Cold Weather Laying

Denser, less porous architectural bricks can take longer to lay in cold weather. This is because the setting time of the mortar takes much longer to harden and take on strength. The excess water in the mortar, which is normally taken up by the hydration process in warmer weather remains for an extended period to impede progress.  In a more porous brick, the excess water may be sucked up into the brick, offsetting this issue. In short, the colder temperatures slow down markedly the chemical reaction (the hydration process) in the mortar leading to slower setting times.

The most practical ways to remedy this is to vary the mortar mix design to say 4:1 sand/cement ratio. This is common practice in cold weathered locations such as the UK weather. Also, an accelerator and water reducer may be used. It may be worth considering extending the mixing time of the mortar and reducing the water contend to make a stiffer mortar. Also, keep bricks covered and dry.