| 摘要: |
| 针对我国西北地区干燥大温差环境造成水泥基材料不可避免的裂缝，从而严重影响混凝土结构寿命的难题，本文利用环形约束试验中应变突变时间表征了粉煤灰-水泥胶凝材料在不同环境条件下的开裂敏感性。通过显微观察、计算机断层扫描（CT）及压汞法的测试，揭示了在干燥大温差环境下粉煤灰-水泥胶凝材料的约束收缩变形、开裂情况及其开裂机理。研究发现：当水胶比提高40%时，开裂时间可延长370.59%；湿度降低40%时，水胶比0.30的试件开裂时间缩短20.30%；当温差为35℃/d时，水胶比0.25试件开裂时间延长40.63%；掺加30%粉煤灰可以使开裂时间延长4.41倍；影响材料开裂敏感性大小的因素依次为水胶比、粉煤灰和温湿度条件，其中水胶比0.25的试样对温度最敏感，而水胶比0.30的试样对湿度变化较敏感。因此，干燥和大温差的环境条件加剧了粉煤灰-水泥胶凝材料的开裂风险。水胶比的增大降低了水泥胶凝材料开裂的风险，粉煤灰能有效抑制水泥胶凝材料的开裂，降低材料开裂敏感性，并揭示了水胶比、粉煤灰掺加与环境温湿度变化导致胶凝材料孔结构的演变对开裂敏感性影响的机理。 |
| 关键词: 干燥大温差 粉煤灰 压汞 CT 开裂敏感性 |
| DOI： |
| 分类号:TU526???? |
| 基金项目:中央引导地方科技发展专项(ZYYD2023B04) |
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| Research on Cracking Sensitivity of Fly-ash-cement-based Cementitious Materials in Dry Environment with Large Temperature Difference |
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xionggenyi1, wanghuaiyi2, yangguiquan2, lishuangxi1, chengningning2
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1.Xinjiang Agricultural University;2.Xinjiang Research Institute of Water Resources and Hydropower
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| Abstract: |
| Aiming at the difficult problem of dry and large temperature difference environment in Northwest China, which causes unavoidable cracks in cementitious materials and thus seriously affects the life span of concrete structures, this paper characterizes the cracking susceptibility of fly ash-cement cementitious materials under different environmental conditions by using the time of strain mutation in the annular confinement test. Through microscopic observation, computerized tomography (CT) scanning and pressed mercury testing, the constrained shrinkage deformation and cracking of fly ash-cement cementitious materials and their cracking mechanism were revealed under dry and large temperature difference environment. It was found that: when the water-cement ratio was increased by 40%, the cracking time could be extended by 370.59%; when the humidity was decreased by 40%, the cracking time of the specimen with a water-cement ratio of 0.30 was shortened by 20.30%; when the temperature difference was 35 ℃/d, the cracking time of the specimen with a water-cement ratio of 0.25 was extended by 40.63%; the addition of 30% of fly ash could prolong the cracking time by 4.41 times; the factors influencing the magnitude of the sensitivity of the material to cracking The factors affecting the size of material cracking sensitivity are water-cement ratio, fly ash and temperature and humidity conditions in order, in which the specimen with a water-cement ratio of 0.25 is the most sensitive to the temperature, while the specimen with a water-cement ratio of 0.30 is more sensitive to the change of humidity. Therefore, the dry and large temperature difference environmental conditions exacerbated the risk of cracking in the fly ash-cement cementitious materials. The increase of water-binder ratio reduces the risk of cement cementitious material cracking, and fly ash can effectively inhibit the cracking of cement cementitious material and reduce the material cracking sensitivity, and reveals the mechanism of the effect of the evolution of the pore structure of cementitious material on the cracking sensitivity due to the changes of the water-binder ratio, the fly ash admixture and the ambient temperature and humidity. |
| Key words: drying large temperature difference Fly ash Mercury injection CT Cracking sensitivity |
