What is the typical practice for addressing cold-weather mortar joints that are cracking due to rapid shrinkage?

• A. Accelerate cure with heat lamps.
• B. Slow cure and protect joints with insulation or enclosures; use warmer conditions and proper curing methods.
• C. Remove and redo joints with faster curing mortar immediately.
• D. Ignore cracks as temporary.

Answer: (B)

In cold weather, mortar can crack from rapid shrinkage as it dries too quickly. The best way to handle this is to slow the cure and protect the joints by insulating or enclosing the mortar work, keeping the area warmer, and following proper curing methods. Slower curing gives the cementitious material time to develop strength gradually, reducing internal tensile stresses that cause cracking. Insulation or enclosures help maintain a stable, warmer microclimate around the joints, minimizing moisture loss and preventing the mortar from drying out too fast. Using appropriate curing practices—such as maintaining moisture, avoiding rapid evaporation, and applying curing blankets or other protective measures—supports even hydration and strength gain.

Accelerating cure with heat lamps can force moisture out too quickly and create thermal stresses that worsen cracking. Removing and redoing joints with faster-curing mortar would not address the underlying problem and would likely recur under cold conditions. Ignoring cracks allows water infiltration and potential long-term damage, so it’s not a viable remedy.