IMPROVEMENTS IN THE CONSTRUCTION OF ROADS OR WAYS AND IN THE MANUFACTURE OF MATERIALS FOR MAKING AND " REPAIRING THEM
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by William Phillips Thompson at the
Office of the Commissioners of Patents on the 16th August 1882. Com-
municated to him from abroad by Monsieur Auguste Combe d'Alma of Paris
in the republic of France
WILLIAM PHILLIPS THOMPSON of the Agency for Foreign Patent Solicitors
6 Lord Street Liverpool in the county of Lancaster and of 323 High Holborn in
the county of Middlesex Civil Engineer "IMPROVEMENTS IN THE CONSTRUCTION
OF ROADS OR WAYS AND IN THE MANUFACTURE OF MATERIALS FOR MAKING AND
"
REPAIRING THEM a communication to me from abroad by Monsieur Auguste
Combe d'Alma of Paris in the republic of France.
This system of macadamizing roads is specially characterized by the nature of
the materials used as well as their preparation and mode of employment The
materials used consist of burnt clay broken into fragments and spread out into
layers the thickness of which and the size and hardness of the fragments being
such as are calculated to obtain the best results and can be varied to suit special
circumstances
Clay of suitable composition and to be found in abundance in nature is employed
for the manufacture of this material and to render the burning more economical
a process of burning by means of gas described in previous French patents of the
same communicator is adopted in which the recovery of the sub products is
beneficial to the burning operation itself
The kilns employed for this operation can also be of any description as well as
the mode of working the clay previously. It is preferred however after the clay,
the composition of which has been suitably chosen or obtained has been prepared
and worked up in the usual way to pass it to a special mould so as to give it all
the cohesion possible. This mould is analogous to those used in the manufacture
of perforated bricks, but differs from them in forming in the blocks produced very
small holes destined not only to facilitate drying but especially to regulate the size of
the fragments produced on breaking; the spacing of the holes is consequently
carefully calculated according to the size of the fragments to be obtained
On coming out of the mould the clay is cut into blocks of appropriate size which
are dried and barnt preferably by the above mentioned processes then broken up

page_text: by any suitable means into fragments sensibly uniform in size as has just been
said but absolutely irregular in shape and similar to the fragments ordinarily
employed for macadam." The small size of the holes formed in the blocks
contributes to obtaining this result and prevents regularity of face, re-entering
angles and too thin sharp edges
The nature or composition of the original material and the amount of burning
to which it is subjected are carefully determined according to the degree of hardness
necessary. It will be thus seen that broken crockery or waste materials from
works are not used but special products of defined character prepared in a particular
manner for the result it is desired to obtain
Further the materials are laid down in a systematic manner. For a new road
the first bed is made of fragments of a size of from seven to eight centimetres and
of similar hardness to ordinary flints and from ten to twelve centimetres in
thickness; upon this foundation a second layer of fragments is laid of a size of
from two to five centimetres and not quite so hard If 20 be taken to represent
the coefficient of hardness of the first layer, 12 to 15 would suffice for the second.
All the fragments in a bed are wedged together and rendered immovable by
numerous smaller pieces of the same material and of the same hardness and laid
down at the same time; in this way all the interstices are more or less filled and
the solidity of the whole is much improved. Although this addition of small
pieces of the same nature as the fragments in the composition of the beds is optional
it is considered very important and gives the best results For the top surface of
the road a powder is employed composed of crushed fragments preferably less
burnt than those of the first two beds. Sand or fine gravel more or less earthy
can also be used for this top bed but the results obtained are not so good.
surface of the road thus formed is perfectly solid and united after having been
rolled. A slight watering much less abundant and especially much less frequent than
what is at present necessary is sufficient to keep the road in excellent condition and
it is expected that there will never be either mud, dust, ruts, or holes, the materials
employed, preferably all of the same kind, holding together almost like cement.
The
For the repair of old roads a bed eight to ten centimetres thick of fragments
of the second kind (two to five centimetres in size) mixed with small pieces and
covered over with the powdered materials as has just been described will suffice to
furnish a very solid macadam
The properties of burnt clay and the particular way in which these special
products are prepared permit of obtaining an unalterable macadam suitable for
all the exigencies of the traffic and applicable to roads serving the most
varied uses.
It is of course also to be understood that the number and thickness and the
composition of the different layers, the size and hardness of the materials composing
them, the degree of fineness and the amount of powdered material placed on the
top can all be varied within wide limits without departing from the principle of
this invention.