Effects of different mineral admixtures on carbonation resistance of lightweight aggregate concrete

• We prepared the lightweight aggregate concrete (LWC) containing different mineral admixtures.
• We studied the carbonization characteristics of LWC.
• Internal pH of sample with grade II fly ash or steel slag decrease significantly.
• High volume mineral admixture replacing cement decreases the internal pore solution’s alkalinity of LWC.
• Effects of pulverized fly ash and granulated blast furnace slag on LWC alkalinity are not obvious.

Cement has been replaced respectively by equivalent grade II fly ash, pulverized fly ash, granulated blast furnace slag and steel slag, preparing the lightweight aggregate concrete containing mineral admixture. The carbonization characteristics of concrete were studied by the accelerated carbonation experiment and the test of concrete pore solution’s pH, afterwards the influence mechanism of different mineral admixtures on carbonation resistance of lightweight aggregate concrete was analyzed. The results indicate that the carbonation depth of the samples containing grade II fly ash and steel slag powder are higher than that of the reference sample, while their pore solution’s pH at different depths are also lower than those of the reference sample. Moreover, the later-stage carbonation resistance of the samples containing 20% of pulverized fly ash and granulated blast furnace slag are better than that of the reference sample, and the 28 days carbonation depth of which are only 77.6% and 86.2% of the reference sample respectively, while their pore solution’s pH are very close. Therefore, it is concluded that the neutralized velocity of the lightweight aggregate concrete could be delayed to some extent because of the higher fineness of pulverized fly ash and granulated blast furnace slag. Moreover, when cement is replaced by large amount of admixture, the carbonation process of lightweight aggregate concrete has an accelerating tendency with the increase of admixture content.