Study on River Sand Alkali Activity and Engineering Applicability in Northeastern Yunnan
The exploitation of mechanism sand resources in the northeastern region of Yunnan is limited.There is abundant river sand,but most of them are siliceous active aggregates.Direct application will have serious adverse effects on the durability of concrete structures.In order to solve the adverse problem of the direct application of active river sand in highway engineering in northeast Yunnan,the alkali activity of river sand in Huize county of Qujing city and Qiaojia county of Zhaotong city was studied by the combination of mortar bar rapid test and small concrete prism test.Three measures to suppress the alkali silica reaction of active silica aggregates was proposed and their effectiveness was verified.Based on the mechanism of alkali silica reaction,the climatic conditions and environment of the structure in the project area were analyzed,and engineering application strategies for active river sand were proposed.The results show that:The comprehensive detection method combining rapid testing with small concrete prism testing using mortar bars can more objectively evaluate the alkaline activity of river sand and the effectiveness of suppression measures;2)The addition of no less than 20%Grade Ⅰ or no less than 25%Grade Ⅱ fly ash can effectively inhibit the alkali silica reaction;3)When using activated aggregates,appropriate application strategies can be adopted according to the engineering environment.For structural concrete that is directly in water,relative humidity of no less than 80%in the air phase,or has been in a dry wet alternating environment,effective suppression measures should be taken,when using in other environments,it can be used directly without taking any suppression measures.
active aggregatemortar barsmall concrete prism specimeninhibition measuresapplication strategy
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