Improvement of the reactivity of soda–lime–silica glass solution as a hardener for producing geopolymer materials

Abstract

The aiming target of this study is to improve the reactivity of the soda–lime–silica glass solution as a hardener for producing metakaolin-based geopolymer cements. The hardeners with molar ratios SiO2/Na2O equal to 1.5 from rice husk ash and waste glass were prepared. Due to the low dissolution of waste glass, the molar ratio SiO2/Na2O in soda–lime–silica glass solution is less than 1.5 suggesting thus the lower soluble silica content. In order to compensate for the deficiency of soluble silica in soda–lime–silica glass solution, the hardener from rice husk ash is added to the soda–lime–silica glass solution at different percentage such as 0, 20, 30, 40, 50, 60, 70, 80 and 100 wt%. The reactivity of the obtained hardeners was evaluated by using them for producing geopolymer cements. The X-ray pattern and infrared spectrum of residual waste glass indicate the higher intensity of the broad hump structure and the higher value of the wavenumber of the main band, respectively. This corresponds to the higher amount of glass phase contained in the residual waste glass. It was found that the values of the compressive strengths and the apparent density increase with increasing the addition of hardener from rice husk ash to the one from waste glass. The micrographs of geopolymer cements from hardeners containing 40, 50 and 100 wt% of sodium waterglass from rice husk ash are homogeneous and compact microstructure. This implies the formation of the higher connectivity and the long chain of poly(sialate-siloxo) network. The new approach for the preparation of a reactive hardener from the waste glass is found promising for the significant reduction of the greenhouse gas emitted during the production of geopolymers.