From the experimental results, it is found that in the concrete system with high active Al 2O 3 contents, the ASR expansion happenes, but the total quantity and the continued period of it is smaller than that of the concrete with common Al 2O 3 contents at the same conditions. The active Al 2O 3 can not only weaken but also brake the ASR expansion. The reason is that the products of the ASR is the alkali alumi silicates but not alkali silicates hydrogel in the concrete of richer active Al 2O 3 presents. This hydrogel has a high tendency of crystallization. Once the zeolite minerals are formed, their volumes will not expand or contract because of the water getting in or out. If the quantity of the Al 2O 3 is properly introduced, the ASR expansion can be forecast and used.