Strength and fire resistance characteristics of geopolymers synthesized from volcanic ash, red clay and waste pen shells

Abstract

This study utilized volcanic ash and red clay, as well as calcined waste pen shell (Baluko) in the production of geopolymer-based materials. The geopolymers were formed by activating the mixture of these raw materials (as the alumina-silica rich materials) with activating solution of 12M NaOH/Na2SiO3 (w/w: 2.5:1). Two sample types, a cube type and a slab type, were used in the study in order to conform to test standards for compressive strength and fire resistance test. The cube type molds were for the compressive strength tests while the slab type was used for the fire resistance tests. Material testing such as Fourier Transform Infrared (FTIR) spectroscopy was used to analyze the chemical characteristics of both the raw materials and the geopolymer specimens. The mixture containing 45% volcanic ash- 45% red clay-10% calcined waste pen shell powder (by weight) was observed to have the highest compressive strength out of all the samples tested. The fire resistance of the geopolymers formed from a ternary mixture of 16% volcanic ash-66.67% red clay- 16% calcined waste pen shell powder (by weight) was also observed to be comparable to that of ordinary Portland Cement (OPC). Furthermore, the FTIR results of both raw materials and geopolymer showed evidence that geopolymerization occurred in the samples, indicating that the selected precursors are viable for use in the formation of geopolymers.