IMPROVEMENTS IN PAVEMENTS
Year: 1873

page_text: PROVISIONAL SPECIFICATION left by George Clark at the Office
of the Commissioners of Patents, with his Petition, on the 31st
December 1873.
I, GEORGE CLARK, of No. 10, Craven Buildings, Drury Lanc, in the
County of Middlesex, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN PAVEMENTS," to be as follows:-
This Invention relates to the use and combination of materials in a
way not hitherto practised for the purpose of improving street road and
other pavements. It has especially for its objects an improved mode of
constructing wood pavement, a plan for altering or laying down pave-
ments of rock asphalte with a view to render them non-slippery, and the
construction of a composite pavement of stone and asphalte, or stone
and wood.
As to wood pavement the following is a description of this part of my
Invention: To render the principles on which it is founded clear I will
first explain that the chief objection to wood as a paving material is its
liability to speedy decay. The experience of more than thirty years,
during which essays of wood paying. havo been made, shows that the

page_text: blocks have rotted in a short time, and various expedients have been
employed for their preservation but without success.
The latest theory relating to the decay of wood blocks on the plans.
before adopted, is that it arose from the continued saturation of the
blocks with water, and that by allowing water falling on the surface of
the pavement to percolate between the blocks and run into the subsoil
this cause will be obviated. To carry this plan into execution the blocks
are laid on a flooring of wood planks, which being frequently in a damp
state are subject to dry rot, and as they form the foundation which
supports the blocks, when the former gives way the latter fall in.
Experience has proved this to be the case.
My said improvements in wood paving arc founded on two principles,
one that the blocks must rest on a solid foundation impermeable to wet,
the other that the joints between the blocks of wood must be so per-
fectly closed that water cannot percolate from the surface to the
foundation.
I will now proceed to describe the manner in which these two
principles are carried out. The ground to be covered with the pavement is
made level and compacted by ramming. This ground surface is covered
with an even layer about 2 inches thick of concrete or cement, and on:
this layer planks are laid longitudinally in the line of the street. A
suitable length of the planks is 9 to 12 feet, and of thickness ½ to % of
an inch, but they may be thicker and should be laid 1 to 2 inches apart
from each other. Over and upon each set of planks another layer of
concrete or cement is laid whilst the lower layer is still moist, and the a
result is that the under and upper layers become united at the spaces
left between the planks, which being thus enclosed and imbedded in
concrete or cement are preserved from decay, and a firm, solid, and even
foundation is formed which is unyielding and impermeable.
To give greater solidity and continuity of stiffness to the whole of this s
work as it proceeds cross planks are laid under the sets of longitudinal
planks, breaking joint at the ends of each set, and supporting the latter
at intervals of 3 to 4 feet between the ends. This combined foundation
being dry and hard, on it are laid wooden blocks about 6 inches deep
and 3 inches wide, in close contiguity to each other in rows across the
These spaces
roadway with spaces 1 to 2 inches between the rows.
may be of a width equal or nearly equal to that of the blocks, and by

page_text: this arrangement a composite pavement of alternate rows of wood and
asphalte is produced. To regulate these spaces two sets of laths in
lengths of 1 to 6 feet, 2 to 3 inches wide, and ½ to % of an inch thick,
and kept apart from each other by means of short stay pieces 1 to 1
inch thick, are placed on the foundation between the rows of blocks,
thereby forming channels between the blocks, and also interstices
between the laths, the width of the latter being determined by the
thickness of the stay pieces fastened between the laths at intervals of
about 2 feet. Or to produce interstices between the laths for the pur-
pose herein-after mentioned the upper part of the width of the laths
may be bevilled on one side, the sides of their lower part abutting
against each other, and by placing the bevilled sides opposite each other
an angular or a V channel is formed between the laths at the top.
When a sufficient surface of the roadway has been thus covered and the
rows of blocks with the intervening laths are securely blocked up at
both ends of such covered surface, wedges are driven into the interstices
or into the V channels between the laths about 18 to 24 inches apart,
and with sufficient force to consolidate the entire mass of blocks, and
retain them securely in their places. These wedges should be 6 to 9
inches wide and of such a length that when driven home into the
interstices or the V channels the top of the wedges shall be flush with or
slightly higher than the top of the laths. Into the openings thus
arranged I pour hot asphaltum, pitch, or other bitumen in a proper fluid
11
11
hatwon the lathe and

page_text: vention of slipperiness. The foundation formed by the combination of
concrete and planks incrusted and imbedded in it is available for any
kind of pavement.
With reference to asphalte paving (the second part of my said Inven-
tion) made of rock asphalte in the various ways hitherto adopted, the in-
herent defect of such pavement is slipperiness when the surface is slightly
wetted, arising probably from the large proportion of alumina or clay,
which is one of the constituents of native asphalte rock. To overcome
this defect, of which the consequence is that in certain conditions of the
weather the surface affords no foothold to horses, I propose as regards
existing asphalte pavements to drill holes about 4 inches in diameter
and 4 inches apart from each other in rows across the roadway about
3 inches asunder, the position of the holes in each row being alternated,
so that the holes of one row are on a line passing between those of the
rows on either side. These holes will be driven through the asphalte
and through the concrete or other foundation to a depth of 9 or
10 inches. Into the bottom of each hole will be dropped 3 or 4 inches
in depth of broken stone or concrete, and the upper part of the hole to
the surface will be filled with a square or angular block or plug of wood
imbedded in concrete of bituminous material and broken stone or of
concrete of Portland or other cement. The mode of effecting this
operation is to partially fill the hole with hot and fluid concrete if bitu-
minous, or moist concrete if cement, and then to ram the wood block
pointed at the lower end into the concrete so as to bring the top surface
of the block level with the surface of the asphalte pavement. Care s
must be taken to place sufficient concrete in the hole to fill the spaces
round the block between its square or angular sides and the circumference
of the hole. To render the process more complete it is desirable to sink
the top of the wood block a little below the surface of the pavement and
then to pour into the cavity thus formed hot asphaltum concrete with
broken stone spread over it and tamped down with a hot iron and after-
wards solidified with a rammer. The surface of the wood blocks and the
roughness of the concrete in which they are imbedded owing to their
proximity to each other will counteract the slipperiness of the asphalte
and afford a hold to horses' feet.
If a new asphalte pavement has to be made on the same principle as
that just above described,.a foundation of concrete 4 or 5 inches thick is
to be laid down in sections across the roadway, and as each section of a

page_text: convenient width is completed wooden blocks or plugs 9 to 12 inches
long and 3 to 4 inches in diameter are rammed into the concrete within
3 or 4 inches of each other all over, leaving the upper part of the wood
projecting above the surface of the concrete the same length as the intended
thickness of the asphalte. When the concrete foundation has hardened,
a ring of asphaltum concrete, composed as herein-before described in a
hot and plastic state, not too fluid, is tamped round the projecting top of
cach block, and when any given area of the foundation is thus prepared
the asphalte in a meted state or pulverised and hot, is poured in over
the concrete foundation between the blocks, and tamped to a lovel
corresponding to that of the wood blocks.
For the purpose of remedying the slipperiness of rock asphalte pave-
ments, of which the upper surface or crust, composed more or less of
hard and sharp grit imbedded in it, thereby giving it roughness, has
worn away, I propose to add to the surface a new coating of similar grit
in the following manner:-I place on wheels a carriage frame carrying
a furnace grating, of which the length and width must be adapted to
circumstances, the bars of this grating being so placed as to be within 2
or 3 inches, or more or less if found necessary in practice, from the
surface of the pavement to be operated upon. Fuel, coke broken in
small pieces being most suitable, is laid on this grating, and ignited by
any suitable arrangement. This furnace is propelled over a given width
and length of the pavement at a slow rate, so that the asphalte shall be
softened and partially melted by the heat of the furnace. Immediately
following the furnace, and it may be on the same carriage frame as the
furnace, is a hopper containing hard grit, which falling through small
apertures at the bottom shall as the carriage proceeds sprinkle the grit
over the surface of the asphalte so softened by heat. Immediately
following the grit hopper a heavy iron roller, heated with ignited fuel
suspended in a basket inside, will pass over the surface thus sprinkled,
and press the grit into the asphalte. By repeating this process on suc-
cessive widths of the pavement any given length of asphalte pavement
will be operated upon, and its surface rendered sufficiently rough to
counteract slipperiness. The expense will be comparatively small, and
by periodical repetition of the process the asphalte will be kept in a non-
slippery state.
1 T

page_text: lay on a concrete foundation paving stones in rows alternating with
asphaltum, concrete, or asphalte filled into channel spaces between such
rows, on the same plan as that of wood blocks in rows, having spaces filled
in the same manner as above described. But to make this composite pave-
ment less noisy the rows of bituminous compound should be about equal i
in width to that of the paving stones. For carrying out this plan the
same combination of laths and wedges as before described for wood
blocks is applied, only the laths should be thicker and decper, rising to
within one or two inches (or even closer) of the top of the paving stones,
so that the wedging process for the consolidation of the paving stones ]
may be effected with solidity. A suitable width for the alternate rows
of stone and asphalte would be 3 to 4 inches each. Paving stones thus
disposed, having asphalte interposed between them, will not tend to wear
away at the edges and become convex, so that their surfaces remaining
level and the asphalte deadening the sound of the passing traffic, the 1
pavement will be less noisy, whilst the alternating surfaces will coun-
teract slipperiness.
As another modification of this kind of composite pavement, paving
stones in rows compressed tightly together by means of laths and wedges
in the same manner as that described for wood blocks may be combined 2
with alternating rows of wood blocks, secured in their position with
asphaltum concrete or asphalte precisely in the same manner as
described for carrying out the first part of my said Invention.
With reference to that part of my said Invention which relates to the
rendering of existing asphalte pavement non-slippery by roughing its 2
surface with hard grit or small broken stones in the way herein-before
described, the process of imbedding such grit or stone in the heated
surface of the asphalte will be improved by heating the grit or broken
stone previous to distributing it over the pavement, and also by covering
the pavement with a thin layer of ground asphalte before the heating 3
furnace is drawn over the pavement to be operated upon, as the pul-
verized asphalte, being melted or softened by the heat of the furnace,
will assist cementation of the grit by the action of the roller into the
surface of the pavement.