Enhancement of the Mechanical Properties of Kaolin Geopolymer Using Sodium Hydroxide and Calcium Oxide

This article presents the effect of adding sodium hydroxide and calcium oxide on the mechanical properties of a kaolin-based geopolymer binder cured at room temperature. A geopolymer binder was first prepared using calcined kaolin as an aluminosilicate precursor and sodium silicate as alkaline activator. The calcium and sodium hydroxide were then added at dosages of 0, 5, 10, 15, and 20% by weight of kaolin, and the compressive strength was measured for specimens cured at room temperature. The results showed that the addition of either 5 wt.% sodium hydroxide or 10 wt.% calcium oxide dramatically increased the room-temperature compressive strength of kaolin geopolymer by 90% and 105%, respectively. The addition of either 5 wt.% sodium hydroxide, or 10 wt.% calcium oxide has also enhanced the water stability of the kaolin geopolymer by about 120%. X-ray diffraction (XRD)and scanning electron microscopy (SEM) test techniques were performed to get insight the binder microstructural phases and its chemical characteristics. (C) 2020 The Authors. Published by Elsevier B.V.