CORROSION AND MECHANICAL PROPERTIES AND MICROSTRUCTURE OF CEMENT MORTAR CONTAINING CALCIUM SULPHATE WASTE

Abstract

The study presents the preliminary research on the possibility to use the calcium sulphate waste (CSW) as replacing of sand in the cement mortar. The waste was chemically and mineralogical characterized. Four compositions of mortar without and with 7.5 %, 18.78 % and 37.50 % waste were prepared. The X-ray powder diffraction evidenced the main mineral compounds in mortar as hydration products of calcium silicates (CSH) with a low index of crystallinity and different oxide ratio CaO:SiO₂:H₂O, quartz, calcite, anhidrite and gypsum. Optical microscopy reveals that the samples contains aggregates as quartz, muscovite and rocks, especially of metamorphic origin (quartzite, micaschists, and quartzitic schists) embedded in a fine matrix resulted by hydration reactions of cement compounds or reactions of waste components with other compounds from system. The corrosion properties of mortar, at different CSW concentrations, on rebar, were investigated by polarization measurements and electrochemical impedance spectroscopy. The results revealed that at 7.5 % addition of waste anticorrosion properties are improved. As expected, the mechanical resistances (compressive and flexural strenght) decrease with increasing of waste in mortar composition.