Research On Performance Of Filling Layer Self-Compacting Concrete In Crts Ⅲ Type System

According to the performance requirements of self-compacting concrete (SCC) in CRTS III track structure filling layer, this paper optimized on the selection of raw materials, proposed a new method of mix design, and optimized the dosage of admixture through the experiments. Besides, this paper researched the influence of rubber powder on the properties of SCC, especially on the improvement of toughness. The main research and achievements of this thesis are as follows.(1) Raw materials used in the experiments were optimized according to the requirements of actual application. Semi-empirical calculation was used to calculate the mix proportion of SCC in the filling layer of CRTS III type system. First, set stone volume dosage, sand ratio, unit water and air volume based on the experience, then calculate the volume of powder, determine the volume of the cement materials according to the dosage of inert powder. The content of the admixtures could be determined by experience, and adjusting the content by experiments.(2) According to the effects of the materials on the properties of SCC, limestone powder could improve the workability and strength of SCC, but increased the shrinkage, the best dosage is7%. Increased water-binder ratio could increase the fluidity, but the other performance of SCC would be declined rapidly, the appropriate water-binder is about0.36. Silica fume could improve the workability and strength of SCC obviously, but had no influence on the drying shrinkage, the dosage should be controlled between5%and10%, and metakaolin could be used instead of silica fume, but the dosage should be under5%, because high content of metakaolin would make the workability plummet. Sand ratio was controlled between50%and55%which made SCC has the best performance, sand ratio has no effects on mechanical property, but the bigger the sand ratio was, the greater the drying shrinkage would be. Polypropylene fiber could be mixed with a small amount, the content should be under0.8kg/m in case the reducing of the workability and the increase of shrinkage.(3) Rubber powder made a great influence on the workability and strength of SCC, but it could decrease the drying shrinkage. When the content was too high, the workability and strength of SCC would drop more apparent, and the improvement of drying shrinkage would be reduced. In addition, rubber powder also made the elastic modulus of SCC reduced, but increased the ductility and the compression resilience, which could improve the impact resistant ability of SCC in CRTS Ⅲ type track system. According to the influence of rubber powder on the properties of SCC, the volume instead of the sand content is approximately10%. Under the same dosage, the workability and compression resilience with smaller rubber powder of SCC is worse than larger size, but the strength is higher and the drying shrinkage is smaller.