Effect Of Salt Containing Al On Inhibiting ASR

AAR is one of the important factors which affect the durability of the concrete. The concrete structures damaged by AAR are diffcult to be repaired. The inhibition of AAR which is happening has been noticed all over the world. In the experimemnt, the samples in which ASR has happened are treated by salt containing Al. The internal mineral compositions and products are also analysed. The effect of Al³⁺ on inhibiting ASR and the mechanism are discussed.Quartz glass is used as the alkali reactive aggregate. By ultra-accelerated mortar-bar test, the effects of different curing mathods are tested, such as different salt containing Al, concentrations of Al³⁺, time of curing in salt solution containing Al and conditions which accelerate Al³⁺ to permeate into the internal of samples. With XRD, SEM and EDS, the reasons of salt containing Al on alkali-silica reaction are investigated.The results show that the effect of salt containing Al on inhibiting ASR is active and the effect of Al(NO₃)₃ on inhibiting ASR is better than that of Al₂(SO₄)₃. Electical field can make Al³⁺ permeate into concret fastly. The results show that when the concentration of Al³⁺ is stationary value, the best curing time is 14 days in the case of no electrical field; the best curing time is 7 days in in the case of electrical field.When Al³⁺ permeates into the interior of samples, the alkali-silica reaction products are altered. The products turn expansive substances into non-expansive zeolite.The adsorption ability of C-S-H gel for alkali is enhanced when Al³⁺ ions are solid solution in C-S-H gel. The adsorption ability of C-S-H for alkali is maximal when the concentration of Al³⁺ reaches deterministic value. The reason is that, the concentrations of Al³⁺ are too high, the C-S-H gel containing Al turns into feldspar, and then the adsorption ability of C-S-H for alkali reduces. The content of available alkali is lower when Al³⁺ permeates into the interior of samples. The content of available alkali is minimal when the concentration of Al³⁺ reaches deterministic value, but the content of available alkali is lower than that of sample untreated by Al(NO₃)₃.