Applied Basic Research Of Performance Enhancing Of High Strength Concrete

The construction scale of high-speed railway increased with the rapid development of our society and economy. The application of high strength concrete is becoming wider and wider, and the amount of high strength concrete is increasing in the railway engineering. However, high strength concrete still exist high viscosity and poor toughness problems. In order to ensure the survice of the structures, the problems of high-strength concrete must be solved, so that four parts were studied.Firstly, Flexural toughness and impact toughness of same strength concrete with different cementitious material content were emphatically compared. The results showed that, Flexural toughness and impact toughness of concrete can be improved significantly by reducing cementitious material content. The toughening mechanism of concrete with low dosage of cementitious material was analyzed by thermal analyzer, mercury porosimeter and medical CT. The flow content reduced with the decrease of cementitious material content and the increase of aggregate content played great role in crack resistance and energy consumption which lead to the improvement of concrete toughness. The research direction of reducing cementitious material dosage was determined which lays a theoretical foundation for low cementitious material content concrete preparation technology.Secondly, low cementitious material content concrete preparation method was proposed on the study of sand ratio, water to cement ratio, paste thickness wrapping around aggregate and composition of cementitious materials.① Sand ratio was determined by packing density of aggregate calculated by CPM, and the max packing density of aggregate calculated was 84% when the sand ratio was 38%. ② Proper water to cement ratio was 0.35 guided by the plastic viscosity of concrete. ③ Paste thickness wrapping around aggregate was selected according to the workability, and then the paste content was calculated. ④ The amount of cementitious materials, water, sand and gravel was calculated by absolute volume method. ⑤ Cementitious material composition of the concrete was determined based on concrete strength. High strength concrete with low cementitious material dosage is prepared by improving the activity of cementitious material. C80 concrete could be prepared using 90% P·W 62.5 white cement and 10% of S95 slag powder when the dosage of cementitious material was 370 kg/m3 and the dosage of water was 130 kg/m3.Thirdly, Workability evaluation methods of low cementitious material concrete and mechanical properties, thermophysical properties, volume stability and crack resistance of the low cementitious material concrete and concrete used in the engineering in the same strength were compared. The results showed that, workability evaluation method should be chosen by the slump of concrete. The adiabatic temperature rise reduced, volume stability and crack resistance improved with the decrease of cementitious material consumption.Finally, engineering application research was carried out in the guide of low cementitious material concrete theory. The results showed that, the work efficiency of track slab and sleeper preparation by low cementitious material concrete improved significantly. The surface of the track slab and sleeper was smooth and compact, and there was less cracking and fall-block.