Concrete is a major invention of human beings. The emergence of concrete has started a revolution in the history of human architecture. The application of concrete admixtures is a major improvement in concrete production.The emergence of concentrated concrete batching
plants has made the production of building material concrete move towards the road of industrialization and conservation. This also puts forward more requirements on the quality control of concrete production, resulting in the overall improvement of concrete quality in recent years. At the same time, due to the low level of quality control technology in some concrete ready-mix plants, it has brought hidden dangers to the project quality, and even appeared. The engineering quality accident that has not been encountered in more than 20 years has caused heavy economic losses.
The main factors that cause the incompatibility between admixtures and cement:
The performance of concrete depends not only on the function of the constituent materials, but also on the adaptability between the materials and the concrete mix ratio. Admixtures (water reducers) are not compatible with cement, that is, the admixtures do not significantly improve the working performance of cement, the slump loss of concrete is too large or the concrete is too fast setting, and even cracks are more likely to occur in concrete structural members.
As the fifth component of concrete, admixture accounts for a small proportion, but it has a great influence on the performance of concrete, which can significantly improve the slump of concrete and adjust the coagulation time, thereby improving the performance of concrete construction or saving costs. The hydration reaction of cement requires less than 25% of the water of the cement mass, but when the cement encounters water, it will form a flocculation structure to wrap the water in it. The addition of the admixture can directional adsorption on the surface of the cement particles, so that the surface of the cement particles has the same charge, which is separated due to the repulsion effect, thereby releasing the water wrapped by the cement flocculation structure, so that more water can be involved in the hydration reaction. , improve activity. The size of the adsorption of cement particles to the admixture and the loss of the effect of the admixture reflect the adaptability of the admixture to the cement.
The problem of incompatibility between admixtures and cement is a problem that worries and headaches for all commercial concrete manufacturers. After the problem occurs, it is ultimately blamed on the admixture. The incompatibility between the admixture and the cement is caused by the admixture itself. Factors of quality and chemical composition, but the main reason is often related to factors such as cement and admixtures, whether it is ordinary water-reducing agent, nylon-based superplasticizer or the third-generation polycarboxylic acid-based superplasticizer will appear.
Post time: Jul-19-2022