Effect of surface activity of recycled fine aggregates from clay bricks on the hydration, microstructure and chloride transport of concrete

• Published in: Construction & building materials Vol. 418; p. 135499
• Main Authors: Dang, Juntao, Zhu, Ruifeng, Xiao, Jianzhuang, Li, Fenglan
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 08-03-2024
• Subjects: Chloride transport; Pore structure; Recycled concrete; Recycled fine aggregate from clay bricks; Surface activity; Recycled fine aggregate from clay bricks; Recycled concrete; Pore structure; Surface activity; Chloride transport
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2024.135499

Use of recycled fine aggregates from clay bricks (RFCB) in the preparation of eco-friendly concrete was proposed to tackle the river sand (RS) shortage and satisfy the construction demand. This study explored the surface activity of RFCB influenced by additional water and particle size distribution (PSD) on the hydration, microstructure and chloride transport of concrete. Compared to the RS, more silica and alumina released from RFCB depending on its PSD under alkaline environment was noted, which verified its appreciable surface activity. Overall, the presence of RFCB could hinder early hydration process because of the higher additional water, while the surface activity and nucleation effect supplied from finer RFCB were beneficial for the improvement of the hydration kinetics. Furthermore, inclusion of RFCB increased the total pore volume and porosity but performed better in refining the pore size distribution, thus decreased the average pore diameter. The surface activity of RFCB decreased CH content while increased chemical bond water and additional hydrates, thereby leading to enhancement of the compactness of interface, cement matrix and surface rim. More importantly, RFCB helped to decrease the chloride migration coefficient and electric flux. Though the surface activity of RFCB was beneficial in the strength development, it could not offset a deteriorated influence of porous RFCB with a higher replacement.
•RFCB possesses an appreciable surface activity depending on its PSD.•Inclusion of RFCB performs better in improving the compactness of interface and surface rim.•Surface activity of RFCB improves the hydration kinetics and mitigate chloride transport.•Surface activity of RFCB cannot compensate its porous structure at a high replacement.