In the cold winter, concrete construction faces many challenges, such as material freezing and increased construction difficulty. To ensure construction quality and efficiency, the following are some key optimization measures.
1、 Concrete raw materials and temperature control measures for mixing
1. Raw material selection and processing
Use conventional Portland cement and add admixtures to enhance frost resistance, with specific proportions determined based on the concrete mix ratio. All raw materials must be cleaned to avoid mixing with ice, snow, and minerals that are easily affected by temperature. Additives should use chlorine free antifreeze to prevent corrosion of steel bars. Construction water needs to be stored in an insulated tank to maintain an appropriate temperature and minimize water usage. Water reducing agents can be added to reduce freezing damage.
2. Concrete mixing technology
Add appropriate additives to improve the workability and strength of concrete, accelerate the hydration process of cement at low temperatures, reduce drying shrinkage performance, and enhance freeze-thaw resistance. Ensure that antifreeze does not affect the subsequent strength of concrete, and prohibit the mixing of water reducing agents and antifreeze on site.
2、 Temperature control measures for concrete transportation and pouring
1. Transportation insulation measures
The dump truck compartment needs to be sealed with insulation rolls, and the top should be covered with canvas or thin iron sheet. The tank truck compartment also needs insulation treatment. The time for concrete to be unloaded from the mixer to the construction site should not exceed 90 minutes, and the pumping pipeline should be insulated to prevent concrete segregation, surface freezing, or collapse. During transportation, the temperature drop rate of concrete should be controlled at no more than 5 ℃ per hour, and the molding temperature should not be lower than 10 ℃.
2. Pouring insulation measures
Key areas such as template joints and reinforcement joints require special insulation. Clean the formwork before formal pouring to prevent debris and snow from affecting it. Measures such as setting up scaffolding to prevent the influence of wind and snow, mechanical vibration to ensure the compactness of concrete, layered pouring to ensure the accuracy of the position of steel bars and embedded parts, and a smooth and even concrete surface after demoulding.
3、 Concrete curing and insulation measures inside the tunnel
1. Insulation inside the tunnel
Storage warehouses and mixing stations should use solar heating systems for heating to ensure that the temperature of concrete entering the mold is greater than 5 ℃. Cover the opening with insulation curtains to prevent cold air from entering, and assign a dedicated person to open and close the insulation curtains when transport vehicles enter and exit. The external water supply pipeline and high-pressure water tank need to be insulated, and a furnace should be installed every 50 meters inside the tunnel for heating, and a smoke exhaust pipe should be installed.
2. Concrete curing
After the template is removed, the temperature difference between the outside and the concrete should be controlled at 10-15 ℃, and the concrete surface should be insulated. The formwork can only be removed after the concrete has cooled to below 5 ℃ and the temperature difference with the environment is not greater than 15 ℃.
These measures can effectively improve the quality of winter concrete construction and ensure the smooth progress of the project.