Relationship between internal humidity and drying shrinkage of recycled aggregate thermal insulation concrete considering recycled aggregate content

• Internal humidity and drying shrinkage tests were performed on RATIC with various RCA contents. • A model was proposed to predict the drying shrinkage of RATIC resulting from the internal humidity. • The drying shrinkage mechanism of RATIC was revealed. The unique internal structure and basic properties of recycled coarse aggregate (RCA) and glazed hollow bead (GHB) complicate the shrinkage deformation of aggregate thermal insulation concrete (RATIC). To reveal the time-dependent law and mechanism of the drying shrinkage of RATIC, we experiment on the internal humidity evolution and drying shrinkage of RATIC with various contents of RCA. Moreover, we establish a model for predicting the time-dependent drying shrinkage of RATIC considering the replacement ratio of RCA and the development of the internal humidity of concrete using regression analysis. The results show that adding recycled coarse aggregate promotes cement hydration and water diffusion but aggravates the reduction of internal humidity and the development of the drying shrinkage of the RATIC. This paper proposes a model describing the drying shrinkage of RATIC at various contents of RCA and relates it to the changes in internal humidity so as to provide possible explanations for the drying shrinkage of RATIC influenced by the internal humidity. Finally, the drying shrinkage mechanism of RATIC is well explained using the capillary theory and the internal curing effect.