Assessment of Sulfate and Chloride in Coastal Soil of Karachi and Their Impacts on Concrete Structure

ABSTRACT

Background and Objective: Coastal corrosion due to sulphate and chloride invasion in concrete structures is common that reduces the life of concrete structures. Hence, selecting the type of cement is one effective measure. Therefore, the main objective of the present study is to determine the sulfate and chloride effects on concrete structures and to suggest cement types for the constructions accordingly. Materials and Methods: For this purpose, soil samples (n = 50) were collected by using a hand auger at a depth of about 4 feet±0.5. The physicochemical and textural characteristics of soil were assessed. Soil pH, Total Dissolved Salts (TDS) and water-soluble salts content (SO4 and ClG) were determined. Results: Data reveal that the soil pH is circum-neutral to alkaline. TDS (range: 0.004-0.4%), chloride (range: 0.001-0.44%) and sulfate (range: 0.04-1.09%) concentrations also cover a wide variations. Sulfate concentration is influenced by the arid climate, soil texture and the occurrence of gypsum fragments. Results of statistical analysis show that soil salinity is mainly influenced by NaCl salts and by soil texture as well. Conclusion: It is concluded that Cl– and SO4 distribution is variable in the study area. Type II, V or I cement+7% silica fume or 20% fly ash is recommended in moderate to severe sulfate exposure sites, respectively. Whereas, Ordinary Portland Cement (OPC) is suggested for minimal sulfate exposure sites such as Benazir Abad Town.