Which method can be used to increase the workability of concrete?

Increasing the workability of concrete is crucial for ensuring that it can be easily mixed, placed, and finished without segregation or excessive bleeding. The correct option involves adding appropriate admixtures, as they can significantly improve the properties of fresh concrete.

Admixtures are chemical additives that can be incorporated into the concrete mix to modify its behavior. For workability, water-reducing admixtures or plasticizers are commonly used. These admixtures allow for a reduction in the water-to-cement (W/C) ratio while maintaining the same workability, making the concrete easier to handle without compromising strength. Additionally, some admixtures can enhance flowability, making it easier to place the concrete in forms or around reinforcement.

Other methods to improve workability, such as adjusting the W/C ratio or aggregate shape, generally do not provide the same level of control or effectiveness as using admixtures tailored specifically for that purpose. For instance, reducing the W/C ratio typically leads to decreased workability unless compensatory measures, such as incorporating admixtures, are taken. Similarly, using smaller, irregular-shaped aggregates can worsen workability by increasing friction and inter-particle forces. Lowering the mixing temperature can reduce the viscosity of the concrete mix but does not reliably enhance workability