Geopolymerization process is the activation process of pozzolanic material with an alkaline activator solution using fly ash as a source of aluminosilicate. This study includes the production of lightweight concrete from fly ash through geopolymerization. The goal of this study is to determine the impact of several key parameters on the properties of fly ash-based geopolymer and its applications as lightweight concrete. Fly ash is the main raw material derived from power plant waste that can cause environmental pollution. Production process of geopolymer concrete involves several major processes namely design, preparation of alkaline activator solution, mixing, sampling and curing (heat treatment). The first phase is the production of an optimum
design through study of the geopolymer paste. Next, studies on the geopolymer concrete with the use of coarse and fine aggregate ratio 60:40 was giving optimum strength. The feasibility of geopolymer as lightweight concrete was also studied. Characterization of samples also made using physical test, compression test, X-ray scattering (XRD), X-ray diffraction analysis (XRF), Fourier transform infrared spectroscopy (FTIR) and morphology by scanning electron microscopy (SEM). From the research, the results suggest that 12M solution of sodium hydroxide (NaOH), the ratio of solid / liquid 2.0, the ratio of alkaline activator 2.5 and curing temperature of 60 °C is the optimum conditions for the production of fly ash-based geopolymer. This was proved by XRD
results that show the intensity of quartz content in 12M very easily detected and contribute to the highest compressive strength. Strength of geopolymer mortar reaches 79.16 MPa at 28 day whereas the strength of geopolymer concrete reach 49.30 MPa with optimum ratio of aggregate to fly ash is 70:30. For lightweight concrete, strength achieved 18:19 MPa at 28 days with density of 1653 kg/m3. This concrete can be classified as lightweight concrete because having density less than 1800 kg/m3.
