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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178
CONCRETE ROADS
necessary, washed, to comply with the conditions hereinafter laid
down.
No aggregate shall be used which is not hard and tough, or
which is laminated, and upon crushing breaks down into flat or
elongated particles. Soft or porous materials, such as broken
brick, breeze, etc., shall be prohibited.
All aggregates used shall be clean and free from clay, dust,
vegetable and other foreign matter. Care shall be taken that the
aggregate is not contaminated with mud, etc., after delivery
to the site of the work.
Coarse Material.—For one-course roads no aggregate shall be
used which will not pass through a screen having square openings
of 1 in. ; but for two-course roads the bottom course may contain
aggregate the largest stones in which will pass through a l|-in.
square opening. None of the coarse material shall pass through
a |-in. square opening. The grading from the maximum to the
minimum sizes shall be regular, and no material shall be used which
contains a large proportion of stones of approximately one size.
Sand or fine material shall all pass through a |-in. square open-
ing, but not more than 10 per cent, by weight shall pass a sieve
having 50 meshes per lineal inch. The grading from the maximum
to the minimum sizes shall be regular, and no material shall be
used which contains a large proportion, of particles of approxim-
ately one size.
Representative samples of the approved coarse material and
sand shall be retained by the surveyor in charge of the work,
and all deliveries shall be required to conform strictly to such
samples.
3. Concrete.—The average compression resistance of not less than
three test pieces of the concrete shall not be less than will comply
with the following formulae :—•
When 4 weeks old :—-C 1 = 2,800—200 V, and
When 13 weeks old :—C 3 — 3,600—-200 V, where
C 1 and C 3 = compression resistance in lbs. per sq. in.
V= Volume of sand and coarse material per volume
of cement.
For determining the compression resistance, tests shall be made
on cubes or cylinders of not less than 6 in. each way. The prepara-
tion, setting and maturing of the test pieces shall, as far as possible,
conform to the conditions that will obtain in the actual execution
of the work, provided that care must be taken to see that the
conditions for all test pieces are as uniform as practicable, and
that none of them is exposed to frost during setting and maturing.
The compression resistance of any test piece which gives such a