Application of mixture design of experiments to the development of alkali-activated composites based on chamotte and waste glass

Abstract

Alkali-activated binders have been indicated as possible replacement for Portland Cement with environmental benefits. However, an adequate dosage of raw materials and alkalis content is mandatory to obtain alkali-activated materials with suitable physical and mechanical characteristics. The aim of this work is the application of mixture design of experiments to determine optimal dosages for pressed alkali-activated composites based on two precursors: chamotte (C) and waste glass (WG). Fine sand (S) was used as aggregate. Ten mixtures were obtained from the experimental design, and cylindrical samples were cast by uniaxial pressing. The alkalis/precursor ratio was kept constant for all the mixtures. After curing, the physical, mechanical and microstructural characteristics of the specimens were assessed. The application of desirability function revealed that the optimal composition was the one with higher content of sand (50%), 30% chamotte and 20% waste glass. The addition of sand contributed to reduce porosity and increase the particle packing, promoting the increase of mechanical strength. Regarding compressive strength, almost all the mixtures met the requirement for solid bricks. This study demonstrates the potential of using mixture design of experiments as an efficient tool to determine the proper composition and predict the behavior of waste-based alkali-activated materials.