西北寒旱环境下泡沫混凝土的可靠度研究

为研究泡沫混凝土在西北寒旱地区的实际服役寿命问题,本文设计了4类不同配合比的泡沫混凝土,标准养护28 d后,进行基准参数分析,同时利用现场暴露试验,定期对泡沫混凝土的动弹性模量、质量等进行无损检测,并结合试件的基准参数从宏观和微观两方面分析了损伤机理和耐久性退化过程,最后通过Wiener退化过程建立了寿命预测模型。结果表明,泡沫混凝土的强度、干缩和孔隙结构与容重、水泥用量等因素有关,且适量的矿粉及粉煤灰可优化泡沫混凝土孔隙结构,从而提高其耐久性。在气候环境与侵蚀性离子综合作用下,4类试件的动弹性模量和质量评价参数均呈先升后降的趋势,并表现出不同的耐久性损伤程度。利用动弹性模量评价参数作为泡沫混凝土耐久性退化指标得到的4类试件的服役寿命分别为12 800 d、14 100 d、17 600 d和16 000 d左右,以质量评价参数作为指标得到的寿命分别为13 800 d、15 000 d、19 600 d和16 000 d左右,其中动弹性模量对泡沫混凝土的耐久性变化更为敏感。综合得到,泡沫混凝土中掺入水泥、矿粉、粉煤灰、石灰、石膏的量分别占总胶凝材料质量的40.0%、32.5%、21.7%、4.2%、1.6%时,试件服役于实际环境的耐久性更为优越。

Reliability of Foam Concrete in Cold and Drought Environment of Northwest China

In order to study the actual service life of foam concrete in the cold and drought areas of Northwest China, 4 types of foam concrete with different mix ratios were designed. After standard curing for 28 d, the benchmark parameters were analyzed.Based on the field exposure test, the dynamic elastic modulus and quality of foam concrete were regularly nondestructively tested.And the damage mechanism and durability degradation process of specimens were analyzed from both macro and micro aspects based on the benchmark parameters of specimens. Finally, a life model was established through the Wiener degradation process. The results show that the strength, drying shrinkage and pore structure of foam concrete are related to the factors such as bulk density and cement content, and appropriate amount of slag and fly ash can optimize the pore structure of foam concrete and improve its durability. Under the combined effects of climatic environment and corrosive ions, the dynamic elastic modulus and quality evaluation parameters of 4 types of specimens all increase first and then decrease, and show different degrees of durability damage. The service lives of 4 types of specimens obtained by using the dynamic elastic modulus evaluation parameter as the durability degradation index of foam concrete are about 12 800 d, 14 100 d, 17 600 d and 16 000 d, respectively, and the lives obtained by using the quality evaluation parameter as the index are about 13 800 d, 15 000 d, 19 600 d and 16 000 d, respectively. The dynamic elastic modulus is more sensitive to the durability change of foam concrete.Comprehensively, when the amounts of cement, slag, fly ash lime and gypsum mixed in the foam concrete are 40.0%, 32.5%, 21.7%, 4.2%, 1.6% (mass fraction), the durability of specimens in the actual environment is better.