Q.: Now that highway departments are beginning to recycle concrete pavements by crushing them for use as aggregate in new concrete, we wonder if it is possible to recycle pavements that have been subject to D-cracking. Would they just begin to break up again in the same old way?

A.: D-cracked pavements have been recycled but it may be too early to know how successful the experience has been. If there is any doubt about future susceptibility to D-cracking it would be well to test the materials concerned. The test method is given in a report by Paul Klieger, Gervaise Monfore, David Stark and Wilmer Teske, "D-Cracking of Concrete Pavements in Ohio," Report Number OHIO-DOT-11-74, National Technical Information Service (NTIS), U. S. Department of Commerce, Springfield, Virginia. (Soft cover, 201 pages, $7.25 from NTIS.)

The first major concrete recycling project in this country to reclaim pavement susceptible to D-cracking is a 16-mile project on U. S. 59 between Worthington and Fulda, Minnesota. Recycling is under way and paving with new concrete made with recycled material is expected to begin about August 1.