Common Misunderstandings Of The Use Of Concrete Admixtures

Mistake 1: Concrete admixtures are directly put into use without testing

Before concrete construction, construction units and supervision units always send building materials such as cement, sand and stone to inspection institutions in batches in accordance with specifications for inspection, but often do not pay enough attention to the performance test of admixtures. In fact, there are many types of concrete admixtures, and there are corresponding quality standards. Its performance directly affects its role in concrete, such as the size of water reduction rate, chloride ion content and so on.

Misunderstanding 2: The use of concrete admixtures without considering the actual situation of the project

1. The purpose of use should be considered when selecting admixtures. When selecting admixtures, it should be determined by test mixing test according to engineering materials and construction conditions. All kinds of admixtures have their own characteristics. In use, should be based on the characteristics of the admixture and the purpose of use, such as considering saving cement, improving concrete performance, accelerating formwork turnover and other comprehensive indicators, that is, through technical and economic comparison, to determine the type of admixture selected.

(1) The purpose of applying admixtures in waterproof concrete is to improve the impermeability of concrete. To improve the impermeability of concrete, the key is to reduce the porosity inside the concrete, block the leakage channel, and apply water reducing agent and air entraining agent. 

(2) The key of mass concrete construction technology is to ensure a good bond between the layered concrete at the initial setting, reduce the temperature rise in the concrete hardening process, and avoid concrete cracking. The use of retarding water reducing agent can meet the above requirements, that is, slow setting, reduce the temperature rise in the hardening process of concrete, thereby improving the quality of concrete. 

(3) In long-span prestressed concrete structures, the self-weight of the structure is often the main contradiction. Therefore, the purpose of using admixtures is to prepare high-strength concrete, reduce the structural weight, and effectively use the stress of high-strength reinforcement. It is advisable to use high efficiency water reducing agent, which can greatly reduce the unit water consumption and improve the strength of concrete.

Hydroxypropyl Methyl Cellulose HPMC

Sodium Lignosulphonate (MN-3)

Sulfonated Naphthalene Formaldehyde