The Inhibition Of Alkali Aggregate Reaction Of Slate

Alkali-aggregate reaction in concrete due to reaction of alkali and aggregate generating expansive gel, cause concrete damage.The chemical reaction impacts the durability and life of concrete structure greatly. One of the features is the reaction time is very long, at least 10 years. Discovery, detection and suppression of alkali-aggregate reaction has a certain degree of difficulty.The mechanism of alkali-aggregate reaction is not very clear now.There are two kinds of AAR:one is alkali-silica reaction, the other is alkali-carbonate reactions.As exposition of the related industry regulations:using suppression measures, the aggregates of weak alkali-silica reaction can be used, but alkali-carbonate reaction prohibited. This paper studies the alkali-silica reaction.Alkali-silica reaction can be tested through observing of aggregate composition, simulation of concrete expansion or testing aggregate active substances and other methods. Observing aggregate composition is carried out through petrographic analysis.The tests of stimulating concrete expansion include motar bar method and prism method.When using different method,the size of the specimen and curing congdition varied correspondingly. The basic principle of all methods is measuring the expansiong of the specimen contain reactive aggregte to evaluate the degree of alkali-aggregate reaction. Testing for discoverying aggregate active substances is chemical method, but the result of the method is unstable and unbelieveble. Sometimes it is a auxiliary method and we use other methods frequently.In this paper, fly ash, slag and silica fume used separately and combined to inhibit alkali-aggregate reaction has been studied by use of the accelerated motar bar. We have found that while using 30% fly ash and 5% silica fume can restrain the alkali-aggregate reaction. Using 30% fly ash mixing in cement is also satisfactory to inhibit ASR. We propose two techniques for suppress ASR. Usually mixing 30% fly ash. Mixing 30% fly ash and 5% silica fume meanwhile under high humidity environment.After that effectiveness of the measures of suppression were studied using small prism method. The expansion rate of the prism made of slate aggretate is lower meeting the requirements and the inhibition rate greater than 75%.The long-term inflation trend of alkali-silica reaction has been studied using the accelerated mortar bar, and the inhibitory effect of the low content of alkaline admixture and the alkali active material. We found that the expansion of ASR developed exponentially and alkali-silica reaction expansion was infinite, but the rate tended to zero. The bar's swelling characteristics of significant changes will occur early, the value and rate of inflation decrease obviously. Over time, low-volume fly ash will promote the alkali-silica reaction expansion. But the corresponding relationship of the failure time between the laboratory and application environment is not clear. Alkali active material inhibitory effect on the ASR expansion is prominent, when the expansion rate in the 224d is still less than 0.01%.