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The New Zealand Railways Magazine, Volume 2, Issue 5 (September 1, 1927)

Concrete Roadbeds

Concrete Roadbeds.

Improvements in railway track have proceeded steadily throughout a century of railway operation. Hitherto, however, attention has primarily been centred around the track itself, rather than upon the bed which carries the slepers and rails. Of the comparatively few innovations introduced in the roadbed itself, none are of greater interest than the concrete track bed recently subjected to experiment in the United States. Reinforced concrete is at present being experimented with on a big scale, by the Pere Marquette Railway, with the idea of effecting cuts in permanent way maintenance costs. It will not be suprising if very shortly similar tests are conducted by the group lines of Britain, for the American trials have aroused immense interest here at Home.

The concrete track bed employed in America is ten feet in width and 21 inches deep. Two upright longitudinal frames, in the plane of the two track rails, supplemented by plain diagonal and cross bars, form the steel reinforcement. Additional support is given by adjustable rods installed at six-feet intervals, and steel bar cross page 31 frames at each alternate adjustable rod. At intervals of twenty-seven inches stirrups are provided, forming seats for the rail slips, and the rails have no direct contact with the reinforcement. About 850 cubic yards of concrete are used on each quarter of a mile of track, and in order to “cure” the concrete, it is kept covered for seven days after laying with blankets of wet sand. No sleepers are required on the concrete track, and it is anticipated that the life of the reinforced concrete bed will be much longer than the conventional roadbed hitherto favoured.