The Role of Double-Cylinder Insulation Technology in Ensuring the Quality of Bored Pile Concrete under Negative Temperature Condition

摘要

In this paper, the cement concrete with low heat of hydration was prepared by adding fly ash, and then used in the double-cylinder insulation technology.Based on heat dissipation test, thermal conductivity test and low temperature strength test of the prepared concrete, the growth law of concrete strength under negative temperature condition was studied.The strengths of three concrete test piles at the corresponding temperature were measured by ultrasonic method, and the influence law of double-cylinder insulation technology on the change of concrete strength was studied.The results show that the curing temperature dropped from 20?C to -3?C, -5?C and -7?C on the 28th day.Compared with the standard curing temperature, the strength loss was 29.7%, 31.7% and 42.8%, respectively.There were similar rules on the 60th day and 28th day.In the first 7 days, the temperature of low hydration heat concrete was 1.~2.8°C lower than that of ordinary concrete.From the 7th day to the 28th day, the temperature of low hydration heat concrete was 0.5°C higher than that of ordinary concrete.After applying the double-cylinder insulation technology to the concrete, the temperature was increased by 7.9°C, 7.3°C and 4.8°C in 0~3rd day, 3rd~7th day and 7th~28th day, respectively.Compared with strength on the 28th day, the strength of low-hydration heat concrete was 2.15% higher than that of ordinary concrete.After applying polyurethane insulation layer, the strength of the low-hydration heat concrete increased by 18.6% compared with that of the low-hydration heat concrete without insulation layer.