Correlation of Thermal Conductivity Versus Bulk Density, Porosity and Compressive Strength of Metakaolin Geopolymer

Abstract

This paper investigates the correlation of thermal conductivity versus bulk density, porosity and compressive strength of metakaolin geopolymer for different mixing parameters (that are, alkali concentration, activator (AA) ratio and metakaolin/activator (MK/AA) ratio). Metakaolin was alkali-activated with NaOH and Na2SiO3 solution to produce geopolymer. Varying NaOH concentration (6M, 8M, 10M, 12 M and 14M), AA ratio (0.4, 0.6, 0.8, 1.0 and 1.2) and MK/AA ratio (0.6, 0.7, 0.8, 0.9 and 1.0) were used to study the effect on bulk density, porosity, compressive strength and thermal conductivity. Result showed that metakaolin geopolymer with maximum compressive strength (33 MPa), bulk density of 1680 kg/m3, porosity of 18% and thermal conductivity of 0.40 W/mK is achieved with alkali concentration of 10M, AA ratio of 1.0 and MK/AA ratio of 0.8. From the gradation analysis of the strength result, AA ratio is the most influential mixing parameter in determining the compressive strength. In contrast, MK/AA ratio significantly affected the thermal conductivity. From the Pearson correlation coefficient, TC had strong relationship with bulk density and porosity and poor relationship with compressive strength.