More or less than the recommended amount of air entrainment can affect what aspect of concrete?

Air entrainment in concrete is fundamentally about creating tiny, uniformly distributed air bubbles within the cement paste. This enhances the durability and workability of the concrete, particularly in cold weather conditions, by allowing the concrete to resist freeze-thaw cycles. The strength of concrete is critically influenced by the air content because too much air can compromise the integrity and load-bearing capacity of the final product, while too little air can lead to other issues such as increased brittleness.

When the amount of air entrainment deviates from the recommended levels, it can significantly alter the concrete's microstructure. For instance, excessive air can lead to a weaker concrete matrix since the bubbles take up space that would otherwise be filled with solid materials, reducing density and overall strength. Conversely, insufficient air can lead to cracking and failure under stress. Therefore, achieving the correct air content is essential for meeting the desired strength specifications required for specific applications.

Other factors listed, such as cost of materials, setting time, and color of concrete, may also be influenced indirectly by air content, but the primary concern and direct effect of air entrainment levels is on the strength of the concrete.