铁路桥梁用超细粉煤灰高性能混凝土的试验研究

我国铁路桥梁工程建设中较少掺用粉煤灰,但粉煤灰混凝土在其他工程领域的应用已经证明其具有优良的耐久性能及长期性能。在本文研究中,突破现行规范,从材性试验的角度以30%左右的超细粉煤灰(UFA)等量取代水泥配制了铁路桥梁用的超细粉煤灰高性能混凝土,并对其力学性能、部分长期性能、水化产物以及水泥石形貌等进行了试验研究。试验结果表明,混凝土早期强度主要取决于W/C和UFA掺量,而后期则主要取决于W/B和UFA掺量;通过应力-应变全曲线分析可知,UFA高性能混凝土可采用现行规范设计;混凝土干缩、抗渗、抗裂性能等均优于基准混凝土;同时在微观测试分析基础上,综合考虑施工及养护条件等因素的变异,认为在实际应用中,UFA掺量以不超过30%为宜。

Experimental Investigation of UFA High Performance Concrete Used for Railway Bridges

While fly ash is less used in railway bridge projects in China,it has been verified in other fields of projects that the fly ash concrete has good durability and long-term properties.To break through the current specifications and stand from the angle of materials tests,Ultra-fine Fly Ash(UFA) equivalent to 30% of the cement is added to replace the same amount of cement and the UFA high performance concrete is produced for use in railway bridge projects.The mechanical properties,part of long-term properties,hydrated products and morphology of harden cement paste of the UFA high performance concrete are studied.The results indicate that the early-stage strengths of the concrete are dependent principally on the cement to water ratio(W/C) and amounts of UFA,and the later-stage strengths of the concrete are dependent principally on the cement to binding materials ratio(W/B) and amounts of UFA.According to the analysis of the stress-strain curve,the current specifications can be adopted to design the UFA high performance concrete.The dry shrinkage,impermeability and cracking resistance of the UFA high performance concrete are better than the ordinary concrete.On the basis of the micro tests and analyses and taking into comprehensive consideration variations in construction and curing conditions,it is concluded that the UFA amount is better not to exceed the proportion of 30% in engineering practice.