New Mix Design Method for Recycled Concrete Using Mixed Source Concrete Coarse Aggregate

Abstract: This study proposes a new mix design method for C30 recycled concrete using recycled aggregate crushed from different strength source concrete (SC). The dosages of cement, water, sand, and coarse recycled concrete aggregate (CRCA) are the same as the corresponding components in natural concrete, but the CRCA should be pre-wetted before casting. Its weighted mean strength has a value of 43.1 MPa for two strengths of SC. Compressive and splitting tensile strength tests on recycled concrete with CRCA (100% substituting limestone aggregate) made from two mixed SC with varying strengths, have been implemented to acquire the mix design method. For investigating the influence of CRCA from two strengths of SC on recycled concrete performance, test parameters of mechanical behavior including compressive strength of SC, strength difference between two mixes of SC, and proportion of two mixed CRCA were taken into account. Test results indicate that when one of the two mixed SC strengths is similar to the target strength, two requirements have to be satisfied to achieve the target compressive strength: one of the SC has to be more than 10 MPa higher than the target strength, and the proportion of the higher strength SC is larger than 75% in weight of the total CRCA. The results provide useful information for recycling multiple strength SC. Graphic Abstract: [Figure not available: see fulltext.].