Development of Eco-Friendly Mortars Produced with Blast Furnace Slag, Calcined Eggshell and Brick Waste: Mechanical Behavior and Microstructure Assessment

The granulated blast furnace slag exhibits pozzolanic reactivity when combined with appropriate activator and can be used in a wide range as cement replacement. The aim of this study is to investigate the effect on the mechanical and microstructure properties of incorporating admixture composed by granulated blast furnace slag (GBFS), calcined eggshell (CES), and brick waste (BW), as replacement of cement in the formulation of mortar. Ten different mixes of mortar prismatic specimens were tested with different replacement levels of raw materials (50, 75, and 100%). The results show that the increase in the proportion of raw materials decreases significantly drying shrinkage, dry unit weight and strengths of mixtures mortar compared to control mortar at early age. The decrease in strengths is less important in the long term due the development of pozzolanic reaction. Moreover, the water absorption and open porosity were increased for all cases. The microscopic analysis by Scanning Electron Microscopy (SEM) shows that the proportion of 15% of calcined eggshell powder in admixture, provides more Calcium Silicate Hydrate gel (C-S-H) in the internal cementitious matrix of the mortar, which explains the best mechanical strength provided by this mixture.