Adding admixtures can delay the setting time of concrete.
Concrete admixtures are chemical substances that are added during the mixing process of concrete, accounting for less than 5% of the cement mass, and can significantly improve the performance of concrete. Concrete admixtures are characterized by many varieties and small dosages, which have a great impact on the performance of concrete. They have the characteristics of low investment, quick results, and significant technical and economic benefits. With the continuous advancement of science and technology, admixtures have been increasingly used, and admixtures have become the fifth important component in addition to the four basic components of concrete.
Admixtures have a certain improvement effect on the carbonation resistance of concrete. There is a certain linear relationship between the carbonation depth and porosity of concrete; admixtures have a great influence on the frost resistance of concrete. Concrete with water-reducing admixtures has better frost resistance, but adding early-strength admixture alone has no effect on improving the frost resistance of concrete.
The most commonly used concrete admixtures are naphthalene-based high-efficiency water-reducing admixtures, polycarboxylic acid high-performance water-reducing admixtures and aliphatic high-efficiency water-reducing admixtures.
Naphthalene series superplasticizer: Naphthalene series superplasticizer is a chemically synthesized non-air-entraining superplasticizer. The chemical name is naphthalene sulfonate formaldehyde condensate, which has a strong dispersing effect on cement particles. It has good use effect for preparing large flow concrete, cast-in-situ concrete and prefabricated components with early and high strength requirements. It can comprehensively enhance and improve various properties of concrete and is widely used in highways, bridges, dams, and ports. Wharfs, tunnels, electric power, water conservancy and civil construction projects, steam curing and natural curing prefabricated components, etc.
Reference materials;
Naphthalene-based water-reducing admixture is the most produced and widely used high-efficiency water-reducing agent in my country (accounting for more than 70% of the water-reducing agent consumption). Its characteristics are: It has a high water reduction rate (15-25), does not entrain air, has little impact on setting time, has relatively good adaptability to cement, can be used in combination with various other admixtures, and is relatively cheap.
Naphthalene-based water-reducing admixtures are often used to prepare high-fluidity, high-strength, and high-performance concrete. The slump loss of concrete simply mixed with naphthalene-based superplasticizer is faster. In addition, the adaptability of naphthalene-based water reducing agents to certain cements needs to be improved.