Study of Concrete Properties under Acid Attacks
Acidic attack on concrete imparts a unique set of damage mechanisms and manifestations compared to other durability issues of concrete. Sulfuric acid attack limits the service life of concrete elements and, thus, results in increased expenditures for the repair or in some cases replacement of the whole structure. To date, there is lack of standardized tests for specifically evaluating the resistance of concrete to sulfuric acid attack, which has caused great variability, for example in terms of solution concentration, pH level control, etc., among previous studies in this area. Accordingly, there are conflicting data about the role of key constituents of concrete e.g. supplementary cementitious materials SCMs , and uncertainty about building codes’ stipulations for concrete exposed to sulfuric acid. Hence, the first objective of this thesis was to assess the behaviour of the same concretes, prepared with single and blended binders, to incremental levels mild, severe and very severe of sulfuric acid solutions over 36 weeks. The test variables included the type of cement general use GU or portland limestone cement PLC and SCMs fly ash, silica fume and nano silica . The severe 1 , pH of 1 and very severe aggression 2.5 , pH of 0.5 phases caused mass loss of all specimens, with the latter phase providing clear distinction among the performance of concrete mixtures. The results showed that the penetrability of concrete was not a controlling factor, under severe and very severe damage by sulfuric acid attack, whereas the chemical vulnerability of the binder was the dominant factor. Mixtures prepared from PLC performed better than that of counterparts made from GU. While the quaternary mixtures comprising GU or PLC, fly ash, silica fume and nano silica showed the highest mass losses after 36 weeks, binary mixtures incorporating GU or PLC with fly ash had the lowest mass losses.
Acid attack, Concrete durability
S. Durgasravanthi | M. Krishna Kumar