Investigation of alkali-carbonate reactivity of dolomitic aggregates

Some reinforced concrete bridges have been deteriorated by alkali-silica reaction (ASR) in our country during the last decades. However, deleterious effects of ASR for concrete structures have been known since 1940. There are a lot of experimental studies denoted on ASR in Turkey and in abroad. Alkali carbonate reaction (ACR) in concrete is a kind of alkali aggregate reactions and detrimental effect of it has been known since 1950. However, the detailed investigations have not been conducted on ACR and damage has not been reported yet due to ACR in our country. Dolomites are now used in the production of concrete and it is expected that this phenomenon will be important for the construction industry in near future. Dolomite and limestone convert to the brucite and calcite due to alkali carbonate reaction which causes expansion in concrete and map cracking. Different investigators suggested different preventing measurements in the literature. According to some resources mineral admixtures and lithium salts are effective for preventing the ACR. However, contradictory test results have also been reported.Firstly, a reactive aggregate from Turkey was chosen. Then, influence of mineral and chemical admixtures on controlling the reaction was investigated by conducting two accelerated test methods (AAR2 and AAR5). In order to compare those test results, Canada aggregate, which is considered as reference Alkali-Carbonate reactive aggregate, was supplied and the same tests were also conducted on this aggregate. Development of the reaction was observed by petrographic examinations and SEM analysis.It was seen that both ASR and ACR are available in both of the aggregates. Mineral and chemical admixtures are effective on certain degrees on controlling the reaction.