ABSTRACT
This section presents the first experimental building, based on recycled aggregate concrete (RAC), carried out in France, within the RECYBÉTON national project. This building, with 40 m3 of concrete, is particularly loaded (750 kg/m2) and is intended for the archive of documents. Two concrete mixtures were manufactured: The first one with natural aggregate concrete (NAC) and the second (RAC) containing 30% of recycled fine aggregates and 50% of recycled coarse aggregates. A first laboratory characterization campaign was carried out by CEMEX company to measure the slump, the shrinkage, the compressive strength, and the Young’s modulus of concrete. Then, tests of suitability were conducted by the Center for studies and expertise on Risks, Environment, Mobility, and Urban and Country Planning (Cerema), mainly devoted to fresh concrete properties (slump) and its compressive and tensile strengths. Results show the necessity of increasing cement content (+5%) and using superplasticizer, in RAC mixture, to reach the same specifications of NAC. An increase of shrinkage (+40%) and a decrease of elastic modulus (−17%) were measured when recycled aggregates were used. For building, the concrete was implemented five times. For every concrete delivery, an experimental characterization was done, through slump, compressive, and tensile tests. Drying shrinkage and durability properties (water porosity, gas permeability, and carbonation depth) were measured once, on both RAC and NAC specimens. On construction site, measured slump, compressive, and tensile strengths were the same as for RAC and NAC. Shrinkage, water porosity, and gas permeability increased, respectively, by 10%, 20%, and 80%, when recycled aggregate was incorporated. The carbonation 408depth, after 1 month, is 4 mm higher in RAC. The detailed inspection of the building carried out after construction and after 3 months do not reveal any defaults or microcracks that could be caused by recycled aggregates. The observed defaults (flatness, apparent steel, segregation) were due to the used framework and the lack of vibration.
