CRTSⅢ型板填充层自密实混凝土配制技术研究

Study on Preparation Technology of Self Compacting Concrete for CRTSⅢSlab Filling Layer

结合京滨铁路CRTSⅢ型板式无砟轨道自密实混凝土的工程应用,研究不同砂率和水胶比对填充层自密实混凝土性能影响,,设计了20组C40自密实混凝土配比进行对比试验,研究不同砂率和水胶比条件下混凝土间隙通过性及抗离析性的变化规律,据此得到自密实混凝土的最优砂率和最佳胶凝材料用量;在最优配合比的基础上研究了投料顺序和搅拌时间对自密实混凝土工作性能和强度的影响。研究结果表明:填充层C40自密实混凝土的最佳砂率为51%,最佳胶凝材料用量为440 kg/m3;自密实混凝土的最佳投料顺序为:先加入砂、石、胶凝材料,然后搅拌30 s后将水和外加剂全部加入,搅拌3 min;搅拌时间越长越有利于拌合物的均匀性,然而快速搅拌也会带来骨料的磨损,增加了粉体体积,消耗用水量,研究证实自密实混凝土适宜搅拌时间为4 min。

In combination with the engineering application of CRTS III type slab ballastless track self compacting concrete on Beijing Binhai Railway,the influence of different sand ratio and water binder ratio on the performance of self compacting concrete in the filling layer is studied.Twenty groups of C40 self compacting concrete are designed for comparative tests to study the variation law of the concrete gap trafficability and anti segregation under different sand ratio and water binder ratio conditions,according to which the optimal sand ratio and the optimal amount of cementitious material of self compacting concrete are obtained.Based on the optimum mix proportion,the effects of feeding sequence and mixing time on the workability and strength of self compacting concrete are studied.The results show that the optimum sand ratio of C40 self compacting concrete in filling layer is 51%,and the optimum amount of cementitious material is 440 kg/m3.The best feeding sequence of self compacting concrete is:first add sand,stone and cementitious materials,mix for 30s,then add all water and additives,and mix for 3min.The longer the mixing time is,the better the uniformity of the mixture will be.However,rapid mixing will also bring aggregate wear,increase the powder volume and consume water.Research has confirmed that the proper mixing time for self compacting concrete is 4 minutes.