Strength and durability properties of concrete blended with pumice and scoria under combined attack of sulphate and chloride

Abstract

Concrete structures suffer serious deterioration under corrosive environment. Consequently, the safety of these concrete structures is decreased. The influence of natural pumice (NP) and natural scoria (NS) as supplementing cementing materials of concrete exposed to sulphate, chloride and combined effect of sulphate and chloride is studied. Portland cement (PLC) was replaced with NP or NS at a substitution level of 10%. Concrete samples were submerged in portable water for 28 days. Afterwards, the specimens were immersed in 5% sodium sulphate (Na2SO4), 5% sodium chloride (NaCl) and combined sodium sulphate and chloride solutions for 28, 56 and 90 days. The results were compared between concrete mixes with NP or NS and control mix (CT) with PLC. The effects of sulphate, chloride and combined sulphate and chloride were evaluated in terms of change in weight, variation in compressive strength and degree of damage. The compressive strength was not compromised at 10% substitution level. It was observed that, concrete containing NP and NS have compressive strength of 46 MPa (7.7%) and 44 MPa (3.04%) higher than 42.7 MPa of CT submerged in water for 90 days respectively. Concrete samples immersed in 5% Na2SO4 solution, NP and NS has a compressive strength around 45.5 MPa (15.4%) and 44.8 MPa (13.6%) higher than 39.4 MPa of CT mix at 90 days, respectively. However, under 5% NaCl solution the compressive strength of concrete containing NP and NS decreased up to 34.2 MPa (7.5%) and 32.5 MPa (7.2%) for 90 days cured samples. Moreover, under combined effect of 5% Na2SO4 and 5% NaCl concrete containing NP and NS has a compressive strength around 29.8 MPa (8%) and 29.2 MPa (7.3%) higher than 27.4 MPa of control mix at the exposure period of 90 days. It can be concluded that NP and NS have extraordinary potential to be utilized as a cementitious material in concrete.