The sun. [volume] (New York [N.Y.]) 1833-1916, 1906-12-02
WATERPROOF ROADS DUSTLESS
BRITISH EXPERT DISCUSSES
THEIR CONSTRI CTTON.
sa;s Tar Makes Good Dressing for High
ways. hut should Be Distilled Before
BEING A~ppllcd-Blast Furnace Stag
Fine Material for Surface Dressing.

BEING AppIlcd-Blast Furnace Stag
FINE Material for surface Dressing.
. With Waterproof Roads as a Solution
OF the Dust Problem" as his subject Doug
lass Mckenzie recently delivered a lecture
before the British Association at York.
England, during which he thoroughly
reviewed the matter and declared that tar
rs by no means the best road dressing.
After pointing out the vital connection be-
tween the foundation and the covering
OF the road in their rcrNective functions
he sho wed how the natural tendency OF a
tarred surface waste break up into dust
under the action Of tires and hoofs, forming
at once an undesirable and offensive nuis-
anoe, and at the same time reducing the
Of the covering to ultimate ex-
hsustion. Referring to the selection and
laying down of material in the average
road. he said in part.
Material for recoating is selected with
q due balancing of its value as a road ma
terial and its cost at the site. IL is broken
10 a size which ~ entirely the whim Of the
particular surveyor. y . IL is gen
orally spread about three inches thick,
steam rolled dry, then soaked with water.
covered with so called binding material
in the worst cases roadside soil or scrap
ings, perhaps gravel, but in the best cases
clippings OF the same material as the road
material-then it ia again steam rolled to
the satisfaction of the surveyor.
The result IL an ~agglomerate composed Of
large pieces of stone, with the interspaces
flied with ground up road metal. binding
material or organic matter. 1t
will thus be seen that the dust originates
IN (d) binding material, which loses its
cohesion when it dries; (b) ground up road
metal; (c) organic matter originating with
the horse. and (D dust blown on to the road
surface from the surrounding land. There IL
only one real remedy for (c) and Cd, namely.
to make a thoroughly smooth waterproof
road 20 that this dust will be washed of
into the channels by every smart shower
For (dD and (bl the remedy is twofold:
use a material sufficiently tough 70 prevent
any movement of the stones On one another
under traf,c, and such that ia equally
Efficient in all weAthers. The answer in
both cases is waterproof but the selection
OF a suitable w~aterproofng and binding
material is by no means easy.
There are many who will advocate a
hard granite covering, and who consider
that such il sufficiently dustless for all
practical purposes; but it must be admitted
that there Is a certain amount of dust from
a hard granite road, and even when binding
material is from the same quarry there is
a certain amount of water absorption at
the surface, and consequently there are
lines, especially in the winter, when the
road is a spongy mass. The very fact
that there are interspaces between the
stones is proof that water can lie on the
road and gradually percolate to the lower
layers, and 80 such a road has in itself the
elements Of destruction, which it should
be the aim of every engineer to avoid.
Avery practical methods Of waterproofng
such a road is to paint The surface by hand