Mortars with what kind of air content are better suited for freeze-thaw resistance?

Mortars with higher air content are better suited for freeze-thaw resistance because the incorporated air voids improve the material's ability to withstand the expansion and contraction that occurs during freeze-thaw cycles.

When water in the mortar freezes, it expands. If there are adequate air voids intentionally introduced into the mix, the expansion has space to occupy, reducing internal pressure and the risk of cracking or other damage. This is particularly important in climates with significant fluctuations in temperature, where water can freeze and thaw repeatedly.

Higher air content not only enhances the durability of the mortar by mitigating the effects of freeze-thaw cycles but also improves workability and helps in bonding by allowing for better adhesion to masonry substrates. In contrast, lower air content can lead to more rigid structures that are more prone to cracking under such conditions.