The air-entraining agents are surfactants and can be divided into anionic, cationic, nonionic and amphionic types. The more widely used are anionic surfactants. The commonly used are the following categories:
- . Rosin-based Air-entraining Agents
Rosin-based air-entraining agents are produced by the reaction and polycondensation of rosin or the saponified product of rosin acid with phenol, sulfuric acid and sodium hydroxide at a certain temperature to form macromolecules and then to become rosin hot polymer by sodium hydroxide treatment.
The rosin-based air-entraining agent has had an application history of more than 60 years, with reliable performance, simple preparation method, low price and better effects. It can significantly improve the workability, impermeability and frost resistance of slurry, but its drawback is difficulty of solution in water, so heating and adding alkali are needed during use.
- . Non-rosin Air-entraining Agents
Non-rosin-based air-entraining agents include sodium alkylbenzene sulfonate, OP emulsifier and acrylic epoxy resin. Such a kind of air-entraining agent is characterized by the introduction of hydrophilic groups on the basis of non-ionic surfactant, making it easily soluble in water, have good foaming property and delicate foams, and better compou7nd with other varieties of additives. And sodium alkylbenzene sulfonate is easily soluble in water and has great foaming capacity, but the foams are easy to disappear.