Deicers and new concrete in its first Maine winter

Published 24 September 2026

The rules for deicers and new concrete in its first Maine winter are short. The Portland Cement Association (PCA, now the American Cement Association) says concrete poured late in the year, which may not dry out before its first freeze, should get no deicing chemicals during its first winter. It also says deicers containing ammonium nitrate or ammonium sulfate should not be used on concrete at all.

Portland averages 68.7 inches of snow a year at the Jetport, and its lows reach freezing on 144.1 days, so a new driveway, walk or set of steps meets ice and melt products within months of the pour. As a Portland concrete company, we give every homeowner the same advice when the forms come off: sand, not salt, for the first winter.

Deicers containing ammonium nitrate or ammonium sulfate are the ones to rule out completely, and calcium and magnesium chloride do damage too. PCA says the ammonium products rapidly disintegrate concrete, and the 2014 edition of the National Ready Mixed Concrete Association's guide to scaling (NRMCA CIP 2) adds magnesium-based salts to the never-use list.

The chlorides work differently. The Federal Highway Administration (FHWA) explains that calcium chloride attacks concrete chemically, and that magnesium chloride does too, because it reacts with calcium hydroxide in the cement paste to form calcium chloride. That calcium chloride forms calcium oxychloride, which expands strongly and breaks the paste down. NRMCA's older guidance went further for young concrete and said to keep calcium and sodium chloride off it in its first year. Read the ingredient list on any bag before it goes near concrete:

• Never: ammonium nitrate and ammonium sulfate (PCA and NRMCA), and magnesium-based salts (NRMCA)
• Chemically harmful to the cement paste: calcium chloride and magnesium chloride (FHWA)
• Not in the first year: calcium chloride or sodium chloride, under NRMCA's older guidance

New concrete is still wet and still gaining strength in its first winter, and PCA names wet, low-strength concrete without entrained air as the kind prone to scale at an early age. Concrete strength is normally measured at 28 days, and NRMCA says new concrete should be kept from freeze-thaw cycles until it reaches at least 3,500 psi.

A slab poured in late fall may not dry out, or reach that strength, before winter sets in. At the Jetport the median first fall freeze is October 15, and the low reaches 32°F or colder on 18.3 days of an average November. That is the late-season concrete PCA's first-winter rule is written for.

NRMCA's advice reaches all new concrete: avoid deicers on it if possible. Our rule for any slab, walk or set of steps we pour is the simple version of both: no chemical deicers in its first winter, whatever month it went in.

Use clean sand for traction; NRMCA recommends it for new concrete in place of deicers. Sand gives grip without adding chemicals, and it sweeps off in spring.

In a city where most homes are rented, the person spreading ice melt may not be the owner, so pass the sand-only rule to whoever clears the walk. A few habits help through the first winter:

• Shovel early, before feet and tires pack snow into ice.
• Keep chemical ice melt off the new surface all winter, whatever the bag says.
• Sweep off slush that collects on the slab, because deicer also rides in on tires and boots from treated roads and walks.

Air-entrained concrete with enough strength, finished and cured properly, is what holds up to deicers over the long run. Entrained air is a network of tiny voids, 0.05 to 1.25 mm across, that gives freezing water room to relieve its pressure; the American Cement Association describes billions of microscopic air cells in each cubic foot. Over-vibrating the concrete can strip that air out locally.

For concrete exposed to deicers, NRMCA recommends 4,000 psi concrete with about 6% total air when the mix uses 3/4-inch or 1-inch aggregate, plus a breathable silane or siloxane sealer. FHWA's protective measures line up: a water-to-cementitious ratio below 0.45, about 6% air for typical paving, supplementary cementitious materials, and penetrating sealers such as silanes and siloxanes.

Finishing and curing matter as well. PCA links scaling to finishing while bleed water is still on the surface, and NRMCA adds too little entrained air, poor curing and overworking the surface; its curing guide notes that well-cured concrete has a harder, more watertight surface that resists scaling. When you hire a concrete contractor for outdoor work, ask what strength and air content they are ordering. We put the mix, the air content and the sealer in the written quote, wait for the bleed water before finishing, and keep the surface covered while it cures.

Deicer damage shows up as scaling, and whether it can be repaired depends on how deep it goes and how sound the concrete underneath is. PCA defines scaling as surface mortar breaking away under freezing and thawing, caused mainly by the pressure of freezing water and made worse by deicer solutions. On a driveway or step it shows as flaking patches where the smooth top layer has come away.

Spalling is a deeper defect, which PCA describes as round or oval pits, or long cavities along joints, with causes that include internal pressure, badly built joints and rusting reinforcing steel.

If you see either, stop using any product from the harmful list and have the surface looked at before another winter. Our page on repairing scaled and spalled concrete sets out the options. When steps tip or crack right through, the cause often lies in the ground beneath them, which we cover in why concrete steps heave and crack.