Development of Green Geopolymer Using Agricultural and IndustrialWaste Materials with High Water Absorbency.

Geopolymer is a promising porous material that can be used for evaporative cooling applications. Developing a greener geopolymer using agricultural and industrial wastes is a promising research area. In this study, we utilize rice husk (RH), rice husk ash (RHA), metakaolin (MK), ground granulated blast furnace slag (GGBS), and palm oil fuel ash (POFA) to prepare geopolymer pastes, with alkali liquid as an activator. Many geopolymer samples have been prepared as per the Design of Experimental software (DOE), and its corresponding response surface mode and central composite design and later they were characterized. The samples were cured in an oven for 2 h at 80 °C, and thereafter stored at room temperature (~25-30 °C) prior to being tested for its water absorption and compressive strength. The effect of the different composition of precursors on water absorption, density, porosity, and the compressive strength of the prepared geopolymers have been investigated. The results showed that the compressive strength of geopolymers is directly proportional to the ratio of the alkali liquid. Post-optimization, the best geopolymer paste mixture was confirmed to contain 10% of RH, 15% RHA, 35% MK, 10% POFA and 30% of GGBS, with 72% desirability for maximum water absorption (~38%) and compressive strength (4.9 MPa). The results confirmed its applicability for evaporative cooling. [ABSTRACT FROM AUTHOR]