How Does Weather Affect Mortar And Concrete

How climate affects mortar and concrete when exposed to different temperatures, humidity, rain, and wind.

According to the American Concrete Institute (ACI) one or a combination of the following weather conditions - heat, cold, humidity, wind, rain - can affect the quality of concrete. Climate can cause the process of concrete setting to accelerate or slow down due to the rate of moisture loss and rate of cement hydration. 

How Long Does Concrete Take To Cure/Set Properly?

Under fair weather conditions, concrete can take anywhere from 8 to 48 hours to set properly. While concrete can reach its full strength in as little time as a week, it also takes nearly a month for it to cure properly.

Does Cold Weather Affect Mortar?

Cold weather can be detrimental to newly poured concrete. It can cause concrete to be susceptible to cracking similar to working in warmer climates or not fully cure properly.

A chemical reaction occurs when concrete powder is mixed with water, resulting in an internal crystallization of the concrete. These crystals will grow for an extended period of time even in cold weather giving concrete the ability to withstand additional pressure that may be caused by frozen water molecules within the concrete.

However, if temperatures drop below 15ºF the crystals will no longer grow and the concrete will not cure at its full compressive strength. 

Does Hot Weather Affect Mortar?

Hot weather can be just as harmful as cold weather causing concrete to be susceptible to cracking and setting quickly.

Warmer temperatures evaporate moisture found in freshly poured concrete at a faster rate and make for a faster setting time. The expedited evaporation process of moisture makes concrete that is poured during warm weather conditions more likely to experience cracks.  Concrete will also be prone to more cracks if it is poured in a location where the weather cools down quickly during the night.

Will Rain Ruin Fresh Mortar?

Rain can weaken and displace the surface mortars and concrete causing surface defects and a weakened top layer. 

Rain can cause salts to come out of the freshly poured cement leaving you with white stains known as leaching. In addition, extra moisture leads to excess water and will weaken mortars and concrete, so stiffer mixes (lower slump) may be used during light rain or drizzle to accommodate the extra moisture provided by the environment.

Does Windchill Affect Mortar?

Strong winds can reduce the temperature of concrete and mortar more quickly than still conditions. When too much water or moisture evaporates too quickly from the concrete surface this causes abrasion resistance and the curing condition of concrete to suffer.

Wind Chills can cause plastic shrinkage cracking by stripping excess heat from the concrete surface making it dry before it has fully cured.

Will Mortar Crack With Heat?

As concrete gets hotter, it expands, and contracts as it gets colder. This repeated process can lead to cracking over time. If concrete wants to contract or expand but can’t it will most likely crack. 

Too much heat can wear and dry out the firebrick and the mortar causing it to become brittle and crack.