Cold weather retards the hydration of the cement in the mortar mix. Mortar mixed during cold weather often has lower water content, increased air content, and reduced early strength compared with those mixed during normal temperatures. Mortar is often mixed with heated materials to produce performance characteristics associated with mortar mixed at normal temperatures, or with admixtures which may improve the early strength and plasticity of the mix. Water, sand, or both are often heated for use in mortar in cold weather. Heating prepackaged materials such as cement and hydrated lime has long been a problem for brick masons.
Mortar freezing should be avoided in all cases. Mortar that freezes is not as weather-resistant or as watertight as mortar that has not been frozen. Significant reductions in compressive and bond strength may occur. Mortar with water content over 6 to 8 percent of total volume will experience disruptive expansive forces if frozen due to the increase in volume of water when it is converted to ice, and the bond between the brick or block and the mortar can be damaged or destroyed.
Experts recommend covering newly-laid brick or block with insulating blankets when temperatures are below 40°F, and using heated enclosures when the temperature is below approximately 25°F. Powerblanket® concrete curing blankets eliminate the need for insulating blankets or for heated enclosures. They maintain the proper curing temperature no matter what changes in weather occur, keeping the mortar bond strong and lasting. Instead of building enclosures, concrete curing blankets can be easily hung on newly-laid walls, eliminating the need for constructing enclosures or other temporary structures.
Concrete curing blankets can also provide a number of advantages before the brick or block is laid. Powerblanket concrete curing blankets can be used to keep the sand pile and dry mix bags warm and dry, and also ensure that crews can lay brick or block in any temperature. Simply pre-heat sand and dry mix, lay the bricks or block, and hang Powerblanket concrete curing blankets on the newly-constructed walls - the result will be durable and long-lasting walls … with predictable scheduling and minimal crew downtime due to bad weather.