Studying the ability of sewage sludge ash in controlling alkali-silica reaction and it's synergic behavior with natural pozzolans

Sewage sludge is one of the subsidiary products of sewage treatment that should be managed in an appropriate way due to its pollutant components and massive production. One of these methods is incineration. In recent decades, many studies have been done on sewage sludge ash (SSA) as a supplementary cementitious material (SCMs) in concrete. On the other hand, one phenomena leading to deterioration of concrete, is alkali-silica reaction (ASR). One way to control this reaction is through using SCMs that prevent the formation of alkali-silica gel and expansion by consuming alkalis available in cement paste. According to results obtained from SSA utilized as SCM in former studies, it is possible that it could prevent ASR in concrete by decreasing the alkali content. However, very few studies have been done on this issue. In this study, SSA was used as a replacement for cement at 10, 30 and 50% levels in order to assess its ability to control ASR. In addition, the effect of trass and pumice as natural pozzolans in improving its ability to control ASR was investigated. The results revealed that only at 50% replacement level, SSA was able to control the ASR expansion in mortars. However adding 5% trass or 10% pumice improved this ability to a considerable extent.