1.Classification of polycarboxylate superplasticizers
In the process of rapid economic and technological development in our country, polycarboxylate superplasticizers with high-efficiency water-reducing properties are often used in construction concrete. The common ones are as follows: polypropylene hydrochloric acid, methylpropionic acid, maleic acid polymers, polymaleic acids, etc. Polypropylene hydrochloric acid water reducing agent has good fusion with other types of cement in the process of use, and has been widely used in the actual use process. In the process of use, the monomer acrylic acid is used as the precursor, and it is combined with polyoxyethylene to obtain a product with a higher molecular weight. Methylpropionic acid and maleic acid polymer is a block-type water-reducing polymer formed by methylpropionic acid and maleic anhydride in the form of monomers, and it is guaranteed by compounding with other water-reducing agents. fluidity and adsorption. Maleic acid is a water-insoluble, polymer-reactive fine-particle water-reducing agent. The main chain in its molecular structure has groups such as acid anhydride and molecular lactone. When ready-mixed concrete, the alkaline component will cause These molecular groups are hydrolyzed, and in this way, the water-insoluble polymer can be effectively turned into a soluble polymer, and at the same time, under the action of the dispersant, it can slowly enter the solution. The hydrolysis phenomenon on the concrete surface is carried out gradually and slowly, and the slump loss of the concrete structure is effectively avoided by means of slow dispersion.
2.Key technologies for the application of polycarboxylate superplasticizers
In recent years, polycarboxylate superplasticizers have been widely used in many construction projects in my country. Modern concrete has high requirements for external functional additives, so when polycarboxylate water reducer is added to the concrete system, the following key technologies should be considered.
(1) Compatibility technology of polycarboxylic acid system. Due to the special structure of polycarboxylate-based high-performance water-reducing agent, it cannot be stored and used together with other water-reducing agents, especially naphthalene-based water-reducing agents. When it is necessary to use alternately with different types of superplasticizers, the relevant containers must be carefully cleaned to prevent cross-contamination from affecting the quality of concrete. The adsorption performance of the superplasticizer is different due to the different types of cement. Since the compatibility range of the polycarboxylate superplasticizer in cement is relatively narrow, it is inevitable that the compatibility is not good. Therefore, it is necessary to increase its dosage or use different types of cement. to effectively solve this problem.
⑵ polycarboxylate water reducing agent retarding technology. In the construction process, due to the short retardation time, the use of retarder can effectively prolong the plasticity of concrete. However, the incompatibility of the two should also be considered to avoid the reduction of concrete performance.
⑶ gas content control. The polycarboxylate water reducing agent has good air-entraining effect and can be used together with defoamer and air-entraining agent. By eliminating first and then introducing, the air content of concrete can be controlled, and its workability and durability can be improved.
⑷ The control of the mud content of sand and gravel. The mud content of sand and gravel will also affect the application effect of polycarboxylate high-performance water reducer. If the mud content in the sand exceeds 2%, the structure between the clay layers will absorb a large amount of water-reducing agent molecules, which will reduce the flow performance of the concrete. If the mud content in the construction process is relatively large, the anti-clay polycarboxylate water reducer should be considered.
Post time: Apr-27-2022