F.) shall be of such consistency as to show a penetration of from forty
to eighty hundredths of a centimeter, as the engineer may direct for
each street, when tested with the standard Dow penetration apparatus,
using a number two cambric needle loaded with one hundred grams. When a
cement of a consistency satisfactory to the engineer has been produced
and approved for any street a sample of it shall be kept as a standard
and all subsequent batches or kettles must be made to conform thereto,
suitable apparatus and tests being employed to determine the
correspondence of each new batch with the standard.[20] The asphaltic
cement when at its melting temperature shall be so viscous that it will
draw out into moderately long fine threads which shall be free from
lumps or raggedness and shall possess satisfactory adhesive and
cementitious qualities.[21]
=51. Composition and Preparation of Asphalt Surface Mixture.=—The
surface-course shall be composed of the materials specified in Sections
43, 44, 45, 46, 47, 48, 49, and 50 mixed in such ratios by weight as the
Engineer may direct or approve. A typical mixture will contain:
Sand 100.0 lbs.
Pulverized mineral matter passing No. 200 screen, including
that found in the paving cement 17.5 lbs.
Pure bitumen (in paving cement) 13.5 lbs.
But the quantities of pulverized stone and of asphaltic cement shall be
varied as may be found necessary or desirable by the Engineer to suit
the purity of the asphaltic cement, the character of the sand, the
climatic conditions, and the varying quantity and character of travel on
the street to be paved; and Portland cement may be substituted partly or
wholly for the pulverized stone, when directed by the Engineer. The
surface-course mixture shall be submitted to the Engineer and approved
by him before any is laid upon the street.
The mixing shall be accomplished in a mechanical mixing apparatus
capable of rapidly and effectually incorporating the materials together,
and each batch must remain in the mixer a sufficient length of time to
effect a perfect mixture. The sand shall be separately heated and shall
reach the mixing apparatus at a temperature not above three hundred and
fifty (350) degrees F., nor below three hundred and twenty (320) degrees
F. The pulverized stone shall be at such a temperature that when mixed
with the sand the temperature of the mixed mass shall not be above three
hundred and fifty (350) degrees F., nor below three hundred and twenty
(320) degrees F. The sand shall be first placed in the mixer, followed
by the pulverized stone, and these two materials shall be thoroughly
mixed together before the asphaltic cement is added. The asphaltic
cement at a temperature not above three hundred and fifty (350) degrees,
nor below three hundred (300) degrees F. shall then be added in such a
way as to evenly distribute it over the sand and pulverized stone, and
the mixing continued until the materials are thoroughly incorporated
into a perfectly uniform and homogeneous mass, with the grains of sand
completely covered with cement. Suitable thermometers shall be
constantly used to determine the temperatures specified herein. Great
care must be taken to accurately weigh and proportion the materials
charged into the mixer.[22]
=52. Stone for Base-course.=—Stone screenings for base-course shall be
of crushed, hard, durable stone. The portion used shall all be retained
upon a No. 8 sieve, or screen, and shall all pass a screen having square
meshes, the linear dimensions of the openings in which are one-half (½)
inch less than the thickness of the base-course.
=53. Composition of Base-course.=—The base-course shall be composed of
the crushed stone specified in Section 52, mixed with the asphaltic
cement, sand and pulverized stone specified in Sections 50, 48 and 49,
but the asphaltic cement shall be of such hardness as the engineer may
direct.
A typical base-course mixture will be composed as follows:
Crushed stone 100 lbs.
Sand 42 lbs.
Pure bitumen (in asphaltic cement) 7 lbs.
Pulverized stone 7½ lbs.
But the mixture shall be such that when placed on the street and
compressed by the roller the mass shall be dense and the voids in the
stone completely filled; and to accomplish this the quantity of crushed
stone used in the mixture may be increased or decreased, as the volume
of its voids may require, in order that they may be completely
filled.[23]
=54. Mixing the Base-course.=—The materials for the base-course shall be
heated and mixed in the same general manner as prescribed for the
surface-course (Sect. 51), the crushed stone being delivered first in
the mixer. The temperature of the mixture as it comes from the mixer
being not above three hundred and twenty-five (325) degrees F., nor
below three hundred (300) degrees F.
=55. Laying Asphalt Pavement, General.=—Asphalt pavement must not be
laid except when the surface upon which it is to be placed is dry; nor
when the temperature of the air is below thirty-two (32) degrees F., or,
if a strong wind prevails, when the temperature of the air is below
forty (40) degrees F.
The pavement mixture, whether for base- or surface-course, shall be
taken to the street as soon after it leaves the mixer as practicable.
When the temperature of the air is below seventy (70) degrees F., the
loaded vehicles conveying the mixture to the street shall be covered by
canvas covers to prevent the escape of heat. When unloaded upon the
street, the temperature of the mass should not be below two hundred and
eighty (280) degrees F., and any load or portions of a load found under
two hundred and forty (240) degrees F. must be rejected. After being
unloaded on the street, the mixture must be shoveled into place in such
a manner that the whole of it will be moved from the pile into which it
was unloaded.
=56. Laying the Base-course.=—The base-course will have an average
thickness of one and one-quarter (1¼) inches after compression. It shall
be laid directly upon the pavement foundation, which must be free from
all loose fragments and rubbish and be swept clean in advance of the
application of the base-course. The base-course mixture shall be spread
upon the foundation and evenly and regularly graded to such a depth that
after compression by the roller its surface will be ... inches below,
and truly parallel to, the pavement datum.
Great care must be taken in handling, spreading and grading the mixture
to maintain the uniform admixture of the crushed stone throughout the
mass. The rakes used must have tines wide apart, and the back of the
rake must be principally used for grading. Immediately after being
graded, and while still hot, the base-course shall be rolled with an
asphalt roller weighing not less than five tons, the rolling being
continued until no further compression takes place.
The base-course must not be laid more than one day’s work in advance of
the surface-course.
When the base-course is completed it must present a uniform appearance
and texture over the whole surface, which must conform so truly to the
designed grade and contour that a twelve-foot template, when applied,
will show no departure from the true surface greater than one-quarter
(¼) inch.
=57. Laying the Surface-course.=—In delivering the surface-course
mixture upon the base-course, care must be taken not to break or disturb
the latter. Any breaks made in the base-course must be so repaired,
before the surface-course is spread, as to be equal in density and
surface to the adjoining base.
Before the surface-course is spread the base-course must be thoroughly
cleaned and all rubbish, loose material and street dirt removed.
The material for the surface-course shall be so evenly spread and graded
with asphalt rakes that after it is properly compacted by rolling, the
surface will coincide with the pavement datum within the limits named
below. In grading the material, all lumps must be broken up and the
whole reduced to a finely comminuted mass of equal density throughout.
Directly after being so graded it shall be rolled with a hand-roller, or
light steam-roller, to partly compress the material, and, when so
directed by the Engineer, the surface shall then be ironed with
smoothing irons heated to a temperature that will melt, but not burn,
the asphaltic cement. A thin layer of hydraulic cement, just sufficient
to prevent adhesion between the material and the roller, shall then be
swept over the surface, which shall at once be thoroughly rolled with a
ten-ton asphalt roller until the material shall be thoroughly compressed
and its surface be brought to the exact grade and contour designed for
the street surface. The work of the ten-ton steam-roller must begin
before the material has cooled below two hundred (200) degrees F., and
be continued until the roller makes no further impression upon the
surface. The first course of the heavy rolling shall be parallel to the
street beginning at the curb and working toward the center on each side,
after which it should be diagonally rolled, and also cross-rolled if the
width of the street permits.[24] Any portions of the surface not
accessible to the roller shall be tamped with hot tampers until
compacted equally with the rolled portion. When completed, the surface
shall have an average thickness of ... inches and must be so free from
waves or irregularities that a template not less than twelve feet long,
when applied to the street surface shall nowhere show a divergence from
the designed true surface of more than three-sixteenths (³⁄₁₆) inch, and
a template sixteen (16) feet long applied to the gutters shall show no
divergence from the true gutter grade greater than one-eighth (⅛) inch.
Before the surface-course is placed, all exposed surfaces of curbs,
crosswalks, manholes, etc., with which the surface-course will be in
contact, must be well painted with hot paving cement or approved pitch.
The street shall not be opened to travel until the pavement has become
cold and hard.
=58. Street Railroad Tracks.=—Where railroad tracks exist on the
streets, the sub-grade and the pavement foundation shall extend under
the tracks, uninterrupted except by the ties and other structures
connected with the track. Where concrete foundation is used, special
care must be taken with the concrete directly under or around the rails,
and concrete made of fine crushed stone and a higher ratio of cement and
sand may be required in contact with the rail. The concrete must be
thoroughly tamped under and against the rail.
The asphalt surface shall be laid directly against the rails, which, if
their temperature be under fifty (50) degrees F., shall be heated by
suitable appliances to a temperature of, or above, sixty (60) degrees F.
immediately before the asphalt material is placed around the rail. The
hot asphalt material must be thoroughly tamped against and along the
rail and under any projecting portions of it, and the surface of the
pavement must be even with, or slightly (not more than one-eighth (⅛)
inch) above the top of the rail. Slot-rails will be treated in the same
manner, subject to such modifications as their forms may
necessitate.[25]
=59. Plant.=—The plant for making asphalt paving mixtures must be of
approved modern design, adapted to do the work properly, and equipped
with efficient machinery. It shall be of sufficient capacity to turn out
at least twelve hundred square yards of pavement surface daily without
crowding. Weighing and measuring devices shall be accurate and adapted
to the purpose, and must be frequently tested and adjusted. Each plant
must be supplied with the apparatus necessary to make all determinations
and tests required at the plant to properly conduct the work in
accordance with these specifications. Steam-rollers must be properly
balanced and the rolling surface must be true and smooth. All the street
tools used must be of approved kind and quality and must be kept in good
working order.
ASPHALT BLOCK PAVEMENT
=60. Sub-grade.=—The sub-grade for asphalt block pavement shall be
prepared as specified in Sect. 26 of these specifications.
=61. Foundation.=—The foundation for asphalt block pavement shall be
hydraulic concrete or broken stone.[26]
Concrete foundation shall be constructed in accordance with Sections 28
to 37 inclusive of these specifications and shall have a thickness
of ... inches.
Broken stone foundation shall be constructed in accordance with Section
40 of these specifications and shall have a thickness, when completed
of ... inches.
=62. Asphalt Blocks.=—Asphalt blocks shall be not less than ten (10)
inches nor more than twelve (12) inches long, not less than four (4) nor
more than six (6) inches wide and not less than two (2) inches nor more
than four (4) inches thick. Blocks for the same street must be of the
same standard size throughout and individual blocks shall not vary in
any dimension more than three-sixteenths (³⁄₁₆) inch from the standard
size. Blocks that are chipped, cracked or are otherwise defective shall
be rejected.
=63. Material and Composition.=—Asphalt paving blocks shall be composed
of crushed trap rock[27] or equally hard and durable rock, sand,
pulverized stone and asphaltic cement.
The crushed rock shall be of such sizes that all will pass a screen
having circular openings one-third (⅓) inch in diameter and that all
will fail to pass a number ten (No. 10) sieve. The stone shall be
freshly crushed, free from foreign substances and clean and bright.
The sand shall be clean and sharp and of such sizes that all will pass
the number ten sieve and not more than five per cent. will pass the
number two hundred sieve. The grain-size of the sand shall preferably be
such that at least fifty per cent. (50%) of it will pass the number
eighty sieve. The screenings from the crushed stone passing the number
ten sieve may be used in place of sand, or thoroughly mixed with the
sand to produce a mass of the above composition. The pulverized stone
shall comply with Section 49 of these specifications. Portland cement
shall be used in place of not more than ten per cent. of the whole if
directed by the engineer, in which case the Portland cement will be paid
for as extra work at the prevailing market price.
The asphaltic cement shall comply with the requirements of Sections 43,
44, 45, 46, 47 and 50 of these specifications.
=64. Typical Composition.=—A typical composition of the blocks, which
must be complied with as nearly as practicable, is as follows; (by
weight)
Bitumen 7%
Mineral material passing No. 200 sieve 13%
Mineral material passing No. 80 sieve 9%
Mineral material passing No. 40 sieve 7%
Mineral material passing No. 10 sieve 28%
Mineral material passing No. 3 sieve 36%
————
100%
=65. Manufacture.=—The crushed rock, sand and pulverized stone shall be
thoroughly mixed together at a temperature not above three hundred and
seventy-five degrees Fahrenheit (375° F.) and not below three hundred
and twenty-five degrees Fahrenheit (325° F.) and the asphaltic cement,
at a like temperature, added and the mixing continued until a perfectly
uniform mass is produced, with every fragment of stone completely coated
with cement.
The hot mixture will then be compressed in molds under a pressure not
less than four thousand (4000) pounds[28] per square inch, after which
the blocks will be removed from the molds and allowed to cool, either in
the air or in water.
The completed blocks after cooling in air shall have a specific gravity
of not less than 2.5. They shall not absorb, when immersed in water for
twenty-four hours, more than one-half of one per cent. of water. When
tested in the standard rattler for testing paving brick the average loss
by abrasion shall not exceed twelve per cent. (12%) of their original
weight, after 1800 revolutions of the rattler.
=66. Laying the Blocks.=[29]—The foundation shall be first cleaned of
dirt, rubbish or loose material.
When the blocks are four (4) inches or less in depth as laid, they shall
be set upon a bed of mortar made and applied to the foundation in the
following manner:
The mortar shall be composed of Portland cement and sand, in the ratio
of one (1) part cement to three (3) parts of sand, thoroughly mixed with
sufficient water to make a rather soft mortar. This mortar shall be
spread over the foundation, which shall be previously wetted, in a layer
approximately one-half (½) inch thick and its top graded by the use of
templates to a surface at such depth below, and truly parallel to the
pavement datum, that when the blocks are firmly set in it and rammed
their tops will be in the true grade and contour of the pavement. The
mortar shall be made and spread only as required in the progress of
block laying, and any mortar that has begun to set before the blocks are
in place and rammed, shall be removed and fresh mortar substituted. The
blocks shall be set upon this mortar bed with their longest dimension
across the street, in continuous courses which shall be straight and at
right angles to the axis of the street. The block layers must stand upon
the blocks already laid and not upon the mortar. The blocks and the
courses of blocks shall be set as closely together as practicable.
Blocks in adjoining courses must break joint not less than four inches.
Whole blocks only will be used, except as fillers at the ends of the
courses or in fitting the pavement around manholes or other structures,
and where thus used the broken ends of the blocks must be dressed to
make close joints. Unless otherwise permitted, each course must be laid
continuously across the street without interruption in time. As each
course is completed the end joints shall be forced close together by the
use of wedges, levers or mauls. Upon the completion of every third
course, the courses shall be forced together by placing a timber
scantling against the face of the last course and striking it with a
sledge or maul. When the blocks are thus laid, and before the mortar
under them begins to set, they shall be well rammed to a solid bearing
in the mortar with a wooden street rammer weighing not less than thirty
(30) pounds, a two inch plank ten (10) inches wide and three (3) feet
long being interposed between the block and the rammer and moved about
so that the whole surface shall be covered and rammed. When the ramming
is completed, the top of the blocks must conform so closely to the
pavement datum that when a template or straight-edge is placed upon the
pavement, its surface shall nowhere depart from the true surface more
than three-sixteenths (³⁄₁₆) inch. Blocks, or portions of the pavement
found too high or too low, must be taken up and reset in fresh mortar to
the true grade. When thus completed to the satisfaction of the Engineer,
a layer of one-half (½) inch of fine dry sand shall be placed over the
surface and swept about with brooms until all joints are completely
filled. The remaining sand shall be removed from the pavement at such
time as the Engineer may direct.
When the depth of the blocks exceeds four (4) inches, they may be set
upon a cushion course of sand, as prescribed for brick pavement, Section
86, the joints to be filled with sand, as specified above in this
Section.
=67. Railroad Tracks.=—Where railroad tracks exist on the street to be
paved, the construction shall be the same as prescribed for granite
block pavement, Section 78.
=68.= The street shall not be opened to travel until the mortar under
the blocks shall have become fully set, and in no case under five days
after the blocks are laid.
GRANITE BLOCK PAVEMENT
=69.= Granite block pavement shall be laid upon a foundation of
hydraulic cement concrete.[30]
=70. Sub-grade and Foundation.=—The sub-grade shall be prepared as
specified in Section 26. The foundation shall be constructed in
accordance with the requirements of Sections 28 to 38 inclusive.
=71. Granite Blocks.=—The blocks shall be made from sound, durable
granite, of uniform texture, composition and hardness throughout. No
outcrop, deteriorated, soft, brittle, or seamy stone shall be used. If
the blocks are obtained from different quarries, or from different parts
of the same quarry where the quality or appearance of the rock differs,
the product of each must be kept separate and laid together on the
street.[31]
The blocks shall be not less than eight (8) nor more than twelve (12)
inches long, not less than three and one-half (3½) nor more than four
and one-half (4½) inches wide, and not less than four and three-quarters
(4¾) nor more than five and one-quarter (5¼) inches deep.[32] They shall
be well-shaped, rectangular, with full edges and corners. Their tops
shall not depart more than one-fourth (¼) inch from a true plane, and
their sides shall be dressed so that joints between the courses will
nowhere exceed three-fourths (¾) inch wide, and their ends so that end
joints shall not exceed one-half (½) inch wide.[33] The size of the
blocks may be varied where necessary to fit the pavement against or
around bridge stones or other street structures.
=72. Sand Cushion.=—The foundation shall be cleaned of all dirt and
rubbish. There shall then be spread evenly over it a layer of clean,
coarse sand to a uniform depth of one and one-half (1½) inches.
=73. Setting the Blocks.=—The blocks shall be set in this bed of sand
perpendicular to the street surface, with their length at right angles
to the street, in courses extending entirely across the street, and at
right angles to its axis, except at street intersections where the
courses shall be arranged as the Engineer may direct.[34] Only stones of
the same width shall be set in the same course. The stones in each
course, and in adjoining courses, shall be set firmly against each
other. The blocks shall be set in the sand bed in such a manner that
their bottom surface shall rest evenly upon the sand and that their tops
shall be even with each other and to such an elevation that after the
pavement is rammed, as hereinafter directed, its general surface shall
conform closely to the pavement datum. Stones in adjoining courses shall
break joint not less than three (3) inches.
=74. Ramming.=[35]—After the blocks are set each individual block shall
be thoroughly rammed to give it a firm bearing in the sand and to bring
its top to the prescribed pavement datum. The rammers used shall have
wooden faces not more than four inches in diameter, and shall weigh not
less than thirty (30) pounds. Blocks or sections of blocks whose tops
under the ramming remain above or sink below the pavement datum shall be
taken up and reset so that after the ramming is completed their tops
shall coincide with the pavement datum.
=75. Filling the Joints.=[36]—After the ramming specified in Sect. 74
shall have been completed, the joints between the paving blocks shall be
filled in the following manner:
All the joints for a distance of three feet out from the curbstones, and
three contiguous joints continuous across the street, with the included
end joints, at intervals of about fifty (50) feet in the length of the
street, shall be filled with gravel and bituminous paving cement. The
gravel used shall be of such size that all will pass through a screen
having five-eighths (⅝) inch meshes, and all will be held on a screen
having one-fourth (¼) inch meshes. When used, the gravel must be free
from refuse and street dirt. The bituminous paving cement shall be
composed by weight of straight-run coal-tar pitch of the hardness
commonly known as number six, to which has been added and thoroughly
mixed, while both are in a melted condition, twenty per cent. (20%) by
weight of refined Trinidad asphalt, or other asphalt, equal for the
purpose, and twenty per cent. (20%) by weight of Portland cement. These
ingredients must be thoroughly mixed, and kept agitated until used.[37]
The joints will first be filled with the gravel, which shall be
perfectly dry, and heated so that when put in the joints it will be at a
temperature of about three hundred (300) degrees F. The paving cement,
heated to a temperature of about three hundred (300) degrees F., shall
be at once, while the gravel is still hot, poured from a spouted vessel
into the joints until the interstices of the gravel are entirely filled
to the surface of the pavement, repouring being resorted to to
accomplish this result whenever necessary.
All the joints in the pavement other than those named above shall then
be completely filled with Portland cement grout, in the following
manner:
The grout shall be composed of equal parts by volume of sand (Sect. 30)
and Portland cement (Sect. 29), a quick-setting cement being preferred.
The sand and cement shall be first thoroughly mixed dry and then enough
water added to make a grout of such consistency that it will flow like
thick cream, and the mixing continued until a homogeneous mass is
produced and until the grout is applied to the pavement. The grout shall
be prepared in water-tight boxes of a convenient size. Before applying
the grout the pavement shall be thoroughly dampened by sprinkling. The
grout shall be removed from the mixing box and spread over the pavement
with scoop shovels, in two courses, the first being sufficient to about
half fill the joints, and the second, which shall be applied before the
first has begun to set, shall be sufficient to entirely fill the
remaining space in the joints. As the grout is applied to the pavement
it shall be swept about with brooms until it all enters the joints.
=76. Order of Work.=—The sand bed shall not be put in place more than
fifty (50) feet ahead of the block setters. The ramming and filling of
the joints shall follow closely the block setting, but no ramming shall
be done within less than six (6) feet of the face of the block setting;
and the final joint filling shall be kept completed to within
twenty-five (25) feet of the ramming; except that all the work rammed
during any day shall have the joint filling completed before the
cessation of work on that day. The street shall not be opened to travel
until the grout has thoroughly set.
=77. Fitting Paving Around Other Structures.=—The size of blocks and the
width of courses shall, as the block laying approaches bridge stones,
curbs and other structures, or in making closures with other sections of
pavement, be so selected and adjusted that joints not over
three-quarters (¾) inch in width shall result, without breaking blocks
or splitting courses.
=78. Street Railroad Tracks.=—Where railroad tracks exist in the street
the paving blocks shall be laid against the rail in the following
manner:
The sub-grade and the pavement foundation shall extend under the rails
uninterrupted except by the ties or other structures connected with the
railroad track. For a distance of sixteen (16) inches, on each side of
the rail, measuring from the center thereof, there shall be spread on
the pavement foundation a layer of mortar not less than one and one-half
(1½) inches thick, composed of one (1) part of cement and three (3)
parts sand, complying with the requirements of Sections 29 and 30. Upon
this layer of mortar shall be set, against the rail, and on each side of
it, selected paving blocks, securely bedded in the mortar before it
shall have begun to set.[38] Alternate blocks shall be long and short so
as to break joint with the blocks of the adjoining pavement. Selected
blocks with well dressed top surfaces shall be used and their tops shall
be set as nearly as practicable at the level of the top of the rail, but
not so high that the car wheels will ride upon them. In setting the
blocks they shall be firmly bedded into the mortar by the use of paving
hammers, but they shall not be thereafter rammed. As the blocks are set,
any space between the paving blocks and the web of the rail shall be
filled with mortar of the quality described above. The placing of these
blocks shall not precede by more than ten (10) feet the block laying on
the street. Care must be taken not to disturb the bedding of these
blocks in the laying of the adjoining pavement, or otherwise. The joints
shall be filled with grout as specified in Sect. 75.
The construction along slot-rails shall be the same as described above,
except that blocks of special size or shape may be required, as the
Engineer may direct.
=79. Bridge Stone Crossings.=—Where directed by the Engineer, the old
bridge stone shall be redressed and relaid, as hereinafter specified for
new bridge stone, and shall be moved from the point where taken up to
the point where they are to be relaid, by the Contractor at his expense.
New bridge stone shall be of the same quality of granite as the paving
blocks and free from imperfections. They shall not be less than three
and one-half (3½) nor more than six (6) feet long, eighteen (18) inches
wide and of a uniform thickness not less than six (6) nor more than
eight (8) inches, but these dimensions may be varied by the Engineer
where necessary to fit the stone into special locations.
Their top shall be well dressed to a true plane surface not varying in
evenness more than one-quarter (¼) inch. The sides shall be dressed
perpendicular to the face so as to joint closely against the paving
blocks. The ends shall be cut to lines making an angle of from 60° to
45° with the longitudinal axis of the stones[39] and so dressed and to
such a bevel that when set in the curved surface of the street, the
joint between adjoining stones shall not be wider than three-eighths (⅜)
inch from top to bottom.
Bridge stones shall be set in advance of the block laying, over the
concrete street foundation, in a bed of sand or gravel in which they
shall be firmly bedded. Their upper surface shall conform truly to the
pavement datum. They shall be set accurately to the lines given by the
Engineer. Where the crosswalk requires more than one width of bridge
stone, the courses shall be laid parallel to, and at such distance from
each other as the Engineer may direct, and the space between courses
shall be filled with paving blocks laid as specified for other parts of
the street.
BRICK PAVEMENT[40]
=80. Sub-grade.=—The sub-grade for brick pavement shall be prepared in
accordance with Sect. 26, and shall be finished to a surface ... inches
below and parallel to the pavement datum.
=81. Foundation.=—The foundation for brick pavement shall be of
hydraulic concrete[41] prepared in accordance with Sections 28 to 37
inclusive. Its thickness shall be ... inches and its upper surface
shall, when completed, be parallel to and at a depth below the pavement
datum equal to the depth of the brick plus one and one-fourth (1¼)
inches. The surface of the foundation shall not vary more than one-half
(½) inch above or below that depth.
=82. Paving Brick.=—The linear dimensions of paving brick may vary
between the following limits: In length, from eight and one-half (8½) to
nine and one-half (9½) inches; in width, from two and one-fourth (2¼) to
three and one-half (3½) inches; in depth, from four (4) to four and
one-eighth (4⅛) inches; but the length shall not be less than two and
one-half (2½) nor more than three and three-fourths (3¾) times the
width.[42] The corners shall all be rounded off to a radius of not less
than one-eighth (⅛) nor more than three-sixteenths (³⁄₁₆) inch. The
brick for any one contract shall be all of the same kind and of the same
standard size, and the individual bricks shall not vary in length more
than three-sixteenths (³⁄₁₆) inch, nor in width more than one-eighth (⅛)
inch from the size adopted as standard. Raised lugs or letters are
permissible on one side of each brick but must not project more than
three-sixteenths (³⁄₁₆) inch from the general surface.[43]
The brick must be specially manufactured for paving purposes. They may
be made from shale or from suitable clay. In either case the material
must be thoroughly pulverized, mixed and tempered, and must be free from
lime nodules or other substances that may disintegrate the brick when
immersed in water. The brick shall be molded in efficient brick machines
to a truly rectangular form, free from cracks, flaws and injurious
laminations. After being dried the brick shall be properly and uniformly
burned in down-draft kilns. Shale brick shall be burned to the point of
incipient fusion or vitrification. After the burning is completed, the
brick shall be allowed to cool with sufficient slowness to insure
thorough annealing.
The completed brick shall be free from flaws, cracks, ragged corners,
and from such distortion or warping as will interfere with their utility
or good appearance in the pavement. Paving brick shall not be
salt-glazed.
=83.= The brick shall be subjected to the following tests to determine
their quality:
When broken by the blows of a hammer the brick shall be strong and
tough. The broken surface shall show a homogeneous composition
throughout the broken section, free from flaws, injurious laminations,
nodules and voids, and shall appear to be uniformly burned from surface
to center.
When subjected to the standard “Rattler” test, in accordance with the
rules adopted by the National Paving Brick Manufacturers’ Association,
the average loss in weight shall not exceed eighteen (18) per cent.[44]
and the loss in weight of any individual brick in the test shall not be
more than twenty-five (25) per cent. greater than the average loss of
the whole charge.
When subjected to the absorption test, in accordance with the rules
adopted by the National Paving Brick Manufacturers’ Association, shale
bricks shall not absorb more than two (2) per cent. nor less than
one-half (½) of one per cent. of their weight of water,[45] and clay
bricks shall not absorb more than six (6) per cent. of their weight of
water; the absorption of any individual brick shall not be more than
fifty (50) per cent. greater than the mean absorption of the whole lot
tested.[46] Brick that do not successfully pass all these tests will not
be accepted.
=84. Samples.=—Where samples of paving brick have been required and
submitted by successful bidders, and tested as described above, it will
be assumed that these samples fairly represent the quality of the brick
to be subsequently supplied for the work, and brick that do not come up
to the standard thus established will not be accepted.
=85. Delivering Brick on Street.=—Unless the sidewalks are too narrow to
permit of it, the brick shall all be delivered upon the street before
the foundation is constructed, and neatly piled upon the outer edge of
the sidewalks; occasional openings being left in the piles for the
accommodation of foot passengers. One-half the brick required shall be
thus delivered and piled upon each sidewalk. In delivering the bricks
from these piles to the bricklayers, they must be carried on pallets, or
other suitable devices must be used to prevent mutilation by rough
handling; they must not be dumped from wheelbarrows upon freshly-laid
brick pavement.
If for any reason the bricks are not delivered before the foundation is
laid, or if the sidewalks are too narrow to permit of the brick being
stored upon them, they may be delivered over the foundation, but not
until the concrete has set so hard that it will not be injured by
transportation over it.
=86. Sand Cushion.=—Directly before the brick are laid into the pavement
there shall be spread over the foundation a layer of sand one and
one-half (1½) inches in depth. The sand shall be free from vegetable or
other refuse matter, and shall not contain more than five (5) per cent.
of clay and loam. Pebbles and fragments of stone exceeding one-fourth
inch in diameter must be screened out. When spread on the street the
sand shall be sufficiently dry to permit of proper gaging by templates,
as hereinafter described. The sand shall be spread and correctly gaged
to the proper thickness and surface by the use of templates formed to
the true designed cross-sectional contour of the pavement. If the width
of the street between curbs does not exceed twenty-five (25) feet, the
template shall be made in one length sufficient to cover the full width
of the street, and its ends shall be so constructed and fitted with iron
rollers, that it will rest upon and roll along the top of the curb at
each end; if the width of the street between curbs be not more than
fifty (50) feet, the template shall be of sufficient length to reach
from the curb to the middle of the street, and constructed to move on
rollers on top of the curb at one end and upon a plank six (6) inches
wide and one and one-half (1½) inches thick laid upon the foundation
along the center line of the pavement. The template shall be worked
forward and backward along the line of the street until the surface of
the sand conforms exactly to the designed contour of the pavement, at a
depth below the pavement datum equal to the depth of the paving brick
minus one-fourth (¼) inch. The whole surface shall then be rolled with a
garden roller not less than thirty-six inches long and not less than
thirty inches in diameter, weighing not less than three hundred pounds.
When completed the surface of the sand cushion shall be smooth and
unbroken, and care must be taken not to disturb it before the bricks are
set upon it.
=87. Setting the Brick.=—Several courses of brick, aggregating a strip
having a width of not less than twelve (12) inches nor more than fifteen
(15) inches on each side of the street, beginning against the curb,
shall be first laid; the brick being set with their long dimension
parallel to the curb.[47] The pavement intervening between these gutter
courses will then be set in courses at right angles to the axis of the
street, except in street intersections, where the courses shall make an
angle of forty-five (45) degrees with the axis of the street. The brick
shall be set upon edge on the sand cushion with their top faces parallel
to the pavement datum, in straight courses, continuous across the
street, the long dimension of the brick being parallel to the courses;
they shall be set as closely together as possible, so that the joints
both between the courses and between individual bricks shall not exceed
one-eighth (⅛) inch, where the bricks are without lugs, and not more
than one-fourth inch where the brick have lugs. Broken bricks and bats
shall not be used except as closers at the ends of the course and in
fitting the pavement around manholes, etc., and nothing smaller than
half-bricks shall be used in either case, and the broken ends must be
shaped to make reasonably close joints. Filling up with bats must follow
the brick-laying closely. Brick with lugs shall be laid with the lugs
all in one direction.
=88. Inspection.=—After the bricks are laid the pavement will be
inspected by the Engineer, or his agent. He may require that the surface
shall be previously wetted by sprinklers, or by a sprinkling nozzle, in
order to detect soft or porous bricks.[48] Defective bricks indicated by
him shall be removed and replaced by acceptable brick.
=89. Rolling and Ramming.=—The surface of the pavement shall then be
rolled and rammed in the following manner:
The roller used shall be of the asphalt roller style, driven by steam
and weighing not less than three and one-half (3½) nor more than five
(5) tons. The rolling shall begin as near the curb as practicable, the
roller being operated slowly, parallel to the axis of the street, and
working outwardly until the center of the street is reached, when the
roller will proceed to the opposite side of the street and the operation
proceed as before. After this longitudinal rolling is completed the
pavement will be continuously rolled a second time, the roller operating
back and forth at an angle of forty-five degrees to the axis of the
street, and a third time, the roller operating at right angles to the
course of the second rolling. After the rolling is thus completed the
brick in the gutters not reached by the roller shall be rammed with a
street rammer weighing not less than thirty (30) pounds, a plank not
less than four (4) feet long, ten (10) to twelve (12) inches wide and
two (2) inches thick being interposed between the pavement and the
rammer and moved about so that the whole surface of the gutter shall be
thoroughly and equally rammed and its surface brought to an even
junction with the rolled portion of the work.
When the rolling and ramming is thus completed the surface of the
pavement shall conform so truly to the designed pavement datum that it
will nowhere depart more than three-sixteenths (³⁄₁₆) inch from properly
formed templates and straight-edges applied to its surface.
=90. Filling the Joints.=[49]—Directly after the completion of the
rolling and ramming, the joints between the bricks shall be filled as
follows:
The joints in the longitudinal gutter courses, and the joints between
six contiguous courses running across the street, from gutter to gutter,
in each length of fifty (50) feet of the pavement, shall be filled with
bituminous cement composed of coal-tar pitch, commercially known as
Number Four, to which has been added twenty (20) per cent. of refined
Trinidad asphalt and twenty (20) per cent. of hydraulic cement, all by
weight. In preparing this bituminous cement, the pitch shall first be
melted and the asphalt, also melted, added and thoroughly incorporated
by agitation. The hydraulic cement shall then be added and the whole
agitated until a complete and uniform mixture results. The bituminous
cement thus prepared shall while sufficiently hot and liquid to flow
freely, be poured from a spouted vessel into the joints until they
appear to be nearly or quite full. After allowing time for the filling
to subside, the joints will be gone over a second time and completely
filled.
All the remaining joints in the pavement shall be filled with Portland
cement grout, as follows:
The grout will be composed of equal parts by volume of sand (Sect. 30)
and Portland cement (Sect. 29), a quick-setting cement being preferred.
The sand and cement shall be first thoroughly mixed dry and then enough
water added to make a grout of such consistency that it will flow like
thick cream, and the mixing continued until a homogeneous mass is
produced and until the grout is applied to the pavement. The grout shall
be prepared in water-tight boxes of a convenient size. Before applying
the grout the pavement shall be thoroughly dampened by sprinkling. The
grout shall be spread over the pavement with scoop shovels, in two
courses, the first being sufficient to nearly fill the joints, and the
second, which shall be applied before the first has begun to set, shall
be sufficient to entirely fill the remaining space in the joints. As
rapidly as the grout is applied it shall be swept with brooms until it
all enters the joints.[50]
=91.= Travel must be excluded from the pavement until the grout has set
firmly; in no case less than five days, and the grout must be kept moist
during this period.
WOOD-BLOCK PAVEMENT
=92. Sub-grade.=—The sub-grade for wood-block pavement shall be prepared
as specified in Section 26, and shall be finished to a surface ...
inches below the pavement datum.
=93. Foundation.=—The foundation for wood-block pavement shall be
Portland cement concrete ... inches thick, prepared as specified in
Sections 28, 29, 30, 31, 32, 33, 34, 35, 36 and 37. The upper surface of
the concrete foundation, when completed, shall be at a distance below
the pavement datum equal to the depth of the blocks to be laid, plus
one-half (½) inch, and must not vary more than one-fourth (¼) inch above
or below that depth.
MATERIALS
=94. Wood-blocks.=—The wood-blocks may be made of Long-leaved yellow
pine (Pinus palustrus), Lob-lolly pine (Pinus tæda), Short-leaved pine
(Pinus echinata), Cuba pine (Pinus heterophylla), Black gum (Nyssa
sylvatica), Red gum (Liquidambar styraciflua), Norway pine (Pinus
resinosa), or Tamarack (Larix laricina), or of other species of wood of
equal strength and toughness and of a texture permitting as satisfactory
preservative treatment as those herein named. But, as far as
practicable, only one species of wood shall be used on any one
contract.[51]
Only wood from live, sound trees shall be used. The lumber from which
the blocks are cut shall be properly manufactured, free from bark, and
with full square corners. It shall be free from decay, dottiness,
brashness, shakes, large season cracks, loose or unsound knots over
three-fourths (¾) inch in diameter, and all other imperfections which
may, in the opinion of the Engineer, be detrimental. “Fat” pine
containing so much resin that it will not take up the specified quantity
of creosote oil in treatment may be rejected. Second-growth timber, and
Southern pine showing, outside of a radius of three (3) inches from the
heart, nine (9) or less annual growth rings to the inch, will not be
accepted.
The paving blocks made from the lumber hereinbefore specified shall be
well manufactured and truly rectangular and square edged. Their depth
(parallel to the fiber) shall be ... inches,[52] their length shall not
be less than six inches nor more than three times their depth, and their
width shall be from two and one-half (2½) to three and one-half (3½)
inches, but at least one-fourth inch less than their depth.
All the blocks for any one contract shall be of the same standard depth
and width, and the individual blocks shall not vary more than one-eighth
inch from the designated depth and width.
=95. Creosote Oil.=[53]—The oil used for the preservative treatment of
the paving blocks shall be coal-tar creosote oil, commonly known as dead
oil of coal-tar, without admixture or adulteration with other oils or
tars. Oils produced or resulting from the distillation of water-gas tar,
blast-furnace tar, producer-tar, lignite-tar, petroleum-oil tar, or
wood-tar, or, containing an admixture of any of these will not be
accepted. The creosote oil shall not contain more than five per cent.
(5%) of tarry matter nor more than two per cent. (2%) of water. Its
specific gravity at a temperature of 100° F. shall be not below 1.03 nor
above 1.08. Not less than ninety-nine per cent. (99%) shall be soluble
in hot benzol. It shall not contain more than eight per cent. (8%) of
tar acids. When two hundred (200) grams are subjected to distillation at
gradually increasing temperatures, not more than five per cent. (5%) of
distillate shall distil over up to a temperature of four hundred degrees
F. (400° F.), nor more than thirty-five per cent. (35%) shall distil
over up to a temperature of four hundred and fifty-five degrees F. (455°
F.), and not more than eighty per cent. (80%) shall distil over up to a
temperature of six hundred degrees F. (600° F.). After complete
distillation there shall not remain more than two per cent. of coke. The
residue remaining, upon sulphonating a portion of the total distillate,
shall not exceed one per cent. (1%). The above tests shall be made in
accordance with the methods prescribed in the “Report of the Committee
on Preservative Treatment of Poles and Cross-arms” of the National
Electric Light Association, 1911.
=96. Preservative Treatment.=—The paving blocks shall, after they are
cut to the proper dimensions, be subjected to preservative treatment
with the creosote oil specified in Section 95.
The contractor may employ any of the standard methods in common use for
impregnating the blocks, provided that uniform results are attained,
complying with the following requirements:
The wood shall not be heated during any part of the process to a
temperature exceeding two hundred and sixty degrees Fahrenheit (260°
F.).
All parts of every block shall be reached and penetrated by the oil. The
quantity of oil found in the blocks after treatment shall average not
less than ... pounds per cubic foot of wood.
The oil in the treating tanks during the process of impregnation shall
not become diluted with water to the extent of more than five per cent.
(5%) and if the percentage of water in the oil during the process of
treatment shall exceed two per cent. (2%) the quantity of the oil to be
injected in the wood as stipulated hereinbefore shall be increased in a
like ratio; for example, if the oil in the treating tanks shall be found
to contain four per cent. (4%) of water the quantity required to be
found in the blocks after treatment shall be four per cent. (4%) greater
than herein specified.
The quantity of oil injected shall be determined primarily by tank
measurements, but shall be verified by actual determination of the
quantity of oil in the treated blocks by the following method:
representative treated sample blocks shall be selected and an auger hole
one inch in diameter bored entirely through the block parallel to the
fiber, the borings all collected, thoroughly mixed, and the quantity and
ratio of oil to wood in the borings determined by extracting the oil
completely with carbon di-sulphide. The center of the auger hole shall
be located midway between the sides of the block and at a distance from
the end of the block equal to one-third (⅓) of the length of the block.
At the time of treatment the blocks shall not be green or saturated with
water, but they shall, preferably, not be thoroughly seasoned. After
treatment, and until used, the blocks shall, during dry weather, be
frequently well drenched with water to prevent excessive drying out and
cracking.
=97. Laying the Wood-Blocks.=—The concrete foundation shall be cleaned
and swept to remove all dirt and débris and shall be thoroughly dampened
immediately in advance of the setting of the blocks. Upon the concrete
foundation shall be spread a layer of mortar about one-half inch thick,
made of one part Portland cement and two parts sand with sufficient
water to make a moderately stiff paste.[54] The mortar shall be
thoroughly mixed and shall be spread in place over the concrete
foundation immediately in advance of setting the blocks to such a
thickness that when the blocks are set and properly tamped their tops
shall conform accurately to the pavement datum.
Upon this mortar bed the blocks shall be set with their fiber vertical,
in straight, parallel courses at right angles to the axis of the street,
except at street intersections where they shall be set at an angle of
forty-five degrees with the axis of the street. The blocks shall be set
as close together as practicable. Blocks in adjoining courses shall
break joint at least three inches. Blocks of such lengths shall be
selected as to make as little splitting as practicable in filling out
ends of courses. Where splitting is necessary, no fractional block shall
be used whose length is not at least equal to its width.
After the blocks are thus set the whole surface of the pavement shall be
rammed with a rammer weighing not less than twenty pounds, a plank ten
(10) inches wide, two (2) inches thick and four feet long being
interposed between the rammer and the pavement and moved about as the
ramming progresses until the blocks are forced into a firm seat in the
mortar bed and their tops brought accurately to the pavement datum. The
ramming shall be completed before the mortar under them has begun to
set, but no ramming shall be done, during the progress of the work,
nearer than three feet to the edge of the block setting, except where
the block setting may be suspended, as at the end of the day’s work,
when all the blocks then set shall be rammed.
The top surface of the pavement when completed shall conform so truly to
the pavement datum that correctly formed templates twelve (12) feet long
applied to the surface shall show at no place a departure of more than
three-sixteenths (³⁄₁₆) inch therefrom.
=98. Filling the Joints.=—After the block setting is completed,
perfectly dry, fine sand shall be spread over the pavement surface and
swept about until every joint into which the sand will penetrate shall
be completely filled. The remaining sand shall be left upon the pavement
for such time as the Engineer may direct, when it shall be removed by
the Contractor.[55]
=99. Inspection.=—The lumber for paving blocks will be inspected before
it is cut into blocks. The blocks will also be inspected upon delivery
to the street and as they are laid. Blocks that have, in treatment or
subsequent handling, developed open season cracks or wind shakes or
other imperfections that may prevent their durability or usefulness in
the pavement shall be rejected and removed from the street.
=100. Chamfered Blocks.=—Where wood-block pavement is laid on streets or
parts of streets having a gradient of more than 3%, the blocks shall not
be less than four (4) inches long, and the upper side-corners of the
blocks shall be chamfered to a depth of three-eighths (⅜) inch, the
chamfered surface to make an angle of 40 degrees with the vertical sides
of the blocks; or such other construction shall be used as will, in the
opinion of the Engineer, provide an equally good foot-hold for horses.
=101. Expansion Joints.=—Before the blocks are set there shall be placed
along and against each curb a board of trapezoidal section having a
width one inch greater than the depth of the blocks, the upper edge of
which shall have a thickness of three-eighths (⅜) inch for each ten feet
or fraction thereof of the width of the street between curbs, and a
bottom width one-fourth (¼) inch less than the top. The paving blocks at
the beginning and end of each course shall be set against this board.
After the ramming of the blocks has been completed, these boards shall
be carefully withdrawn and the space between the curbs and the paving
blocks shall be completely filled with the bituminous paving cement
described in Section 90.
=102.= The street shall not be opened to travel until such time as the
mortar under the blocks shall have become well set, nor until the
Engineer shall so direct.
BITUMINOUS CONCRETE PAVEMENT
_Note._—The phrase, Bituminous Concrete Pavement, has been applied to a
large variety of roadway surfaces differing materially from each other
in composition, construction and utility. Some of these are covered by
United States patents, the scope and limitations of which are not yet
fully determined or understood. The necessity of avoiding infringement
of these patents has to be kept in mind in framing specifications for
public use, and this consideration does not permit the presentation here
of specifications which, in the opinion of the author, would secure an
ideal pavement of this general character.
Bituminous concrete pavements constructed in substantial conformity with
these specifications have been laid on a number of city and town streets
and country roads and have proved satisfactory and fairly durable in
use. It is believed that they do not infringe any existing patents.
Our rather limited experience with pavements of this character seems to
indicate that if good materials are used and the work properly done,
they are suitable for use on city streets of light travel, and on
suburban streets and country roads carrying an amount of travel
considered heavy for these classes of roadways. Where the results have
been unsatisfactory, the cause can generally be traced to unsuitable
materials or unskillful construction, the result of ignorance or
carelessness on the one hand, or of the attempt to reduce first cost
below normal figures on the other. Many people are searching for a
pavement or roadway that will have all the good qualities of the
standard pavements but can be built about as cheaply as a common macadam
road. It is possible that something of the kind may be discovered; but
in the present state of the art it is chimerical. High quality and low
first cost do not go together in street paving. The question to be
considered is, rather, how can we invest a dollar in street or road
building so that it will, in the long run, yield the best return upon
the investment. The pavement provided for in these specifications is not
a cheap pavement, but where it is suitable for the conditions to be met,
it will be well worth its cost.
SPECIFICATIONS
=103. Sub-grade.=—The sub-grade except where old pavement is utilized
for foundation shall be prepared in accordance with Section 26 of these
general specifications.
=104. Foundation.=[56]—The foundation for bituminous concrete pavement
shall be a properly prepared old pavement, or hydraulic concrete, or
compressed broken stone, as determined by the engineer.
=105.= Old macadam pavement or road to be utilized for foundation, shall
be prepared in the following manner:
All high places or humps shall be dressed down to a plane two (2) inches
below the pavement datum, the work being done with care so as to disturb
as little as possible the macadam that is to remain. Depressions in the
old macadam shall be carefully cleaned out so as to remove all earth and
other débris and loose material, and filled with hydraulic concrete.
Newly dug or filled trenches and holes extending through the macadam
shall be excavated and cleaned out so as to admit the use of at least
four (4) inches of hydraulic concrete. The hydraulic concrete for thus
leveling up the roadway shall be composed of one (1) part of approved
Portland cement, four (4) parts of clean sand and nine (9) parts of
sound, hard crushed stone, well mixed into a wet concrete. After
placing, the concrete shall be well tamped so as to form a compact body,
conforming to a plane two (2) inches below the pavement datum. The
concrete shall be protected from travel and allowed to become well set
before the surface of bituminous concrete is applied.
=106.= Old stone block or brick pavement may be utilized for foundation,
provided that the blocks or bricks do not require to be taken up and
reset, or, if so taken up and reset, that the joints shall be completely
filled with grout composed of one (1) part Portland cement and two (2)
parts of good sand. Depressions, trenches and holes shall be treated as
specified in Section 105.
=107.= Hydraulic concrete foundation shall be constructed in compliance
with the requirements of Sections 28, 29, 30, 31, 32, 33, 34, 35, 36 and
37 of these specifications. Its depth or thickness shall be ... inches.
=108.= Broken stone foundation shall be ... inches in thickness after
completion. It shall be constructed in accordance with Section 40 of
these specifications.[57]
=109.= When completed the upper surface of the foundation shall nowhere
be more than two and one-half (2½) inches nor less than one and
three-fourths (1¾) inches below the pavement datum. No travel shall be
permitted upon the foundation until the bituminous concrete shall have
been laid.
=110. Bituminous Concrete.=—The bituminous concrete shall be composed of
crushed stone, sand, pulverized stone, and asphaltic cement.
A typical composition for the bituminous concrete, to be as closely
approximated as practicable, is as follows, the percentages being by
weight:
Pure bitumen in asphaltic cement. 8.5%
Pulverized stone passing No. 200 sieve. 8.5%
Sand passing No. 80 sieve. 10.0%
Sand passing No. 40 sieve. 23.0%
Sand and fine stone passing No. 10 sieve. 15.0%
Crushed stone passing a screen having four meshes to the linear
inch. 25.0%
Crushed stone passing a screen having two meshes to the linear
inch. 10.0%
——————
100.0%
The crushed stone shall be trap rock, granite, or hard, sound, durable
limestone. It shall be crushed to such sizes that all will pass through
a screen with two meshes to the linear inch and shall be of such
assorted sizes of fragments as will, when incorporated with the sand,
pulverized stone, and bitumen, produce a mixture substantially
conforming to the percentages of each named in the preceding paragraph.
The stone shall be freshly crushed, clean and free from clay, loam,
organic matter and refuse of every kind.
The sand shall be silicious, and free from clay, loam and refuse of all
kinds. The grains shall be of such sizes that approximately twenty-five
per cent. (25%) of the whole will pass the number eighty (80) sieve,
fifty-eight per cent. (58%) shall pass the No. 40 sieve and not more
than seventeen per cent. (17%) will pass the number 10 sieve, when used
in the order named. The pulverized stone shall conform to the
requirements of Sect. 49. Portland Cement may be substituted for not
more than twenty per cent. (20%) of the pulverized stone if the Engineer
so directs, in which case the Portland Cement actually so used shall be
paid for extra at the prevailing market price, to be agreed upon in
advance. The asphaltic cement shall comply with the requirements of
Sects. 43, 44, 45, 46, 47, and 50, except that it may have a somewhat
higher penetration, as may be determined by the Engineer.[58]
=111. Mixing.=—The materials composing the concrete shall all (except
the pulverized stone and Portland cement) be uniformly heated to a
temperature not exceeding three hundred and fifty degrees Fahrenheit
(350° F.) and not below three hundred degrees Fahrenheit (300° F.), and
while at such temperature shall be incorporated and mixed in a
mechanical mixer. The stone, sand, and pulverized stone shall be placed
in the mixer in the order named and well mixed together, after which the
asphaltic cement shall be added and the mixing continued until each
fragment is thoroughly coated with cement.
=112. Laying on the Street.=—The mixed concrete shall be taken to the
street as soon as practicable after leaving the mixer. It shall be
unloaded on the street, properly spread and truly graded with asphalt
rakes to such a depth that after compression by rolling it will have a
thickness of not less than two inches. The concrete when unloaded on the
street shall be at a temperature not below two hundred and eighty
degrees Fahrenheit (280° F.). In spreading and grading, all material
must be moved from the pile into which it was unloaded. As soon as
practicable after the concrete shall be graded, the surface shall be
thoroughly rolled with a ten-ton asphalt roller and the rolling
continued until the roller makes no further impression on the concrete
surface. When completed the surface must conform closely to the pavement
datum so that there will be no depressions or elevations exceeding
one-fourth inch above or below the pavement datum.
HYDRAULIC CONCRETE ROADWAY PAVEMENT[59]
=113.= The sub-foundation for hydraulic concrete pavement shall be
prepared as specified in Section 26.
=114.= The pavement shall be constructed in two courses called the
bottom course and the top course, as hereinafter specified.[60]
=115. Bottom Course.=—The bottom course shall be four (4) inches in
thickness[61] and shall be composed of the materials specified in Sects.
29, 30, and 31. The concrete shall be composed of one part Portland
cement, three parts sand and six parts of broken stone, and shall be
mixed and placed as specified in Sects. 35 and 36, but its top surface
when properly compacted shall be parallel to and not less than two (2)
nor more than two and one-half (2½) inches below the pavement datum.
=116. Top or Surface Course.=—The top course shall be composed of the
Portland cement specified in Sect. 29, the sand specified in Sect. 30
except that it shall be especially clean, and the grains shall be of
such size that at least seventy-five per cent. (75%) of the mass will
fail to pass a screen having thirty (30) meshes to the linear inch, and
shall be of superior quality for making concrete; and of crushed Trap
Rock,[62] or of stone equally hard, strong and durable.
The trap rock shall be crushed to such sizes that all will pass through
a screen having meshes one and one-fourth (1¼) inch square and that none
will pass through a screen having meshes one-half (½) inch square,[63]
and it shall be free from clay, refuse or other foreign substances.
=117.= The surface-course concrete shall be composed of one part
Portland cement complying with Sect. 29, one and three-quarters (1¾)
parts of sand, and, generally, three and one-half (3½) parts of crushed
stone, but the ratio of crushed stone shall be such that in the
completed concrete the volume of mortar in the compressed mass shall
exceed by about fifteen per cent. (15%) the voids in the stone.[64] The
cement and sand shall be thoroughly mixed together dry, enough clean
water then added to make a rather wet mortar and the mixing continued
until the materials are thoroughly incorporated into a homogeneous mass.
The crushed stone shall then be added, and the mixing continued until
every fragment of stone is completely covered with mortar. Sufficient
water shall be added during the mixing, if necessary, to make a “wet”
concrete, but not so wet that free water will flow from the mixed mass.
In handling and adding the stone to the mortar care must be taken to
prevent the stone segregating into masses of different sizes. The
concrete for the top course shall be made with special care and thorough
work, the intention being to secure a superior quality of concrete.[65]
=118.= The concrete thus prepared shall be placed upon the bottom course
before the latter has begun to set[66] and carefully graded so that when
properly compacted its top surface will coincide with the pavement
datum. The concrete will then be well rammed by rammers having a face of
6 by 6 inches and weighing not less than twenty (20) pounds after which
the surface will be completed by rolling with a power roller of the
asphalt type weighing not less than five (5) tons.[67] All these
operations must be completed before any of the concrete in either course
shall have begun to set. The surface shall not be plastered with neat
mortar nor shall it be trowelled.
=119.= The completed surface must coincide with the pavement datum to
the extent that a properly formed template when applied to the surface
shall show no departure from the pavement datum exceeding
three-sixteenths (³⁄₁₆) inch.
=120.= After the laying of the pavement has been completed it shall be
allowed to stand until the concrete of both courses shall be fully set,
which period shall be not less than ten (10) days, or longer, if
conditions make a longer time necessary, as the engineer may direct, of
which he shall be the sole judge. During this period the concrete shall
be kept in a moist condition throughout, by sprinkling with hose or
otherwise. No travel shall be allowed upon the street until the engineer
shall open it for public use. The concrete shall not be laid during rain
storms or when the thermometer is below forty-five (45) degrees F., and
in case there may be danger from frost the whole surface of the concrete
shall be covered by straw or hay. Manure must not be used for this
purpose.
=121. Expansion Joints.=[68]—An expansion joint along the curbing on
each side of the street shall be provided in accordance with Sect. 101.
Expansion joints shall also be provided and constructed as follows:
Wherever the width of the pavement exceeds twenty (20) feet between
curbs there shall be a expansion joint along the longitudinal center of
the street; expansion joints shall also be made, at right angles to the
street and extending continuously from curb to curb, at distances apart
not exceeding twenty (20) feet. These expansion joints in the body of
the pavement shall be made by cutting entirely through both courses of
concrete along a straight line, using a special straight-edged cutter
not more than three-sixteenths (³⁄₁₆) inch thick, when the concrete is
laid in hot weather and not more than three-eighths (⅜) inch thick if
the concrete is laid when the thermometer is below sixty (60) degrees F.
The cutting of the expansion joints shall be carefully and skillfully
done, and after each joint is cut a special T-shaped smoother, the stem
of which is one inch deep and of the same thickness as the cutter shall
be worked back and forth in the joint until the edge of the concrete
adjoining the joint shall be well and smoothly compacted. The smoother
shall be so formed as to round off the corners of the concrete to a
circular form having a radius of one-fourth (¼) inch. All these
operations shall be completed before the concrete has begun to set.
After the concrete has set and before the street is opened to travel all
expansion joints shall be poured full of bituminous cement, as specified
in Section 90.[69]
=122. Bituminous Coating.=[70]—After the concrete shall have become
fully set as determined by the engineer and before the street is opened
to travel the whole surface of the pavement shall be covered by a
finishing coat of bituminous road oil as hereinafter specified.
The road oil shall be prepared from native asphalt or from a crude oil
having an asphaltic base. Not less than 95 per cent. of the oil shall be
soluble in cold carbon di-sulphide, and it shall contain not less than
thirty (30) per cent. of solid asphalt, nor more than ten per cent. of
fixed carbon. It shall be of such consistency as to flow freely at a
temperature of seventy-five degrees (75°) F. The oil shall not be
applied except when the road surface is perfectly dry and when the
temperature of the air is not below 60° F.
The oil shall be evenly distributed over the whole surface of the street
at the rate of one-half (½) gallon of oil per square yard of surface,
and well worked over the surface with squeegees or other suitable
devices.
Not less than twenty-four hours after the application of the oil the
surface of the pavement shall be evenly covered to a depth of one-fourth
inch with clean, dry stone screenings or coarse sand, after which the
street may be opened to travel.
GENERAL SPECIFICATIONS FOR EXPERIMENTAL OR UNTRIED PAVEMENTS[71]
=123.= Contractors or promoters submitting proposals for the
construction of new, experimental, or special street pavements, the
merits of which have not been established by experience in the city
of ..., must submit with their proposal a full and complete set of
specifications for the construction of the pavement. If contract shall
be awarded under said proposal, said specifications will be made a part
of the contract entered into. The Engineer will enforce compliance with
these specifications, as the construction work proceeds, without
assuming or incurring any responsibility for the character, quality,
serviceability or durability of the resulting pavement. But the
Contractor shall be subject to and shall comply with the requirements
and stipulations of Sects. 1 to 25, inclusive, of these specifications.
=124. Special Guaranty.=[72]—Inasmuch as the pavement to be constructed
under the special specifications submitted by the Contractor is more or
less of an experimental character, having not been heretofore used in
the city of ... to an extent sufficient to establish its value, the
Contractor shall be held wholly responsible for the utility,
serviceability and durability of the pavement so constructed; and he
shall enter into a guaranty to the effect as follows:
That the pavement will fulfill all the usual and legitimate requirements
of a satisfactory roadway pavement upon the street upon which it is to
be laid.
That the pavement will successfully serve and endure the travel to which
the street may be subjected for a period of ... years next following the
date of the certificate of its completion and acceptance, and shall be
in good condition at the end of that period, ordinary and reasonable
wear and tear, and accidental or other injuries not due to defects in
the pavement itself, excepted.
That the Contractor will, at his own cost, keep the said pavement in
satisfactory repair during said period of ... years, and will leave it
in a condition of satisfactory repair at the end of that period.
That the Engineer, or his successor or successors in office, shall be
the sole and final judge as to whether the conditions of this guaranty
shall be, or shall have been complied with.
That in case the pavement shall not, in the judgment of the Engineer,
fulfill the terms and conditions of this guaranty at any time during
said period of ... years, or upon its expiration; or in case the
Contractor shall fail to make all or any of the repairs that may in the
judgment of the Engineer be or become necessary during said period
of ... years, within a reasonable period to be determined by the
Engineer, but not to be less than twenty (20) days after notice to make
such repairs has been given him by the Engineer, he (the Engineer) may
proceed to make or to have made such repairs, or to repave the street,
in any manner that he may deem necessary or advisable, and to charge the
cost of such repairs or repavement to the Contractor, provided, that the
sum or sums so charged against the Contractor shall not, in the
aggregate, be more than the amount paid to the Contractor for the
construction of the pavement.
=125. Bond.=—The Contractor shall give bond with sureties satisfactory
to the Engineer in a sum not less than the estimated cost of the
pavement at the contract prices, the term of the bond to extend over the
entire period of ... years, for which the pavement is guaranteed.
=126.= During the said period of ... years the Contractor shall, upon
being notified by the Engineer so to do, make any repairs to the
pavement that may become necessary by reason of cutting into it for the
purpose of constructing or repairing pipes, conduits or other
underground structures, or street railroad tracks, or by reason of
accidental or unusual causes, or of any causes other than those due, in
the opinion of the Engineer, to the failure of the pavement to meet and
fulfill the terms of the guaranty stipulated in Section 124. And for
making such repairs the Contractor shall be paid the price of ... per
square yard for the repairs actually so made. Repairs so made shall be
subject to the terms of the guaranty, stipulated in Section 124, until
the expiration of the said term of ... years after the date of the
original certificate of completion and acceptance. In case the
Contractor shall neglect or fail to make such repairs within a period of
twenty (20) days after he shall have received notice to do so, the
Engineer may proceed to make or to have made such repairs, and he shall
charge to and collect from the Contractor the cost of the repairs so
made.
HYDRAULIC CONCRETE COMBINED CURB AND GUTTER[73]
=127.= Hydraulic concrete combined curb and gutter shall be constructed
in accordance with general plan No. ... attached to and made a part of
these specifications, but the rise from the gutter to the top of the
curb may be varied so as to facilitate drainage.[74]
=128. Excavation.=—All excavation required for the curb and gutter shall
be completed and trimmed to the proper lines as shown by the drawing.
The drainage trench under the curb and gutter shown on the drawing shall
have the top width and general form shown in the drawing but its depth
may be varied to secure proper drainage, as the engineer may direct,
provided that its depth below the base of the concrete shall not be less
than nine inches nor more than two feet.
=129. Broken Stone Drainage.=[75]—After the excavation shall have been
completed the trench shall be filled up to the level of the base of the
concrete with sound, durable broken stone, or coarse gravel, from which
the small fragments shall have been removed by screening over a wire
screen having openings not less than one inch square. The stone or
gravel shall be thoroughly tamped in the trench in layers not more than
six (6) inches thick by the use of rammers weighing not less than thirty
(30) pounds and having a face area not exceeding thirty-six (36) square
inches, and its completed top surface shall conform truly to the
designed base of the concrete. These drains shall be connected at
suitable intervals with sewers, drains or other outlets to keep them
free from standing water. The trench filling shall be completed at least
twenty-five feet in advance of placing the forms for the concrete.
=130. Concrete.=[76]—The concrete shall be made of one (1) part Portland
cement, one and three-fourths (1¾) parts of sand and three (3) parts of
crushed stone or clean gravel. The Portland cement shall comply in all
respects with the requirements of Section 29 of these specifications.
The sand shall be clean, sharp silicious sand made up of grains of such
size that not more than fifteen per cent. (15%) will pass a number
thirty (30) sieve. It shall not contain more than five per cent. (5%) of
clay or loam nor more than two per cent. (2%) of organic matter or other
refuse. The stone shall be sound, hard, durable, and freshly broken,
free from clay, loam, organic matter, or other impurities. Trap rock or
granite will be preferred, but limestone, if hard and sound, may be used
with the approval of the engineer. Only those fragments of the crushed
stone that pass a screen with openings three-fourths inch square and
those that are held on a screen with openings one-fourth inch square
shall be used in the concrete.
=131. Mixing and Placing Concrete.=—The concrete shall be mixed in
accordance with Section 35 of these specifications. Very thorough mixing
will be required.
The mixed concrete shall be handled so as to prevent as far as
practicable any separation or segregation of the stone and mortar. When
in place it shall be compacted by tamping and where placed against
forms, forking or other effective means must be used to bring mortar to
the surface and to secure complete contact between mortar and forms, so
as to leave a solid, homogeneous and unbroken surface when the forms are
removed. Where the concrete may not be laid against forms, all exposed
surfaces must be troweled to a true surface conforming accurately to the
lines shown by the plans, templates and straight-edges being used where
necessary.
=132. Weather.=—Concrete in combined curb and gutter shall not be laid
in freezing weather nor shall frozen materials be used in the work.
Completed work must be securely protected from frost for at least seven
days after it is laid. Any concrete curb and gutter that may become
frozen within that period shall be wholly removed and replaced with new
work.
=133. Expansion Joints.=—The combined curb and gutter shall be divided
into blocks or panels not more than twelve feet long, by clear, open
expansion joints perpendicular to the face of the curb, extending
entirely and continuously through the whole mass of the concrete. These
expansion joints shall be three-eighths inches wide and may be formed
either by cutting through the completed curb and gutter with a suitable
tool, or by the use of iron forms or partitions, but in either case the
corners at the ends of the blocks must be made solid and dense and
troweled with a suitable tool.
=134. Circular Corners.=—At the intersections of streets, circular
corners, having a radius equal, generally, to one-fifth of the width of
the roadway of the narrower street, shall be constructed of the same
dimensions and quality as on the body of the street, and the curb and
gutter will be extended along the line of the cross street back to the
front lot-lines. Properly curved circular curb and gutter shall also be
constructed at all angles exceeding five degrees in the line of the
curbing.
=135. Corner Protection.=—Galvanized steel corner protectors or
nose-pieces shall be used to protect the upper and outer corner of the
curb at all circular corners and angles in the street. This steel
protection may be of any pattern or section procurable in the market and
approved by the engineer. It shall be firmly anchored and secured into
the concrete.
=136. Finishing.=—After the forms have been removed and before the
concrete has set up too hard to be affected by the brush, the face and
top of the curb shall be lightly scrubbed by a suitable wire brush so as
to completely remove any glazed surface and to produce a surface of
uniform texture and appearance. Dry cement or neat cement mortar shall
not be used for dressing up exposed surfaces.[77]
=137. Forms.=—The forms used may be of dressed lumber or of metal as the
contractor may prefer. But they shall have sufficient strength and
rigidity to hold the concrete firmly in place, and to preserve the
correct dimensions, alignment and levels of the curb and gutter.
=138. Protection.=—The completed curb and gutter shall be protected from
fracture, deformation or spalling until the concrete has fully set. The
concrete must be kept moist for at least five days after it has been
laid. Any part of the curb and gutter that shall have become injured
before it is accepted or the street is opened for travel shall be taken
up and replaced by the contractor.
=139. Payment.=—Concrete combined curb and gutter will be paid for by
the linear foot in place, the measurement to be made along the upper and
outer corner of the curb. The price per linear foot named in the
contract will cover all the excavation or grading required and all the
materials and labor, including all necessary forms, for constructing the
curb and gutter complete. But the crushed stone used for drainage will
be paid for by the cubic yard measured in place, and steel corner
protection will be paid for by the linear foot in place, at the prices
named in the contract.
HYDRAULIC CONCRETE SIDEWALKS
_Note._—These specifications conform to the common practice of laying
the sidewalk in two courses.
In the author’s judgment this is neither necessary nor desirable. He
believes that it would be better and somewhat cheaper to use a single
course of concrete four inches in thickness. He suggests for this
concrete the ratios of one cement, two sand, and three and one-half
stone, the latter to be crushed to pass a screen with five-eighths inch
square openings.
Tamping will bring a sufficient quantity of mortar to the surface to
permit of satisfactory finishing. While the materials for such a single
course of four inch concrete would cost somewhat more, the saving in
cost of labor would, at usual prices of material and labor, make the
single-course construction somewhat cheaper, while the solid four inches
of richer concrete would make the walk much stronger. In fact, a single
course of such concrete three inches thick would be sufficient in a
great majority of cases. While the surface might not have the glazed
appearance common in the two-course work it would be really better for
use—a polished and slippery surface on sidewalks is not desirable.
SPECIFICATIONS[78]
=140.= The hydraulic concrete sidewalk shall be ... feet in width and
its outer edge shall be ... feet from the outer face of the street
curbing. It shall be constructed with two courses of Portland cement
concrete as hereinafter specified.
=141. Excavation and Grading.=—The ground to be occupied by the sidewalk
shall be excavated or filled to a sub-grade which after being compacted
shall be ... inches[79] below the finished surface of the sidewalk. The
sub-grade shall be neatly dressed to a plane surface sloping downward
toward the street one-fourth inch in one foot horizontal, and to such
longitudinal gradients as the engineer may prescribe. The completed
sub-grade shall project four (4) inches in excavation and eighteen (18)
inches in embankment on each side beyond the edges of the completed
sidewalk. After the grading is completed the surface shall be compacted
by rolling or ramming.
=142. Drainage Course.=—Upon the sub-grade prepared as specified in