10 Feb What Temperature is Needed for Mudjacking in Winter?

In any season, sinking or settled concrete slabs are urgent issues that you have to address immediately. However, this is especially true during winter months, when snow can blanket the slab and catch snow shovels or plows, or ice makes walking on uneven sideways even more dangerous.

Mudjacking in winter is certainly doable, given certain conditions. For instance, contractors mudjacking interior slabs, such as those in basements or heated garages, will not typically experience any issues, thanks to the building’s frost walls which keep the temperature in the area from freezing and causing frost heave. Because of this controlled thermal envelope, interior leveling indoors can often be performed all throughout the year without a hitch.

Unfortunately, the same cannot be said for mudjacking concrete slabs outdoors. With the process being governed by strict thermodynamic and geotechnical rules, mudjacking in winter requires a deep understanding of thermal thresholds, material science, and soil mechanics.

Temperature Requirement for Mudjacking in Winter

Mudjacking is best performed when temperatures keep the pace of hydration steady and predictable. Hydration is the process or chemical reaction between water and cement that turns the slurry from a paste to hard cement. The optimal temperature range for mudjacking is between 50°F (10°C) and 95°F (35°C). Both of these limits have their basis on guidance set by the American Concrete Institute (ACI), a leading authority on concrete practices.

For mudjacking in winter, those working in the industry turn to the institute’s ACI 306R-16, Guide to Cold Weather Concreting, which defines cold weather conditions as a period when the average daily air temperature falls below or is expected to fall below 40°F (4.44°C) for more than three consecutive days.

According to experts, the curing process begins to slow down as soon as the temperature hits below 50°F (10°C). Below this temperature, the hydration of the cement in the slurry slows significantly, and concrete will almost stop curing at around 40°F (4.44°C). In other words, 40°F (4.44°C) is the threshold where chemical complications start to occur.

The appropriate temperature is crucial in mudjacking because a delay in setting time increases the window of vulnerability, during which water in the slurry mixture could freeze and crystallize. This destroys the internal structure of the repair before it gains strength, which for mudjacking in winter is a compressive strength of at least 500 psi before the cement is exposed to its first freezing cycle. Because of this, the material will not have enough integrity to resist the expansive forces of ice formation.

How Mudjacking Slurry Behaves in Winter

The mudjacking slurry mixture is composed of soil, sand, cement, and water. When the temperature reaches 32°F (0°C), water in the mudjacking slurry mixture freezes and creates problems for contractors.

Water Expansion (Part 1)

Most materials possess a denser solid form than their liquid form. This is opposite for water. When water freezes, it expands by around 9%.

The mudjacking slurry contains water, which when frozen expands. However, because the slurry is pumped underneath the concrete slab, this expansion is restricted. As a result, when water freezes, it forces the slab upwards.

Cement Strength Decline

Water in the slurry mixture affects cement strength. If cement freezes immediately after it is injected, the resulting concrete could lose up to 50% of its ultimate strength.

If the slurry mixture has more water, the likelihood of reduction in cement strength is also high. For every gallon of water, at least 200 psi of strength is lost.

How Frozen Soil Complicates Mudjacking in Winter

Aside from air temperature, contractors also have to consider ground temperature when mudjacking in winter. Unlike air, soil and concrete act as natural insulators, which means they hold onto frost longer. For instance, while air temperature may be at 45°F (7.22°C) on a sunny January afternoon, the concrete slab and the ground beneath it may still be frozen solid.

This phenomenon is known as thaw lag, which refers to the time delay, which can often range from days to weeks, between rising air temperatures and the actual melting of the frozen ground. Frozen ground presents several risks which professional mudjacking contractors generally avoid, including:

Water Expansion (Part 2)

Water in the ground freezes and is in an expanded state during winter. This expansion heaves the ground upward, giving the impression of false height. So, when a contractor injects the mudjacking slurry, he is basically filling a void. Spring arrives and the water in the soil begins to thaw. The soil contracts or shrinks back down and no longer supports the slab, and you’re back to square one.

Ice Adhesion

Another issue that mudjacking contractors face during winter is ice adhesion. This happens when frozen moisture glues the bottom of the concrete slab to the soil. Water can be a powerful adhesive, so any attempt to lift the slab using the slurry injection can backfire and result in cracks or the slab shatters before the ice bond breaks.

Mortar Temperature Limit

Mudjacking uses holes drilled into the concrete, and once the slurry has been injected, contractors fill the holes with mortar plugs. Similar to concrete, mortar has temperature requirements too.

Most mortar mixtures will not set correctly at temperatures below 15°F (-9.44°C), leading to cracking or collapse shortly after installation. The Brick Industry Association (BIA) sets the ideal temperatures for mortar between 60°F (15.6°C) and 80°F (26.7°C). When temperatures are below 20°F (-6.7°C), the association recommends implementing cold weather procedures.

Balancing Urgency and the Risk of a Failed Repair

While it is technically possible for contractors to perform mudjacking in winter, the real question homeowners and business owners should ask is “Is it worth it?”

On the one hand, you are worried about the risk of someone getting hurt in your home or property. You need to immediately reduce this liability risk. However, mudjacking in winter poses several potential problems, and the risk of a failed repair is higher than normal. If not done properly, you could be needing a concrete repair again in springtime.

If possible, you’ll want to limit your winter repairs to interior slabs. Otherwise, ask your mudjacking contractor if they see a possible stable warm window in their winter work schedule. If there’s one, they’ll use heated materials, chemical accelerators, and insulated curing blankets to get the job done. This will be more expensive than usual, but you have a higher chance of seeing level concrete even after the snow has melted.