Mechanism of action of sodium sulfonate superplasticizer
Release time:
2017-11-25
Mechanism of action of sodium sulfonate superplasticizer
Most water reducing agents are surfactants. Therefore, the mechanism of action of sodium lignosulfonate is surface activity. After adding surfactants to aqueous solutions, they can reduce the surface tension (water gas phase) and interfacial tension (water solid phase) of water. Surfactant molecules generally have two functional groups: hydrophilic and hydrophobic. Hydrophobic groups are various alkyl or alkaryl groups; Hydrophilic groups are generally salts that can dissociate ions. According to the different ions dissociated by hydrophilic groups, surfactants can be divided into.
Anionic surfactants; Cationic surfactants; Amphoteric surfactants; Non ionic surfactants. After adding sodium lignosulfonate as a water reducing agent to concrete, the hydrophobic group of the water reducing agent is oriented and adsorbed on the surface of cement particles, while the hydrophilic group points to the aqueous solution, forming a single-molecule or multi-molecule adsorption membrane. This disperses cement particles due to mutual repulsion of the same surface charge, releasing excess water from the particles to achieve the goal of water reduction.
At the same time, due to the reduction of the surface tension of water and the interfacial tension between cement particles, while maintaining the same fluidity, the corresponding reduction in water consumption also plays a role in reducing water consumption. Water reducing agents can significantly reduce the hydration of concrete, reduce porosity, increase the compactness of concrete, and thus greatly improve the strength and impermeability of concrete. Lignosulfonate is a natural polymer compound with a molecular weight of 1000-30000.
It is made from the leftovers of pulp production, which are fermented to extract alcohol, and then neutralized with alkali. The main products include calcium lignosulfonate, sodium lignosulfonate, magnesium lignosulfonate, etc. Among them, the most widely used calcium lignosulfonate is made from sulfite pulp waste liquid. This type of water reducing agent has a rich source of raw materials, simple manufacturing process, low price, and is widely used in China, accounting for about 80% of the total production of water reducing agents. However, its effect is not very good, and it has the functions of air entrainment and retarder. It belongs to the category of ordinary water reducing agents, and its composite use with early strength agents has a good effect.
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