What is polycarboxylic acid superplasticizer?
As an admixture, concrete superplasticizer is added to concrete to reduce water consumption and increase the strength of concrete. At present, the high-performance water-reducing agents used in concrete engineering are mainly polycarboxylic acid superplasticizer products.
1. Features of high performance water reducing agent concrete
(1) High water reduction rate. Under the same slump, the water reducing rate of high-performance water reducing agent is relatively high, and its water reducing rate is generally above 35%. Due to the high water-reducing rate of the water-reducing agent, the water consumption of concrete is greatly reduced. When calculating the parameters of the water reducing agent, it should be calculated according to 0.25% of the cement amount, and high-performance concrete can be prepared by increasing the amount of admixtures.
(2) Good liquidity. Generally speaking, in the application process of high-performance water reducer, the flow performance will not deteriorate, which is beneficial to reduce the occurrence of concrete segregation or tube pump blockage. To ensure the performance of the concrete mixture, the water reducing agent should be selected according to the variety of cement to ensure the quality of the construction project.
(3) The strength of the mixture is improved. Adding water reducing agents (such as slag, fly ash, etc.) to concrete can improve the strength of the mixture. In the case of ensuring the stability of the cement dosage, adding a high-performance water reducer to the concrete can increase the strength of the concrete to more than 70%.
(4) The total alkali content is low. Adding an appropriate amount of high-performance water reducer to concrete will reduce the alkali content of concrete, reduce the incidence of alkali-aggregate reaction to a certain extent, and improve the durability of concrete.
(5) The shrinkage is lower. Since the performance of polycarboxylate water reducer is relatively good, it can ensure the quality of formula raw materials in the selection of raw materials. In addition, the total alkali content of the water reducing agent is low, which is conducive to maintaining the stability of the concrete and preventing the occurrence of concrete cracks.
2. Types of high performance superplasticizers
High-performance water reducers are mainly divided into three types: slump-preserving type, functional type and shrinkage-reducing type. These types are briefly described below.
(1) Collapse protection type. The slump-preserving water-reducing agent is generally used in the development of concrete. By adding this type of water-reducing agent, the slump of concrete can be ensured and the fluidity of concrete can be reasonably controlled.
(2) Functional type. The functional type of water reducing agent is mainly divided into two functions, one is early strength type and the other is retarded type. Among them, the early-strength water-reducing agent can make the concrete meet the exothermic requirements in the early stage and promote the coagulation of the concrete, which is beneficial to the construction of the concrete in winter. However, the application of retarder water reducing agent in concrete mainly reflects the ability to maintain the concrete state, so as to facilitate the repair of concrete in the later stage. However, if these two water reducers are used in combination, they can play a role in retarding the setting of cement.
(3) Reduced type. The shrinkage-reducing type of the water-reducing agent is mainly synthesized by esterification, which not only has a certain water-reducing effect and shrinkage-reducing function, but also fully exerts the water-reducing effect of concrete.
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