Why Reno is hard on concrete in winter
It's not the cold so much as the swings. Clear skies at 4,500 feet mean the top of a slab can freeze every night and thaw in the sun the next afternoon, over and over from November to March. Every one of those cycles freezes whatever water has soaked into the surface, and water grows about 9 percent when it turns to ice.
Concrete made with entrained air has millions of tiny bubbles that give that ice somewhere to go. Concrete without it doesn't, so the top layer slowly pops off. That's called scaling, and once it starts it doesn't stop.
Seal it while the afternoons are still warm
If your driveway, walk or patio hasn't been sealed in the last few years, now's the time. A penetrating sealer (look for silane or siloxane on the label) soaks into the surface and keeps water and de-icing chemicals out without making it slick.
Most sealers want at least 50 degrees while they go on and for a day after, plus a dry surface. In Reno that usually means a sunny afternoon in October. Once nights are staying in the 20s, it's probably a spring job.
Fill the cracks before water gets in
Water that gets into a crack freezes, expands and pushes the crack a little wider every time. Over a winter, a hairline crack can open up enough to catch a fingertip.
Clean it out with a wire brush and a shop vac, then fill it with a flexible polyurethane or self-leveling crack sealant. Skip mortar and patching cement for ordinary cracks. They're rigid, the slab still moves, and they'll pop right back out by spring.
Watch where the meltwater goes
The Sierra sun is strong even in January, so snow piled along the edge of a driveway melts every afternoon and refreezes every night. If you can, pile shoveled snow on the yard side instead of right along the concrete.
Same with downspouts. If one dumps onto a driveway or a walk, add an extension so the water ends up in the yard. Any spot where water sits and freezes every night is going to take a beating.
Mag chloride rides home on your tires
NDOT treats the interstates and highways around here with liquid de-icer, mostly magnesium chloride, and it comes home on your car all winter. It drips off in the garage and wherever you park. Magnesium chloride is harder on concrete than plain salt, so on a warm day it's worth hosing off the spot where you park, especially in the garage.
Be picky about ice melt
This is the big one. A few rules we give everybody:
- Nothing on concrete less than a year old. Not rock salt, not ice melt, not anything. New concrete is still gaining strength and it's easy to damage. Use sand for traction.
- Skip anything with ammonium nitrate or ammonium sulfate. Those attack concrete chemically. Read the label, because some fertilizer-type products sneak them in.
- Go easy on rock salt. It works and it's cheap, but it's hard on newer concrete.
Calcium magnesium acetate (CMA) is the gentlest option if you want something that melts. Honestly, though, the best thing for your concrete is shoveling early, before snow gets packed into ice, and sand for grip. Sand doesn't melt anything, so it doesn't add another freeze-thaw cycle.
Up at Truckee and Incline
Everything above goes double at the lake. Plow blades and snowblowers chew up slab edges, so ask whoever plows for you to keep the blade up a touch, and stake the edges of walks and driveways before the first big storm. On stamped or sealed concrete, use a plastic shovel or one with a plastic edge.
What to look for in the spring
Once the snow's gone, take a walk around. Flaking or pitting on the surface, cracks that have clearly gotten wider, or one section that's lifted or dropped compared to the next are all worth a look before next winter makes them worse.
Not sure whether it's a quick fix or a replacement? Give us a call at (775) 264-5350 and we'll come take an honest look.