Thermodynamic Control of the Mixing Process: Concrete Workability Maintenance Technology in High-Temperature Environments

Thermodynamic Control of the Mixing Process: Concrete Workability Maintenance Technology in High-Temperature Environments

When producing or constructing concrete in high-temperature environments, excessively high temperatures accelerate the reaction between cement and water, causing the concrete to thicken and dry too quickly, shortening its workable time, and potentially affecting its final strength. To address this challenge, it is necessary to actively manage the concrete temperature through thermodynamic control of the mixing process to maintain its good fluidity and workability.

The core objective is to control the concrete's outlet temperature. This is primarily achieved by controlling the temperature of the raw materials. The most effective measure is to reduce the temperature of the mixing water, such as by using cooling water or adding ice; secondly, cooling the coarse aggregate can be achieved through water spraying, shading, or using a cold air circulation system. In extreme cases, the cement silo can also be shaded and insulated. By calculating and adjusting the temperature and proportion of various raw materials, the temperature of the fresh concrete can be controlled within a target range (generally recommended not to exceed 30-35℃).

The use of retarders is a key chemical control method. At high temperatures, adding retarders or water-reducing agents with retarding properties to concrete can effectively slow down the early hydration reaction rate of cement, prolonging the time the concrete remains in a fluid state and providing a longer workable window for transportation, pouring, and vibration. The optimal dosage needs to be determined through testing based on the specific temperature, cement type, and project requirements.

Optimizing mixing and construction organization are crucial process management measures. In the mixing stage, delayed addition processes can be adopted, such as pre-cooling and mixing aggregates and some water before adding cement and remaining water, to reduce the cement's heating time. In construction organization, the time from concrete leaving the mixer to completion of pouring should be minimized. Insulated transport trucks should be used, on-site pouring should be continuous and rapid, and freshly poured concrete should be properly shielded, insulated, and cured promptly to prevent excessive moisture evaporation.

By comprehensively utilizing these physical cooling, chemical retarding, and process optimization techniques, the negative effects of high temperatures can be effectively offset, ensuring that concrete maintains good workability under hot conditions, thereby guaranteeing construction quality and structural durability.