IMPROVEMENTS IN ASPHALTIC PAVEMENTS
Year: 1879

page_text: PROVISIONAL SPECIFICATION left by John Thomson King at the Office of
the Commissioners of Patents on the 30th January 1879. A communication
from abroad by William W. Averell, of the City and State of New York,
United States of America.
JOHN THOMSON KING, of Liverpool, in the County of Lancaster, Patent Agent.
"IMPROVEMENTS IN ASPHALTIC PAVEMENTS.” [A communication from abroad by
William W. Averell, of the City and State of New York, United States of
America.]
This Invention relates to improvements in that class of pavements heretofore
known as the Grahamite asphalt pavement or Grahamite and Trinidad asphalt
pavement, and the Invention consists,-
1st. In the combination of a refined natural asphalt and the residuum of petro-
leum forming an asphaltic cement.
2nd. In the combination of such asphaltic cement and a silicious sand forming an
asphaltic concrete.
3rd. In a pavement composed of a hydraulic concrete or other suitable base or
foundation, a wearing or surface layer of the said asphaltic concrete with or without
an interposed cushion coat of the same, and
4th. In the manner of separately applying such parts so that the respective
layers will merely rest in contact and not adhere to each other, and whereby an
independent movement of either or both layers, caused by the expansion and
contraction of the same, and a renewal of the wearing or surface layer, is secured.
The asphaltic cement is composed of four (4) parts of refined Trinidad or other
asphalt and one (1) part of the residuum of petroleum. In preparing this cement I
take crude Trinidad or other asphalt and refine it by the application of heat to such
a degree as to resist a fire test or prevent evaporation under two hundred (200)
degrees Fahrenheit, and to give by distillation thirty-six (36) per cent. of hydro-
carbon oil of twenty-two (22) degrees Baumé. This will preserve the cementing
qualities and eliminate all objectionable matter. The residuum of petroleum which
is added to the refined asphalt should be a pure hydro-carbon liquid bitumen of a
density from fourteen (14) to eighteen (18) degrees Baumé, and resist a fire test of
two hundred (200) degrees Fahrenheit.
In lieu of the residuum of petroleum, heavy petroleum oil, wood or coal tar or their
products may be used, but these substances are not desirable as substitutes for the

page_text: ingredients should be mixed with the sand or stone dust if not found naturally
therein.
This cement, when prepared substantially as specified, will posses the quality of
pliability in summer and malleability in winter. It contains no water nor
ingredient that is soluble in water or in the urine of animals, nor an ingredient
that is oxidisable, and remains unaffected by the elements. It withstands a fire
test of at least two hundred and twelve (212) degrees Fahrenheit, and therefore is
not affected by solar heat.
The asphaltic concrete is preferably composed of about eighty (80) parts by
weight of silicious sand or silicious stone dust containing from six (6) to eight (8)
per cent. of calcareous matter, three (3) to four (4) per cent. of aluminous matter,
and about twenty (20) per cent. of asphaltic cement.
The manner which I have found best in practice of mixing and applying the
asphalt concrete is as follows:-
The sand or stone dust is heated to about three hundred (300) degrees Fahrenheit
and thoroughly incorporated with the melted cement by means of any suitable
heating or mixing apparatus and transported to the street in heated carts, where
it is carefully and rapidly spread to the required thickness, and preferably stamped
with hot iron stampers weighing about twenty pounds until it is solid. It may
then be smoothed or levelled with heavy hot irons, and subsequently rolled to
remove the minor undulations from its surface.
The foundation upon which this concrete is laid should be firm and substantial
and may consist of dry concrete composed of broken stone, gravel, and sand, or one
or all of such materials, cemented with the products of wood or coal tar, or any kind
of stone foundation or firmly settled macadam. A. foundation of hydrulic concrete
well set is best adapted for this purpose. This structure is composed of a firm
foundation of any suitable material, and of sufficient thickness to suit the kind of
traffic to which the street may be exposed, and upon such foundation a cushion
coat of asphalt concrete about one half an inch in thickness is applied.
This cushion coat is composed of coarse sand heated as already described, and
mixed with from ten (10) to twenty (20) per cent. of the asphaltic cement.
The object of this coat or layer is to perfect the grade, and act as an interposed
cushion between the foundation and wearing coat to receive and distribute all forces
of impact or blows upon the wearing or surface coat; it serves to prevent the
destructive action of the hydraulic cement (when said material is employed in the
foundation) upon the asphaltic_cement contained in the surface or wearing coat
and also arrests the rising moisture. This cushion coat may be laid without
tamping except in the gutters, the rolling and smoothing devices being sufficient ;
and in many situations, such, for example, as side walks and private roadways, this
coating may be omitted from the structure.
The surface or wearing coat is composed of the asphaltic concrete, and may be
from one and one half (1) to three (3) inches in thickness and is applied in
substantially the same manner as the cushion coat after the latter has become
firmly set.
The tamping process is preferably resorted to in applying this surface layer,
but is not absolutely essential, the situation and requirements of the pavement
governing the necessity.
The different layers composing the structure simply rest in contact, there being
no adhesion of the same, and this feature is an important part of my Invention.
It permits an independent movement of either layer that may be caused by a
varying expansion or contraction, and whereby the cracking of one by the unequal
expansion of the adjacent layer is prevented, and when the foundation and cushion

page_text: coat are laid they may remain undisturbed for an indefinite period, it being only
necessary in repairing this pavement to renew the surface layer, and which may be
removed without in the least disturbing the permanent foundation. The lasting
benefit to be derived from this feature of my Invention should in itself commend
its use on the question of relative economy with other known and amalgamated
concretes.