Now is the Ideal Time to Assess Any Winter Damage to Concrete Walkways

Spring has finally arrived in New England after a long and cold winter. As a commercial building owner, now is an ideal time to assess and repair any damage that may have occurred over the winter months.

Concrete damage, a common issue, is caused by a number of factors related to cold weather temperatures. Concrete is a very porous material that will absorb moisture at the surface. When the absorbed moisture in concrete freezes, it exerts tremendous expansive force, in turn weakening the entire concrete surfaces. These “freeze/thaw cycles” reoccur frequently throughout the winter, over time causing visible damage to concrete pads, such as spalling or cracking. Another common issue, concrete heaving, occurs when the concrete is shifted in its place by the movement in the ground beneath it. This is normally caused by frost heaving. Frost heaving is when the ground below a concrete pad freezes and expands upwards. A concrete pad can be shifted by a frost heave enough to make a lip or difference in height where two concrete sections meet.

For property owners, these damages can be a serious safety issue or liability due to trip hazards, especially if the concrete pad acts as a walkway for the building. Other problems that arise include reduced curb appeal and “ponding water”. Over time these problems only get worse, especially if they are left unrepaired for multiple winters.

Below are several tips for identifying and repairing various symptoms of concrete damage:

Problem: Spalling

Scaling, flaking or cracking in the top layer of the concrete pad often occurs and in many cases leaves pits. This is primarily caused from continuous “freeze/thaw cycles” or the use of de-icing products which include chemicals that are harmful to concrete.

Solution:

• Any loose material will need to be removed from the damaged area to insure effective bonding. Power washing may be     necessary in some circumstances.
• For small to medium sized repair jobs, epoxy based resurfacing products are recommended.
• Larger damaged areas will require use of a 100% epoxy concrete patch with a sand aggregate.
• Color additives are available in order to match the solution as close as possible to the original concrete.
• Once the damaged area is completely dry, pour and fill the hole with epoxy solution, making sure to push out any trapped air.
• Smooth the solution out using a margin trowel and allow 24 hours for the repair to set.
• After area is completely dry, the repair will need to be sanded down so it is even with the existing concrete pad.

Problem: Heaving

Uneven and cracked concrete pads caused by frost heaves create unsightly and hazardous conditions to building walkways. If left untreated, these cracks can spread and make slabs vulnerable to further damage.

Solution:

• For uneven areas, level out the difference in elevation using a concrete grinder. This will fix the immediate issue of having a trip hazard at your building but will not solve the root problem and will lead to additional issues in the future. After grinding, the stone will be unprotected from the weather and may lead to further damage.
• For cracking in concrete slabs, fill the cracked areas using caulking material that is specifically designed for concrete repair.
• Without addressing the root cause of this issue, an uneven subgrade, the damage will likely continue. See the next solution for reestablishing soft or uneven subgrades.

Problem: Concrete Depressions

Depressions in concrete pads that cause trip hazards and ponding water are primarily caused by continuous frost heaving to the ground beneath the concrete pad. Over time, the soil will sink or shift, in turn leaving limited support for the concrete pad above. Reestablishing the subgrade and replacing the concrete pad is the only solution to this issue.

Solution:

• Remove the damaged section by cutting the concrete slab into smaller sections.
• Once all concrete and rubble are cleared from the area, reestablish the subgrade by filling, leveling and compacting the ground below. Add a layer of gravel and compact to help improve drainage. The thickness of the subgrade is dependent on thickness of the concrete slab.
• Pour the new concrete pad, making sure to match the elevation and size of the other sections of the walkway. Unfortunately, matching the color of the concrete to the existing walkway will be nearly impossible due to variables in sand, color gradients and brand of cement.

With all of the above solutions, a silicon based liquid sealer is used to waterproof the repaired area by filling the concrete pores. This solution is applied after all the moisture has left the repaired area, usually around 28 days.

Safe Alternative to De-Icing Products:

Most De-Icing products contain a variety of different chemicals that are harmful to concrete surfaces. The chemicals in these products increase the number of freeze/thaw cycles experienced by concrete in the winter months, in turn amplifying the weakening effects produced by freezing moisture at the surface of concrete. As a general rule, De-Icing products should not be applied to exterior concrete that is less than one year old.

A suggested alternative to combat icy and slippery walkways is to use sand or cat litter. This will eliminate the slip hazard while ensuring concrete areas do not endure additional damage caused by freeze/thaw cycles.

Contact Your General Contractor to Address Issues:

Munger Construction can offer free evaluation of your buildings’ walkways to determine the best option for repairing damaged concrete. Our Repair and Maintenance team will address any issues and present the best solution to keep your walkways safe!