Lightweight brick reduces the overall self-weight of the structures resulting in the reduction of the foundation size, cost, and other specifications. However, conventional lightweight brick production causes several environmental impacts and produces low mechanical properties, so there is a clear need to search and replace for more efficient and durable alternatives beyond the limitations of the conventional lightweight brick. Geopolymer represents an excellent opportunity to ensure greater sustainability in the construction industry especially for the use of industrial waste such as fly ash. This research focuses on the production of fly ash-based lightweight geopolymer brick using superplasticizer as a foaming agent. The effects of geopolymeric synthesis parameters such as the sodium hydroxide (NaOH) concentration (6, 8, 10, 12 and 14 M), ratio of foaming agent to water (1/10, 1/20, 1/30 and 1/40) by volume, ratio of foam to geopolymer paste (0.5, 1.0, 1.5 and 2.0) by volume, on the lightweight geopolymer paste that affect the mechanical and microstructure properties were studied in detailed. The compressive strength, water absorption and density were analyzed to determine the mechanical properties of lightweight geopolymer brick. The microstructure properties of lightweight geopolymer brick were tested by using Scanning Electron Microscope. The results indicated that the lightweight geopolymer brick has an optimum NaOH concentration of 12 M, with highest compressive strength of 15.2 MPa at 7 days, an optimum ratio of foaming agent to water (1/10) and ratio of foam to geopolymer paste (1.0) with the highest strength of 16.6 MPa (7 days). A potential new lightweight brick can be produced by using a low-cost foaming agent and easy to process for addition to geopolymer paste.
