混凝土冻融耐久性与气泡特征参数的研究

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发布时间：2021-09-17

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混凝土冻融耐久性与气泡特征参数的研究
陈霞，杨华全，周世华，王仲华
(1．长江科学院材料与结构研究所，湖北武汉430010；2．武汉大学博士后流动站，湖北武汉430072)
摘要：采用快速冻融法，研究了水胶比、粉煤灰掺量和气泡特征参数对混凝土冻融耐久性的影响．
结果表明：随着水胶比增大，粉煤灰掺量增多，受冻融混凝土耐久性指数显著降低，质量损失逐渐
增大．混凝土冻融循环次数与气泡平均半径呈对数关系，为了保证混凝土抗冻标号达到D ，气泡
平均半径应小于150 m且弦长大于50 txm 气泡的体积分数应小于4．5 ．混凝土冻融循环次数与
气泡数量呈抛物线关系，即气泡数量存在一个最佳值，为3 500个／em。左右．混凝土气泡间距越
小，其冻融耐久性越好；当气泡间距小于240“m 时，混凝土具有高冻融耐久性．
关键词：混凝土；冻融耐久性；耐久性指数；气泡平均半径；气泡间距
中图分类号：TU528．0 文献标志码：A doi：10．3969／j．issn．1007—9629．2O11．02．022
Research on Concrete Freezing and Thawing Durability and
Characteristic Parameters of Bubbles
CHEN Xia ， YANG H ua—quan ， ZHOU Shi—hua ， WANG Zhong—hua
(1．Department of Materials and Structure，Changjiang River Scientific Research Institute，W uhan 430010，China；
2．Post-doctor Station，W uhan University，W uhan 430072，China)
Abstract：W ith accelerated freezing and thawing tests，the influence of water-binder ratio，fly ash use level
and characteristic parameters of bubbles on concrete freezing and thawing durability were investigated．Re—
sults show that with increase of water—binder ratio and fly ash use level，the durability factor will decrease
and mass loss of concrete increase after alternating freezing and thawing cycles． The number of freezing
and thawing cycles is in logarithmic relation to mean radius of bubbles．In order to reach D3o0，mean radius
of bubbles should be less than 150 m and bubble volume fraction with chord larger than 5O m should be
less than 4．5 ．The number of freezing and thawing cycles is in parabolic relation to bubbles amount and
there exists an optimal value around 3 500／cm。．The less the spacing factor of bubbles is，the better the
freezing and thawing resistance of concrete will be．Spacing factor less than 240 um could ensure good
freezing and thawing durability of concrete．
Key words：concrete；freezing and thawing durability；durability factor；mean radius of bubbles；spac—
ing factor
混凝土冻融耐久性是其暴露于交替冻融条件下
抵抗体积膨胀开裂的能力．在冰冻温度下，毛细孔内
可冻水结冰体积膨胀约为9 ，而过冷水发生迁移
形成的渗透压也会造成混凝土体积膨胀，若这两者
共同产生的膨胀应力大于混凝土的抗拉强度，则混
凝土会产生局部裂缝或发生内部微裂纹扩展．交
替冻融循环会加剧裂缝扩展并导致混凝土结构的最
终破坏．在混凝土中掺入优质的引气剂或引气减水
剂，可使混凝土内部形成大量微小、稳定、分布均匀
的封闭气泡，缓解孔隙水结冰时产生的膨胀压，阻塞