Div_60.pdf

Lower Rio Grande Flood Control Project Rehabilitation of Main Floodway, From 23rd Street to FM 1015 Hidalgo County, Texas

DIVISION 60-

USIBWC Contract No.: IBM09B0005 STRUCTURES

US INTERNATIONAL BOUNDARY & WATER COMMISSION

GOVERNING TECHNICAL SPECIFICATIONS AND PROVISIONS

DIVISION 60 – STRUCTURES

DIVISION 60-

USIBWC Contract No.: IBM09B0005 STRUCTURES

This Page Intentionally Blank

EXCAVATION AND BACKFILL FOR STRUCTURES

USIBWC Contract No.: IBM09B0005 Page 60.10.00 - 1

SPECIFICATION 60 10 00

This specification includes requirements for the excavation and backfill of structures within the Work area, and includes the following:

1.0 General

2.0 Materials & Equipment

3.0 Construction Methods

4.0 Measurement and Payment

PART 1 - GENERAL

1.1 RELATED DOCUMENTS, CONTRACT CLAUSES, & SPECIFICATIONS

The following may not include all related documents, contract clauses, & technical specifications, and does not relieve the Contractor of the responsibility of performing work associated with this specification in accordance with all terms of the Contract herein.

A. Related documents: As described in paragraph 1.2 of SPECIFICATION 01 01 00.

B. Contract: Section I, 52.236-21“Specifications and Drawings for Construction”

C. Technical Specifications:

• SPECIFICATION 60 20 00, “Concrete Structures”

• SPECIFICATION 60 21 00, “Hydraulic Cement Concrete”

D. References:

• American Association of State Highway and Transportation Officials (AASHTO) Standard Specifications for Highway Bridges, 17th Edition

• Texas Department of Transportation Department Material Specification (DMS)-4600 Hydraulic Cement, March 2009

• Texas Department of Transportation Testing Standard (Tex)-120-E Soil-Cement Testing, August 1999

• 2003 Texas Manual on Uniform Traffic Control Devices

1.2 GENERAL

In general, the Contractor shall excavate for placement and construction of structures and backfill structures; and cut and restore pavement.

PART 2 – MATERIALS & EQUIPMENT

2.1 MATERIALS

USIBWC Contract No.: IBM09B0005 Page 60.10.00 - 2

The Contractor shall use materials that meet the requirements of the following:

• DMS-4600, “Hydraulic Cement.”

2.2 EQUIPMENT (No Requirements Defined for this Specification)

PART 3 – CONSTRUCTION METHODS

3.1 EXCAVATION

A. General. The Contractor shall excavate to the lines and grades shown on the plans; provide slopes, benching, sheeting, bracing, pumping, and bailing as necessary to maintain the stability and safety of excavations up to five (5) feet. Excavation protection for excavations deeper than five (5) feet will require trench protection and / or safety shoring. The Contractor shall use satisfactory excavated material as backfill or as embankment as required by the plans; dispose of material not incorporated into the final project off the right of way in accordance with federal, state, and local regulations. When excavating for installation of structures across private property or beyond the limits of the embankment, keep any topsoil removed separate, and replace it, as nearly as feasible, in its original position. Restore the area to an acceptable condition.

(1) Obstructions. The Contractor shall remove obstructions to the proposed construction, including trees and other vegetation, debris, and structures, over the width of the excavation to a depth of one (1)-foot below the bottom of excavation. If abandoned storm drains, sewers, or other drainage systems are encountered, remove as required to clear the new structure, and plug in a compliance-confirmed manner. After removing obstructions, restore the bottom of the excavation to grade by backfilling in accordance with this Item.

Dispose of surplus materials in accordance with federal, state, and local regulations.

(2) Excavation in Streets. When structures are installed in streets, highways, or other paved areas, cut pavement and base to neat lines. Restore pavement structure after completion of excavation and backfilling.

(3) Maintain and control traffic in accordance with the compliance-confirmed traffic control plan and the Texas Manual on Traffic Control Devices.

(4) Utilities. The Contractor shall conduct work with minimum disturbance of existing utilities, and coordinate work in or near utilities with the utility owners. Inform utility owners sufficiently before work begins to allow them time to identify, locate, reroute, or make other adjustments to utility lines.

(5) Avoid cutting or damaging underground utility lines that are to remain in place. If damage occurs, promptly notify the utility company. If an active sanitary sewer line is damaged during excavation, provide temporary flumes across the excavation while open, and restore the lines when backfilling has progressed to the original bedding lines of the cut sewer.

(6) De-Watering. Do not construct or place structures in the presence of water unless compliance-confirmed. Place pre-cast members, pipe, and concrete only on a dry, firm surface. Remove water by bailing, pumping, well-point installation, deep wells, USIBWC Contract No.: IBM09B0005 Page 60.10.00 - 3 underdrains, or other compliance-confirmed method.

(7) If structures are compliance-confirmed for placement in the presence of water, remove standing water in a manner that does not allow water movement through or alongside concrete being placed. Do not pump or bail while placing structural concrete or for a period of at least thirty-six (36) hours thereafter unless from a suitable sump separated from the concrete work. Pump or bail during placement of seal concrete only to the extent necessary to maintain a static head of water within the cofferdam. Do not pump or bail to de-water inside a sealed cofferdam until the seal has aged at least thirty-six (36) hours.

(8) If the bottom of an excavation cannot be de-watered to the point that the subgrade is free of mud or it is difficult to keep reinforcing steel clean, place a stabilizing material in the bottom of the excavation. Stabilizing material may be flexible base, cement-stabilized base or backfill, lean concrete, or other compliance-confirmed material. If lean concrete is used, provide concrete with at least two hundred seventy-five (275) pounds of cement per cubic yard, and place to a minimum depth of three (3) inches stabilizing material placed for the convenience of the Contractor will be at the Contractor’s expense.

B. Bridge Foundations and Retaining Walls. Do not disturb material below the bottom of footing grade. Do not backfill to compensate for excavation that has extended below grade. If excavation occurs below the proposed footing grade, fill the area with concrete at the time the footing is placed. The additional concrete placed will be at the Contractor’s expense. If requested, take cores to determine the character of the supporting materials. Provide an intact sample adequate to judge the character of the founding material. Take these cores when the excavation is close to completion. Cores should be approximately five (5) feet deeper than the proposed founding grade. If the founding stratum is rock or other hard material, remove loose material, clean, and cut to a firm surface that is level, stepped, or serrated. Clean out soft seams, and fill with concrete at the time the footing is placed. If the material at the footing grade of a retaining wall, bridge bent, or pier is a mixture of compressible and incompressible material, do not place the foundation until the Government has inspected the excavation and authorized changes have been made to provide a uniform bearing condition.

C. Cofferdams. The term “cofferdam” designates any temporary or removable structure constructed to hold surrounding earth, water, or both out of the excavation whether the structure is formed of soil, timber, steel, concrete, or a combination of these. Cofferdams may require the use of pumping wells or well points for dewatering. For sheet-pile or other types of cofferdams requiring structural members, submit details and design calculations bearing the seal of a licensed professional engineer for review before constructing the cofferdam. The Government reserves the right to reject designs. Design structural systems to comply with the AASHTO Standard Specifications for Highway Bridges or AASHTO LRFD Bridge Design Specifications. Interior dimensions of cofferdams must provide sufficient clearance for the construction, inspection, and removal of required forms and, if necessary, sufficient room to allow pumping outside the forms.

In general, extend sheet-pile cofferdams well below the bottom of the footings, and make concrete seals as well braced and watertight as practicable. For foundation seals, use Class E concrete unless otherwise specified. Place concrete foundation seals in accordance with SPECIFICATION 60 20 00, “Concrete Structures.” Seals placed for the convenience of the

USIBWC Contract No.: IBM09B0005 Page 60.10.00 - 4

Contractor will be at the Contractor’s expense. When the Government judges it to be impractical to de-water inside a cofferdam and a concrete seal is to be placed around piling driven within the cofferdam, make the excavation deep enough to allow for swelling of the material at the base of the excavation during pile-driving operations. After driving the piling, remove swelling material to the bottom of the seal grade. Where it is possible to dewater inside the cofferdam without placing a seal, remove the foundation material to exact footing grades after driving piling. Do not backfill a foundation to compensate for excavation that has been extended below grade; fill such areas below grade with concrete at the time the seals or footings are placed. Unless otherwise provided, remove cofferdams after completing the substructure without disturbing or damaging the structure.

D. Culverts and Storm Drains. When the design requires special bedding conditions for culverts or storm drains, an excavation diagram should be shown on the plans. Do not exceed these limits of excavation. Unless otherwise shown on the plans, construct pipe structures in an open cut with vertical sides extending to a point one (1)-foot above the pipe. When site conditions or the plans do not prohibit sloping the cut, the excavation may be stepped or laid back to a stable slope beginning one (1)-foot above the pipe. Maintain the stability of the excavation throughout the construction period. For pipe to be installed in fill above natural ground, construct the embankment to an elevation at least one (1)-foot above the top of the pipe, and then excavate for the pipe.

(1) Unstable Material. When unstable soil is encountered at established footing grade, remove the material to a depth of no more than two (2) feet below the grade of the structure unless the Government authorizes additional depth. Replace soil removed with stable material in uniform layers at most eight (8) inches deep (loose measurement). Each layer must have enough moisture to be compacted by rolling or tamping as required to provide a stable foundation for the structure.

(2) When it is not feasible to construct a stable foundation as outlined above, use special materials such as flexible base, cement-stabilized base, cement-stabilized backfill, or other compliance-confirmed material.

(3) Incompressible Material. If rock, part rock, or other incompressible material is encountered at established footing grade while placing prefabricated elements, remove the incompressible material to six (6) inches below the footing grade, backfill with a compliance-confirmed compressible material, and compact in accordance with “Backfill” herein.

3.2 SHAPING AND BEDDING

For precast box sections, the Contractor shall place at least two (2) inches of fine granular material on the base of the excavation before placing the box sections. For pipe installations, the Contractor shall use bedding as shown in Figure 1; use Class C bedding unless otherwise shown on the plans. The Government may require the use of a template to secure reasonably accurate shaping of the foundation material. Where cement-stabilized backfill is indicated on the plans, undercut the excavation at least four

(4) inches and backfill with stabilized material to support the pipe or box at the required grade.

USIBWC Contract No.: IBM09B0005 Page 60.10.00 - 5

3.3 BACKFILL

A. General. As soon as practical, the Contractor shall backfill the excavation after placement of the permanent structure; use backfill free from stones large enough to interfere with compaction, large or frozen lumps that will not break down readily under compaction, and wood or other extraneous material; obtain backfill material from excavation or from other sources. In areas not supporting a completed roadbed, retaining wall, or embankment, the Contractor shall place backfill in layers at most ten (10) inches deep (loose measurement). In areas supporting a portion of a roadbed, retaining wall, or embankment, the Contractor shall place backfill in uniform layers at most eight (8) inches deep (loose measurement); compact each layer to meet the density requirements of the roadbed, retaining wall, embankment material, or as shown on the plans;

bring each layer of backfill material to the moisture content needed to obtain the required density;

use mechanical tamps or rammers to compact the backfill. Rollers may be used to compact backfill if feasible. Cohesionless materials such as sand may be used for backfilling. Compact cohesionless materials using vibratory equipment, water-ponding, or a combination of both.

B. Manholes. Do not place backfill against the structure until the concrete has reached the design strength required in SPECIFICATION 60 21 00, “Hydraulic Cement Concrete.” Rock or gravel mixed with soil may be used if the percentage of fines is sufficient to fill all voids and ensure a uniform and thoroughly compacted mass of proper density. Where backfill material is being placed too close to the structure to permit compaction with blading and rolling equipment, use mechanical tamps and rammers to avoid damage to the structure. Avoid wedging action of backfill against structures. To prevent such action, step or serrate slopes bounding the excavation. Place backfill uniformly around bridge foundations. Place backfill along both sides of culverts equally and in uniform layers. The Government may require backfilling of structures excavated into hard, erosion-resistant material, and subject to erosive forces, with stone or lean concrete.

C. Pipe. After installing bedding and pipe as required, the Contractor shall bring backfill material to the proper moisture condition and place it equally along both sides of the pipe in uniform layers at most eight (8) inches deep (loose measurement); compact each lift mechanically. The Contractor shall thoroughly compact materials placed under the haunches of the pipe to prevent damage or displacement of the pipe; continue to place backfill in this manner to the top-of-pipe elevation;

place and compact backfill above the top of the pipe in accordance with “General” herein. The Government may reject backfill material containing more than twenty percent (20%) by weight of material retained on a three (3)-inch sieve; with large lumps not easily broken down; or that cannot be spread in loose layers. Material excavated by a trenching machine will generally meet the requirements of this Part as long as large stones are not present. Where pipe extends beyond the toe of slope of the embankment and the depth of cover provided by backfill to the original ground level is less than the minimum required by the specifications for the type of pipe involved, place and compact additional material until the minimum cover has been provided.

D. Cement-Stabilized Backfill. When shown on the plans, the Contractor shall backfill the excavation to the elevations shown with cement-stabilized backfill. Use cement-stabilized backfill that contains aggregate, water, and a minimum of seven percent (7%) hydraulic cement

USIBWC Contract No.: IBM09B0005 Page 60.10.00 - 6 based on the dry weight of the aggregate, in accordance with Tex-120-E; use clean sand as aggregate for cement-stabilized backfill unless otherwise shown on the plans; use only compliance-confirmed aggregate; place cement-stabilized backfill equally along the sides of structures to prevent strain on or displacement of the structure; fill voids when placing cement-stabilized backfill; use hand operated tampers if necessary to fill voids.

E. Flowable Backfill. When shown on the plans, the Contractor shall backfill the excavation with flowable backfill to the elevations shown; prevent the structure from being displaced during the placement of the flowable fill, and prevent flowable fill from entering culverts and drainage structures.

3.4 EXCAVATION / BACKFILL FOR FLOODWALL TIE-IN TO EARTHEN LEVEE

In addition to the requirements included herein, special attention is directed to the tie-in of the floodwall to the earthen levee:

• All excavation into the existing levee on the west end of this project shall be limited to excavation for the new wall structure and shoring protection.

• Back fill of the existing levee shall consist of a cement stabilized backfill. The amount of cement shall be 3 percent (3%) by weight.

• Place cement stabilized back fill equally along the sides of the structures to prevent strain on or displacement of the structure. Fill voids when placing cement stabilized backfill. Use hand operated tampers if necessary to fill voids.

PART 4 – MEASUREMENT AND PAYMENT

4.1 MEASUREMENT

Unless shown on the plans as a pay item, structural excavation quantities shown are for information purposes only. When structural excavation is specified as a pay item, structural excavation for pipe headwalls, inlets, manholes, culvert or storm drain extensions less than fifteen (15) feet long, bridge abutments, retaining walls, and side road and private entrance pipe culverts will not be measured. No allowance will be made for variance from plans quantity incurred by an alternate bid. When specified as a pay item, structural excavation will be measured by the cubic yard as computed by the average end areas method. Excavation diagrams on the plans take precedence over the provisions of this Part.

4.2 PAYMENT

The Work performed by the Contractor under this Specification shall not be paid for directly, but shall be considered subsidiary to the various Bid Items under this Contract.

- END OF SPECIFICATION -

CONCRETE STRUCTURES

USIBWC Contract No.: IBM09B0005 Page 60.20.00 - 1

SPECIFICATION 60 20 00

This specification includes requirements for the construction of concrete structures within the Work area, and includes the following:

1.0 General

2.0 Materials & Equipment

The following may not include all related documents, contract clauses, & technical specifications, and does not relieve the Contractor of the responsibility of performing work associated with this specification

C. Technical Specifications:

• SPECIFICATION 60 40 00, “Reinforcing Steel”

• Portland Cement Association’s Design and Control of Concrete Mixtures

• DMS-4640 Chemical Admixtures for Concrete, March 2008

• DMS-4650 Hydraulic Cement Concrete Curing Materials and Evaporation Retardants, May 2006

• DMS-6100 Epoxies and Adhesives, October 2007

• DMS-6160 Water Stops, Nylon Reinforced Neoprene Sheet, and Elastomeric Pads, January 2005

• DMS-6310 Joint Sealants and Fillers, April 2009

• Tex-426-A Estimating Concrete Strength by the Maturity Method, August 2002

• Tex-440-A Initial Time of Set of Fresh Concrete, July 2008

1.2 GENERAL

In general, the Contractor shall furnish all materials, equipment and incidentals, and construct concrete structures.

USIBWC Contract No.: IBM09B0005 Page 60.20.00 - 2

PART 2 – EQUIPMENT & MATERIALS

A. Concrete. The Contractor shall provide concrete conforming to SPECIFICATION 60 21 00, “Hydraulic Cement Concrete”. For each type of structure or unit, provide the class of concrete shown on the plans or in pertinent governing specifications.

B. Grout or Mortar. The Contractor shall provide grout or mortar conforming to SPECIFICATION

60 21 00, “Hydraulic Cement Concrete”.

C. Latex. The Contractor shall provide an acrylic-polymer latex admixture (acrylic resin emulsion per DMS-4640, “Chemical Admixtures for Concrete”) suitable for producing polymer-modified concrete or mortar. Do not allow latex to freeze.

D. Reinforcing Steel. The Contractor shall provide reinforcing steel conforming to

SPECIFICATION 60 40 00, “Reinforcing Steel”.

E. Expansion Joint Material. The Contractor shall provide materials that conform to the requirements of DMS-6310, “Joint Sealants and Fillers”:

(1) Provide pre-formed fiber expansion joint material that conforms to the dimensions shown on the plans. Provide preformed bituminous fiber material unless otherwise specified.

(2) Provide a Class 4, 5, or 7 low-modulus silicone sealant.

(3) Provide asphalt board that conforms to dimensions shown on the plans.

(4) Provide re-bonded neoprene filler that conforms to the dimensions shown on the plans.

F. Waterstop. The Contractor shall provide rubber or polyvinyl chloride (PVC) waterstops that conform to DMS-6160, “Waterstops, Nylon Reinforced Neoprene Sheet, and Elastomeric Pads,” unless otherwise shown on the plans.

G. Evaporation Retardants. The Contractor shall provide evaporation retardants that conform to the requirements of DMS-4650, “Hydraulic Cement Concrete Curing Materials and Evaporation Retardants.”

H. Curing Materials. The Contractor shall provide membrane curing compounds that conform to the requirements of DMS-4650, “Hydraulic Cement Concrete Curing Materials and Evaporation Retardants.”

(1) Provide cotton mats that consist of a filling material of cotton “bat” or “bats” (at least twelve (12) ounces per square yard) completely covered with un-sized cloth (at least six (6) ounces per square yard) stitched longitudinally with continuous parallel rows of stitching spaced at less than four (4) inches, or tuft both longitudinally and transversely at intervals

USIBWC Contract No.: IBM09B0005 Page 60.20.00 - 3 less than three (3) inches. Provide cotton mats that are free from tears and in good general condition. Provide a flap at least six (6) inches wide consisting of two (2) thicknesses of the covering and extending along one side of the mat.

(2) Provide polyethylene sheeting that is at least four (4) mils thick and free from visible defects. Provide only clear or opaque white sheeting when the ambient temperature during curing exceeds sixty degrees Fahrenheit (60°F) or when applicable to control temperature during mass pours.

(3) Provide burlap-polyethylene mats made from burlap impregnated on one side with a film of opaque white pigmented polyethylene, free from visible defects. Provide laminated mats that have at least one (1) layer of an impervious material such as polyethylene, vinyl plastic, or other acceptable material (either as a solid sheet or impregnated into another fabric) and are free of visible defects.

I. Epoxy. Unless otherwise specified, provide epoxy materials that conform to DMS-6100, “Epoxy and Adhesives”.

2.2 EQUIPMENT

A. Fogging Equipment. The Contractor shall use fogging equipment that can apply water in a fine mist, not a spray; produce the fog using equipment that pumps water or water and air under high pressure through a suitable atomizing nozzle; use hand-held mechanical equipment portable enough to use in the direction of any prevailing wind and adaptable for intermittent use to prevent excessive wetting of the concrete.

B. Transporting and Placing Equipment. The Contractor shall use appropriate transporting and placing equipment such as buckets, chutes, buggies, belt conveyors, pumps, or other equipment as necessary. Do not transport or convey concrete through equipment made of aluminum; use carts with pneumatic tires for carting or wheeling concrete over newly placed slabs; use tremies to control the fall of concrete or for underwater placement; use tremies that are watertight and of large enough diameter to allow the placement of the concrete but less than fourteen (14) inches in diameter. For underwater placements, the Contractor shall construct the tremie so that the bottom can be sealed and opened once the tremie has been fully charged with concrete; use pumps with lines at least five (5) inches inside diameter where Grade 2 or smaller coarse aggregate is used, and at least eight (8) inches inside diameter for Grade 1 coarse aggregate.

C. Vibrators. The Contractor shall use immersion-type vibrators for consolidation of concrete;

provide at least one (1) standby vibrator for emergency use.

D. Screeds and Work Bridges for Bridge Slabs. Not required under this Contract.

E. Temperature Recording Equipment. For mass concrete operations or as otherwise specified, the Contractor shall use strip chart temperature recording devices, recording maturity meters in accordance with Tex-426-A, or other compliance-confirmed devices that are accurate to within plus or minus two degrees Fahrenheit (±2°F) within the range of thirty-two to two hundred twelve

USIBWC Contract No.: IBM09B0005 Page 60.20.00 - 4 degrees Fahrenheit (32°F ~ 212°F).

F. Artificial Heating Equipment. The Contractor shall use artificial heating equipment as necessary for maintaining the concrete temperatures as specified in “Placing Concrete in Cold Weather” herein.

G. Sawing Equipment. The Contractor shall use sawing equipment capable of cutting grooves in completed bridge slabs and top slabs of direct-traffic culverts; provide grooves that are one-eighth (1/8) to three-sixteenth (3/16)-inch deep and nominally one-eighth (1/8)-inch wide. Groove spacing may range from five-eighths (5/8) to one (1) inch. The Contractor shall use sawing equipment capable of cutting grooves in hardened concrete to within eighteen (18) inches of the barrier rail or curb.

H. Spraying Equipment. The Contractor shall use mechanically powered pressure sprayers, either air or airless, with appropriate atomizing nozzles for the application of membrane curing.

Mechanically driven spraying equipment, adaptable to the rail system used by the screeds, may be used for applying membrane curing to bridge slabs. If compliance-confirmed, the Contractor shall use hand-pressurized spray equipment equipped with two (2) or three (3) fan-spray nozzles;

ensure that the spray from each nozzle overlaps the spray from adjacent nozzles by approximately fifty percent (50%).

I. Concrete Testing Equipment. The Contractor shall provide testing equipment for use by the COR in accordance with “Testing Equipment.”

Before starting work, the Contractor shall obtain compliance-confirmation for proposed construction methods. Compliance-confirmation of construction methods and equipment does not relieve the Contractor’s responsibility for safety or correctness of methods, adequacy of equipment, or completion of work in full accordance with the Contract. Unless otherwise shown on the plans, it is the Contractor’s option to perform testing on structural concrete (structural classes of concrete are identified in Table 5 of “Classification and Mix Design”) to determine the in-situ strength to address the schedule restrictions in “Schedule Restrictions.” The Government may require the Contractor to perform this testing for concrete placed in cold weather. For Contractor-performed testing, make enough test specimens to ensure that strength requirements are met for the operations listed under this Specification. Make at least one (1) set of test specimens for each element cast each day. Cure these specimens under the same conditions as the portion of the structure involved for all stages of construction. Ensure safe handling, curing, and storage of all test specimens. Provide testing personnel, and sample and test the hardened concrete in accordance with “Sampling and Testing of Concrete.” The maturity method, Tex-426-A, may be used for in-situ strength determination for schedule restrictions if compliance-confirmed. Coring will not be allowed for in-situ strength determination for schedule restrictions. Provide the Government the opportunity to witness all testing operations. Report all test results to the Government. If the Contractor requests not to perform schedule restriction testing, with Government compliance-confirmation, the COR’s 7-day lab-cured tests, performed in accordance with “Adequacy and Acceptance of Concrete,” may be used for schedule restriction determinations. The Government may require additional time for strength gain to

USIBWC Contract No.: IBM09B0005 Page 60.20.00 - 5 account for field curing conditions such as cold weather.

3.1 SCHEDULE RESTRICTIONS

Unless otherwise shown on the plans, the Contractor shall construct and open completed structures to traffic with the following limitations:

A. Setting Forms. Attain at least two thousand, five hundred (2,500) pounds per square inch compressive strength before erecting forms on concrete footings supported by piling or drilled shafts, or on individual drilled shafts. Erect forms on spread footings and culvert footings after the footing concrete has aged at least two (2) curing days as defined in “Curing Concrete” herein.

Place concrete only after the forms and reinforcing steel have been inspected by the COR.

B. Support tie beam or cap forms by falsework on previously placed tie beams only if the tie beam concrete has attained a compressive strength of two thousand, five hundred (2,500) pounds per square inch and the member is properly supported to eliminate stresses not provided for in the design. Maintain curing as required until completion of the curing period.

C. Place superstructure forms or falsework on the substructure only if the substructure concrete has attained a compressive strength of three thousand (3,000) pounds per square inch.

D. Removal of Forms and Falsework. Keep in place weight-supporting forms and falsework for bridge components and culvert slabs until the concrete has attained a compressive strength of two thousand, five hundred (2,500) pounds per square inch in accordance with “Removal of Forms and Falsework.” Keep all forms for mass placements defined in “Mass Placements,” in place for four (4) days following concrete placement.

E. Placement of Superstructure Members. Do not place superstructure members before the substructure concrete has attained a compressive strength of three thousand (3,000) pounds per square inch.

F. Longitudinal Screeding of Bridge Slabs. Place a longitudinal screed directly on previously placed concrete slabs to check and grade an adjacent slab only after the previously placed slab has aged at least twenty-four (24) hours. Place and screed the concrete after the previously placed slabs have aged at least forty-eight (48) hours. Maintain curing of the previously placed slabs during placement.

G. Staged Placement of Bridge Slabs on Continuous Steel Units. When staged placement of a slab is required, ensure that the previously placed concrete attains a compressive strength of three thousand (3,000) pounds per square inch before placing the next stage placement. Multiple stages may be placed in a single day if compliance-confirmed.

H. Storage of Materials on the Structure. Obtain compliance-confirmation to store materials on completed portions of a structure once a compressive strength of three thousand (3,000) pounds per square inch has been attained. Maintain proper curing if materials will be stored on structures before completion of curing.

USIBWC Contract No.: IBM09B0005 Page 60.20.00 - 6

I. Placement of Equipment and Machinery. Do not place erection equipment or machinery on the structure until the concrete has attained the design strength specified in “Classification and Mix Design,” unless otherwise compliance-confirmed.

J. Carting of Concrete. Once the concrete has attained a compressive strength of three thousand

(3,000) pounds per square inch, it may be carted, wheeled, or pumped over completed slabs.

Maintain curing during these operations.

K. Backfilling. Backfill in accordance with “Backfill” herein.

3.2 PLANS FOR FALSEWORK AND FORMS

The Contractor shall submit two (2) copies of plans for falsework and forms for piers, superstructure spans over twenty (20) feet long, bracing systems for girders when the overhang exceeds three and a half (3.5) feet and bridge widening details; submit similar plans for other units of the structure; show all essential details of proposed forms, falsework, and bracing; have a licensed professional engineer design, seal, and sign these plans. Government compliance-confirmation is not required, but the Government reserves the right to request modifications to the plans. The Contractor is responsible for the adequacy of these plans.

3.3 FALSEWORK

The Contractor shall design and construct falsework to carry the maximum anticipated loads safely, including wind loads, and to provide the necessary rigidity; submit details in accordance with “Plans for Falsework and Forms.” The Contractor shall design job-fabricated falsework assuming a weight of one hundred fifty (150) pounds per cubic feet for concrete, and include a liveload allowance of fifty (50) pounds per square feet of horizontal surface of the form. Do not exceed one hundred twenty-five percent (125%) of the allowable stresses used for the design of structures. For commercially produced structural units used in falsework, do not exceed the manufacturer’s maximum allowable working loads for moment and shear or end reaction. Include a liveload allowance of thirty-five (35) pounds per square feet of horizontal form surface in determining the maximum allowable working load for commercially produced structural units. The Contractor shall provide timber that is sound, in good condition, and free from defects that would impair its strength; provide timber that meets or exceeds the species, size, and grade requirements in the submitted falsework plans; provide wedges made of hardwood or metal in pairs to adjust falsework to desired elevations to ensure even bearing. Do not use wedges to compensate for incorrectly cut bearing surfaces; use sills or grillages that are large enough to support the superimposed load without settlement. Take precautions to prevent settling of the supporting material unless the sills or grillages are founded on solid rock, shale, or other hard materials. Remove falsework when it is no longer required or as indicated on the submitted falsework plan. Pull or cut off foundations for falsework at least two (2) feet below finished ground level.

3.4 FORMS

The Contractor shall submit formwork plans in accordance with “Plans for Falsework and Forms” herein.

A. General. Except where otherwise specified or permitted, the Contractor shall provide forms of either timber or metal; design forms for the pressure exerted by a liquid weighing one hundred

USIBWC Contract No.: IBM09B0005 Page 60.20.00 - 7 fifty (150) pounds per cubic feet; take the rate of concrete placement into consideration in determining the depth of the equivalent liquid; include a liveload allowance of fifty (50) pounds per square feet of horizontal surface for job-fabricated forms. Do not exceed one hundred twenty-five percent (125%) of the allowable stresses used by TxDOT for the design of structures. For commercially produced structural units used for forms, do not exceed the manufacturer’s maximum allowable working loads for moment and shear or end reaction. Include a liveload allowance of thirty-five (35) pounds per square feet of horizontal form surface in determining the maximum allowable working load for commercially produced structural units. Provide forming systems that are practically mortar-tight, rigidly braced, and strong enough to prevent bulging between supports, and maintain them to the proper line and grade during concrete placement.

Maintain forms in a manner that prevents warping and shrinkage. Do not allow offsets at form joints to exceed one sixteenth (1/16)-inch. For forms to be left in place, use only material that is inert, nonbiodegradable, and nonabsorptive. Construct all forms to permit their removal without marring or damaging the concrete. Clean all forms and footing areas of any extraneous matter before placing concrete. Provide openings in forms if needed for the removal of laitance or foreign matter. Treat the facing of all forms with bond-breaking coating of composition that will not discolor or injuriously affect the concrete surface. Take care to prevent coating of the reinforcing steel. Complete all preparatory work before requesting permission to place concrete.

If the forms show signs of bulging or sagging at any stage of the placement, cease placement and remove the portion of the concrete causing this condition immediately if necessary. Reset the forms and securely brace them against further movement before continuing the placement.

B. Timber Forms. The Contractor shall provide properly seasoned good-quality lumber that is free from imperfections that would affect its strength or impair the finished surface of the concrete;

provide timber or lumber that meets or exceeds the requirements for species and grade in the submitted formwork plans; maintain forms or form lumber that will be reused so that it stays clean and in good condition. Do not use any lumber that is split, warped, bulged, or marred or that has defects that will produce inferior work, and promptly remove such lumber from the work.

Provide form lining for all formed surfaces except:

(1) the inside of culvert barrels, inlets, manholes, and box girders;

(2) the bottom of bridge slabs between beams or girders;

(3) surfaces that are subsequently covered by backfill material or are completely enclosed; and

(4) any surface formed by a single finished board or by plywood.

The Contractor shall provide form lining of a compliance-confirmed type such as masonite or plywood. Do not provide thin membrane sheeting such as polyethylene sheets for form lining.

Use plywood at least three-quarter (3/4)-inch thick. Place the grain of the face plies on plywood forms parallel to the span between the supporting studs or joists unless otherwise indicated on the submitted form drawings. Use plywood for forming surfaces that remain exposed that meets the requirements for B-B Plyform Class I or Class II Exterior of the US Department of Commerce Voluntary Product Standard PS 1. Space studs and joists so that the facing form material remains in true alignment under the imposed loads. Space wales closely enough to hold forms securely to the designated lines, scabbed at least four (4) feet on each side of joints to provide continuity.

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Place a row of wales near the bottom of each placement. Place facing material with parallel and square joints, securely fastened to supporting studs. For surfaces exposed to view and receiving only an ordinary surface finish as defined in “Ordinary Surface Finish,” place forms with the form panels symmetrical (long dimensions set in the same direction). Make horizontal joints continuous. Make molding for chamfer strips or other uses of materials of a grade that will not split when nailed and that can be maintained to a true line without warping. Dress wood molding on all faces. Unless otherwise shown on the plans, fill forms at all sharp corners and edges with triangular chamfer strips measuring three-quarter (3/4)-inch on the sides. To hold forms in place, use metal form ties of a compliance-confirmed type or a satisfactory substitute of a type that permits ease of removal of the metal. Cut back wire ties at least one-half (1/2)-inch from the face of the concrete. Use devices to hold metal ties in place that are able to develop the strength of the tie and adjust to allow for proper alignment. Entirely remove metal and wooden spreaders that separate the forms as the concrete is being placed. Provide adequate clean-out openings for narrow walls and other locations where access to the bottom of the forms is not readily attainable.

C. Metal Forms. Requirements for timber forms regarding design, mortar-tightness, filleted corners, beveled projections, bracing, alignment, removal, reuse, and wetting also apply to metal forms except that metal forms do not require lining unless specifically noted on the plans. Use form metal thick enough to maintain the true shape without warping or bulging. Countersink all bolt and rivet heads on the facing sides. Design clamps, pins, or other connecting devices to hold the forms rigidly together and to allow removal without damage to the concrete. Use metal forms that present a smooth surface and that line up properly. Keep metal free from rust, grease, and other foreign materials.

3.5 DRAINS

The Contractor shall install and construct weep holes and roadway drains, if required, as shown on the plans.

3.6 PLACING REINFORCEMENT

The Contractor shall Place reinforcement as provided in SPECIFICATION 60 40 00, “Reinforcing Steel.” Do not weld reinforcing steel supports to reinforcing steel except where shown on the plans.

3.7 PLACING CONCRETE

The Contractor shall give the Government a minimum 24-hour advance notice before placing concrete in any unit of the structure to permit the inspection of forms, reinforcing steel placement, and other preparations. Follow the sequence of placing concrete shown on the plans or specified. Do not place concrete when impending weather conditions would impair the quality of the finished work. If conditions of wind, humidity, and temperature are such that concrete cannot be placed without the potential for shrinkage cracking, place concrete in early morning or at night or adjust the placement schedule for more favorable weather. Consult the evaporation rate nomograph in the Portland Cement Association’s Design and Control of Concrete Mixtures for shrinkage cracking potential. When mixing, placing, and finishing concrete in non-daylight hours, adequately illuminate the entire placement site as compliance-confirmed. If changes in weather conditions require protective measures after work starts, furnish adequate shelter to protect the concrete against damage from rainfall or from freezing temperatures as outlined in this Item. Continue operations during rainfall only if compliance-confirmed.

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Use protective coverings for the material stockpiles. Cover aggregate stockpiles only to the extent necessary to control the moisture conditions in the aggregates. Allow at least one (1) curing day after the concrete has achieved initial set before placing strain on projecting reinforcement to prevent damage to the concrete.

A. Placing Temperature. The Contractor shall place concrete according to the following temperature limits for the classes of concrete defined in SPECIFICATION 60 21 00, “Hydraulic Cement Concrete”.

(1) Place Class C, F, H, K, or SS concrete only when its temperature at time of placement is between fifty (50) and ninety-five degrees Fahrenheit (95°F). Increase the minimum placement temperature to sixty degrees Fahrenheit (60°F) if ground-granulated blast furnace (GGBF) slag is used in the concrete.

(2) When used in a bridge slab or in the top slab of a direct-traffic culvert, place Class CO, DC, or S concrete only when its temperature at the time of placement is between fifty and eighty-five degrees Fahrenheit (50°F ~ 85°F).

(3) Increase the minimum placement temperature to sixty degrees Fahrenheit (60°F) if GGBF slag is used in the concrete. The maximum temperature increases to ninety-five degrees Fahrenheit (95°F) if these classes are used for other applications.

(4) Place Class A, B, and D concrete only when its temperature at the time of placement is greater than fifty degrees Fahrenheit (50°F).

(5) Place mass concrete, defined by “Mass Placements” herein, only when its temperature at the time of placement is between fifty and seventy-five degrees Fahrenheit (50°F ~ 75°F).

B. Transporting Time. The Contractor shall place concrete delivered in agitating trucks within sixty

(60) minutes after batching; place concrete delivered in non-agitating equipment within forty-five

(45) minutes after batching; revise the concrete mix design as necessary for hot weather or other conditions that contribute to quick setting of the concrete; submit for compliance-confirmation a plan to demonstrate that these time limitations can be extended while ensuring the concrete can be properly placed, consolidated, and finished without the use of additional water.

C. Workability of Concrete. The Contractor shall place concrete with a slump as specified in

SPECIFICATION 60 21 00, “Hydraulic Cement Concrete”. Concrete that exceeds the maximum slump will be rejected. Water may be added to the concrete before discharging any concrete from the truck to adjust for low slump provided that the maximum mix design water–cement ratio is not exceeded. After introduction of any additional water or chemical admixtures, mix concrete in accordance with SPECIFICATION 60 21 00, “Hydraulic Cement Concrete”. Do not add water or chemical admixtures after any concrete has been discharged.

D. Transporting Concrete. Use a method and equipment capable of maintaining the rate of placement shown on the plans or required by this Item to transport concrete to the forms.

Transport concrete by buckets, chutes, buggies, belt conveyors, pumps, or other methods. Protect concrete transported by conveyors from sun and wind to prevent loss of slump and workability.

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Shade or wrap with wet burlap pipes through which concrete is pumped as necessary to prevent loss of slump and workability. Arrange and use chutes, troughs, conveyors, or pipes so that the concrete ingredients will not be separated. When necessary to prevent segregation, terminate such equipment in vertical downspouts. Extend open troughs and chutes, if necessary, down inside the forms or through holes left in the forms. Keep all transporting equipment clean and free from hardened concrete coatings. Discharge water used for cleaning clear of the concrete.

E. Preparation of Surfaces. Thoroughly wet all forms, pre-stressed concrete panels, T-beams, and concrete box beams on which concrete is to be placed before placing concrete on them. Remove any remaining puddles of excess water before placing concrete. Provide surfaces that are in a moist, saturated surface-dry condition when concrete is placed on them. Ensure that the subgrade or foundation is moist before placing concrete for bridge approach slabs or other concrete placed on grade. Lightly sprinkle the subgrade if dry.

F. Expansion Joints. Construct joints and devices to provide for expansion and contraction in accordance with plan details. Prevent bridging of concrete or mortar around expansion joint material in bearings and expansion joints. Use forms adaptable to loosening or early removal in construction of all open joints and joints to be filled with expansion joint material. To avoid expansion or contraction damage to the adjacent concrete, loosen these forms as soon as possible after final concrete set to permit free movement of the span without requiring full form removal.

When the plans show a Type A joint, provide preformed fiber joint material in the vertical joints of the roadway slab, curb, median, or sidewalk, and fill the top 1 in. with the specified joint sealing material unless noted otherwise. Install the sealer in accordance with the manufacturer’s recommendations. Use light wire or nails to anchor any preformed fiber joint material to the concrete on 1 side of the joint. Ensure that finished joints conform to the plan details with the concrete sections completely separated by the specified opening or joint material. Remove all concrete within the joint opening soon after form removal and again where necessary after surface finishing to ensure full effectiveness of the expansion joint.

G. Construction Joints. A construction joint is the joint formed by placing plastic concrete in direct contact with concrete that has attained its initial set. Monolithic placement means that the manner and sequence of concrete placing does not create a construction joint. Make construction joints of the type and at the locations shown on the plans. Do not make joints in bridge slabs not shown on the plans unless compliance-confirmed. Additional joints in other members are not permitted without compliance-confirmation. Place authorized additional joints using details equivalent to those shown on the plans for joints in similar locations. Unless otherwise required, make construction joints square and normal to the forms. Use bulkheads in the forms for all vertical joints. Thoroughly roughen the top surface of a concrete placement terminating at a horizontal construction joint as soon as practical after initial set is attained. Thoroughly clean the hardened concrete surface of all loose material, laitance, dirt, and foreign matter, and saturate it with water.

Remove all free water and moisten the surface before concrete or bonding grout is placed against

it. Draw forms tight against the existing concrete to avoid mortar loss and offsets at joints. Coat the joint surface with bonding mortar, grout, epoxy, or other material as indicated in the plans or other Items. Provide Type V epoxy per DMS-6100, “Epoxies and Adhesives,” for bonding fresh concrete to hardened concrete. Place the bonding epoxy on a clean, dry surface, and place the

USIBWC Contract No.: IBM09B0005 Page 60.20.00 - 11 fresh concrete while the epoxy is still tacky. Place bonding mortar or grout on a surface that is saturated surface-dry, and place the concrete before the bonding mortar or grout dries. Place other bonding agents in accordance with the manufacturer’s recommendations.

H. Handling and Placing. Minimize segregation of the concrete and displacement of the reinforcement when handling and placing concrete. Produce a uniform dense compact mass.