Water-reducers, or plasticizers, are chemical admixtures used in concrete to improve strength and workability. These additives reduce the water-cement ratio without compromising workability, lower the cement content while maintaining the same workability, or increase workability to assist concrete placement in inaccessible areas.
Plasticizers function by using surface-active agents to create repulsive electrostatic forces between cement particles. This dispersion enhances the concrete's workability and reduces the need for mixing water by 5 to 15 percent. Despite the retardation of setting time with certain plasticizers, the workability loss over time is not necessarily diminished. It's important to have trial mixes to ensure compatibility with air-entraining agents, which can introduce air pockets that affect the concrete's final properties.
These admixtures enhance the strength of concrete, particularly at early stages, due to the more uniform hydration of cement. They are generally effective across all cement types, with a more pronounced strength increase in cement with low tricalcium aluminate or alkali content. Correct usage of water-reducers can improve the durability of the concrete as well. However, before implementation, it's critical to test for possible negative effects like segregation or bleeding to ensure the long-term viability of the concrete structure.
