混凝土冻融耐久性与气泡特征参数的研究

Research on Concrete Freezing and Thawing Durability and Characteristic Parameters of Bubbles

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D300,气泡平均半径应小于150μm且弦长大于50μm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/cm3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240μm时,混凝土具有高冻融耐久性.

With 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.Results 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 D300,mean radius of bubbles should be less than 150 μm and bubble volume fraction with chord larger than 50μm 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 3500/cm3.The less the spacing factor of bubbles is,the better the freezing and thawing resistance of concrete will be.Spacing factor less than 240μm could ensure good freezing and thawing durability of concrete.