How can you improve the workability of fresh concrete?

1 Adjust the water-cement ratio

The water-cement ratio (w/c) is the ratio of the weight of water to the weight of cement in a concrete mix. It influences the strength, shrinkage, and permeability of hardened concrete, as well as the workability of fresh concrete. Generally, a lower w/c ratio results in higher strength and lower workability, while a higher w/c ratio results in lower strength and higher workability. Therefore, to improve the workability of fresh concrete, you can increase the w/c ratio slightly, but not too much to compromise the strength and durability. A typical range of w/c ratio for normal concrete is 0.4 to 0.6.

2 Use well-graded aggregates

Aggregates are the inert materials, such as sand, gravel, or crushed stone, that make up most of the volume of concrete. They affect the workability of fresh concrete by their shape, size, texture, and gradation. Well-graded aggregates have a good distribution of different sizes, which allows them to pack more densely and reduce the voids and the amount of cement paste required. This improves the workability of fresh concrete by reducing the friction and cohesion between the particles. On the other hand, poorly-graded aggregates have a narrow range of sizes, which leads to more voids and more cement paste required. This reduces the workability of fresh concrete by increasing the friction and cohesion between the particles.

3 Add admixtures

Admixtures are substances that are added to concrete before or during mixing to modify its properties. There are many types of admixtures, but some of the most common ones that can improve the workability of fresh concrete are water reducers, plasticizers, and superplasticizers. Water reducers are chemicals that reduce the amount of water needed to achieve a certain level of workability, without affecting the strength and durability of concrete. Plasticizers are chemicals that increase the workability of concrete by reducing the friction and cohesion between the cement paste and the aggregates, without reducing the water content. Superplasticizers are chemicals that have a higher effect than plasticizers, and can produce very high workability or flowability of concrete, with minimal water content.

4 Control the temperature

The temperature of fresh concrete affects its workability by influencing the hydration rate of cement, the viscosity of water, and the expansion or contraction of aggregates. Higher temperatures accelerate the hydration rate of cement, which reduces the setting time and the workability of fresh concrete. Higher temperatures also increase the viscosity of water, which reduces the fluidity and the workability of fresh concrete. Higher temperatures also cause aggregates to expand, which increases the volume and the friction of fresh concrete, and reduces its workability. Therefore, to improve the workability of fresh concrete, you should try to keep the temperature of fresh concrete as low as possible, within the recommended range of 10 to 32 degrees Celsius.

5 Mix properly

The mixing process of fresh concrete affects its workability by ensuring a uniform distribution of water, cement, aggregates, and admixtures. Proper mixing can improve the workability of fresh concrete by reducing the air bubbles, the lumps, and the segregation of materials. Improper mixing can reduce the workability of fresh concrete by causing air entrapment, cement balls, and bleeding of water. Therefore, to improve the workability of fresh concrete, you should follow the guidelines for the mixing time, speed, and method, depending on the type and size of the mixer, the concrete mix design, and the site conditions.

6 Here’s what else to consider

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