Experimental evaluation of the performances of concrete manufactured by partial substitution of natural aggregates with GA

The paper focuses on the re-use of grinded asphalt as a partial replacement of natural aggregates for concrete manufacturing. Concrete mixtures were designed by considering up to 20% substitution of natural aggregates. The rheological and mechanical properties of concrete manufactured with grinded asphalt were compared to the reference concrete (RC, w/c equal to 0.53) manufactured by using natural aggregates. The superplasticizer dosage was adjusted to attain a slump value equal to 190 mm at the end of the mixing procedure. The mixture showed a marked tendency to bleeding and segregation at the highest replacement percentage. The workability loss up to 60 minutes was also evaluated; a positive effect of recycling aggregates addition was noticed. The higher the grinded asphalt substitution the lower the compressive strength; a 50% strength decrease was noticed for the higher substitution value; the penalization can be ascribed to the weakness of cement paste/recycling aggregate interface. As a matter of fact, the reduction of the w/c to 0.45 permits to mitigate this effect. The maximum substitution of the recycling aggregates was limited to 15% to avoid both rheological and mechanical underperformances. Dry shrinkage and elastic modulus of hardened concrete was also evaluated. Dry shrinkage tests were carried out on reference concrete (w/c ratio equal to 0.53) and grinded asphalt mixture (GAC, w/c equal to 0.45) at 5 and 15% natural aggregates substitution; similar behaviour was evidenced. The experimental results confirmed the possibility of the partial substitution of natural aggregates with grinded asphalt for concrete manufacturing; however the use should be limited to accessory structures such as paving...