Study of Chloride Ingress in Concrete Containing Supplementary Cementitious Materials Using Qualitative and Quantitative Tests

Abstract

Chloride ion penetration is one of the process, which is responsible for the degradation of concrete. Concrete structures are exposed to aggressive chloride environments due to constant contact with water having high amount of salts. Chloride ions can break the passivating film of reinforcing bars and lead to the reduction of structural capacity and loss of durability. In recent years, the reduction of water / cement ratio by using superplasticizers and usage of mineral admixures have led to high performance of concrete. In this study, experiments are conducted for evaluation of compressive strength and chloride resistance of concrete by measuring the chloride ion penetration depth and reduction in compressive strength of concrete. In order to evaluate effect of supplementary ce-mentitious material replacement was done of Ordinary Portland Cement with fly ash ,ground granulated blast furnace slag , silica fume and its effect on compressive strength &chloride ion penetration. To find chloride ion penetration depth cylindrical core concrete specimens of size 100 mm diameter and 50 mm height was prepared for Rapid Chloride Permeability Test and Rapid Chloride Migration Test. Here, the two different types of concrete grade i.e. M25 and M40 were prepared by replacing the Portland Cement with 20% and 30% of class F fly ash, 30% and 40% of ground granulated blast furnace slag and 5% of silica fume. Specimens were cured under two curing conditions i.e water curing and curing in sodium chloride solutions. Each set of specimens were cured for 28 days and 90 days with normal water curing and each set of specimens was exposed to 5% sodium chloride solution for 28 days to simulate the seawater conditions. Chloride penetration depth measurements, as well as different non-destructive tests like Rebound Hammer, Ultrasonic Pulse Velocity, Electrical Resistivity were performed at 28 days and 90 days. Correlations was developed between the Rapid Chloride Permeability (RCPT) and Rapid Chloride Migration Tests (RCMT). The results of RCPT and RCMT methods show a considerable decrease in chloride permeability of mixes containing silica fume at the age of 28 and 90 days compared to OPC mix.