NaOH were used as alkaline activators. The samples were cured for 24hours in the oven and tested on the seventh day. The result revealed that the maximum compressive strength (67.04MPa) was obtained at a temperature of 60°C. However when the geopolymers sample cured at temperature more than 60°C, the compressive strength decreased. From the FTIR spectra, the higher content of Si on sample cured at 60°C also contributed to higher compressive strength. Moreover, SEM analysis showed a denser matrix as well as less unreacted fly ash of the sample cured at 60°C compared to other temperatures

This paper investigates the effect of the solids-to-liquids (S/L) and Na₂SiO₃/NaOH ratios on the production of palm oil boiler ash (POBA) based geopolymer. Sodium silicate and sodium hydroxide (NaOH) solution were used as alkaline activator with a NaOH concentration of 14 M. The geopolymer samples were prepared with different S/L ratios (0.5, 1.0, 1.25, 1.5, and 1.75) and Na₂SiO₃/NaOH ratios (0.5, 1.0, 1.5, 2.0, 2.5, and 3.0). The main evaluation techniques in this study were compressive strength, X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscope (SEM). The results showed that the maximum compressive strength (11.9 MPa) was obtained at a S/L ratio and Na₂SiO₃/NaOH ratio of 1.5 and 2.5 at seven days of testing. v

Geopolymer, produced by the reaction of fly ash with an alkaline activator (mixture of Na₂SiO₃ and NaOH solutions), is an alternative to the use of ordinary Portland cement (OPC) in the construction industry. However, there are salient parameters that affecting the compressive strength of geopolymer. In this research, the effects of various NaOH molarities, Na₂SiO₃/NaOH ratios, fly ash/alkaline activator, and curing temperature to the strength of geopolymer paste fly ash were studied. Tests were carried out on 50 x 50 x 50 mm cube geopolymer specimens. Compression tests were conducted on the seventh day of testing for all samples. The test results revealed that a 12 M NaOH solution produced the highest compressive strength for the geopolymer. The combination mass ratios of fly ash/alkaline activator and Na₂SiO₃/NaOH of 2.0 and 2.5, respectively, produced the highest compressive strength after seven days. Geopolymer samples cured at 60 °C produced compressive strength as high as 70 MPa.

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.