High Speed ​​rail Slab Track Structure Filling Layer Of Self-compacting Concrete Technology

Filling layer is an important component of ballastless track of the high-speed railway, which plays the role of bracing and transfering force. Engineering Material for filling layer has become one of the most important fields focused by scholars all over the world. Based on the analysis of the characteristics of the ballastless track, A new self-compacting concrete, which is expected to be used to construct filling layer, is developed by lots of experiments in this paper. And also the relationship between compositions and properties of fresh SCC is analyzed. The main achievements obtained in present paper are as follows:(1) Three indexes, such as flowability, stability and filling capability, were proposed to evaluate the properties of fresh SCC, which is applied to the filling layer based on consideration of structural characteristics of ballastless track.(2) Based on the theoretical analysis and and experimental practice, a experimental device to test and evaluate the filling capability of SCC is designed. And the corresponding parameters were put forward, including the slump flow, T50, the stability index (segregation percent),the filling time, the ratio of the surface bubble area and the vertical expansion etc.(3)Through the experiments, the influence that some factors such as mineral admixtures (fly ash, limestone powder, silica fume, etc.), thickener, the water to binder ratio, defoamer, superplasticizers, expanding agent etc. have on the flowability, stability, and filling capability of the fresh SCC was studied systemly; meanwhile, the basic makeup and mix-design method of SCC which meets the requirements of the filling layer was obtained.(4)The experiments prove that filling layer placed by self-compacting concrete has good quality when the slump flow of the fresh SCC mixture ranges from 600mm to 750mm, T50 of 2s to 5s, segregation percent with no more than 10%, the filling-time with 5s to 15s.