The Effect of Rice Husk Ash Geopolymer Microstructure Reactivity on the Bonding of Alkaline Solutions and Its Impact on Geopolymer Concrete Strength

This study explored the impact of rice husk ash (RHA) granulometry on the adhesive strength of geopolymer concrete material and examined how the various sizes of RHA influence the overall strength of geopolymer concrete. The RHA is burned at a temperature of 700°C using a furnace, followed by filtration and grinding to produce a finer RHA powder. The RHA powder is mixed with sand, ordinary Portland cement (OPC), and a 12M alkaline solution until it becomes a paste, then placed into a mold to form test specimens. The compressive strength of the test specimens was evaluated after a curing period of 28 days. The Scanning Electron Microscopy (SEM) test was carried out to demonstrate that the bonding of RHA particle sizes affects the adhesive strength. The results show that (a) typical chains of manually and furnace-burned RHA both result in amorphous particles with short-chain bonds, and (b) manually burned RHA exhibits higher compressive strength, which can be explained by the fact that amorphous silica reacts with Ca(OH)₂ in the cement to form C-S-H gel, enhancing strength. These findings are discussed in the context of the reactivity of the geopolymer microstructure between manually burned RHA and furnace-ground RHA.