Zhang Shuhua, Tan Guangrong, Qi Zhiqiang, Tian Bin, Cao Jijun, Chen Bofu
The Seventh Geological Brigade of Hubei Geological Bureau, Yichang 443000, China.
Key Experiment of Geological Resources and Geological Engineering in Yichang, Yichang 443000, China.
Materials (Basel). 2024 Dec 18;17(24):6191. doi: 10.3390/ma17246191.
Concrete structures in cold regions are affected by freeze-thaw cycles (FTCs) and carbonation, which lead to the premature failure of concrete structures. The carbonation depth, relative dynamic elastic modulus (RDEM), compressive strength, porosity, and pore size distribution of concrete under FTC conditions were tested through an accelerated carbonation experiment to study the carbonation performance evolution. The freeze-thaw effect mechanism on concrete carbonation was further analyzed via the obtained relationship between carbonation depth and pore structure. The results showed that the FTC, as a powerful source of concrete damage, accelerates the carbonation reaction. Carbonization products fill some microcracks caused by the freeze-thaw process, improve the compressive strength and dynamic elastic modulus, and alleviate the damage to concrete caused by the FTC. After carbonization under freeze-thaw damage conditions, the content of macropores with d > 1000 nm decreases, while the content of transition pores with d ≤ 10 nm increases, which is the direct reason for the decrease in porosity and the improvement in strength. Therefore, the carbonation durability of concrete under freeze-thaw conditions can be improved by controlling the content of macropores with d > 1000 nm and increasing the content of transition pores with a pore size of 10 nm ≤ d < 100 nm. In addition, the relationship between carbonation depth and pore structure under freeze-thaw conditions was established, and the research results can provide a reference for the study of the carbonation performance of concrete under freeze-thaw conditions.
寒冷地区的混凝土结构受到冻融循环（FTCs）和碳化的影响，这会导致混凝土结构过早失效。通过加速碳化试验，测试了FTC条件下混凝土的碳化深度、相对动弹模量（RDEM）、抗压强度、孔隙率和孔径分布，以研究碳化性能的演变。通过获得的碳化深度与孔隙结构之间的关系，进一步分析了冻融对混凝土碳化的作用机理。结果表明，FTC作为混凝土损伤的一个强大来源，加速了碳化反应。碳化产物填充了冻融过程产生的一些微裂缝，提高了抗压强度和动弹模量，并减轻了FTC对混凝土造成的损伤。在冻融损伤条件下碳化后，孔径d>1000nm的大孔含量减少，而孔径d≤10nm的过渡孔含量增加，这是孔隙率降低和强度提高的直接原因。因此，通过控制孔径d>1000nm的大孔含量并增加孔径10nm≤d<100nm的过渡孔含量，可以提高冻融条件下混凝土的碳化耐久性。此外，建立了冻融条件下碳化深度与孔隙结构之间的关系，研究结果可为冻融条件下混凝土碳化性能的研究提供参考。
