Typical deleterious features of alkali-aggregate reaction in concrete structures include cracking and spalling of fragments of surface concrete as ‘op-outs’. Most of the standard tests predict aggregate reactivity by measuring the expansion of specimens. The results just show the change in length and are unable to know the causes of cracking and process of cracking due to AAR. Furthermore, the database for potential alkali reactivity of aggregates in Taiwan contain various test data of aggregate reactivity , the investigation results of suspected cases and the methods of inhibitive AAR. Nevertheless, some regions still lack the inspection results of aggregate reactivity or inspection results differ from investigated results of suspected case. Therefore, we should be carried out the supplementary investigations to add the inspection results.
In the study, a scanner is used to get surface image of the specimens which are made with andesite aggregate grains and immersed in a 1-N concentration sodium hydroxide solution. We can realize that deleterious features due to AAR by observing these images. Therefore, this work which contain the investigation of suspected case and sampling in Su-hua road, No.9 road and rivers of the west are enforced. The aggregates from these areas were carried out mortar bar test, concrete prism test and accelerated mortar bar test to predict potential alkali reactivity of aggregates from areas above mentioned.
The results indicate that the surface crack is caused by differential expansion between the surface and the interior concrete. The other deleterious features include pop-outs, stripes of aggregate particles of surface specimen and the cracks passing through aggregate etc. According to the results of supplementary investigation, we obtain a result that the potential alkali reactivity of aggregates which come from the river along Su-hua road is high. In addition, according to the inspected results of aggregate which come from the river around suspected cases of No.9 road, we know that deleterious features of these suspected cases are possibly caused to AAR.||en_US|