An investigation of mechanical behaviour and elastic properties of recycled aggregate concrete (RAC) is presented. RACs were prepared by using a coarse aggregate fraction made of recycled concrete coming from a recycling plant in which rubble from concrete structure demolition is collected and suitably treated. Several concrete mixtures were prepared by using either the only virgin aggregates (as reference) or 30% coarse recycled aggregate replacing gravel and by using two different kinds of cement. Different water-to-cement ratios were adopted ranging from 0.40 to 0.60. Concrete workability was always in the range 190–200？mm. Concrete compressive strength, elastic modulus, and drying shrinkage were evaluated. Results obtained showed that structural concrete up to C32/40 strength class can be manufactured with RAC. Moreover, results obtained from experimentation were discussed in order to obtain useful information for RAC structure design, particularly in terms of elastic modulus and drying shrinkage prediction. 1. Introduction Crushing concrete to produce coarse aggregate for the production of new concrete is one common means for achieving a more environmentally friendly concrete. Recycling concrete wastes will lead to reduction in valuable landfill space and savings in natural resources. In fact, the use of recycled aggregate concrete (RAC) is acquiring particular interest in civil construction as regards to sustainable development. Many studies demonstrate the feasibility of the use of crushed concrete as coarse aggregates [1–10], its use being already accounted for in the regulations of many countries. In Italy, the use of 30% recycled concrete instead of virgin aggregate is definitively allowed for producing structural concretes (up to C 30/37 strength class) since July 2009 [11]. Nevertheless, in the Italian regulations no indication about predictions of RAC elastic modulus and drying shrinkage is reported. The study of the elastic behaviour of concretes made of 30% recycled-concrete aggregates, discussed here, just had the aim to provide useful information. 2. Experimental Program 2.1. Materials Two commercial portland-limestone blended cements were alternatively used, type CEM II/A-L 42.5 R and type CEM II/B-L 32.5 R according to EN-197/1 [12] (the main difference is the content of calcium carbonate that in the first case is less than 20% and in the second case is included in the range 21–35% according to EN-197/1). The Blaine fineness of cements were 0.42？m2/g and 0.40？m2/g, respectively, and their specific gravity were 3.05？kg/m3. The first
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