EVALUATING THERMAL PROPERTIES OF GEOPOLYMER PRODUCED FROM RED MUD, RICE HUSK ASH AND DIATOMACEOUS EARTH

Abstract

In this paper, thermal properties of geopolymer from the mixture of red mud, rice husk ash, and diatomaceous earth were investigated. Red mud is an industrial waste from bauxite plants which has a negative impact to the environment if not properly managed, especially for countries mining this bauxite ore. On the other hand, rice husk ash is an agricultural waste abundant in Asian countries whereas diatomaceous earth is a natural mineral locally abundant in some parts of Vietnam. In this study, red mud was mixed with rice husk ash and diatomaceous earth at high alkaline condition to synthesize geopolymer, an inorganic polymer materials produced from geopolymerization reactions forming the alumino-silicate network. For thermal specifications of the geopolymer products, thermal conductivity, the thermal expansion and thermal gravimetric (TG) values from room temperature to 950 oC are measured. For example, the coefficient of thermal conductivity at room temperature was measured around 0.5 W/m-K, the coefficient of thermal expansion around 950 oC is in range of 5.71x10-6 K-1 to 12.42x10–6 K–1 and TG at 950 oC is below 10%. Response surface method was also used to determine the thermal properties of geopolymer as a function of mix proportions of raw materials. The study also investigated the changes of microstructure when the geopolymer is subjected to high temperature via X-ray diffraction (XRD) and scanning electron microscopy (SEM).