Snowplows, Salt and an Asphalt Driveway: Getting Through an Anderson Winter

The short answer: water does the damage, not salt

Rock salt and a plow blade do far less harm to a sound asphalt driveway than most owners expect. The asphalt industry's engineering institute states that research has shown well-designed and well-constructed asphalt pavements are not damaged by the sodium chloride and calcium chloride salts used for snow and ice control. What wears a driveway out over an Anderson winter is water: water that slips through open cracks, sits in the stone base, and then freezes and thaws for months.

That changes the winter checklist. The work that matters most happens in October and early November, before the first snow, when cracks can still be closed and edges can still be supported. Once snow arrives, the aim is to move it with a shovel, blower or plow first, and to treat deicer as a helper that works only inside a certain temperature range.

What a winter here puts a driveway through

Anderson does not get buried. The NOAA normals collected on this site's paving data page add up to 19.6 inches of snow in an average year, with 7.4 inches in January, 5.0 in February, 4.9 in December and 1.5 in March. The harder number for pavement is temperature. In every month from December through March the normal low sits under 32 degrees while the normal high sits over it, so snowmelt that runs across a driveway in the afternoon is often ice again by morning.

A Purdue civil engineering professor once described what that cycle does below the surface. After a long cold stretch the frost reaches deep into the ground. When a warm spell follows, even a short one, the thaw works from the top down, and the result is a bowl of wet soil sitting on frozen ground with too little strength to hold up the pavement over it. Any crack that lets meltwater in feeds that bowl. The surface then flexes under a car or a delivery truck, and a tight crack in November can be a loose, broken patch by April.

Fall jobs that pay off in January

Everything on the fall list is about keeping water out and giving a plow nothing to catch. None of it takes long, and all of it is easier on a mild afternoon in October than after the ground has frozen.

• Fill open cracks. A homeowner guide published through the asphalt industry's institute notes that small holes and cracks can be filled with driveway maintenance products sold in hardware and building supply stores. Wider or spreading cracks call for professional asphalt driveway repair.
• Build up low shoulders. An edge that hangs over soft lawn tends to break when a tire or a plow truck drops off the side, so pack stone or soil against it.
• Mark both edges with tall stakes, along with anything that sticks up near the drive: a drain grate, a valve box, landscape stone or a culvert end.
• Clear leaves and check where water goes. Downspouts and low spots that drain across the pavement turn into ice sheets by midwinter.
• Do not rush a sealer onto a new drive. The same institute says a well-built driveway should not need sealing for approximately 2 to 5 years, depending on climate and the quality of the original work.

Plowing without scarring the surface

A steel blade sliding over smooth, sound asphalt usually leaves it alone. Indiana's highway department says much the same about its own trucks: the damage they cause is not typically from the plow blade itself but from the force of the snow being thrown. A university pavement reference adds that an occasional nick from a snowplow may be unavoidable, and that pavement layers with a proper structural design resist that kind of damage. Thickness and base matter in winter, which is one more reason they are settled at the start of any driveway paving job.

What a blade does catch is anything raised: the lip of an open crack, a patch that sits proud of the surface, a heaved edge, or the joint where asphalt meets a concrete apron. Fixing those in the fall protects them. Whoever plows should also know where the pavement ends, because a blade that runs off the side peels sod and gouges the shoulder that supports the edge. Stone sections need a different setup, with the blade riding slightly high, as the earlier post comparing surfaces for a long country lane explains.

Using salt so that it works

Salt is a helper, not a snow remover. A winter maintenance bulletin from a state university road program calls plowing the primary way to clear snow and slush, and explains that a deicer has to dissolve into brine and draw heat from the air, the sun or the pavement before it melts anything. Temperature controls the result. The bulletin shows a pound of salt melting five times as much ice at 30 degrees F as at 20, and puts the normal lower limit for salt at 15 to 20 degrees. A federal highway manual likewise reports that some agencies find salt impractical below 15 degrees unless calcium chloride is added. With a normal January low of 19.3 degrees in Anderson, plenty of winter nights sit right at that limit.

Three habits follow from that. First, clear the snow, then spread a thin layer on what is left, because salt thrown on deep snow is mostly wasted. Second, time it: the state pretreats highways with brine ahead of a storm to keep snow and ice from bonding to the pavement, and a light application early does more than a heavy one on packed ice. Third, let the sun help. The same bulletin notes that sunshine can lift pavement temperature 10 degrees or more over the air temperature and that dark asphalt absorbs more solar heat, so a cleared drive often finishes the job by itself on a bright afternoon. On clear nights the pavement runs colder than the air, and sand, which melts nothing, is the better choice for traction.

Where salt does cause trouble, and the spring check

The asphalt is not the weak point, but its neighbors can be. The university bulletin warns that deicing chemicals can speed up deterioration in concrete and steel, and the pavement reference notes that concrete surfaces sometimes scale and spall when chemicals combine with freeze and thaw action. On a typical lot that means the concrete garage apron, the sidewalk, the porch steps and the bottom edge of a steel garage door deserve a lighter hand than the driveway itself. The bulletin also reports that harm to soil and plants is greatest close to the pavement, so piling salty snow on the same strip of lawn all winter tends to show in spring.

When the thaw comes, walk the drive on a dry day and note every new crack, soft spot and broken edge while they are still small. Owners who find more than a few can ask paving contractors serving Anderson to judge whether filling and patching will do or whether the base needs attention before next winter.

More from the blog

• The Paving Season in Anderson, Month by Month
• Four Surfaces for a Long Country Drive Near Anderson