1. The coarse aggregate should be continuously graded and the fine aggregate should be medium sand.
2. The admixtures should be retarder and water reducer, and the admixtures should be fly ash and slag powder.
3. On the premise of ensuring the strength and slump of commercial concrete, the content of admixture and aggregate should be increased to reduce the cement consumption of commercial concrete.
4. Cement with low hydration heat and long setting time shall be selected as far as possible, and medium heat Portland cement, low heat slag Portland cement, dam cement, slag Portland cement, fly ash Portland cement, pozzolanic Portland cement, etc. shall be preferred.
However, the slag cement with low hydration heat has higher water evolution property than other cement, and there is a small amount of water precipitation on the surface of pouring layer. This kind of bleeding not only affects the construction speed, but also affects the construction quality. Due to the precipitation of water gathered between the surface of the upper and lower pouring layers, the water cement ratio of commercial concrete is changed, and some mortar is taken away when water is extracted, thus forming a layer of interlayer with more water content, which destroys the cohesive force and integrity of commercial concrete.
The size of the bleeding property of commercial concrete is related to the water consumption, the water consumption is large, the bleeding property is large; and it is related to the temperature, the time of water complete precipitation increases with the increase of temperature; in addition, it is also related to the composition and fineness of cement. Therefore, in the selection of slag cement, the type of bleeding should be selected as far as possible, and water reducing agent should be added into commercial concrete to reduce water consumption. During the construction, it is necessary to drain the water or mix some dry and hard commercial concrete in time, and pour it evenly at the water drainage place, and then continue to pour the upper layer of commercial concrete after vibrating with vibrator.