It doesn’t look like anybody’s going to be working outside today in New York! However, in the weeks to come, it’s important to be mindful of the extra precautions you need to take while working in winter weather. For masons, it’s especially important to be aware of the temperature around 40°F, because once it drops under 40, there is special cold weather masonry protocol they should follow.
Much like we discussed when we looked at cold weather concrete, the hydration process in the mortar is slower than usual in cold weather masonry work. When the water in the mortar freezes, mortar expansion occurs, which is a destructive change in the mortar’s volume. The expansion in any mortar that is more than 6% water is enough to crack the mortar and damage the job. The architect or engineer should specify how the masonry should be wetted if it needs to be rewetted, and should also specify how the masons should test to confirm that the procedure was successful. Remember that wet or icy unit surfaces make it difficult for a firm bond to be made between the unit and the mortar.
Tips for Cold Weather Masonry Work
- It’s helpful to use a speed hydration method, such as using high-early cement or by using an accelerator. Beware that using type III cements may potentially change the mortar color, which can affect the required appearance for your job.
- Be mindful of how admixture could affect cold weather masonry and reactions.
- All masonry materials need to be protected from the elements, especially from being wet by rain or snow. Protect all materials by placing them on planks and covering them with tarps when they’re not being used.
- Consider which of your masonry materials may need to be heated prior to using them in order for cement hydration to properly occur.
- If you’re trying to accelerate stiffening, use masonry units with high rates of absorption.
- Although calcium chloride is often used as an accelerator in concrete (at a maximum of 2% by weight of the cement), it is strictly forbidden to be used in mortar by the Specification for Masonry Structures (ACI 530.1-95/ASCE 6-95/TMS 602-95).