[Amended 2-28-1950 by G.O. No. 6-1950]
For parking areas, including access and service roads, asphaltic-concrete
pavement on a broken-stone base, on a portland-cement base or on asphalt-macadam
base (penetration method) is hereby prescribed, approved and adopted,
the same to be in accordance with the requirements set forth in this
article.
[Amended 2-28-1950 by G.O. No. 6-1950; 7-3-1990 by L.L. No. 5-1990]
A.
Excavation. The roadbed shall be excavated to subgrade and thoroughly
rolled with a ten-ton roller until the surface of the subgrade is
solid and parallel with the proposed finished grade of the pavement.
Depth below the finished grade shall be determined by the thickness
of the broken stone or concrete base and the asphaltic-concrete top
called for on the plans and in the job specifications.
B.
Base. Upon the subgrade prepared as above shall be laid a base of
concrete, of broken stone or of asphalt macadam as called for and
of such thickness as shown on the plan and designated in the job specifications.
C.
Pavement to be one-course or two-course. The asphaltic-concrete pavement
shall be either one-course of two-inch or two-and-one-half-inch compacted
thickness or two-course of three-inch compacted thickness, as called
for on the plans and in the job specifications.
D.
One-course pavement. On the broken-stone or concrete base shall be
placed on asphaltic-concrete wearing course, to be leveled, raked
and rolled with a ten-ton roller to the satisfaction of the Engineer
and to a compacted thickness of two inches or 2 1/2 inches, as
called for on the plans and in the job specifications.
E.
Two-course pavement.
(1)
On the broken-stone or concrete base shall be placed an asphaltic-concrete
binder course, to be leveled, raked and rolled with a ten-ton roller
to the satisfaction of the Commissioner of the Department of Public
Works and to a compacted thickness of 1 1/2 inches. The surface
of the binder course after compaction shall be 1 1/2 inches below
and parallel to the established grade for the finished pavement and
shall be free from depressions exceeding 1/4 inch, as measured with
a ten-foot straightedge paralleling the center line of the street.
(2)
On the compacted binder course shall be placed a wearing course of
asphaltic concrete, either graded stone aggregate mix or sheet mix
as called for in the job specifications. Such wearing course shall
be leveled, raked and rolled with a ten-ton roller to the satisfaction
of the Engineer and to a compacted thickness of 1 1/2 inches.
The surface of the wearing course after compaction shall conform to
the established grade for the finished pavement and shall be free
from depressions exceeding 1/8 inch as measured with a ten-ton straightedge
paralleling the center line of the street.
F.
Materials.
(1)
In the wearing course, the graded stone aggregate mix shall consist of a graded stone aggregate passing a one-half-inch screen and all retained on a No. 10 screen, a graded fine aggregate of sand or stone screenings, all of which shall pass a No. 10 screen, a mineral filler and asphalt cement, all of which are to be proportioned and mixed according to approved manufacturer's specifications. It is intended that the paving mixture shall have an approximate composition as follows: 50% coarse aggregate, 36.5% fine aggregate, 6% mineral filler and 7.5% cement. The above percentages are not rigidly fixed and are subject to the final approval of the City's testing agency. See Subsection I below.
(2)
In the wearing course, the sheet mix shall consist of a graded sand aggregate, all of which shall pass a No. 10 sieve, a mineral filler and asphalt cement, all of which are to be proportioned and mixed according to approved manufacturer's specifications. It is intended that the paving mixture called for under this subsection shall have an approximate composition as follows: 73% sand, 16% mineral filler and 11% asphalt cement. The above percentages are not rigidly fixed and are subject to the final approval of the City's testing agency. See Subsection I below.
(3)
The binder course shall consist of a mixture of graded stone aggregate, all passing a one-inch screen and all retained on a No. 10 screen, a graded fine aggregate of sand or stone screenings, all of which shall pass a No. 10 screen, and asphalt cement, all to be proportioned and mixed according to approved manufacturer's specifications. It is intended that the paving mixture shall have an approximate composition as follows: 75% coarse aggregate, 20% fine aggregate and 5% asphalt cement. The above percentages are not rigidly fixed and are subject to the final approval of the City's testing agency. See Subsection I below.
(4)
Broken stone shall be produced from tough, durable rock and shall
be free from elongated pieces, soft or disintegrated stone, dirt or
other objectionable material.
(5)
Sand shall consist of clean, hard, durable grains, free from clay,
loam and other foreign materials.
(6)
Mineral filler shall consist of limestone dust or other approved
material.
(7)
Asphalt cement shall be refined asphalt and flux, of suitable consistency
for paving purposes.
G.
Spreading and rolling.
(1)
Unless otherwise permitted by the Commissioner of the Department
of Public Works, the asphaltic concrete shall be placed by means of
a mechanical spreader so operated that the mixture as spread is free
from lumps, of uniform density and to the desired cross section.
(2)
After spreading, the mixture shall be thoroughly and uniformly compressed
by a three-wheel, power-driven roller, weighing not less than 10 tons,
as soon after being spread as it will bear the roller without undue
displacement. Delays in rolling freshly spread mixture will not be
tolerated. Rolling shall start longitudinally at the sides and proceed
toward the center of the pavement, overlapping on successive trips
by at least 1/2 the width of a rear wheel. Alternative trips of the
roller shall be of slightly different lengths. The pavement shall
then be subjected to diagonal rolling in two directions with a tandem
roller weighing not less than 10 tons, the second diagonal rolling
crossing the lines of the first.
(3)
The speed of the roller shall not exceed three miles per hour and
shall at all times be slow enough to avoid displacement of the mixture.
Any displacements occurring as a result of reversing the direction
of the roller or from any other cause shall at once be corrected by
the use of rakes and of fresh mixture where required. Rolling shall
proceed continuously until all roller marks are eliminated and until
the finished course shall have a density not less than 95% of the
laboratory-compacted density. If the surface course is being placed
at a rate in excess of 300 square yards per hour, the contractor shall
use an extra roller. To prevent adhesion of the mixture to the roller,
the wheels shall be kept properly moistened, but an excess of either
water or oil will not be permitted.
H.
Smoothing irons. Heated smoothing irons shall be used to finish the
pavement along curbs, around manhole heads and elsewhere where necessary.
I.
Intent of specifications; approval of sources of supply for aggregates
and mineral filler.
(1)
It is the intent of these specifications to secure a pavement that
will conform to the latest construction specifications of the Asphalt
Institute. The contractor shall submit samples with manufacturer's
specifications for the asphaltic-concrete mixtures he proposes to
use in the work, and these are to be examined and passed upon by the
testing agency engaged by the City. The contractor shall make such
changes in the formulas submitted as may be required by the testing
agency in order that the mixture delivered and used in the work will
be such as to produce the pavement required.
(2)
Approval of sources of supply for aggregates and mineral filler shall
be obtained from the Commissioner of the Department of Public Works
before being used in the mixture.
