Mechanical properties of recycled aggregate concrete proportioned with modified equivalent mortar volume method for paving applications

The equivalent mortar volume (EMV) mix design method, which was originally proposed by Fathifazl et al., was successfully verified in their previous studies for concrete mixes containing coarse recycled concrete aggregate (RCA). However, especially for paving concrete mix, which is typically proportioned with a marginal amount of sand, the nature of the EMV mix proportions leads to a far lower amount of sand. Thus, a modified EMV proportioning method is proposed, assuming that the residual mortar (RM) volume VRMRAC in RCA concrete (RAC) can be represented as the sum of the volume fraction of mortar VRMaRAC and the other volume fraction of coarse aggregate VRMbRAC. To verify this modified EMV method, four series of concrete mixes were made using the modified EMV mix design, along with the original EMV and the conventional mix designs, with various sources of RCAs. For each mix, the slump, air content, compressive strength and elastic modulus were measured. Test results show that the modified EMV method yields modulus properties comparable or superior to those of similar mixes made with natural coarse aggregates or those of conventional mixes with RCA. Furthermore, it is demonstrated that this modified method applies well to paving concrete mixes, regardless of the absorption capacity of RCA.