Effect of borax in slag-fly ash-based alkali activated paste

Abstract

Alkali Activated Concrete (AAC) uses source materials rich in aluminosilicates to gain the properties superior to OPC based concrete. Alkaline chemicals are used to activate reaction in aluminosilicate precursors. In this study a combination of Ground Granulated Blast Furnace Slag (BFS) and fly ash with low calcium content (class F) is used as precursor and the activator used to activate the precursor is a combination of NaOH pellets and sodium silicate solution. Research interest in alkali activated materials (AAM) has grown as a result of its unique characteristics, which include less greenhouse gas emissions during its production, effective utilization of industrial waste materials, and sustainable as well as economic attributes. However, its quick setting as well as poor workability are deterring its widespread popularity. Though borax has been identified as a good retarder for cement-based materials, its effect on the blast furnace slag-fly ash-based alkali activated system with respect to the control factors were less investigated. The setting time, penetration resistance and workability of Alkali Activated Paste (AAP) is studied to identify the effect of borax with respect to the control factors. The potential of borax in AAM to improve its workability qualities were studied. According to the experimental results obtained, borax is a good retarder for slag-fly ash-based AAP and it could improve workability.