About 50 years ago it was discovered that concrete with entrained air was remarkably more durable when exposed to freezing and thawing than was concrete without air. In spite of that breakthrough, pavement scaling problems have by no means disappeared. Research and theorizing continue in an effort to find a more complete solution. With almost 40 years of successfully constructing concrete street pavements without a scaling problem, the City of Milwaukee may already have that solution.
CONCRETE STREET PAVEMENT PERFORMANCE
Since 1948 the City of Milwaukee has constructed about 850 miles of concrete street pavements, all of which were built under the city's specifications and control. In the 35-year period of 1948 to 1982 scaling has never been a problem, nor has there been any other major pavement failure.
CITY STREET SPECIFICATIONS AND DURABILITY
Milwaukee publishes its own Street Construction Specifications. The concrete specifications contain the routine requirements of 6 sacks of cement per cubic yard, 4 to 7 percent air and a maximum slump of 3 inches. Milwaukee's subdivision control ordinance gives the Department of Public Works full control over all street paving. All paving contracts are let by the City. All work is done under City specifications and with City inspection. The City requires an estimated concrete strength of 3600 psi at 28 days. Pavement performance under these specifications has been so highly satisfactory that there have been few changes. Starting in 1972, Type I cement with an air entraining admixture was first allowed. In 1979, either a water reducer or 75 pounds of fly ash was permitted to replace 1/2 sack of cement.
While street pavements have shown no scaling, some scaling has occurred on private driveways, parking areas and, in general, on non-specification flatwork. In fact, it has not been unusual to find a scaled residential driveway immediately next to a concrete street on which there is no scaling.