Concrete with fine and coarse recycled aggregates: E-modulus evolution, compressive strength and non-destructive testing at early ages

The combined use of fine and coarse recycled aggregates in the manufacture of concrete has multiple advantages from the economic and environmental points of view. There is a lack of knowledge about the behavior of concretes containing recycled aggregates, manifested by strong limitations (even prohibitions) in international standards for structural purposes. This paper aims to study the influence of fine and coarse recycled aggregate of concrete (jointly), with particular emphasis on the evolution of the kinetics of E-Modulus and its relationship with compressive strength and non-destructive testing. Concretes with different degrees of replacement of natural aggregates by recycled aggregates were studied: 0% (reference concrete), 8%, 20% and 31% of the total amount of aggregates. E-Modulus Measurement through Ambient Response Method (EMM-ARM) was used to monitoring the E-Modulus evolution. We also studied the influence of these recycled aggregates on the correlation between E-Modulus and compressive strength, as well as with two non-destructive testing techniques: Ultrasonic Pulse Velocity, and electrical conductivity. The activation energy of the studied concretes, based on data computed from compressive strength measurements at different curing temperatures was calculated. We observed a negative influence of recycled aggregate on the evolution of E-Modulus from the first 12 h, compared to the reference mixture. The crossover effect on E-Modulus evolution produced by high curing temperatures affects more to the concretes with recycled aggregate. Our data evidenced that the maturity correction for E-Modulus evolution, based on the activation energy of compressive strength, produced accurate superposition of E-modulus in the equivalent age domainProject of Program FEDER-INNTERCONECTA ITC-20113055 “Development of value adding technologies for RCDs for innovative applications”, convened by the Center for Industrial Technological Development (CDTI, for its initials in Spanish), dependent on the Ministry of Economy and Competitiveness and co-funded by the Technological Fund – FEDER Funds. Funding provided by the Portuguese Foundation for Science and Technology (FCT) to the Research Project IntegraCrete PTDC/ECM-EST/1056/2014 (POCI-01-0145-FEDER-016841), as well to the Research Unit ISISE (POCI-01-0145-FEDER-007633) is also gratefully acknowledged. The support of CONSENSOR BV