Commonly used compound materials include sodium gluconate, dextrin, air-entraining agents, defoaming agents, sodium nitrate, inorganic salts, alcoholamine enhancers, etc.
The compounding methods are:
Mixed with traditional water-reducing agent.
The molecular structure of early-strength superplasticizers is artificially designed, and most of them are "comb-shaped" or "dendritic", with multiple molecular backbones connected to them. A branch chain with a certain length and stiffness. There are also sulfonate or other groups on the main chain that can charge the cement particles. Once the main chain is adsorbed on the surface of the cement particles, the branch chains will form three-dimensional intersections with the branch chains on the surface of other particles, preventing the particles from approaching each other, thereby achieving Dispersion (i.e. water reduction) effect.
The molecules of traditional water-reducing agents (lignosulfonate, naphthalenesulfonic acid condensate, sulfonated melamine, etc.) are all linear structures. Once the molecules are adsorbed On the surface of cement particles, the sulfonate groups of the molecules charge the surface of the cement particles, forming an electric field. Since the charged particles repel each other, the particles are dispersed in the medium (water), thereby achieving water reduction. The two have different proportions of active ingredients and a large difference in molecular weight. If used together, adverse reactions will occur and the concrete will not work.
Compounded with retarder:
Due to the collapse of high-efficiency water-reducing agents such as naphthalene series The reason for the large drop loss is that in the past, water-reducing admixtures often used compound retarders to solve this problem. There are many kinds of retarders, and their adaptability is not exactly the same as that of early-strength water-reducing agents.
Among them, sodium citrate is not suitable for compounding with early strength water reducing agent. Its combination with early-strength superplasticizer not only fails to retard the setting, but may cause accelerating coagulation, and the mutual solubility between sodium citrate solution and early-strength superplasticizer is also very poor.
Saccharide retarder, which is also the retarding modification component of naphthalene series water reducing agent, is mainly sodium gluconate, which is the same as early strength series water reducing agent. The compound has good operability and good retarding effect. Under appropriate conditions, it can also increase the strength of concrete.
Early strength water reducing agent:
Early strength water reducing agent (Polycarboxylate Superplasticizer) is A high-performance water-reducing agent and a cement dispersant used in cement concrete applications. Widely used in highways, bridges, dams, tunnels, high-rise buildings and other projects. This product is green and environmentally friendly, non-flammable and non-explosive, and can be safely transported by train and car.
Polycarboxylate Superplasticizer is a high-performance water-reducing agent and a cement dispersant used in cement concrete applications. It can chemically Divided into two categories, the main chain is methacrylic acid, the side chain is carboxylic acid group and MPEG (Methoxy polyethylene glycol), and the polyester structure.
In terms of historical development, before the emergence of early strength admixtures, there were lignin sulfonate admixtures, naphthalene sulfonate formaldehyde condensates, and melamine Formaldehyde condensation polymers, acetone sulfonate formaldehyde condensates, sulfamate formaldehyde condensates, etc. These products have certain advantages in cost and are adaptable to high mud content in materials such as sand and gravel. They are firmly established in the market. It has a large share and is used to varying degrees in concrete projects. </p
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