水浸泡和潮湿环境下CO_2侵蚀对水泥基材料孔结构的影响

Effect of CO_2 erosion on the pore structure of cement-based materials in water soaking and moist environment

引水隧洞等地下工程结构处于复杂的水环境。引水隧洞运行和检修期,混凝土结构分别处于水浸泡和潮湿环境,其服役环境下CO2对混凝土结构的侵蚀作用与大气环境下的碳化作用存在一定差异。本文采用氮吸附法分析水浸泡和潮湿环境下CO2侵蚀后水泥基材料的孔结构,并与大气环境下侵蚀后的孔结构作对比。研究结果表明:CO2侵蚀作用下,水泥基材料吸附能力提高,而水浸泡和潮湿环境下水泥基材料碳化后吸附能力较大气环境下要大;CO2侵蚀后,水泥基材料小孔隙数量明显增多而大孔隙数量减少,而水浸泡和潮湿环境下水泥基材料小孔隙数量较大气环境下要多,其中水浸泡环境下水泥基材料总孔体积、平均孔径以及所有孔径的孔隙数量均大于潮湿环境,水浸泡环境会进一步加剧孔隙的发育和扩展。

The underground engineering structures,such as diversion tunnel,are in a complex water environment.The concrete structure of a diversion tunnel is in water soaking and moist environment respectively during its operation and maintenance period.Within the service period,the erosion effect of CO2 on the concrete structure is different from that by the carbonation under the atmospheric environment.The pore structure of the cement-based materials after CO2 erosion in a water immersed and humid environment was analyzed by nitrogen adsorption method and compared with that after erosion in an atmospheric environment.The results showed that the adsorption capacity of the cement-based materials was always improved under the erosion of CO2,but the adsorption capacity in the water soaking and moist environment was greater than that in the atmospheric environment.After the CO2 erosion,the number of small pores in the cement-based materials increased significantly while that of large pores decreased.In the water soaking and moist environment,the number of small pores was more than that in the atmospheric environment.The total pore volume,average pore size and the number of pores of all sizes in the water soaking environment were all greater than those in the moist environment,and the water soaking environment would further aggravate the development and expansion of the pores.