The molecules of early-strength (salt) water-reducing agent are artificially formed through “molecular design” with a “comb-like” or “dendritic” structure, and there are many branches with a certain length and stiffness connected to the main chain of the molecule. chain (side chain). There are also sulfonates or other groups on the main chain that can charge the cement particles, which can play the role of traditional water-reducing agents. More importantly, once the main chain is adsorbed on the surface of the cement particles, the branch chains will interact with the surfaces of other particles. The branched chains form three-dimensional intersections, which prevent the particles from approaching each other, thereby achieving dispersion (i.e. water reduction).
This steric hindrance effect will not weaken with time. Therefore, the dispersion effect of early-strength superplasticizer is more lasting.
The early-strength series high-performance water-reducing agent is the third generation of high-performance water-reducing agent developed after the ordinary water-reducing agent represented by lignocalcium and the high-efficiency water-reducing agent represented by the naphthalene series. It is currently the world’s most cutting-edge, high-efficiency water-reducing agent with the highest scientific and technological content, the best application prospects, and the best overall performance. It has a high proportion of active ingredients and a concentrated molecular weight range. Therefore, compared with other water-reducing agents, early-strength water-reducing agent not only has a higher water-reducing rate and maintains a lower slump, but also has a smaller dosage. Concrete prepared with early-strength high-performance water-reducing admixture will not have obvious segregation or bleeding even under high slump conditions, and the concrete will have a uniform appearance and color. It is extremely beneficial for preparing high-fluidity concrete, self-leveling concrete, self-compacting concrete, and fair-faced concrete. When used to prepare high-grade concrete, the concrete has good workability and cohesion, and the concrete is easy to mix. It has good compatibility with different types of cement and admixtures, solving the problem of compatibility between other types of water reducing agents and cementitious materials.
Water reducing effect is an important role played by surfactants in the cement hydration process. Water reducing agent can reduce the unit water consumption without affecting the workability of concrete; or it can improve the workability of concrete without changing the unit water consumption; or it can have the above two effects at the same time without being significant. Admixtures that change the air content. Currently, the concrete water-reducing agents used are surfactants, which are anionic surfactants. After the cement is mixed with water, a hydration reaction occurs, and some flocculation-like structures appear, which wrap a lot of mixing water, thereby reducing the workability of fresh concrete (also known as workability, which mainly refers to the fresh concrete during construction, that is, The performance of being able to maintain uniformity and density without stratification and segregation during mixing, transportation, watering, etc.). In order to maintain the required workability during construction, the amount of mixing water must be increased accordingly. Because the increase in water amount will form excessive pores in the cement stone structure, which will seriously affect the physical and mechanical properties of hardened concrete, if these wrapped When the moisture is released, the water consumption of concrete can be greatly reduced.
In the process of preparing concrete, adding an appropriate amount of water reducing agent can play such a role well. After water-reducing agent is added to concrete, the hydrophobic groups of the water-reducing agent are directionally adsorbed on the surface of cement particles, while the hydrophilic groups are directed toward the aqueous solution, forming a single-molecule or multi-layer adsorption film. Due to the directional adsorption of the surfactant, the surface of the cement particles has charges of the same sign. Therefore, under the action of same-sex repulsion, not only can the cement-water system be in a relatively stable suspended state, but also the cement can be added with water. The flocculated structure formed in the initial stage is dispersed and disintegrated, thereby releasing the water in the flocculated structure to achieve the purpose of water reduction. After the water-reducing agent is added, not only can the workability of fresh concrete be improved, but also because the water-cement ratio in the concrete has dropped significantly, the internal pore volume of the cement stone has been significantly reduced, the cement stone has become denser, and the resistance of the concrete has increased. The compressive strength is significantly improved. The addition of water reducing agent also affects the hydration rate and setting time of cement. These properties are very important in practical applications. </p
微信扫一扫打赏
