Question

What admixture is needed when placing concrete in areas of closely spaced and congested reinforcing steel to improve concrete flow without weakening the concrete mix?

1) Calcium chloride
2) Superplasticizer
3) Corrosion inhibitors
4) Air entrainment

Answer 1

To improve concrete flow around congested reinforcement without weakening the mix, a superplasticizer is used as it enhances flowability without additional water.

Step-by-step explanation:

When placing concrete in areas with closely spaced and congested reinforcing steel, the admixture required to improve concrete flow without weakening the concrete mix is a superplasticizer.

Superplasticizers are high-range water reducers that allow the concrete to flow easily around congested reinforcement without the need to add extra water, which can compromise the strength and durability of the concrete. They are particularly useful in scenarios where lightweight concrete is used, as they aid in maintaining the strength while providing the benefits of reduced load and enhanced thermal protection.