An experimental investigation into the mechanical performance and microstructure of cementitious mortars containing recycled waste materials subjected to various environments

This paper deals with an experimental investigation into the mechanical performance and microstructure characteristics of the cementitious mortars containing recycled waste materials subjected to acidic, neutral and alkaline environments. The recycled waste materials include glass, eggshell, iron and rubber powder in various amounts, namely 7, 14 and 21% by volume, as the replacement for ordinary Portland cement (OPC). In this respect, to examine the mechanical performance of the specimens, the compressive, tensile and bending strength tests as well as water absorption test were carried out at the ages of 7, 28 and 90 days. Moreover, to study the microstructure of the specimens, the scanning electron microscopy (SEM) and x-ray diffraction (XRD) tests were conducted accordingly. For curing the specimens, three different environments with PH values of 2.5, 12.5 and 7 representing the acidic, alkaline and neutral environments, were taken into account. Promisingly, it was observed that inclusion of the recycled waste ma-terials, significantly enhanced the mechanical properties of the mortar when exposed to the acidic curing conditions. Lastly, the results derived from the microstructure tests revealed that as a result of replacing cement with the glass, iron and eggshell powders, the width of cracks and volume of the pores decreased by three times and importantly, the bonding between the cement paste and additives was strengthened.