With the development of the national construction industry, the requirements for building materials are getting higher and higher. Concrete, which is the main building material, not only requires strong solidity, but also features such as condensation, large flow, and high durability. And pay attention to the cost of construction and maintenance convenience. In this case, concrete additives have a place to use. There are many types of concrete admixtures, mainly based on their function. The effect of the admixture on the performance of the concrete needs to be controlled from the type of addition and the amount added. Therefore, in the concrete configuration, how to properly use the concrete admixture is very important.
Concrete additive is an admixture added during concrete mixing. It is mainly used to improve the performance of concrete. From the point of addition ratio of admixture, it is generally not more than 5%. Although it contains a small amount, it has played an active role in improving the performance of concrete and has become an indispensable part of the current development of concrete. The additives used in concrete mainly refer to different types of water reducing agents. The extensive promotion of concrete admixtures has led to significant improvements in the strength of the concrete, its brittleness and its own weight, and has improved the applicability of concrete construction. For example, adding antifreeze to concrete can make concrete construction work in the cold winter. The use of superplasticizers enables the renewal of concrete placement and flow regimes. Regardless of China's environmental protection or economic benefits, the emergence of concrete additives has greatly improved the level of technological development in the construction industry.
According to the function of concrete admixtures, there are mainly four categories. One is an admixture for controlling the rheology of concrete. Commonly used are water reducing agents, pumping agents and air entraining agents. The second is to change the setting time and hardening degree of the beam concrete. There are mainly retarders, accelerators or early strength agents. The third is to improve the durability of concrete. There are mainly air entraining agents, waterproofing agents, and rust removing traces. The fourth is the improvement of other properties of concrete. Commonly used are expansion agents, colorants, antifreeze and defense
Water and so on.
The water reducing agent is mainly to ensure the reduction of water consumption on the basis of ensuring the workability of concrete. Or it is to improve the workability of concrete without changing the water consumption. The water reducing agent can improve the strength and deformation ability of the concrete, and at the same time, it is beneficial to the improvement of the impermeability, and does not corrode the steel bars, and is beneficial to the anti-rust treatment of the steel bars. Water reducing agents can be subdivided into ordinary water reducing agents and superplasticizers.
Ordinary water reducers enable concrete to achieve at least 5% water reduction. For concrete aged 3-7 days, the compressive strength of concrete can be increased by 10%, and the concrete strength of about 28 days is increased by at least 5%. Ordinary water reducing agent is mainly calcium sulfonate water reducing agent. The calcium lignin sulfonate water reducing agent belongs to an anionic surfactant. In the case of concrete incorporation, the amount is 0.2%-0.3% of the amount of cement, and the water reduction rate is about 5%-15%. When the water consumption is constant, the concrete strength can be increased by about 10%-15%. The water-cement ratio of C50 concrete is generally about 0.3, the water-to-binder ratio is lower, the admixture is 4%, and if the C30 strength is required, the dosage is 2.5%. When the strength requirements are the same, the cement consumption can be saved by 20%. These water-reducing agents are highly applicable and can be used in various precast and cast concrete, steel and prestressed concrete, large-volume large-module concrete, pumping and waterproof concrete, large formwork and slipform concrete construction. However, steamed concrete is not suitable.