As the air content in mortar increases, what generally happens to compressive and bond strength?

When the air content in mortar increases, the overall density of the mortar typically decreases. This reduction in density leads to a decrease in both compressive strength and bond strength.

Compressive strength refers to the ability of a material to withstand axial loads without failure. An increased air content introduces more voids within the mortar mix, which weakens the interparticle bonds and reduces the overall strength of the material when subjected to compression.

Bond strength, on the other hand, measures the adhesion between the mortar and the masonry units it is intended to bind. An increase in air content can negatively impact bond strength due to the presence of additional voids, which can hinder the effective interlocking and adhesion between the mortar and the surfaces of the masonry units.

Therefore, as air content rises, both compressive strength and bond strength are likely to decline, which leads to the conclusion that both properties generally decrease with increased air content in mortar.