Mechanical strength properties of RCA concrete made by a modified EMV method

Abstract

This study used two types of Recycled Concrete Aggregates (RCAs) with the same original virgin aggregate, but with different amounts of residual mortars. To verify that the mechanical properties of the concrete were affected by changing the unit volume of residual mortar, fresh mortar, and total mortar of the concrete, a series of paving concrete mixes were made using a modified equivalent mortar volume (EMV) mix design, along with a conventional American Concrete Institute (ACI) mix design. The test results showed that the RCA concrete with the conventional mix design, which led to a prominent decrease in compressive strength and elastic modulus at each age, had 10% greater total mortar volume than that with the modified EMV mix design. As for the conventional ACI mix, it appears that the replacement ratio of RCA and the volume of the residual mortar in RCA directly affect the modulus of elasticity as well as the compressive strength of concrete. However, for the modified EMV mix, the modulus of elasticity of the concrete may be increased to be equivalent to the companion concrete with natural aggregate by controlling the new mortar volume so that the total mortar volume remains the same regardless of the RCA replacement ratio. It was observed that the smaller new volume requirement makes the RCA paving concrete more environmentally friendly and economically profitable.