Mechanical, microstructural and acid resistance aspects of improved hardened Portland cement pastes incorporating marble dust and fine kaolinite sand

Abstract The objective of this research is the implementation of low cost solid wastes like marble dust (MD) and fine kaolinite sand (FKS) aspiring to upgrade mechanical, microstructure and acid resistance aspects of the hardened Portland cement pastes. Diverse blends of (OPC-MD-FKS) were adapted and then were cured under tap water for hydration up to 90 days. Physico-chemical and mechanical aspects of the fabricated specimens were evaluated via determination of compressive strength values (MPa) and water absorption percentages (%) at diverse durations of hydration (1, 3, 7, 28 and 90 days). The deterioration actions of disparate acidic media towards selected hardened mixes were assessed via immersing the 28-days hydrated pastes in 5% sulfuric or 10% acetic acid solutions for 1, 2, 4 and 6 months. Microstructure and phase configuration of the developed hydrates were explored via scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential thermal analysis (DTA) techniques. The attained consequences acknowledged that partial substitution of OPC by up to 20% MD boosted compressive strength magnitudes and sorptivity of the hardened pastes. In addition, OPC-MD hardened pastes exhibited higher resistance to the deterioration action of sulfuric acid compared to those containing additional FKS. On the other hand, acetic acid ascertained to have severe deterioration action towards all investigated blends after 6 months of immersion due to the progression of soluble salts.