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.
A masonry wall, when exposed to rainwater, often collects water in the mortar-filled joints of the wall.
The water collected in the joints, when subjected to repeated expansion upon freezing and subsequent melting upon thawing, develops cracks in the mortar binding the masonry units.
Eventually, the mortar in the joints splits and flakes off, making the masonry units loose and creating pathways for water to penetrate the wall through the joints.
This is avoided by thoroughly filling the masonry joints with water-resistant mortar and tightly compacting it when the masonry is laid.
Masonry walls exposed to severe climatic conditions can experience considerable deterioration of the mortar joints.
In such conditions, repointing is done, which involves raking and cutting out the deteriorated mortar to a uniform depth.
This is followed by removing the debris in the joints and wetting the area to be repointed.
Finally, the joint is filled with fresh mortar, which is then finished using a joint tool, making it resistant to water penetration.
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