Evolution of drying shrinkage and water migration of concrete: Effects of pore feature and water desorption of recycled fine brick aggregate

Abstract

Porous nature and water desorption capacity of recycled fine brick aggregate (RFCB) is crucial to the long-term evolution of shrinkage behavior of recycled concrete (RC) exposed to the dry environment. Thus, this study assessed both the pore feature and water desorption of RFCB with different particle sizes (including 0–5 mm, 0.075–5 mm and 0.15–5 mm), followed by the effect of particle size, replacement level and initial saturation degree of RFCB on the microstructure, strength development, water migration and drying shrinkage of RC. Results shown that the pore feature of RFCB yielded coarse pore size and high porosity with an increase in particle size, which in turn endowed a superior water desorption potential. Microstructure revealed that incorporating porous RFCB into RC increased the pore volume, porosity and total capillary pores, whereas performed better in improving the average pore diameter and interface bonding. The presence of RFCB imposed a deteriorate effect on the compressive strength, relative humidity, electrical resistivity and drying shrinkage, and this degraded effect exacerbated as particle size and replacement ratio raised. However, introducing full saturation degree of fine RFCB was beneficial for mitigating the relative humidity reduction, electrical resistivity increment and drying shrinkage development. Finally, the drying shrinkage-prediction model considering RFCB coefficients was developed based on the CEB-FIP model, which was helpful for the design of low-carbon and durable RC.