Properties of fly ash and rice husk ash blended geopolymer with sodium aluminate as activator solution

摘要

The study investigates properties of blended geopolymer based on fly ash (FA) and rice husk ash (RHA) activated with sodium aluminate as aluminum additive. Five series of geopolymer paste were studied with ratios of FA: RHA as 100:0, 75:25, 50:50, 25:75 and 0:100. Phase identification and quantification were performed by X-ray Diffraction (XRD). Fourier Transform Infrared Spectroscopy (FTIR), field emission scanning electron microscope (FESEM) were used to characterize the microstructure of the specimen. Quantification of the elements present were performed by Energy dispersion X-Ray Analysis (EDX). Compressive strength along with physical parameters such as bulk density, water absorption, sorptivity, apparent porosity was determined. Results shows that 25% replacement by RHA is the optimal percentage on physical-mechanical properties of the blended geopolymer. The finer particles of RHA filled the voids present in the geopolymer matrix through filling effect and enriched the gel which densify the specimen. SEM micrographs also validates the denser matrix of the specimen at the optimal replacement percentage. However, it was seen that blending of RHA with FA beyond the optimal 25% has a negative effect on the properties studied. The observation may be attributed due to the presence of zeolite X as confirmed by Quantitative XRD. Increase in the amount of zeolite X and its crystalline size has a negative impact on the compressive strength of the blended geopolymer. The present study is expected to provide a practical solution of utilizing FA and RHA solid waste in construction activities.