Concrete Roads
and Their Construction
År: 1920
Serie: Concrete Series
Forlag: Concrete Publications Limited
Sted: London
Sider: 197
UDK: 625.8 Con-gl.
Being a Description of the concrete Roads in the United Kingdom, together with a Summary of the Experience in this Form of Construction gained in Australia, Canada, New Zealand and the United States of America.
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138
CONCRETE ROADS
secure the maximum pressure on the roller, whilst still retaining
sufficient “ weight ” on the rear wheels to ensure satisfactory
driving up steeply inclined gradients.
For road-making, a steam-roller should have sturdy construc-
tion and ample boiler capacity, with the boilers and cylinders
mounted so as to facilitate quick repairs.
The design should be as simple as possible, as such machines
work continually under adverse conditions and frequently in
out-of-the-way places. In order that the roller may be stable,
its centre of gravity should be low, yet there should be sufficient
space above the ground to prevent the engine being damaged by
obstacles which the roller has failed to crush or by the machine
having to work on very irregular ground.
As steam-rollers are not required the whole of the time, it is
convenient to attach a belt to the fly-wheel and from this to drive
a crusher, screen or other machinery which can be operated at
intervals.
Motor Rollers in all sizes have been in successful use for a great many
years. They are manufactured in both the single and double
cylinder types, and some of them can be run on paraffin, the
advantages of the motor-rollers being that they can Joe operated by
one man, that keeping them supplied with fuel is less costly, and
that they do not require a constant supply of water.
Machines at present on the market are manufactured by Messrs.
Barford & Perkins, Peterborough, and the Austin Manufacturing
Company of Chicago.
Preparing the Concrete
The chief mechanical devices used in preparing the concrete are
ci’ushers for the coarse aggregate, sand washers, screens, measuring
devices, appliances used for transporting the raw materials as well
as the concrete “ slop,” mixers and engines for the supply of power.
It is convenient to consider each of these separately.
Crushers should reduce the large lumps of stone or other material
used for coarse aggregate so as to produce angular fragments
of the required size. Machines which produce rounded pieces
are useless for road-concrete. Jaw-crushers and gyratory crush-
ers are the most satisfactory ; in the former the lumps are crushed
between two plates, one of which moves towards and away from