Impact of organic carbon on hardened properties and durability of limestone cement concrete

In this paper, the effect of organic carbon in ground limestone on the properties and behavior of Portland limestone cement (PLC) concrete in normal and aggressive medium was studied. Three different sources of limestone with total organic carbon of 0.94, 0.48 and 0.18% were considered, the cement replacement ratios were 0, 10, 15, 20 and 25% by weight and water to binder ratio was 0.55. Mechanical properties, XRD and TGA experiments were conducted to evaluate the effect of the previous variables on hardened properties of concrete and hydration process of cement paste. Corrosion rate and polarization resistance of reinforcing PLC concrete specimens immersed in 5.0% sodium chloride solution for 12 months were measured using potentiodynamic polarization resistance technique. The sulfate resistance of PLC concrete specimens was also investigated. Concrete specimens exposed to wetting and drying cycles in 5% magnesium sulfate solution for 18 months were tested. SEMs of limestone cement paste after magnesium sulfate exposure were performed. The results emphasize the essential role of organic carbon on the properties and behavior of PLC concrete for both normal and aggressive medium especially at high ratios of cement replacement with limestone. (C) 2015 Elsevier Ltd. All rights reserved.