The Antifreezing Construction Technology Of Tunnel Concrete In Cold Region

This thesis contains explanations to what the cold region is and the type of tunnels in cold region, analyzing the frost-damage phenomenon and the frost-damage mechanism of Tunnel concrete in cold region, especially analyzing the frost-damage that the cold weather caused to fresh concrete and hardened concrete. An example is Bocetu Tunnel Project in bocetu Town of Inner Mongolia Autonomous Region, which is mainly researched on the antifreezing construction technology of concrete in cold region when constructing it. The content includes:(1) the type of admixture and its amount can be confirmed according to the demand of frost resistance and so on at a project; (2) At first, raw materials of soil, crushed stones, cement and so on were tested in accordance to the relevant standard to make sure that the result can meet the requirements of relevant technologies. Then the mix-proportion of the raw materials were initially designed according to the design strength. After experiments, the base mix-proportion was given according to the water-retention and cohesiveness of the mixture. At that time, test samples were made in the base proportion and tested the strength to confirm the mix-proportion obtained from experiment. Finally, the construction mix proportion of concrete should be conversion accroding to the water content ratio of soil and crushed stones which was tested at the construction site.(3) According to the conditions at construction site, some feasible heat preservation measures were proposed, and the lowest heating temperature of every raw material should be confirmed by the empirical formula for thermal calculation.At the same time, the heat preservation measures at the process of concrete mixture, transportation, pouring and the period of maintenance were proposed,etc. (4) Through temperature test of every step, engineers should adjust the measure to keep temperature of raw material at the process of concrete mixture, transportation and pouring to make sure to meet the requirement of the lowest temperature. (5) Test samples should be inspected to test the cubic compressive strength of the concrete through experiments of resist compressive and rebound test, and evaluated on The antifreezing construction technology of concrete at the process of construction. The result shows, through the above construction measures, a sound effect is achieved on the antifreezing construction technology of concrete and the quality of project is guaranteed, which has some practical value to some extent.