Water reducing agents, also known as plasticizers, are additives used in concrete and other cementitious materials to reduce the amount of water needed to achieve the desired workability and strength. The mechanism of action of water reducing agents can be explained by their effect on the physical properties of cementitious materials.
Water reducing agents work by adsorbing onto the surface of cement particles and changing the electrostatic charges on the particles. This reduces the repulsive forces between the particles, allowing them to pack together more tightly. As a result, the void spaces between the particles are reduced, and the water required to fill those spaces is decreased.
The use of water reducing agents can also improve the workability of the concrete or cementitious material, making it easier to handle and place. This is due to the reduction in viscosity of the mixture, which allows for improved flow and consolidation.
Water reducing agents can be classified into two main categories: lignosulfonates and synthetic polymers. Lignosulfonates are derived from wood pulp and are commonly used in low to moderate strength concrete. Synthetic polymers are manufactured from chemicals and can provide a greater reduction in water demand and improved workability, making them suitable for use in high-performance concrete.
In summary, the mechanism of action of water reducing agents involves adsorption onto cement particles and changing the electrostatic charges on the particles. This reduces the repulsive forces between particles and allows them to pack together more tightly, reducing the void spaces and decreasing the amount of water needed. The use of water reducing agents can also improve the workability of the concrete or cementitious material, making it easier to handle and place.