What is the impact of a 1% increase in air on the slump of the concrete?

When considering the properties of fresh concrete, the slump is a measure of its workability and consistency. One key factor influencing slump is the air content in the concrete mix. If the air content in the concrete increases by 1%, it generally leads to a reduction in the effective density of the mixture, making it less cohesive. This loss of cohesion can cause the mixture to perform differently, often resulting in a decrease in slump.

Higher air content can trap more air bubbles within the concrete, which can complicate the flow of the material, leading to a stiffer mix. Therefore, a 1% increase in air can adversely affect the overall workability, resulting in a decrease in slump, hence supporting the notion that with additional air, the concrete is less likely to flow and settle easily.

To further clarify, the slump can be significantly impacted by various factors, including the specific mix design and the type of aggregate used. However, the general consensus in material science and concrete technology is that an increase in air content leads to a decrease in slump due to these changes in workability and density.