Effect of nano sand on the properties of metakaolin-based geopolymer: Study on its low rate sintering

The main goal of the present work is to optimize the effective percentage of nano sand which leads to improving the properties of kaolin-based geopolymer. An attempt to study the low rate sintering of the prepared geopolymer at 800, 1000 and 1200 degrees C was also investigated. Various percentages of nano sand i.e. 2.5, 5, 7.5 wt-%, were added to alkali-activated kaolin-based geopolymers. The phase composition and microstructure of none sintered and sintered geopolymers were examined by X-ray diffraction and scanning electron microscope. Fourier-transform infrared spectroscopy was also utilized to confirm the composition of prepared geopolymers. Furthermore, the bulk density, apparent porosity and compressive strength of prepared geopolymers were also determined. The results showed that the physical properties, microstructure and compressive strength of none sintered and sintered geopolymers were improved after adding 2.5% nano sand. 2.5% nano sand was suitable to increase the polymerization, fill the open pores and consequently enhanced the properties. The compressive strength of none sintered geopolymer that contains 2.5% nano sand was 60 MPa while that of geopolymer sintered at 1000 degrees C was 95 MPa. The higher percentages of nano sand (5 and 7.5%) deteriorated the properties of prepared geopolymers. (C) 2020 Elsevier Ltd. All rights reserved.