Driveway Scaling Resistance Test: ASTM C672 Method

What the Driveway Scaling Resistance Test Actually Tells You

If your driveway turns into a flaky, pitted mess after one bad winter, you already know what “scaling” looks like. The ASTM C672 test is the industry’s way of predicting—before the first snowflake falls—how badly that surface will deteriorate when salt, water and freeze-thaw cycles gang up on it. In plain English, it answers the homeowner question: “Will this concrete still look good five winters from now?”

Drivewayz USA runs the test on every mix design we place, and we encourage owners to ask for the numbers before they sign a contract. Below you’ll learn how the test works, what the ratings mean, and how to use the results to save thousands in future repairs.

Why Scaling Resistance Is a Big Deal for Residential Driveways

Scaling isn’t just ugly—it’s the first domino. Once the paste layer peels off, water infiltrates, rebar corrodes, and cracks race through the slab. A $9,000 driveway can turn into a $4,000 patch-and-overlay job in less than a decade. The ASTM C672 test gives you an early warning system so you can:

• Compare mix designs apples-to-apples
• Negotiate a performance warranty with real data
• Adjust sealer schedules before damage starts

How the ASTM C672 Test Is Performed

Step 1 – Casting the Test Slab

Laboratory technicians cast a 7 × 14 × 3-inch concrete slab using the exact mix design proposed for your driveway—same cement, fly ash, air content, water reducer, pigment, everything. The slab is cured 14 days in standard 73 °F lime water so the hydration window matches field conditions.

Step 2 – The Freeze-Thaw & Salt Cycle

At day 14 the slab is removed and placed in a 100 % relative humidity box at 73 °F for 24 h. Then the fun starts:

1. A 4 % calcium-chloride brine (simulating de-icing salt) is ponded 1/8-inch deep on the surface.
2. The slab goes into a freezer at 0 ± 4 °F for 16–18 h.
3. It is pulled out, thawed at 73 °F for 6–8 h, and the brine is refreshed.
4. The cycle repeats every 24 h for 50 cycles—roughly the salt exposure of two tough winters compressed into two months.

Step 3 – Visual Rating

After 50 cycles a technician photographs the surface and assigns a rating from 0 to 5 based on the area of visible scaling:

• 0 – No scaling
• 1 – Very slight (3 mm max, <5 % area)
• 2 – Slight up to 1/8-inch depth
• 3 – Moderate, some aggregate exposed
• 4 – Severe, heavy aggregate loss
• 5 – Up to 1/4-inch paste gone

Anything rated 2 or lower is considered acceptable for exterior flatwork in northern zones.

Reading the Lab Report Like a Pro

When your contractor emails you a one-page PDF titled “ASTM C672 Scaling Resistance Summary,” zero in on these three lines:

1. Visual Rating – Should be ≤ 2 for driveway duty. Ask for color photos; numbers can hide patchy scaling.
2. Mass Loss – Optional but telling. < 0.5 kg/m² is excellent.
3. Air Content & Spacing Factor – Good scaling resistance needs 6 ± 1.5 % air with a spacing factor < 0.008 in. If those boxes aren’t checked, the low scaling rating may be a fluke.

Practical Mix Tweaks That Pass the Test

You don’t need a Ph.D. in concrete—just insist on these field-proven adjustments:

• Limit water-cement ratio to 0.45. Every 0.05 jump above that can double scaling loss.
• Use a ternary blend: 10 % silica fume + 25 % Class F fly ash. The pozzolans eat calcium hydroxide, tightening the surface.
• Don’t overdose air entrainer. > 8 % air weakens the paste and can increase scaling.
• Order 4,000 psi minimum even if your city allows 3,000. Strength and scaling resistance track closely.

Sealer Strategy: Double Down on the Lab Work

A mix that scores “0” in the lab can still scale if you skip sealer maintenance. Treat the test as your baseline, then add these layers of protection:

• Day 14–28: Apply a breathable silane/siloxane sealer at 200 sq ft/gal. It cuts chloride ingress by 80 %.
• Year 2 and every 3 years after: Re-seal high-traffic lanes where tires grind in de-icers.
• Winter habit: Switch to calcium-magnesium acetate (CMA) for the first storm; it’s 70 % less aggressive than rock salt.

What the Test Costs and Who Pays

A single ASTM C672 run by an AASHTO-accredited lab runs $900–$1,200 and takes eight weeks. For a standard 1,200 sq ft driveway that’s 75 ¢ per square foot—cheaper than one sack of patch mix. Most reputable contractors roll the fee into the project price; if a bid omits it, ask. The test is valid for two years on the same mix, so you can leverage one report across multiple pours (neighbor joint bids, walkway, patio, etc.).

Red Flags That Mean “Keep Shopping”

• Contractor can’t produce a C672 report or shows one dated 1998.
• Report lists a different w/c ratio than the mix you’re buying.
• Rating is 3 or higher with the disclaimer “field performance may vary.”
• Only 25 cycles run instead of the required 50.

Homeowner Checklist: From Test to Pour Day

1. Request the scaled photos and rating before signing.
2. Verify air content ticket at the plant—aim 6–7 %.
3. Require 0.45 max w/c in the contract, not just “per code.”
4. Insist on 7-day wet cure (plastic or burlap) to hit surface strength.
5. Schedule sealer no earlier than 14 days, no later than 28.

Frequently Asked Questions