Characteristics of metakaolin-based geopolymers using bemban fiber additives

Abstract

The aim of this study was to investigate the chemical composition and thermal properties of kaolin, the physical properties of metakaolin, and the mechanical properties of metakaolin-based geopolymers using bemban fiber. Kaolin was calcinated to become metakaolin at 600 ℃ for 2 h for optimum conditions. The chemical composition of kaolin mostly consisted of 59.30% SiO2, 34.30% Al2O3, and 3.06% Fe2O3. The transformation of kaolin into metakaolin with temperature was determined through thermal stability tests and analyzed using thermogravimetric analysis (TGA) and differential thermal analysis (DTA). Regarding the thermal properties of kaolin, predehydroxylation occurred at 31.07–92.69 ℃, dihydroxylation occurred at 400–600 ℃, and the endothermic peak in the DTA curve was recorded at 505.63 ℃. This research also analyzed the physical and mechanical characteristics of metakaolin-based geopolymers, with the additional variation percentages of bemban fiber alloys resulting from a 3% NaOH alkalization treatment for 2 h. The test results indicate that the bemban fiber improves the physical and mechanical characteristics of geopolymers. This improvement is related to the enhanced geopolymer characteristics, including a water absorption capacity of 1.10%, porosity of 2.32%, compressive strength of 35.33 MPa, and splitting tensile strength of 11.29 MPa with the addition of 1.5% bemban fiber. Although the split tensile strength increases as the fiber content increases, adding 1.5% of bemban fiber is optimum because a higher content decreases the workability of mixtures.

Keywords

• geopolymer mortars
• bemban fiber
• metakaolin
• porosity
• compressive strength