Journal of South China University of Technology(Natural Science Edition) ›› 2026, Vol. 54 ›› Issue (3): 160-171.doi: 10.12141/j.issn.1000-565X.250120

• Materials Science & Technology • Previous Articles     Next Articles

Study on the Durability of Recycled Concrete Load-bearing Block in Severe Cold Regions of Qinghai-Tibet

QI Yunpeng1  WANG Qiusheng1  LI Zhiyi2   XIONG Yijun1   

  1. Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education, Beijing University of Technology, Beijing 100124, China;

    2. Hunan Economic Institute Electric Power Design Co., Ltd., Changsha 410004, Hunan,China

  • Online:2026-03-25 Published:2025-10-10

Abstract:

In order to realize the resource utilization of solid waste and improve the performance of recycled concrete blocks in severe cold regions of Qinghai-Tibet. On the basis of 100% recycled coarse aggregate, the effects of recycled fine aggregates and active admixtures on the impermeability, water resistance and frost resistance of high-volume solid waste recycled concrete load-bearing blocks were studied. The microstructure was analyzed by SEM and NMR. The results show that the permeability and water absorption of recycled concrete load-bearing blocks gradually increase with the increase of recycled fine aggregate, and decrease first and then increase with the decrease of fly ash and slag mixed ratio, while the frost resistance and softening coefficient change oppositely. When the replacement rate of recycled coarse aggregate is 100 % and the mix ratio of fly ash and slag is 3 : 1, the compressive strength is 11.77 MPa, the flexural strength is 3.89 MPa, the softening coefficient is 0.99, the water absorption rate is 0.7 %, the mass loss rate after 50 freeze-thaw cycles is 2.2%, and the loss rates of compressive strength and flexural strength are 10.2% and 13.9% respectively, which meet the requirements of load-bearing and durability in severe cold regions and can be used as a recommended mix ratio. Microscopically, alkali excitation promotes the secondary hydration of the composite cementitious materials, generates more hydration products to optimize internal pores, and the concrete structure is dense. With the increase of the number of freeze-thaw cycles, the number of pores in the block gradually increases, and the micropores and mesopores gradually derive into large pores and fissures, and the performance of the block deteriorates. Based on the performance-cost-carbon emission analysis, 100 % recycled coarse aggregate is not conducive to low-carbon emission reduction. The recommended mix ratio of mixed recycled aggregates and active admixtures has a carbon emission reduction rate of 31.03%.

Key words: solid waste, recycled concrete load-bearing block, severe cold regions, durability, microstructure