The Influence Of Sulphate Attack On ASR In Concrete

Alkali-silica reaction(ASR) and sulfate attack are two of the mostimportant contents in concrete durability. They can both cause expansionand damage in concrete structures. Study on the effect of this interaction，and the resulting concrete damage pattern and interaction mechanism, isneeded in order to have a better understanding of ASR durability．Thisstudy is also important to further understanding of concrete durability．This paper takes compressive and flexural strength, expansion ratio,and relative dynamic elasticity modulus as the macro-parameters tocharacterize concrete damage. The degradation evolution of concretesubjected to combined action of ASR and sulfate attack is detail describedby measuring the changes of these parameters in different age, combinedwith the development of the cracks in the concrete surface. Besides, themechanisms of sulfate attack accelerating ASR, and fly ash and LiOHinhibiting concrete deterioration are further explored by means of SEM,EDS, XRD, MIP and TMS.The thesis concludes that sulfate attack will accelerate ASR and in a certain range, the higher the sulfate concentration is, the more obvious theaccelerating effect is; fly ash and LiOH can inhibit the deterioration ofconcrete caused by combined action of ASR and sulfate attack to a certainextent; the mechanism of sulfate attack accelerating ASR is that, ASRproduces early expansion and causes cracks in concrete surface, after thatASR and sulfate attack occur simultaneously and promote each other;mechanism of fly ash’s inhibition is that fly ash can reduce the formation ofettringite by pozzuolaric reaction and the same time inhibit the furtheroccurrence of ASR; mechanism of LiOH’s inhibition is that the priorreaction between Li~+and silica suppressed the reaction between Na~+(K~+)and silica, forming non-expansive product coating the surface of theaggregate particles, and consequently preventing the further reaction.