活性粉末混凝土在海水冻融作用下的耐久性

Durability of Reactive Powder Concrete under Action of Seawater Freeze-Thaw Cycle

通过海水冻融循环试验,对不同配合比的活性粉末混凝土进行抗压强度和氯离子渗透性变化规律研究,并在此基础上建立基于冻融破坏和氯离子侵蚀为控制因素的使用寿命预测模型。结果表明:粉煤灰和矿粉替代部分硅粉降低了活性粉末混凝土的28d抗压强度,但提高了抗海水冻融能力;冻融破坏为混凝土材料寿命的控制因素时,在海水冻融循环作用下,掺入粉煤灰或矿粉的活性粉末混凝土的使用寿命均大于单掺硅粉的活性粉末混凝土,且活性粉末混凝土的使用寿命均超过90a,而C50高性能混凝土使用寿命仅为24.4a。基于Monte Carlo随机模拟和Weibull分布理论,建立以氯离子侵蚀破坏为控制因素的混凝土结构使用寿命预测模型,对不同配合比活性粉末混凝土使用寿命的分析表明,保护层厚度的增加能显著提高活性粉末混凝土的使用寿命,粉煤灰和矿粉替代硅粉也可提高使用寿命,粉煤灰存在最佳替代率,而矿粉替代率越高寿命越长。

Seawater freeze-thaw cycle tests on reactive powder concrete with different mix proportions were carried out,and the variations of compressive strength and chloride ion permeation were studied.On thisbasis,service life prediction models were established based on freeze-thaw failure and chloride ion corrosion as control factors.Results show that the replacement of partial silica fume by fly ash and mineral powder reduces the 28 d compressive strength of reactive powder concrete,but improves the resistance to seawater free-thaw cycles.With freeze-thaw failure as the control factor for theservice life of concrete materials and under the action of seawater freeze-thawcycle,the service life of the reactive powder concrete mixed with fly ash or mineral powder is longer than that of reactive powder concrete with single siliconpowder.The service lives of all reactive powder concrete samples with different mixture compositions are more than 90 a,while the service life of C50 high performance concrete is only 24.4 a.Based on random Monte Carlo simulations,followed by the analysis using the Weibull distribution,service life prediction models for concrete structure were established with chloride ion corrosion as control factor.The service life of the reactive powder concrete with different mixproportions was analyzed.Results show that the service life of reactive powderconcrete can be significantly improved by increasing the thickness of protectivelayer.The service life can also be improved by replacing silica fume with flyash and mineral powder.For fly ash,an optimum degree of cement replacement isfound,whereas,for mineral powder,the service life of the concrete increases with its increasing addition.