The Mechanical Properties and Thermal Resistance of Fly Ash Geopolymer Foams

摘要

In the present work, a comparative study of the thermal performance of unfoamed and foamed geopolymers was investigated. The geopolymers were prepared by mixing fly ash with alkali activator (a mixture of sodium hydroxide and sodium silicate). The geopolymer foams were prepared by adding hydrogen peroxide (H_2O_2, 2wt.% and 4wt.%). The geopolymers were cured at room temperature (29°C) for 24 hours and at 60°C for another 24 hours. The bulk density and compressive strength decreased with increasing H_2O_2 up to 2wt.% and increased when 4wt.% of H_2O_2 was added. In order to test the thermal resistance, the geopolymers were heated at elevated temperature (200-1000°C). Unheated geopolymers showed bulk density and compressive strength in the range of 1.6-1.7g/cm and 15-17MPa, respectively. When heated up to 1000°C, the geopolymers could withstand high temperature without any disintegration and spalling. Both unfoamed and foamed geopolymers showed highest compressive strength at 200°C (17-22MPa). Further decreased in compressive strength was observed upon heating up to 800°C (10-17MPa). The compressive strength regained (14-21 MPa) when heated up to 1000°C The compressive strength was even higher than that recorded at room temperature. In the present work, unfoamed geopolymers showed overall higher thermal resistance than foamed geopolymers.