The amount of water added during the mixing process of concrete is called mixing water, which is calculated based on the concrete water-cement ratio in the mortar mix ratio (referring to the weight ratio of concrete source water to concrete demand). Stirring water consists of two parts, divided into free water and combined water. Free water ensures the workability and fallability of concrete. Combined water is the water used when concrete is solidified. Sufficient combined water can ensure sufficient hydrolysis and solidification of respirable particulate matter in concrete, converting it into crystals and solidification. However, this type of water demand is too small and usually only accounts for mixing. Two-fifths of water.
Free water slowly evaporates during the solidification and curing process of concrete and enters the gaps in the concrete, thereby reducing the compaction and compressive strength of the concrete. The combined water and concrete minerals can inhale particulate matter and cause crystallization and gelation, which will remain in the concrete. Therefore, the greater the free water in concrete, the smaller the density and compressive strength of concrete. Therefore, the water-cement ratio of concrete should be configured according to specifications, and water should be used as little as possible while ensuring the working performance of concrete (by controlling the slump of concrete).
Although this operation can save effort, adding more water when mixing "thin and soft" concrete or adding water to the already mixed concrete will inevitably increase the intrinsic void ratio of the concrete and damage the compressive strength. . Under this situation, only the required amount of concrete can be increased to ensure the required concrete water-cement ratio, but this leads to extravagant waste of concrete. Therefore, in the concrete specifications, the concrete water-cement ratio and the minimum amount of concrete required are limited according to the place and conditions where it is used. In order to reduce the demand for concrete and fully consider the slump requirements, admixtures can be added to the concrete. As mentioned above, the water used for concrete solidification only accounts for two-fifths of the required amount of mixing water. The amount required is very small. Admixtures The key is to make up for the loss of random water, so the addition of admixtures is a prerequisite for ensuring the solidification effect and taking into account the strength requirements of the concrete without reducing the strength level of the concrete.
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