Abstract

Objective To mitigate chloride attack on recycled fine aggregate-ultra-high performance concrete （RFA-UHPC）， prevent deterioration of its internal structure， and improve its durability， an in-depth investigation is conducted into the resistance of RFA-UHPC to chloride attack.

Methods Firstly， RFA-UHPC was prepared by replacing 50% of mass of natural sand with RFA. Secondly， chloride ion resistance tests were conducted. The specimens were immersed in NaCl solutions with mass fractions of 0%， 3%， 7%， and 10% for a total duration of 900 days， resulting in four types of RFA-UHPC specimens. Thirdly， mechanical property tests were performed to determine the mass loss fraction， relative dynamic elastic modulus， compressive strength， and chloride ion mass fraction of each specimen. Meanwhile， the phase composition and microscopic morphology were characterized. Finally， the influence of NaCl mass fraction on the mechanical properties， chloride ion resistance， and microstructure of RFA-UHPC was analyzed.

Results and Discussion As the immersion time and NaCl mass fraction increased， the mass loss fraction of RFA-UHPC gradually increased， while the relative dynamic elastic modulus and compressive strength gradually decreased. When the immersion time was 900 days and the NaCl mass fraction was 10%， the mass loss fraction of RFA-UHPC was 0.57%， the relative dynamic elastic modulus was 76%， and the compressive strength was 97.7 MPa. The chloride ion mass fraction inside RFA-UHPC decreased with increasing depth from the surface and increased with increasing NaCl mass fraction. When the immersion time was 900 days and the NaCl mass fraction was 10%， the chloride ion mass fraction in the 0-3 mm surface layer of the RFA-UHPC specimen reached its maximum value of 0.90%. Furthermore， when the NaCl mass fraction was 10%， the carbonation reaction of RFA-UHPC reached its maximum， and the alteration of the C-S-H gel structure was the most significant.

Conclusion Under high-concentration chloride attack， the carbonation reaction inside RFA-UHPC gradually intensifies， inhibiting the formation of ettringite and altering the main structure of the C-S-H gel. The interfacial transition zone gradually deteriorates， accompanied by the propagation of microcracks and pores， which adversely affects the macroscopic durability of RFA-UHPC. However， the dense structure of the C-S-H gel in the matrix can still effectively delay further penetration of chloride ions， ensuring the integrity and stability of the overall RFA-UHPC structure.

Keywords： recycled fine aggregate； ultra-high performance concrete；chloride attack； mechanical properties

Get Citation：Ma Zhipeng， Xu Qiqi， Wu Chenjie， et al. Chloride ion resistance of recycled fine aggregate-ultra-high performance concrete［J］. China Powder Science and Technology， 2026， 32（4）： 1-10.

Received：2025-10-10， Revised： 2026-04-02，Online： 2026-06-08.

Funding：The research was supported by the National Natural Science Foundation of China (Grant No. 52368037, 51968060), the Key Research and Development Program of Ningxia (Grant No. 2022BEE03001), the Natural Science Foundation of Ningxia (Grant No. 2023AAC03040), and the Ningxia First Class Discipline Project (Grant No. NXYLXK2021A03).

DOI：10.13732/j.issn.1008-5548.2026.04.009

CLC No.：TU528； TB4

Type Code：A

Serial No.：1008-5548（2026）04-0001-10