Stabilized homogeneous porous structure and pore type effects on the properties of lightweight kaolinite-based geopolymers

Abstract

Hydrogen peroxide and metal powders are widely used as foaming agent to prepare lightweight cementitious materials including geopolymers; however, it is difficult to control the generated cell size due to high reactivity of the system. This study aimed to investigate the influences of sodium lauryl ether sulfate (SLES) foaming agent on pore types and properties of lightweight kaolinite-based geopolymers suggested to be used as thermal insulation. The results revealed that the SLES enhanced the porosity, therefore leading to low density, strength, and thermal conductivity. The lightest geopolymer having a bulk density of 0.69 g cm−3 and total porosity of 72.34% was obtained when 15 wt% SLES was employed. It exhibited adequate compressive strength of 4.69 MPa with very low thermal conductivity of 0.197 W m−1 K−1 that suitable for using as thermal insulation. In addition, the open and total porosity of geopolymer increased significantly as the amount of SLES increased, while the closed porosity increased to the maximum value at 10 wt% SLES and decreased afterward. At this condition, a stabilized homogeneous porous structure was obtained. Regression analysis was adopted to study the relationships between the amount of SLES and pore types with properties of the lightweight geopolymers. It was revealed that the amount of SLES exhibited linear relationships with porosities and properties of the lightweight geopolymers. R-squared values indicated that the total porosity had the strongest effect on all properties except for water absorption, which was highly affected by the open pores. The closed pores had the strongest effect on the compressive strength.