Advances in recycled concrete research - improving shrinkage for sustainable building applications

With the rapid development of urbanization, a large number of construction solid waste has brought great pressure on the ecological environment. How to make full use of recycled concrete to reduce the harm to the environment has become a prominent issue. The shrinkage deformation of recycled concrete is often higher than that of natural concrete. Therefore, this paper summarizes the strengthening effect on volume shrinkage of recycled concrete and its prediction model from the aspects of surface strengthening of recycled aggregate, mineral strengthening, fiber strengthening and carbonization strengthening, in order to provide reference for the shrinkage deformation research of recycled concrete in the future. The results show that the surface strengthening of the aggregate (mechanical strengthening, prepreg chemical strengthening, mineral coating strengthening) can optimize the interface structure of the reclaimed aggregate and the cementified material. By changing the cementing material composition of concrete matrix, the micro-aggregate effect and volcanic ash effect of minerals can be exerted to improve the stacking form between particles. The addition of appropriate amount of fiber can play the role of skeleton support, which can not only restrain the shrinkage cracking of RAC, but also play a better role in the toughness of concrete. However, excess fibers may increase the volume shrinkage of recycled concrete. Carbonated recycled aggregates can absorb carbon and solidify it, and the generated calcium precipitation can repair surface defects of recycled aggregates, refine pores, and enhance the density of recycled concrete.