dowel joint which, unless one free end is provided, causes the dowel to buckle and spall out the concrete or raise one slab above the other; and the failure to carry a joint entirely through the concrete which, on account of concentrated pressure, shatters the concrete. This is shown to advantage in the illustrations. (Illustrations 6, 7, 8, 9, 10.) And after everything else is as good as it can be the pavement may be spoiled by over finishing, which draws the poor or fine parts of the sand to the surface and either brings out check cracks or causes the top surface to spall off. We can then secure good concrete pavements by scrupulous care in regard to foundations, drainage, design, specifications, materials and methods of construction. We must be of guard against cold weather conditions, too quick drying out, poor or dirty aggregates, faulty joint construction, over-finishing. Yet where high intelligence and skill and the best methods are employed, there is the desire to add all possible safeguards. On a cheap, slovenly built piece of pavement one may take a chance, but on a costly beautiful stretch, built with consideration of all the above factors, one wants all the insurance possible. I have found, for the same expenditure, no other guarantee of success so certain as the use of small amounts of steel to strengthen the concrete. During the stresses set up in the concrete by the contractions due to drying out during the curing period, small quantities of steel well distributed beneath the surface, hold the slab together and limit the formation of fine hair cracks. Later, if cracks do appear the positions of the steel when a sufficient amount is used transversely, limits them to transverse cracks that merely break the slab across and prevents those disastrous diagonal cracks, leaving "V" shaped corners, that under impact split the slab into fragments. The steel acts further as an offset to fatigue stresses. Wherever it has been used in actual practice the results have been good. Where it has been used on test roads like the one now being built at Syracuse, the tests have shown that the pavement slabs containing it have had greater strength than those of plain concrete. It was This Syracuse road is an interesting experiment. built at Syracuse, New York, this summer and finished in September under the auspices of the New York State Highway Department, under immediate supervision of Colonel William M. Acheson, Division Engineer. The information derived will benefit not only New York State but every engineer who is interested in giving his community good concrete pavements. The motive for the Syracuse road was the realization that in many cities streets would have to be widened and strengthened and that much resurfacing would soon have to be done. Pavements that already have been resurfaced with concrete have been satisfactory in all cases I know of, but they have left many doubts in the minds of engineers about what would prove most truly economical in design and procedure. Before we consider the test road, let me suggest two interesting jobs in resurfacing. Gratiot Boulevard, Detroit, Mich., is an example of 4-inch resurfacing of a Dolarway pavement built in 1910 of 1, 22, 5 concrete. The resurfacing was done in 1917 and the surface widened from 16 to 20 feet with a 1-11-22 mix, the large aggregate being trap rock graded from 1/4 inch to 1 inch, No. 26 triangle wire mesh used as reinforcement, new expansion joints placed in all cases over the old. In 1923 a traffic count included over 20,000 vehicles in a 24-hour day. Last March, on my last inspection, the surface was uniform and in excellent condition, and though some cracks had appeared, there were no spalled or disintegrated areas. Bridge Street, Oswego, New York, is another example of resurfacing. On the main street through the city the original 6-inch concrete pavement, a 3-inch black top, laid in 1898, on foundation was replaced in 1919 by a 41⁄2 concrete resurfacing, reinforced with 120 pounds of metal per 100 square feet of pavement. The mix was 1-12-3. The street is 54 feet wide. with a car track in the center. After six years the surface is in excellent condition. (Illustration No. 11.) The Syracuse Test Road, formally known as Syracuse Cicero State Highway No. was built in 1914 of 1-112-3 concrete, sixteen feet wide, 434 inches thick on the outside edges and 634 inches thick at the center. This pavement was still giving good service, but some of the areas were badly cracked. The idea in resurfacing at this time was to utilize all of the pavement which still had a salvage value. The old pavement is an example of some that were built with an excessively fine sand of low strength. A traffic count shows 10,000 vehicles over it in 24 hours. The resurfacing has consisted of placing a top course with sections 450 feet long of the following thicknesses: 234, 32, 4 and 42 inches. Reinforcement of three different weights were used with each thickness. In addition to the resurfacing a strip, 8 feet wide, was placed longitudinally to give a pavement 24 feet in width. The whole job is over a mile in length. The 8-foot slab was laid in thickness of 6 inches, 7 inches and 8 inches, and reinforced with various weights of reinforcing, some of it placed both top and bottom. There were also some unreinforced sections of the 7 and 8-inch thickness. Steel fabric and bar mats were the type of reinforcing used, but there were no combinations of the two. Edge strength on the resurfacing and new slabs was secured in the steel fabric mats by using heavier wire at the edge, and also with sheets of metal wider than the slab, turned down along the edge so that a heavy member is placed at the bottom. Additional end strength for the new slab as shown in the sketch was secured by cutting a sheet of metal in two and using one-half at each end of the slab with the heavy members running across the pavement. This method means using only one kind of steel on the job. It is an excellent method of reinforcing for loading at unsupported corners, for as the bending moment increases the area of concrete and steel increase thereby increasing the resisting moment. (Illustration No. 12.) Bar mats were also used, both single and double layer in |