Investigating the effect of cement and air entrained admixture (AEA) on the capillary water absorption in concrete lining of water conveyance canals

In this study, the effect of different amounts of AEA and amount of cement on the capillary water absorption of concrete was studied. For this purpose, 15 concrete mix designs with w/c of 0.45, Dmax=19mm and 4 levels of cement: 275, 325, 350, 375 and 400 kg/m3, and three levels of AEA( zero, 0.01% and 0.03% of cement weight) was considered. Various experiments included: total air, density and slump on fresh concrete and capillary water absorption on specimens of hardened concrete were studied. The results showed that in non-AEA mixtures, the total air content decreased and the density increased with increasing cement content. By increasing the amount of AEA, in mixtures with 275 and 325 kg/m3 of cement, the amount of total air of mixture decreased and the density increased, but for mixtures with higher than that, the total amount of air was increased and the density decreased. The results on specimens hardened concrete showed that increasing the cement content increased the amount of capillary water absorption. Also, for concrete samples with cement of 275 and 325, by increasing the amount of AEA, the amount of capillary water absorption increased, while for concrete samples with cement of 350, 375 and 400 kg/m3, decreased. Based on results, it was found that in concrete lining in conveyance canals, amount of cement should not be less than 330 kg/ m3. There is not difference between 0.01% and 0.03% of AEA, and therefore, an amount of 0.01% cement weight is recommended.