Development of Hybrid Composite Rice Husk Ash (RHA)–Geopolymer for Bricks Bearing Buildings

The aim of this study is to synthesize hybrid composite rice husk ash (RHA)-geopolymer as materials for bricks bearing buildings application. Class-C fly ash was used as raw material and rice husk ash (RHA) taken directly from the field, washed and dried at 100°C for 4 hours. Geopolymers were synthesized through alkali activation method at 60°C for 1 hour with its molar oxide ration of SiO 2 /Al 2 O 3 = 3.0, Na 2 O/SiO 2 = 0.2, and H 2 O/Na 2 O = 10. There were three series of samples produced by mixing fly ash with addition of 5%, 10% and 15% RHA (relative to the mass of fly ash). The samples were tested after 7 days. The highest compressive strength were 26 MPa which is reached by samples containing 10% RHA. The fire resistance measurement showed that the addition of RHA improved fire retardancy of geopolymers. The samples were immersed in 1 M H 2 SO 4 solution for 4 days for acid resistance examination. The X-Ray Diffraction was performed to examine the chemical compositions of the samples before and after the test took place. Scanning Electron Microscopy (SEM) was performed to examine the morphology of these samples surfaces. The addition of 10% RHA in geopolymer showed its excellent properties in terms of mechanical strength, thermal properties, and acid resistance. The study suggests that hybrid composite RHA-geopolymer and can be developed as bricks bearing buildings.