Suppressing Measure And Suppressing Mechanism Study On Alkali-Aggregate Reaction

As early as the late 1950s China had learned from the damage due to AAR in the overseas civil engineering, and takes the corresponding preventive measures. But until 1990 before the destruction caused by the AAR in the intersection, airports, industrial and civil buildings, we attached importance to study alkali-aggregate-reaction. Mineral admixture is one of the most commonly used measures, A number of experts and scholars studied the mechanism of depressing AAR on the slag, fly ash and etc. but because of the environment and the different methods, the conclusions are not always the same. In order to resolve the differences, and take more effective preventive measures, It's necessary to have a deep study on the mechanism of the admixture depressing alkali-silica reaction.The study is combined with the latest domestic research results "the experimental practices of the effectiveness about the beam-concrete' admixture depressing the alkali-aggregate reaction in Qinghai-Tibet Railway ", taking the Accelerating Motar-bar Method to study the mechanism of lag, fly ash, sulfur-aluminum cement depressing alkali-silica reaction, then observing the reaction products of different specimen under the scanning electron microscopy.The main conclusions reached by the analysis: 20℃is a better temperature for testing in the Accelerating Mortar-bar Method; Much of Ca (OH)₂ is used up, the hydration calcium silicate which has lower n(Ca)/n(Si) is produced,numbers of alkali is fixed and reduce the reaction with the active SiO₂ are the reason why the slag and fly ash can depress alkali -silica reaction; sulfur-aluminum cement lacks of Ca(OH)₂, and it's not easy to react with the active SiO₂. So it can be used to guard against the alkali-silica reaction with the Portland cement or only itself.