EFFECT OF SURROUNDING CONDITION AND ACID CONCENTRATION ON THE DEGRADATION OF ORDINARY PORTLAND CEMENT BASED CONCRETE IN SULPHURIC ACID

Abstract

As opposed to what was previously believed, the corrosion of concrete sewer pipes brought on by sulfuric acid attack is an issue that affects all countries, not only those with hot temperatures. Only when the pipe fails, causing surface flooding and other severe consequences, is the size of this problem truly understood. Millions of dollars are annually spent worldwide on the maintenance and replacement of cement concrete pipelines that have been affected by sulfuric acid attack. However, there are very few published research that look into the fundamental factors controlling corrosion. Given the aforementioned concern, this study was conducted to examine the effects of exposure circumstances (flowing and stagnant) and acid concentration (pH) on the properties of concrete made using Ordinary Portland Cement (OPC) in sulphuric acid. For a period of 12 months, concrete samples were cast and subjected to sulphuric acid attack with pH 1 and 2 in both flowing and stagnant surroundings. Reduction in compressive strength was used to measure concrete degradation. A scanning electron microscope (SEM) was also used to look at the microstructure of the crumbling concrete in pH 1 after it had been exposed to an acidic atmosphere for a year. At the end of the testing period, it was revealed that samples exposed to the stagnant condition suffered less compressive strength loss than those exposed to the flowing condition. For the concrete specimen in flowing condition the loss of strength was 5.26% and for stagnant condition it was 4.80% for pH 1 while it was 3.5% and 3% for pH 2 with respect to the reference sample at the end of year. Additionally, it was evident from the SEM results that the samples exposed to the stagnant condition had denser structures than the samples exposed to the flowing condition, which led to the degradation of concrete more rapidly in the flowing condition.