3501 Lexington Ave - Specs for Reinforced ConcreteX00-7 t
GREAT RIVER. ENERGY SPECIFICATION FOR REINFORCED CONCRETE
GRE SPECIFICATION SP-3.3
Revised November, 2002
GRE Specification for Reinforced Concrete
All concrete work called for in the plans and specifications shall be performed in
accordance with the following specifications:
1. EXCAVATION
(a) If foundations are to be installed in a station where a layer of crushed rock is
existent, then the crushed rock shall be removed from the construction area
and stockpiled taking care not to mix any earth with the rock.
(b) Foundations shall be excavated to the depths and dimensions specified on the
plans. All dirt and loose material shall be removed from the excavation prior to
the placing of concrete.
(c) The bottom of foundation excavations shall be thoroughly tamped to prevent
settlement. If over-excavation should occur, the excess depth shall be filled
with concrete or shall be backfilled with crushed rock, which shall be
compacted to a 95% Procter density.
(d) Excavations shall be free from frost and ice when foundations are poured and
the earth temperature shall be at least 40 degrees F. The surfaces of
absorptive materials against which concrete is placed shall be moistened to
avoid drawing water from the freshly placed concrete.
(e) Concrete should not be poured in any excavation containing standing water or
mud, however, it is recognized that many areas have a high water table that
must be dealt with. Where water is encountered in an excavation, one of the
following methods shall be used to assure that an adequate foundation is
obtained.
(1) In dense clay soils with stable embankments, pumping the hole dry may be
sufficient to allow placement of the concrete.
(2) In sandy soil where there is constant ingress of water it may be necessary
shore up the excavation with removable slip-forms or coat the embankment
with Bentonite (drilling mud) and continue pumping until placement of
concrete is complete.
(3) Another method is to drive well points around the foundation area and to
pump for a sufficient time to lower the water table in the immediate area.
(4) In extreme cases when the above methods are not workable, the cement
may be installed by the Tremi method. This method shall be used only with
the approval of the GRE Construction supervisor and the Engineer. The
Tremi tube shall extend to the very bottom of the excavation and shall
gradually be withdrawn as the concrete level rises. In no case shall the
concrete be dropped directly into water.
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GRE Specification for Reinforced Concrete
2. PLACING OF FORMS
(a) Forms shall conform to grade, lines and dimensions of the concrete as called
for on the plans and shall be sufficiently strong to carry the dead weight of the
concrete without undue deflection or bulging and sufficiently tight to prevent
leakage of mortar. They shall be properly braced and tied together so as to
maintain position and shape.
(b) Forms used at exposed surfaces shall be lined with plywood that is smooth and
free from loose knots or other defects. Joints in forms shall be horizontal or
vertical. At all unexposed surfaces and rough work, undressed lumber may be
used. Lumber reused in forms shall have nails withdrawn and surfaces to be in
contact with concrete thoroughly cleaned before being used again.
(c) Form spreaders and ties shall be metal so arranged that when forms are
removed no metal shall be within one (1) inch of any surface. All openings left
by rods or bolts shall be suitably closed and pointed with cement mortar. No
wire ties shall be used.
(d) The inside of forms shall be coated with nonstaining mineral oil or approved
material. When oil is used, it shall be applied before the reinforcing is placed.
(e) All inserts, anchor bolts, etc., as may be required and all recesses shall be built
into the construction. Forms shall be inspected and approved by the Engineer
before the depositing of concrete is begun. The dimensions of anchor bolts
and inserts shall be checked before pouring is begun, and shall be checked
again after pouring is complete to assure that they are still in position.
3. PLACING OF STUB ANGLES FOR STEEL TOWERS
(a) Stub angles for tower attachment shall be set carefully in the forms prepared for
them and maintained at the lines and grades shown on the drawings well within
the following maximum tolerances:
(1) Anchor elevation difference of 0.12" between adjacent legs on any face of
tower, provided the difference in elevation between any two diagonally
opposite legs shall not exceed 0.12".
(2) The dimension as measured along any face shall be ±0.125" from the plan
dimension and the diagonal shall be +0.25" from the dimension shown on
the plan.
(3) Batter shall conform to the values shown on the drawings.
(4) There shall be no twist in the stub angle.
(5) Alignment of 1.00" either way from the center line of transmission line.
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GRE Specification for Reinforced Concrete
(b) Any tower footing which does not satisfy the specified requirements for line,
grade, batter and twist shall be rejected. No payment shall be made for any
such defective work until the Contractor has completed, to the satisfaction of
the Engineer, the necessary corrective work. The Contractor shall bear the full
expense of all such work. Stub angles shall be maintained in their proper
position and care shall be exercised to avoid jarring them after concrete has
been placed around them.
4. REINFORCING STEEL
(a) Reinforcing bars conform with the latest revision of ASTM A615 Grade 60 or
ASTM A706 (weldable) Grade 60. Deformations on reinforcing bars shall
conform to the latest revision of ASTM A615. Welded wire fabric for concrete
reinforcement shall comply with the latest revision of ASTM A185. Contractor
shall provide certification of reinforcing steel to GRE and the Engineer of
Record.
(b) The reinforcing steel shall be free from rust, scale, paint, oil or coatings of any
character that will prevent its bond with the concrete. Reinforcing steel shall be
placed accurately in position shown on drawings, securely tied at all
intersections with #18 gauge black annealed wire, and shall be securely held in
place during the placing of concrete by spacers, chairs, or other suitable
support. Care shall be exercised to see that the clearance from rebars to the
surface of concrete structures is maintained in accordance with the plans. If
welding is allowed, it shall conform to latest revisions of AWS-D1.4 and ACI -
318 and only on reinforcing steel conforming to the latest revision of ASTM-
A706.
(c) When splices in reinforcing steel are required, they shall meet the requirements
of Chapter 12 of the latest revision of ACI-318 and shall be approved by GRE
and the Engineer of Record.
(d) Bends for ties and stirrups shall be made around pins having a diameter of at
least four times the bar diameter. Bends for other bars shall be made around
pins having a diameter of at least six times the bar diameter for bars under one
inch and eight times the bar diameter for bars over one inch in diameter. All
bars shall be bent cold except that bars over one and one-fourth (1-1/4) inch
diameter may be bent hot with the approval of GRE and the Engineer of
Record.
5. CEMENT SPECIFICATIONS
Portland cement per the latest revision of ASTM C150 shall be used. Unless
otherwise designated on the plans, the cement shall be Type IIA-modified cement,
air-entrained or Type II-modified cement with an approved GRE air-entraining
agent added. In special cases the Engineer of Record or the GRE Field Inspector
may specify high early strength, air-entrained, Type IIIA cement.
SP-3.3, Revised November, 2002 Page 3 of 10
GRE Specification for Reinforced Concrete
6. FINE AGGREGATE
(a) Fine aggregate shall conform to the latest revision of ASTM C33 and shall be
clean sand or clean, hard, dense, durable rock fragments, free from dirt,
organic matter or other deleterious substance.
(b) The fine aggregate shall be well graded from coarse to fine and when tested by
means of laboratory sieve shall conform to the following requirements:
Passing No.
Passing No.
Passing No.
Passing No.
Passing No.
7. COARSE AGGREGATE
3/8" sieve-- 100 percent
4 sieve--95 to 100 percent
16 sieve--50 to 85 percent
50 sieve--5 to 30 percent
100 sieve--0 to 10 percent
(a) Coarse aggregate shall conform to the latest revision of ASTM C33 and shall
be washed gravel or crushed limestone free from from dirt, organic matter or
other deleterious material.
(b) Coarse aggregate shall be well graded and be of such a size as to pass
through a one-inch screen and be retained on a 1/4 inch screen. Percentage
passing laboratory sieves having square openings shall conform to the
following requirements:
Passing No. 1 1/2" sieve--100 percent
Passing 1" sieve--90 to 100 percent
Passing 1/2" sieve--25 to 60 percent
Passing No. 4 sieve--0 to 10 percent
8. WATER
The water used in the concrete mix shall be clean and free from oil, alkalies, acids,
salts, organic matter or other substance deleterious to concrete or reinforcement.
9. DESIGN OF CONCRETE MIX
(a) Mixing. Ready-mix concrete shall be supplied from a single source approved
by GRE in accordance with the latest revision of ASTM C94. Placement of
each load of concrete shall be completed within 1 1/2 hours of the time water
was introduced into the mix at the plant. If the construction site is so distant
from the ready-mix plant that this cannot be achieved, then water shall be
placed in the mixing drum at the construction site and mixing shall be done
there. (See Par. 10.7 of ASTM C94.) Any concrete remaining in the mixer
longer than the above limits shall be wasted and not used. No water shall be
added at the site to pre-mixed concrete except as permitted by ASTM C94.
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GRE Specification for Reinforced Concrete
(b) Mix Design. Submit two copies of the mix design to GRE and the Engineer of
Record for review 14 days prior to concrete placement.
(c) Water-Cement Ratio. The maximum water-cement ratio for concrete exposed
to freezing and thawing or deicing chemicals shall be 0.45. The maximum
water-cement ratio for other situations shall be 0.5.
(d) Minimum Compressive Strength, f'c, shall be 4500 psi at 28 days. When
Type I I I or IIIA cement is used, f'c shall be 4500 psi at 7 days.
(e) Slump shall be between 2 to 4 inches.
(f) Air-Entrainment. Concrete shall have an air content of 5% ±2% as determined
by the latest revision of ASTM C173 or ASTM C231. Air-entraining agents
used in lieu of air-entraining cement shall be approved by GRE and meet the
requirements of ASTM C260 - latest revision.
(g) Admixtures. All admixtures shall be approved by GRE and the Engineer of
Record and shall conform to ASTM CF494 - latest revision. Calcium chloride or
admixtures containing calcium chloride shall not be used in the concrete unless
specifically approved by GRE and the Engineer of Record.
10. REPORTS
The Contractor shall obtain a report on each truck load of concrete delivered
stating the following information:
(a) Yardage in load.
(b) Minimum compressive strength.
(c) Percent of air-entrainment.
(d) Water/cement ratio.
(e) Admixtures.
The Contractor shall supply a copy of this report to GRE and the Engineer of
Record.
11. FIELD TESTS
(a) Slump Test. The Contractor shall periodically run a slump test in accordance
with the latest revision of ASTM C143. The slump shall be between 2 inches
and 4 inches.
(b) Test Cylinders. The Contractor shall cast one set of three test cylinders for
every five piers or 50 cubic yards of concrete or when the material or method of
placement is changed, in accordance with the latest revision of ASTM C31 and
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GRE Specification for Reinforced Concrete
ASTM C172. Test cylinders shall be stored as near to the point of casting as
possible. They shall receive the same protection from the weather conditions
as is given to the foundation(s) which they represent. Testing shall be
completed in accordance to the latest revision of ASTM C31. One cylinder
shall be tested at 7 days and one at 28 days for Type IIA or Type II cement.
One cylinder shall be tested at 3 days and one at 7 days for Type IIIA or Type
III cement.
12. PLACING OF CONCRETE
(a) Depositing Concrete. No concrete shall be placed until all form work,
installation of parts to be embedded and preparation of surfaces involved in the
placing have been approved. No concrete shall be placed in water except with
the written permission of the Engineer, and in that event, the method of
depositing the concrete shall be prescribed by the Engineer. Concrete shall not
be placed in running water and shall not be subjected to the action of running
water until after the concrete has hardened to the satisfaction of the Engineer.
All surfaces of forms and embedded materials that have become encrusted
with dried mortar or grout from concrete previously placed or with ice, mud or
other foreign material, shall be cleaned of all such refuse before the
surrounding or adjacent concrete is placed. Immediately before placing
concrete, all surfaces of foundation upon or against which the concrete is to be
placed shall be free from standing water, mud and other foreign matter. The
surfaces of concrete which has set and against which new concrete is to be
poured, shall be thoroughly cleaned to remove all foreign material and laitance
and be saturated with water immediately before placing concrete. Concrete
shall be deposited continuously and as rapidly as possible until the unit being
poured is complete. The concrete shall not be dropped more than five (5) feet
from the end of the chute to the point of deposit unless approved by the
Engineer.
(b) Vibration and Puddling. Concrete shall be consolidated to the maximum
practical density, without segregation, by vibration or puddling so that it is free
from pockets of course aggregate and closes against all surfaces and
embedded materials. Vibration of concrete in structures shall be by electric or
pneumatic-driven, immersion type vibrators operating at speeds of at least
8,000 rpm when immersed in concrete. Vibrators shall be inserted vertically at
close enough intervals so that the zones of influence overlap. The vibrators
shall be inserted to the full depth of the layer being treated. When concrete is
being placed in layers, the tip of the vibrator shall extend approximately four (4)
inches into the underlying layer. Vibrators shall not be used to move concrete
horizontally. Care shall be exercised to avoid contamination of the concrete
through careless use of vibrators or puddling tools. Puddling tools shall be of a
type acceptable to the Engineer.
SP-3.3, Revised November, 2002 Page 6 of 10
GRE Specification for Reinforced Concrete
(c) Construction Joints
(1) Construction joints, both vertical and horizontal, shall be made at locations
indicated on the plans and where breaks occur in walls necessitated by the
sequence of construction, or at such other locations as designated or
approved by the Engineer. They shall be so designed and located as least
to impair the strength and appearance of the structure. In no case shall
vertical joints be made in walls at or near corners. All corners shall be
poured monolithically.
(2) Keys shall be provided in all joints where required to provide for either sheer
or water tightness. Where joints occur at or near points of maximum sheer,
such as the base of retaining walls, the width of keys shall be one-half as
deep as they are wide.
(3) All concrete shall be deposited in forms at such a rate that the forms will be
filled at any point with a vertical rise of the concrete surface of not less than
two (2) feet per hour. Where necessary, the forms shall be bulk-headed off
and construction joints made to provide a form which will be filled at the
above specified rate. The location of these construction joints shall be
approved by the Engineer.
(4) If any concrete is allowed to stand at any elevation below the finish grade
top surface, for more than two (2) hours without fresh concrete being
applied thereon, the top surface of such concrete shall be considered to be
a construction joint, and shall be so constructed in accordance with these
specifications, and provided with keys and metal sealing strips if required for
shear or water-tightness.
(5) At all construction joints the concrete surface shall be thoroughly cleaned
and washed free of all laitance and loose materials.
(6) Wherever concrete pouring in a wall section is stopped and the wall steel is
not carried though, there shall be provided steel dowels to equal wall steel.
All dowels must be of sufficient length to provide at least forty (40)
diameters of concrete on each side of the joint.
(7) Copper dams of at least eight-inch height must be provided in all joints in
walls retaining liquids.
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GRE Specification for Reinforced Concrete
13. FINISHING
(a) Smooth, solid concrete surfaces are required throughout the work. The top
surface of the concrete anchors shall be crowned to provide drainage of water
with an additional build-up between the inside faces of the leg angles. In
general, wood float finish on the concrete is required. When directed by the
Engineer, a steel trowel finish may be required, but care shall be taken in the
steel troweling not to bring excessive fine material to the surface. Finishing of
concrete surfaces shall be performed only by skilled workmen.
(b) Transformer, breaker and regulator slabs, building stoops and other surfaces
upon which a workman may stand shall be finished with a light broom finish to
improve traction under icy conditions.
(c) All concrete in structure shall be so finished that it give a solid smooth surface,
and any exposed rock or honeycomb shall be sufficient cause for removal and
replacement of concrete if so ordered by the Engineer.
(d) If the exposed surfaces of walls, slabs, piers and other areas where forms are
used are not smooth, they shall be carefully rubbed with carborundum stone
and cement mortar after the removal of the forms, if so ordered by the
Engineer.
(e) Floor Finish. All cement floor constructed in the work shall be finished by
means of dust coat finish as follows:
(1) Rough concrete shall be brought to proper grade and screeded so as to
work the finer particles of cement and sand to the surface.
(2) A dry mixture of one (1) cement sack of sand and one (1) cement sack of
Portland cement shall be thoroughly mixed to uniform color and when the
surface water has disappeared, ninety (90) pounds of this mixture shall be
uniformly dusted over each one hundred (100) square feet of surface.
(3) The surface shall be floated and troweled twice. The first operation shall not
take place until the surface is set sufficiently to retain knee boards and shall
be done in such a way as to prevent drawing up too much fine materials.
The surface shall receive a second troweling to eliminate all irregularities
and leave the floor with a smooth hard finish, free from blemishes and other
marks. All floors shall be sloped to floor drain or pit to afford proper
drainage.
14. PROTECTION AND CURING
(a) Protection: Concrete when deposited shall have a temperature of not less than
40 degrees Fahrenheit and not more than 80 degrees Fahrenheit. In freezing
weather, suitable means shall be provided for maintaining concrete at a
temperature of at least 50 degrees Fahrenheit for five days or more after
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GRE Specification for Reinforced Concrete
placing, or until the concrete has thoroughly hardened. The methods of heating
the materials and protecting the concrete shall be approved by the Engineer.
After concrete has been deposited it shall be kept wet for a period of at least 72
hours.
(b) Curing: All exposed concrete shall be properly cured for seven days by moist
curing using wetted burlap, covering with Kraft paper or polyethylene sheets to
prevent evaporation, or by spray application of a liquid membrane-forming
compound conforming to ASTM Designation C309-58, Type 1. The membrane
shall be applied according to the manufacturers recommendations. Surface
defects shall be filled prior to application of membrane curing compound. The
application shall be made with spraying equipment capable of applying a
smooth, even-textured coat and compressed air line shall be trapped to prevent
moisture or oil from getting into the compound. All concrete surfaces on which
membrane compound has been applied shall be adequately protected for the
duration of the curing period from any cause which would disrupt the continuity
of the curing membrane. No membrane curing compound shall be used on
surfaces of construction joints or on surfaces requiring subsequent bonding.
(c) Removal of Forms: Forms shall not be disturbed until the concrete has
hardened sufficiently to support any loads that may be imposed upon the
concrete. When stripping forms, metal wedges or tools shall not be used to pry
panels loose. If wedging is necessary, it shall be done with wood wedges
lightly rapped to break adhesion.
15. TOLERANCES FOR CONCRETE CONSTRUCTION
(a) General: The intent of this paragraph is to establish tolerances that are
consistent with modern construction practice, yet governed by the effect that
permissible deviations will have upon the structural action or operational
function of the structure. Deviations from the established lines, grades and
dimensions will be permitted to the extent set forth herein: Provided, that GRE
reserves the right to diminish the tolerances set forth herein if such tolerances
impair the structural action or operational function of a structure.
Where tolerances are not stated in the specifications or drawings for any
individual structure or feature thereof, permissible deviations will be interpreted
conformably to the provisions of this paragraph. Notations on the drawings,
included in these specifications, or specific maximum or minimum tolerances in
connection with any dimension shall be considered as supplemental to the
tolerances specified herein. The Contractor shall be responsible for setting and
maintaining concrete forms sufficiently within the tolerances specified herein.
Concrete work that exceeds the tolerances limits specified herein shall be
remedied or removed and replaced at the expense of and by the Contractor.
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GRE Specification for Reinforced Concrete
(b) Tolerances for reinforced-concrete structures --
(1) Variation in the thickness of slabs
Minus ........................ 1/4 inch
Plus ....................... 1 /2 inch
(2) Footings -- Variation of dimensions in plan
Minus ........................ 1/2 inch
Plus ....................... 1 inch
(3) Misplacement of eccentricity
Two percent of the footing width
in the direction of misplacement
but not more than...... 1 inch
(c) Tolerances for placing reinforcement steel --
(1) Variation of protective covering
With cover of 2 and 1/2 inches or less ...... 1/4 inch
With cover over 2 and 1/2 inches .............. 1/2 inch
(2) Variation from indicated spacing ............... 1 inch
16. CLEANUP AND RESTORATION OF GRADE
(a) After forms have been removed, the Contractor shall backfill around the
completed foundations to restore original grade lines, or if grading work is being
done, to the proposed grade lines. The material excavated from the footing
shall be used for backfill, if suitable, otherwise material conforming to GRE
Specification GS40 (or MNDOT C1. #5 road base material) shall be furnished
for backfilling.
(b) The backfill shall be installed in lifts not to exceed 8 inches and shall be
thoroughly tamped to prevent settlement.
(c) All excess excavation material shall be removed from the site or spread out in
an area designated by the GRE Construction supervisor.
(d) If surface rock was existent at the construction site, the Contractor shall restore
it to the depth and grade lines existing. Any rock that has become mixed with
earth shall be disposed of and matching new rock installed in its place.
SP-3.3, Revised November, 2002
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