Effect of Glutinous Rice Flour on Mechanical Properties and Microstructure of Cement-based Materials

The mechanism of glutinous rice flour, a kind of natural admixture, on the hydration process, setting time, and microstructure of the Portland cement was investigated. The experimental results show that the glutinous rice flour has an obvious setting retarding effect on cement pastes. The optimal dosage of the glutinous rice flour is 3wt%. In this case, the initial and final setting time of the paste are delayed by 140 and 185 min, respectively. The flexural and compressive strengths of the hardened paste are increased by 0.35% and 0.07% after 56 d of curing. The glutinous rice flour hinders the mineral dissolution process and decreases the concentration of calcium ion at the initial stage of hydration due to the complexation effect, thereby hindering the nucleation and growth of CH and C-S-H phases and prolonging the hydration process. However, C-S-H phases combine with the glutinous rice flour to contribute the bonding effect together, which compacts the microstructure of hardened cement pastes at the later hydration stage of cement pastes. Thus, in-depth investigation on the utilization of glutinous rice flour as the admixture for the Portland cement is expected to be meaningful for the control of hydration exothermic rate and setting time.