Effect of water on the thermal properties of argillite – based geopolymers.

Abstract

This study focuses on the effect of consolidation time and water immersion on the thermal behavior of geopolymers based on mixture of kaolin and argillite calcined at 750 °C. In order to assess the fire resistance water and thermal treatment at 1000 °C were performed. Compressive strength and structural changes of the samples before and after treatment were investigated. It was demonstrated that the age of geopolymer (7, 14 and 28 days of consolidation) does not have a significant effect on strength neither before (22 MPa) nor after (30 MPa) thermal treatment. The results also show that all samples present higher compressive strength ratio (σafter/σbefore ~ 1.4). The geopolymer samples do not exhibit structural variation over the time in agreement with the compressive strength values. The good performance of compressive strength after 1000 °C was due to the formation of the same crystalline phases after heat treatment such as zeolite (4%) and leucite type phases (62%) and wollastonite (18%) which were also evidenced by SEM observations. The decrease of compressive strength after water immersion (16 MPa) and after thermal treatment (19 MPa) was explained by the decrease of arcanite by 70% as well as the amorphous phase content. Nevertheless, leucite (46%) and wollastonite (24%) were formed. In conclusion, the use of mixture of kaolin and argillite calcined at 750 °C leads to water and thermal resistant geopolymers.