2.12 : Mortar Joint Deterioration in Masonry

Mortar joint deterioration is a significant concern in masonry structures, with water accumulation in the joints leading to damage from freeze-thaw cycles. The repeated expansion of water during freezing and its melting during thawing develop and propagate cracks in the masonry joints. Eventually, this leads to the spalling of mortar from the joints, loosening masonry units and weakening the structure. The deteriorated mortar joints are also vulnerable to moisture intrusion into the walls.

The integrity of the mortar joints can be preserved by using weather-resistant mortar and ensuring the mortar is well-filled in the joints and compacted adequately during bricklaying. In severe climates, even with these measures, mortar joints in masonry walls will exhibit considerable deterioration. In such conditions, deteriorated mortar joints must be repointed. Repointing involves removing deteriorated mortar by cutting, raking, and replacing it with new mortar. In the case of hairline cracks in mortar joints, surface grouting is done in the joints to preserve masonry walls' structural integrity and appearance.