CONCRETE ON THE ROADS.

Kaipara and Waitemata Echo, 11 January 1917, Page 3

CONCRETE ON THE ROADS.

CONCRETE FOR BRIDGES

Full Particulars of a Most Welcome Innovation, as supplied in a Pamphlet issued by Wilson's Portland Cement Co. Auckland. (Continued from week to week.) STORY OF A WAYNE COUNTY CONCRETE ROAD. A twelve-inch plank is suitable for widths of road metal up to 18 feet. If the road is wider than this, a built-up form of strike is necessary, which is trusted to prevent a sag or flattening of the crown. The strikeboard is sawed back and forth on the side rails, and moved slightly forward at each stroke, giving the concrete its initial shape. After this operation no workman is permitted to disturb the concrete in any way, either by stepping on it or by throwing anything upon it. This rule is imperative, as a violation of it means a road with waves and depressions by causing the neat cement and i finer particles to rise to the top. We aim to have the stone take the wear, as it is the hardest part of the aggregate.

The final finishing up of the roads is done by two men whom we term " floaters," who work from a bridge which rests on the side rails, having no actual contact with the concrete. A wooden trowel of home manufacture is used for this purpose. The use of a trowel of this natuie prevents the road from becoming slippery.

Joints are placed every 25 feet, using a metal plate three-six-teenths of an inch thick and 3 inches wide. These metal plates are intended to protect the edges from spallingand chipping. They are curved to conform to the crown of the road. Three thicknesses of asphalted felt (about \i of an inch) are inserted between these metal plates cutting the entire depth of the concrete. These plates are provided with shear members, which tie them securely to the concrete. We exercise a great deal of care to get these joints flush with the road surface, as a jolt is experienced by a fast-moving vehicle in passing if they are too high or two low. Our whole aim is to provide a level, even surface, and the roads we are building at the present time show a vast improvement on this score over those built three or four years ago.

When the concrete will stand its own weight, the side rails are removed, and a three-inch bevel is.made at about 45 degrees by cutting off the edge with a shovel, and allowing the surplus thus out off to fall to the side. This prevents a sharp division line between the ooncrete and the shoulders, Eaoh day's ,work is finished up to an expansion joint, and no more than 20 minutes is permitted to elapse between batches during the day. The day following the laying of the concrete it is covered with a couple of inches of sand or loose soil, such as is available, and is sprinkled during the day for eight continuous days. This prevents the road from drying out, and is an important factor in properly ouring the concrete so that it will attain its maximum hardness a^d strength, Plenty qf water- 4s vitally essential in ppoduoing good concrete.

Roads are not opened for traffic until from two to five weeks have elaped after the last batch Qf cq^crete js laid ) the length qf time depends upon the season of the year, as concrete sets much more slowly in cold weather than when it hot and dry.

Shoulders Qf crushed stone or gravel, whichever is the more available, are hu^lt three to seven inches thioh an,d three feei wide on ea.ch side of the concrete 5 on mar*y roads additional width of earth shoulders are built, This work is not started until after the road is at least three weeks old.

All of our work is specialised, one crew doing^ i^\e grading, another building, culvert, another digging, ditches and making shoulders, another ur^oajing and hauling, and another a.^roadb,uiluin^ proper.. These various opera,tiq'n;S are. usually- cajrried out simultaneously/ a,t -\?ayiaus points atoftg § ' given, road. Machinery, js us,§d wherever possible, sine,e man a.nd horse Jabour- a.re aoayce and expensive in the QQuntry districts during the road building season. Many labour-saving devices have been worked out, which increase both the quantity and quality of our work, and a persona,), inspection of our crews io, operation, 'is an ; in^i-.esting. and'instructive sight. j; M;o road i^ b,ui]jt kss than 23 feet \\n width over all of material upon which traffic can turn out at any season of the year.