Omaha daily bee. (Omaha [Neb.]) 187?-1922, 1905-08-27

last decade also been admitted into the Sc
cret sanctuaries of the laboratories and
has discovered that, aside from the shape
of the streets and the asphalt used, the
sand which constitutes 80 per cent of the
surface covering, exerts very much innu-
ence upon the result. Numerous analysis
of poor pavements have shown that 1t was
not always wise to let the bidders make
specifications and that many important
requisites should be provided for in
the specifications. In place of and per
cent Of bitumen in the asphalt mixtures
frequently found in poor pavements Of our
cities, 1t has been demonstrated that good
pavements should have at laRst 10 per
cent of bitumen. This applies equally to
bituminous limestone pavements as to BIZ
luminous sandstone pavements.
Careful study OF the requisites further
shows that the more compact any pave
ment is the better its wearing qualities,
so It is found essential that to secure the
minimum of voids in the sand the grains
should be so graded TO admit of pack
ing, and finally, after this, the further
addition OF fine powdered filler will make
the mass still more compact. Stone dust
has been and is largely used for this
purpose, but In larger quantities than In
years past, and as an improvement finely
ground Portland cement is being substi-
tiIted in place of the stone dust This
has been used, with evidently very ex-
cellent results, on the Fifth avenue pave
ments I'm New York and those OF London,
and the same filler was used In Sixteenth
street, the leading thoroughfare OF
Omaha, and is required in all pavements
now laid in this city, 20 an extent OF not
less than per cent. and II per cent will
- g., he graFi6CatiOn
hereafter. The difference in cost Of few
cents per yard will not Justify its exclu-
sion on economical grounds.
To Make n Good Road.
with these facts bearing on the his
tory of it's development and relative TO the
materials needed In asphalt pavements in
view, the factors which enter into the
| construction OF an asphalt pavement, It's
maintenance and cost. can more readily
be comprehended. In this class, as in all
pavements, the first essential to good,
| durable construction is a proper base. A
good earth road requires first OF all,
| proper drainage, both for surface and sub
| surface. The solution OF this feature is a
simple engineering proposition. The next
essential is consolidation-the more COM
pact, the less will the surface yield to
vehicle trahic and the greater It's dura-
| bliity. The fact that earth yields readily
! 10 the softening and dissolving influence
| OF water, demands a very high crown
! upon an earth road that II may shed water
as fast as possible to escape its softeing
| agency. The fact that It partly dissolves
| when wet makes a soil yield more readily
| when porous because these voids will
| quickly absorb or MI with the dissolving
agent, hence the more compacted and less
porous the less Il will be exposed TO
moistening influences.
| Again, II the earth roadbed is subjected
( TO water from beneath the surface, IL will
not only be undergoing constant change IN
the summer period. but when winter comes
the water. when freezing, will expand and
hsave up the surface. With these funda-
mental principles outlined, We next come
20 the pavement proper.
Experiments in Paving.
Divested OF all verbiage a pavement Is
a veneering. or wearing road surface. II
! is placed there 20 protect the base and
give Il durability. The early attempts az
pavements were OF the old Roman road
order consisting OF layers OF large blocks
OF stone in mortar, which distributed the
load over a much wider area than that
directly exposed 10 the tires Of the wheels
These roads, with numerous variations
such as slabs OF granite, laid IN parallel
rows for the wheels 70 run on. tram rail-