Study On Alkali Aggregate Reaction Of Concrete In Qinghai-Tibet Plateau

Alkali Aggregate Reaction is the most important factor affecting the durability of concrete,because the characteristics of the reaction are slow,even for decades,and the short term is not easy to be found in the actual project.Once the reaction occurs,the crack is not easy to repair.At present,the most effective way to prevent the destruction of alkali aggregates is by adding mineral admixture.In this paper,the alkali activity of aggregates in Xining city and surrounding areas was studied,and the inhibition measures were put forward for the active aggregates of Alkali Aggregate Reaction.Research of mineral admixtures on Qinghai-Tibet Plateau region of Alkali Aggregate Reaction silicon inhibition,advance through outdoor on the aggregate survey sampling and identification of Qinghai-Tibet Plateau,and through the rapid screening of aggregate,mortar bar late selection of fly ash and silica fume mineral admixtures for Alkali Aggregate Reaction activity of sand and gravel aggregate inhibition and microscopic mechanism research.The following main conclusions are obtained through experiment and analysis show that:(1)For the two lower activity north of the city of stone,stone aggregate of Datong,when choose the content of 10% or15%or20% silica fume,expansion rate is less than 0.1% in the next 14 days,the expansion could effectively inhibit AAR.And for the north sand high activity of aggregates,when choose the admixture of 20% silica fume,the expansion of 14 days is less than 0.1%,can effectively inhibit AAR expansion.The higher the activity of the active aggregates,the lower the expansion inhibition rate of silt.(2)For the three lower activity south of the city of sand,stone aggregate of Duoba,when choose the content of 10%or 20% or30% of fly ash,expansion rate is less than 0.1% in the next 14 days,the expansion could effectively inhibit AAR.For the Huzhu sand with high activity of aggregates,when choose the admixture of 30% fly ash,its 14 days expansion is reduced to 96%,which can effectively inhibit the expansion of Alkali Aggregate Reaction.In the case of the four active aggregates with 10% mixing amount,the inhibition effect of 10% silica fume is better than that of 10% fly ash.There is a certain inhibitory effect on the reaction of the mixture to the base silicic acid.When the silica fume and fly ash content are different,the inhibitory effect is different.Only when the silica fume and fly ash content ratio is 3,the aggregate expansion rate of each region is the lowest,and the inhibition effect is the best.(3)The addition of mineral admixtures can reduce the content of Na and K,and consume the alkali content in the solution,so as to make the morphology system more dense and prevent further reaction of alkali and aggregates.(4)Using the fly ash and silica fume can effectively inhibit the Alkali Aggregate Reaction of sand and stone aggregates in Xining area.