Cold Weather Masonry: Heated Mortar

If you’re a mason, or you run a construction company employing masons, then you know how much the cold slows masonry work. With today’s technologies and old-school techniques for cold weather masonry, many companies continue their work well into the winter months. 

Heating Mortar Ingredients for Cold Weather Masonry

Cold Weather Masonry Problems

Slow Cure Time

Every mason knows that when the water in your mix is exposed to near freezing and subfreezing conditions, it drastically slows the curing time of your work. When the temperature drops, the setting time for mortar increases almost tenfold. In fact, if it gets cold enough, the hydration process will stop altogether.

Because of this sluggish hydration process, the mortar takes longer to strengthen. As heavy masonry units are laid, your mortar will not be strong enough to support the weight and will squeeze out and seep between bricks.

Compromised Strength

Sub-freezing temperatures also compromise the strength of your project. Water expands when it freezes, and so will the water within your mortar mix. Expanding mortar between the masonry units jeopardizes the integrity of your structure. In addition, freezing cycles early on in the curing process also result in a weaker cure strength in the mortar itself.

Weaker Bond

If there is any ice on your sub-grade or masonry units, the mortar will not bond properly with your bricks and blocks. For large projects, keeping every single masonry unit free from ice can be quite challenging.

Cold Grout

Frozen grout can be an even bigger problem than frozen mortar. Grout typically contains more water than mortar, so cold temperature expansion can be even more destructive. If grout is allowed to freeze, it can expand so much it will crack any masonry units around it.

Overusing Accelerators

It is incorrect to assume that adding accelerators to your mortar or grout mix will save you from cold weather masonry problems. The masonry experts at TCC Materials warn that “accelerators should not be considered anti-freeze. Mortars or grouts that contain accelerators must still be protected from freezing.” Many accelerators can cause corrosion in any metal reinforcements or anchors within your masonry.  Accelerators can also cause efflorescence and other discoloration defects.

Cold Weather Masonry Solutions

Heat Your Ingredients

These are the dilemmas posed by cold weather masonry, but the solution to the problem is pretty straight forward. Masonry work can be continued in cold weather with planning, precautions, and the right tools for the job. The first precaution is to heat your water. Heating the water before mixing will allow your mortar and grout to stay at the ideal temperature for much longer.

Be sure to heat your dry mixes as well. Keeping your cement, sand, and other admixtures warm before mixing will give your cure an advantage over the cold.

Prep Your Sub-grade

Even if you heat your mortar and grout, when you place it on or against a frigid cold surface it will not adhere correctly. Thawing and warming your sub-grade will ensure you have cemented strong bonds in your masonry work.

Do More Than Just Insulate

It is important to keep your masonry above freezing after it’s all been laid. Masons employ different techniques to accomplish this, including laying insulating blankets or tarps over their masonry. However, insulation alone is not enough. Concrete curing blankets are a more efficient choice. A curing blanket that both heats and insulates is the ideal choice. This will allow the units to remain at the ideal temperature for the duration of the cure. In fact, a good blanket will actually speed up the curing process significantly, ensuring a fast and strong cure.

Powerblanket Masonry Solutions

Here at Powerblanket, we excel at cold weather construction solutions so you can get back to work. Our innovative heating solutions can protect every step of your masonry project.

Ground Thawing Blankets

Before you even begin to lay masonry, your ground and sub-grade should be warmed and prepped to improved your bonds. Some crews try laying down insulation or building enclosures around their site to try and thaw sub-grade. These methods are inefficient, time consuming, and will not provide the heating power necessary to adequately thaw and start building. Ground thaw blankets from Powerblanket provide deep and even heating to the most stubborn frozen sub-grade.

Bulk Material Heaters

Mortar and grout ingredients don’t always come in uniform container shapes or sizes. The revolutionary design of Powerblanket Hot Boxes provides uniform heat to all materials stored inside. This reduces the chance of having any hot and cold spots. If stored properly, cement mixes, sand bags, stacks of masonry units, hydrating lime, and other admixtures will work more effectively. Our versatile hot boxes are perfect during storage, transportation, as well as on the job site itself.

Concrete Curing Blankets

Cure your grout and mortar 2.8x faster than conventional insulated blankets with our concrete curing blankets. Powerblanket can help you maintain moisture during the entire hydrating process and produce a strength of 3,925 psi in just 72 hours.

Contact Powerblanket today to find the right winter masonry solutions for your needs at 844.455.3210 or [email protected].

Powerblanket's industrial drum & barrel heaters provide even and consistent heating, eliminating waste and lowering costs.


Shelby Thompson

Shelby Thompson is the head of standard product sales for Powerblanket. He has a distinguished military career, having served in both Afghanistan and Iraq. In his time in the Marines, Shelby acquired an impressive skillset that he now uses in his current role. When he's not working, Shelby loves spending time outdoors with his wife, son, and daughter. He is also a semi-keen hunter, fair weather fisherman, and shooter. Unfortunately, Shelby also has something of an unlucky streak when it comes to Fantasy Football at the company.

One thought on “Cold Weather Masonry: Heated Mortar

  1. A mason I know thinks that , because of the mpemba effect, that heating water to mix mortar with in the winter will cause it to freeze. I say that is totally way off. I suppose it could freeze quicker than non heated mortar, but only if your intention was to try to freeze the mortar.

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