| 摘要: |
| 为准确评估混凝土早期受冻对其服役期性能的影响,模拟早期突然受冻环境,测试了不同早期受冻环境下混凝土服役期的抗压强度、劈拉强度、动弹性模量等宏观性能参数和孔隙结构、吸水特征等微观指标;分析了受冻温度、受冻时长、起冻时刻等环境参数对混凝土服役期性能的影响规律和影响机理.结果表明：受冻温度越低、受冻时长越长,混凝土服役期宏观性能劣化越明显,浆气比减小,含气量、吸水率、吸水孔率增大,各孔径的气孔数量均有所增加;受冻温度从-1℃降到-5℃、受冻时长从2h延长至4h时,混凝土服役期性能劣化明显,而受冻温度从-5℃降到-9℃、受冻时长从4h延长至8h时,混凝土服役期性能劣化程度较小;初凝后、终凝前受冻的混凝土服役期性能劣化最显著,初凝前受冻的混凝土服役期性能劣化次之,终凝后受冻的混凝土服役期性能劣化程度较小且损失程度随受冻时混凝土龄期的增长而减小;随着起冻时刻的延后,混凝土的浆气比增大,而含气量、吸水率、吸水孔率减小,终凝前起冻的混凝土各孔径梯度的气孔数量明显大于终凝后起冻的混凝土. |
| 关键词: 混凝土 早期受冻 服役性能 起冻时刻 受冻温度 受冻时长 |
| DOI：103969/j.issn.1007 9629202005010 |
| 分类号: |
| 基金项目:国家自然科学基金资助项目(51308441,51678473,51590914);长江学者和创新团队发展计划(IRT_17R84);陕西省教育厅重点实验室科研项目(18JS062) |
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| Effect of Early Frost Environment on Service Performance of Concrete |
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HU Xiaopeng, PENG Gang, NIU Ditao, YANG Chao
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chool of Civil Engineering, Xian University of Architecture and Technology, Xian 710055, China
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| Abstract: |
| To evaluate the effect of early freeze on service performance of concrete, the frost environment for early age concrete was simulated. Macro property parameters such as the compressive strength, splitting tensile strength, dynamic elastic modulus, and micro indexes such as pore structure and water absorption characteristics during service period of early frozen concrete were tested. The effects of frost environmental parameters, such as the frost onset time, frost temperatures and frost durations, on the service performance of early frozen concrete and damage mechanisms were analyzed. Results show that accompanied by the decreasing frost temperature and the increasing frost duration, the deterioration of macro properties of early frozen concrete during service and the paste to air ratio increases, whereas the air content, the water absorption after immersion and volume of permeable pore space decrease. Moreover, the greater bubble amount under different pore diameters is observed. The performance degraded significantly with the frost temperature decreased from -1℃ to -5℃ or the frost duration increased from 2h to 4h, but only slightly with the further decreasing frost temperature from -5℃ to -9℃ or the further increasing frost duration from 4h to 8h. For the early frozen specimens with different frost onset times, the degradation in service performance caused by freezing between the initial setting and final setting time is the most severe, followed by that before the initial setting time, and decreases gradually with increasing frost onset time after the final setting time. With the delaying frost onset time,the paste to air ratio increases whereas the water absorption after immersion and volume of permeable pore space decrease gradually. The bubble amount under different pore diameters of concrete frozen before the final setting is greater than that after the final setting. |
| Key words: concrete early frost service performance frost onset time frost temperature frost duration |
