Post Date:20,Feb,2023
What is water reducing agent?
Water reducing agent, also known as dispersant or plasticizer, is the most widely used and indispensable additive in ready mixed concrete. Due to its adsorption and dispersion, wetting and slippery effects, it can significantly reduce the water consumption of fresh concrete with the same working performance after use, thus significantly improving the strength, durability and other properties of concrete.
Water reducing agent can be divided into two types according to its water reducing effect: ordinary water reducing agent and high efficiency water reducing agent. The water reducing agent can be compounded with other admixtures to form early strength type, common type, retarding type and air entraining type water reducing agent according to the engineering needs in application.
Water reducing agents can be divided into lignosulfonate and its derivatives, polycyclic aromatic sulfonic acid salts, water-soluble resin sulfonic acid salts, aliphatic sulfonic acid salts, higher polyols, hydroxy carboxylic acid salts, polyol complexes, polyoxyethylene ethers and their derivatives according to their main chemical components.
What is the action mechanism of water reducer?
All water reducing agents are surface active agents. The water reducing effect of water reducing agent is mainly realized by the surface activity of water reducing agent. The main action mechanism of water reducer is as follows:
1) The water reducer will adsorb at the solid-liquid interface, reduce the surface tension, improve the surface wetness of cement particles, reduce the thermodynamic instability of cement dispersion, and thus obtain relative stability.
2) The water reducer will produce directional adsorption on the surface of cement particles, so that the surface of cement particles will have the same charge, generating electrostatic repulsion, thus destroying the flocculated structure of cement particles and dispersing cement particles. For polycarboxylate and sulfamate superplasticizers, the adsorption of the superplasticizer is in the form of ring, wire and gear, thus increasing the distance between cement particles to generate electrostatic repulsion, showing better dispersion and slump retention.
3) The solvated water film is formed through the hydrogen bond association between the water reducer and water molecules to produce space protection, prevent the direct contact of cement particles and prevent the formation of condensed structure.
4) As an adsorption layer is formed on the surface of cement particles, it can inhibit the initial hydration of cement, thus increasing the free water volume and improving the fluidity of cement paste.
5) Some water reducing agents will also introduce a certain amount of micro bubbles to reduce the friction between cement particles, thus improving the dispersion and stability of cement slurry.
Post time: Feb-20-2023