For the first time in 30 years, a major street in Manhattan was paved in concrete rather than the more commonplace asphalt economy being a prime factor. The three-mile job on First Avenue from East 72nd Street to East 125th Street in New York City will have pavement with a design life of 40 years and a cost reported to be $2 million lower than the nearest competing asphalt bid. For removal of the old pavement consisting of 3 inches of asphalt plus an 11-inch concrete and cobblestone base, the contractor decided to crush the old base and recycle the material back to First Avenue as a base for the new pavement.
PAVING MACHINES AND WORK SEQUENCE
Two identical form-riding paving machines were selected to cope with the irregularities of city operation: one machine was used to spread, vibrate, and rough finish the bottom 7 inches of the slab. Welded wire fabric reinforcement was then hand placed on the wet base concrete and shear-cut to fit around manhole covers, utility valve boxes, inlets and other obstructions. The second paver, working about 40 feet behind the first one, then spread the final course and finished the pavement. Workers came along after the machine to float the surface and touch up near curbs, expansion joints, manholes and other inserts.
READY MIX CONCRETE, SOME COLORED BLACK
Concrete came by ready-mix truck from a plant about a mile from the north end of the project. From nine to seventeen ready-mix trucks supplied the seven-bag, 4000-psi mix. Although the mix usually had a 1- to 3-inch slump, the use of form pavers, rather than slipformers, permitted greater variation in slump if supply units were delayed in traffic. In some cases, 28 pounds of carbon black per cubic yard was added to the mix a few minutes before placement to color the surface course along the 13-foot-wide curb lane for an exclusive bus lane.