Post Date:23,Dec,2024

When cement hydrates, it forms a flocculation structure that wraps water inside. In order to make the hydration more complete and improve the construction performance of concrete, more water needs to be added. The addition of admixtures can be directional adsorbed on the surface of cement particles, so that the surface of cement particles has the same charge, which is separated by repulsion, releasing the water wrapped in the cement flocculation structure, allowing more water to participate in the hydration reaction and improve fluidity.

However, due to various reasons, admixtures and cement are also prone to incompatibility problems. The main manifestations are:

(1) The admixture does not significantly improve the working performance of cement;

(2) The slump loss of concrete is too large or the concrete sets too quickly;

(3) It makes cracks more likely to appear in concrete structural components.

These problems will seriously affect the quality of cement concrete, bring hidden dangers to the quality of the project, and even cause engineering accidents in serious cases, resulting in significant economic losses.

To solve the problem of incompatibility between admixtures and cement, prevention is the key, and attention should be paid to the selection of materials and the inspection of incoming materials. The compatibility of admixtures and cement is a more complicated issue. If there is an incompatibility problem between admixtures and cement, concrete manufacturers should take countermeasures in time. According to the situation, based on experiments, analyze and find the reasons, adjust the concrete mix ratio, increase the factory slump, and reduce the slump loss.

Usually, the amount of fly ash can be adjusted, the amount of admixture can be increased, the liquid phase residue of admixture in concrete can be increased, the water-cement ratio can be kept unchanged, and the amount of cement can be increased, but this will undoubtedly increase the unit cost. The secondary addition method can also be used during production, that is, the factory slump is controlled at 80-100, and the admixture solution is stirred for about 2 minutes before use on the construction site to adjust it to 140. This treatment is more economical and effective.

Concrete manufacturers often need admixtures to adapt to cement due to large inventory, that is, the admixture manufacturer needs to adjust the formula, adjust the type and dosage of water reducer and retarder in the admixture according to the cement used by the concrete manufacturer, or add plasticizer and air entraining agent with bubble stability, etc. When determining the concrete mix ratio during construction, the setting time of concrete needs to be taken into account, and the admixture should contain a retarding component. If the high temperature suddenly drops, too much admixture is used in the concrete, and the formula is not adjusted in time, the concrete will not set for a long time, which will seriously affect the strength of the concrete. In summer, construction should avoid the high temperature and strong wind at noon, and the raw materials should be cooled. The sand ratio during construction should be adjusted accordingly according to the size of the sand fineness and the porosity of the coarse aggregate.