冻融作用下粉煤灰引气混凝土动弹性模量的衰减规律研究

针对我国西北寒旱区水工混凝土结构长期遭受冻融循环作用导致耐久性能衰减的问题,以研究冻融作用下混凝土力学性能变化规律为目标,依据实际工程,采用室内加速试验与理论分析方法,以试块相对动弹性模量为评价指标,研究了混凝土水胶比、粉煤灰掺量、引气剂掺量及冻融循环次数对混凝土耐久性衰减的影响规律,采用回归分析法建立了混凝土动弹性模量损失的衰减模型,并基于该模型构建冻融循环作用下混凝土的寿命预测模型。结果表明:以初始动弹性模量的60%(2.424×10~4MPa)为破坏条件,甘肃省景泰川提灌工程二期总干渠5#渡槽的混凝土能经历1 502次快速冻融循环,渡槽材料耐久性安全运行年限为153年。研究成果为冻融环境下混凝土结构的寿命预测提供了参考和依据。

Study on attenuation law of dynamic elastic modulus of fly ashaerated concrete under freezing thawing effect

Aiming at the problem that the attenuation of the durability of the hydraulic concrete structure in the cold and arid regions of the Northwest China caused by the long term freezing thawing cyclic effect，the changing law of the dynamic performance of concrete under the freezing thawing effect is taken as the study objective，and then the laws of the effects from the concrete water cement （binder） ratio，the fly ash mixture，the dosage of air entraining agent and the number of freezing thawing cycles on the attenuation of the durability of the concrete are studied by taking the relative dynamic elastic modulus of the specimen as the evaluating index with the indoor accelerated test and the relevant theoretical analysis method in accordance with an actual project，for which a attenuation model for the dynamic elastic modulus of concrete is established with the regression analysis method，and based on this model，a life prediction model for the concrete under the effect of the freezing thawing cycle is built as well. The result shows that by taking 60% （2.424×104MPa） of the initial dynamic modulus，the concrete of the No.5 aqueduct of the Phase II Main Channel of Jingtaichuan Pumping lrrigation Project in Gansu Province can withstand the freezing thawing cycles for 1 502 times，while the safe operation life of the construction materials of the aqueduct is 153 years. The study result provides areference and a basis for the life prediction of concrete structure within the freezing thawing environment.