Recycled aggregate concrete: Experimental shear resistance of slabs without shear reinforcement

Abstract

The recycling of demolition rubble and its reuse in building materials is desired, but the question rises how reinforced concrete members made with recycled aggregate concrete has to be designed. Since a similar flexural behavior of recycled aggregate concrete and natural aggregate concrete was shown in several studies, this paper focuses on the shear resistance of slabs without shear reinforcement. The slabs were made of concrete using different types of aggregates: (a) 100%wt recycled concrete aggregate, (b) 50%wt mixed rubble aggregates and 50%wt natural aggregates, (c) 100%wt mixed rubble aggregates as well as (d) natural aggregates. The latter was used as a reference concrete. In order to determine the shear resistance, slabs were loaded until shear failure occurred in a four-point-bending test. The slabs made of recycled aggregate concrete showed similar crack distributions as the slabs made of natural aggregate concrete. Predictions for the shear resistance were obtained using the critical shear crack theory of Muttoni as well as the Swiss and the European standards (SN 505 262 and Eurocode 2). The predictions by the critical shear crack theory and the European standard showed good correlation with the experimental results (mean ratio between experimental and predicted value: 1.00±0.05 and 0.99±0.04, respectively). But the predictions by the critical shear crack theory and the European standard overestimated the shear resistance of the slabs made of concrete with 100%wt mixed rubble aggregate. Especially for these slabs the Swiss standard predicted 8–11% lower shear resistances than the critical shear crack theory and the European standard.