Carbonation and electrical resistance of self compacting concrete made with recycled concrete aggregates and metakaolin

The paper presents the results of an investigation conducted to examine the carbonation and electrical resistance of self compacting concrete (SCC) made with coarse recycled concrete aggregates (RCA). Self compacting concrete mixes were prepared by systematically replacing coarse Natural Aggregates (NA) by RCA at 0, 25, 50, 75 and 100%. In order to study the carbonation resistance of SCC made with RCA, accelerated carbonation tests were conducted for an exposure period of 4, 8, 12 and 16 weeks. The four probe method was used for electrical resistivity tests. The results indicate that with the increase in RCA content as replacement of NA, decrease in the carbonation resistance of SCC has been observed. For example, at 28 days of curing and 16 weeks of exposure, the carbonation depth of SCC mix containing 100% RCA has been found to increase nearly by 58% compared to that of SCC mix made with 100% NA. Similarly, electrical resistivity of SCC made with 100% RCA has been found to decrease nearly by 48% compared to that of control concrete at 28 days of curing. The addition of 10% Metakaolin (MK) has been found to compensate the loss in the carbonation and electrical resistance on account of substitution of NA with RCA up to some extent.