Chloride diffusion and binding capacity of sustainable cementitious materials with construction waste powder as cement replacement

Abstract

Reusing construction waste powder (CWP) for sustainable cementitious materials is an effective method to reduce the amount of construction waste, and the CWP blended cementitious materials has been applied in construction engineering at a large scale and is inevitably exposed to a chloride attack environment. Therefore, this work studied the chloride diffusion and chloride binding capacity of cementitious materials incorporating CWP. The addition of CWP enlarged the pore diameter and porosity of blended paste, but mixing active admixture can refine the pore structure of CWP mixed paste. Incorporating CWP reduced the compressive strength and elevated total porosity of blended mortar, while the mix of active admixture improved the compressive strength and reduced the total porosity of CWP mortar. The chloride diffusion of mortar was elevated as CWP replacement rate and particle size increased, and the free chloride concentration increased but chloride diffusion coefficient decreased as chloride exposure time was prolonged. Mixing both CWP and silica fume or metakaolin could prepare sustainable mortar with a similar chloride resistance to plain mortar. The total chloride concentration of mortar was elevated as CWP was incorporated, whereas the chloride binding capacity reduced with the growth of CWP substitution rate. When CWP replacement percentage was identical, the mortar with CWP ground from cement paste waste had better chloride binding capacity than the mortar with CWP ground from mortar and concrete waste. Through optimizing CWP replacement and active admixture content, good strength and chloride resistance can be guaranteed in CWP blended cementitious materials.