| Summary: | The use of construction and demolition waste in the construction industry has been a constant issue for several years due to the amount of waste generated as well as the need to reduce the consumption of natural aggregates. This study has the aim of optimizing recycled aggregate from construction and demolition to verify its influence on the elastic modulus in structural concrete. For this, the substitution of coarse natural aggregate by coarse recycled aggregate was evaluated at replacement percentages of 0%, 25%, 50%, 75%, and 100% for concrete with different water/cement ratios (0.40, 0.50, and 0.60). With these criteria, macrostructural tests (compressive strength, splitting strength, porosity and water absorption), microstructural tests (scanning electron microscopy and X-ray microtomography), and accelerated carbonation were employed. The results showed that the mechanical and durability properties in relation to CO2 diffusion decreased as the substitution content of natural aggregate for recycled aggregate increased. The lower the a/c ratio, the denser the concrete and, consequently, the concrete properties are improved. Results showed that there are correlations between the mechanical properties and the carbonation of concrete with recycled aggregate. Through the proposed equations, it is possible to estimate elastic modulus from a given compressive strength at 28 days and with a w/c ratio ranging from 0.4 to 0.6. Based on the compressive strength and w/c ratio, it is possible to estimate the amount of substitution of natural aggregate needed in concretes for an expected elastic modulus.
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