03 31 23.pdf

Charleroi Locks and Dam - Upper and Lower Guard Walls

SECTION TABLE OF CONTENTS

DIVISION 03 - CONCRETE

SECTION 03 31 23

CONCRETE: DRILLED SHAFTS

PART 1 GENERAL

1.1 SUMMARY

1.2 RELATED WORK SPECIFIED ELSEWHERE

1.3 REFERENCES

1.4 SUBMITTALS

PART 2 PRODUCTS

2.1 MATERIALS

2.1.1 Materials for Drilled Shafts

2.1.2 Pile Top Grout

2.1.3 Grout for Core Holes

2.2 CONCRETE MIXTURE PROPORTIONS

2.3 CROSSHOLE SONIC LOGGING (CSL) MATERIALS

2.3.1 CSL Access Tubes

2.3.2 CSL Equipment

PART 3 EXECUTION

3.1 EQUIPMENT

3.1.1 Transporting and Placing Equipment

3.2 PREPARATION FOR PLACING

3.3 TRANSPORT AND PLACEMENT OF CONCRETE

3.3.1 Transport of Drilled Shaft Concrete

3.4 PLACEMENT OF DRILLED SHAFT CONCRETE

3.4.1 General

3.4.2 Concrete Placement and Driving/Drilling Operations

3.4.3 Interrupted Concrete Placement

3.4.4 Time Interval Between Mixing and Placing

3.5 CONSOLIDATION AND FINISHING

3.6 CURING AND PROTECTION

3.7 TESTING OF DRILLED SHAFT CONCRETE

3.7.1 Nondestructive Testing

3.7.2 CSL Logging Procedures

3.7.3 CSL Testing Results

3.7.4 Evaluation of CSL Test Results

3.7.5 Alternative Testing Procedures

3.7.6 Coring for Defective Drilled Shafts

3.7.7 Repair of Unacceptable Concrete

3.7.8 Backfilling Core Holes

3.8 CONTRACTOR QUALITY CONTROL

-- End of Section Table of Contents --

SECTION 03 31 23 Page 1 W911WN-09-B-0004 Revised by Amendment No. 0002

SECTION 03 31 23

CONCRETE: DRILLED SHAFTS

PART 1 GENERAL

1.1 SUMMARY

This section addresses the requirements for conveying and placing all drilled shaft concrete to be placed under this contract.

1.2 RELATED WORK SPECIFIED ELSEWHERE

Section 31 63 26.00 10 DRILLED SHAFTS

Section 03 20 02 CONCRETE: STEEL BARS AND WELDED WIRE FABRIC FOR

CONCRETE

REINFORCEMENT

Section 03 30 00.40 CONCRETE: MIXTURE PROPORTIONING

1.3 REFERENCES

The publications listed below form a part of this specification to the extent referenced. The publications are referred to in the text by basic designation only.

ASTM INTERNATIONAL (ASTM)

ASTM A 53/A 53M (2007) Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-Coated, Welded and Seamless

ASTM C 109/C 109M (2008) Standard Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2-in. or (50-mm) Cube Specimens)

ASTM C 150 (2007) Standard Specification for Portland Cement

ASTM D 2113 (2006) Rock Core Drilling and Sampling of Rock for Site Investigation

NATIONAL DRILLING ASSOCIATION (NDA)

DCDMA TM (1991) DCDMA Technical Manual

THE INTERNATIONAL ASSOCIATION OF FOUNDATION DRILLING (ADSC)

ADSC-TL4 (1999) Drilled Shafts: Construction Procedures and Design Methods

SECTION 03 31 23 Page 2

1.4 SUBMITTALS

Government approval is required for submittals with a "G" designation;

submittals not having a "G" designation are for information only. When used, a designation following the "G" designation identifies the office that will review the submittal for the Government. Submit the following in accordance with Section 01 33 00 SUBMITTAL PROCEDURES:

SD-01 Preconstruction Submittals

Concreting Plan; G, ED

A plan shall be submitted to the Contracting Officer for comment and approval at least 90 days prior to the start of placement of any drilled shaft concrete, and shall be submitted as an Appendix to the Drilled Shaft Installation Plan as described in Section 31 63 26.00 10 DRILLED SHAFTS. The plan shall show and describe the equipment and methods proposed and shall include, but not be limited to, the following:

1) Preparation of foundations and construction joints.

2) Transportation and conveyance from the Points of Delivery to the point of placement.

3) Placement, including required work platforms and tube and cap assembly.

4) Procedures for interrupted concrete placements.

5) Consolidation.

6) Finishing.

7) Curing and Protection.

8) Identification of Defective Concrete (CSL Testing and

Alternative Testing)

9) Repair of Defective Concrete.

The timing and sequence of the various steps shall also be described. The plan shall be of sufficient detail to demonstrate that equipment and methods are appropriate for the specific type of concrete, and that the work conforms to the requirements of Division 03 CONCRETE. The plan shall be subject to review and comment by the Contracting Officer. Once approved, the Contractor shall follow all procedures set forth in the plan. Any revisions to the plan shall be submitted to the Contracting Officer for approval.

Cross Hole Sonic Logging (CSL Testing) Experience; G, RE

The testing organization shall have performed CSL tests on a minimum of three large diameter drilled shaft projects in the last two years. Personnel conducting the tests for the testing organization shall have a minimum of three years experience in CSL testing. Evidence that the testing organization meets these qualifications shall be provided to the Contracting Officer in writing at least 30 days prior to beginning shaft construction.

SD-07 Certificates

Access Tube Materials; G, RE

Submit certification for access tubes.

SECTION 03 31 23 Page 3

Cementitious Grout

Descriptive literature of the grout proposed for use containing certified laboratory test results showing that it meets the specified requirements shall be submitted 60 days prior to its use together with a certificate from the manufacturer stating that the grout is suitable for the application or exposure for which it is being considered. In addition, a detailed plan shall be submitted for review, showing equipment and procedures for use in mixing and placing the grout.

SD-11 Closeout Submittals

Quality Control Inspection Forms; G, RE

The Contractor's CQC Manager shall submit QC inspection forms as identified in paragraph " CONTRACTOR QUALITY CONTROL," herein.

The inspection forms shall include those made for all laboratory and field tests of drilled shaft concrete including strength, slump, slump flow and air content. Weather and temperature records, curing and cold weather protection records shall also be submitted.

Concrete Curves; G, RE

The Contractor shall submit a set of "Concrete Curves" for each drilled shaft. The format of the "Concrete Curves" shall be similar to that presented in ADSC-TL4, Appendix G, as attached at the end of Section 31 63 26.00 10 DRILLED SHAFTS.

PART 2 PRODUCTS

2.1 MATERIALS

2.1.1 Materials for Drilled Shafts

Concrete meeting the requirements specified in 03 30 00.40 CONCRETE:

MIXTURE PROPORTIONING will be furnished by the Government as specified in Sections 03 30 00.10 CONCRETE: GENERAL REQUIREMENTS and Section 03 30 00.50 CONCRETE: PRODUCTION AND TRANSPORT. Steel reinforcement shall be in accordance with Section 03 20 02 CONCRETE: STEEL BARS AND WELDED WIRE

FABRIC FOR CONCRETE REINFORCEMENT.

2.1.2 Pile Top Grout

Grout for pile top grouting shall be designed and tested in accordance with Section 03 30 00.40 CONCRETE: MIXTURE PROPORTIONING.

2.1.3 Grout for Core Holes

The grout shall be a cement grout using Type I, Type II or Type III cement in accordance with ASTM C 150. The water-cement ratio shall be proportioned as required for strength, except that it shall not be higher than 0.45 by weight. Unless otherwise specified on the drawings or elsewhere in the specifications, the grout shall have a minimum compressive strength of 4,000 psi at 7 days when tested in accordance with

ASTM C 109/C 109M.

SECTION 03 31 23 Page 4

2.2 CONCRETE MIXTURE PROPORTIONS

Concrete meeting the requirements specified in 03 30 00.40 CONCRETE:

MIXTURE PROPORTIONING will be furnished by the Government as specified in Sections 03 30 00.10 CONCRETE: GENERAL REQUIREMENTS and Section 03 30 00.50

CONCRETE: PRODUCTION AND TRANSPORT.

2.3 CROSSHOLE SONIC LOGGING (CSL) MATERIALS

2.3.1 CSL Access Tubes

ASTM A 53/A 53M, Schedule 40, steel pipe of the diameter and lengths shown. Six access tubes shall be installed within each 78-inch shaft, four access tubes shall be installed within each 54-inch shaft, and ten access tubes shall be installed in each 102-inch drilled shaft as shown on the contract drawings. The diameter of the pipe shall be nominal 1.5-inches.

The length shall be adequate to extend from the bottom of the drilled Shaft to an elevation adequate for testing access. Access tubes shall have a round, uniform internal diameter free of defects and obstructions, including at pipe joints (all pipe joints shall be threaded without any couplings), in order to permit the free unobstructed passage of the CSL source and receiver probes that are typically 1.3 inches in diameter. All joints within access tubes shall be made watertight. Access tubes shall each be fitted with a watertight shoe on the bottom and a removable cap on the top.

2.3.2 CSL Equipment

Typical CSL test equipment includes but is not limited to the following components:

a. A microprocessor based CSL system for display of individual CSL records, analog-digital conversion and recording of CSL data, analysis of receiver responses and printing of CSL logs.

b. Ultrasonic source and receiver probes for testing tubes, as appropriate.

c. An ultrasonic voltage pulsar to excite the source with a synchronized triggering system to start the recording system.

d. A depth measurement device to determine and record depths.

e. Appropriate filter/amplification and cable systems for CSL testing.

PART 3 EXECUTION

3.1 EQUIPMENT

3.1.1 Transporting and Placing Equipment

Requirements for placing equipment for drilled shaft concrete shall be in accordance with Section 03 30 00.50 CONCRETE: PRODUCTION AND TRANSPORT.

The tremie pipes and hoppers shall conform to the requirements of Section 03 30 00.50 CONCRETE: PRODUCTION AND TRANSPORT. Any concrete transferred from one conveying device to another shall be passed through a hopper which is conical in shape and shall not be dropped vertically more than three feet, except where suitable equipment is provided to prevent segregation and where specifically authorized. A stable platform shall be provided to

SECTION 03 31 23 Page 5 support the pipe during placements. All work platforms shall be capable of supporting the tremie pipe and shall be capable of adjusting the height of the pipe during the placement.

3.2 PREPARATION FOR PLACING

Before placement of drilled shaft concrete, the rebar cage and CSL tubes shall be securely fixed against movement while concrete is placed. Filling the shaft with concrete is adequate to cause the rebar cage to displace or "float", and methods shall be adequate to prevent this tendency. The methods shall also be adequate to prevent the rebar cage and CSL tubes from moving vertical and from twisting, and any movement that will cause distortion of the reinforcing assembly. Preparation of the shaft and rock socket shall be in accordance with Section 31 63 26.00 10 DRILLED SHAFTS.

3.3 TRANSPORT AND PLACEMENT OF CONCRETE

3.3.1 Transport of Drilled Shaft Concrete

Transport of concrete shall be in accordance with Section 03 30 00.50 CONCRETE: PRODUCTION AND TRANSPORT. Concrete shall be conveyed from the Points of Delivery to the drilled shaft within the time interval specified in paragraph "Time Interval Between Mixing and Placing," herein, by methods that will prevent segregation or loss of ingredients. The capacity of the transporting system shall be sufficient to supply concrete at a rate that allows the concrete to form a uniform and homogenous lift of concrete.

Placement shall be made at a rate that loss of flowability with time does not affect the continuous melding of the concrete as it is placed. The methods used for transporting concrete shall be designed to expedite delivery and to assure a continuous supply of concrete to the placement site.

3.4 PLACEMENT OF DRILLED SHAFT CONCRETE

3.4.1 General

All procedures for placement of drilled shaft concrete shall be included for approval in the Concreting Plan as specified in paragraph "SUBMITTALS".

Reinforcement cages shall be secured in place, anchors, access tubes, and other embedded items shall have been positioned. All required prerequisite work shall be accepted by the Contracting Officer prior to placing concrete. Concrete shall be placed immediately after final acceptance of the completed shaft and shall continue until all required concrete is placed. Drilled shaft concrete shall be placed in accordance with Section 03 30 00.60 CONCRETE: PLACEMENT REQUIREMENTS. The capacity of the placing system shall be sufficient to supply concrete at a rate that allows the concrete to form a uniform and homogenous lift of concrete. Placement shall be made at a rate that loss of flowability with time does not affect the continuous melding of the concrete as it is placed. All concrete placing equipment and methods shall conform to Section 03 30 00.50 CONCRETE: PRODUCTION AND TRANSPORT, and shall be subject to approval. A watertight plastic cap, reinforced with a steel plate shall be secured to the bottom of the tremie pipe to prevent contact of the concrete with water until the start of the placement. Before concrete is placed in the tremie pipe, the pipe with the steel reinforced plastic cap in place shall be lowered and put in contact with the bottom of the placement. After QC verification of a dry pipe, the pipe and hopper shall be fully charged, then the pipe shall be raised 6-inches to initiate flow of concrete.

Additional concrete shall be ready at the point of placement to allow a

SECTION 03 31 23 Page 6 continuous flow of concrete down the pipe. Concrete shall be continuously placed by methods that insure against segregation and shall completely fill the drilled shaft. Concrete placements for drilled shafts will not be permitted when, in the opinion of the Contracting Officer, weather or river conditions prevent proper placement and consolidation. When nearing completion of the tremie placement, it may be necessary to raise the tremie pipe position in the concrete column as the differential head decreases between the concrete in the tremie pipe and the concrete and water column in the drilled shaft. A sufficient head of concrete shall be maintained within the tremie pipe to sustain a positive differential head relative to the surrounding concrete and water column in the shaft. Placement shall proceed without interruption until the concrete has been brought to the required height. The tremie pipe shall not be moved horizontally during a placing operation unless removed, moved, and properly restarted. The Contractor shall continuously measure and record the level of concrete within the drilled shaft. Concrete curves shall be monitored by the Contractor's CQC staff during the placement. The tremie placement shall be continued until it reaches the required elevation. The Contractor shall monitor the amount of concrete in the tremie pipe to assure that the shaft is not over-placed or under-placed. If, for unforeseen circumstances, the concrete can not be placed in a continuous operation and a construction joint is unavoidable, follow the procedures submitted within the Concreting Plan as specified in paragraph "SUBMITTALS". The Contracting Officer shall review all proposed procedures for making construction joints.

3.4.2 Concrete Placement and Driving/Drilling Operations

Placing or advancing casing, or performing drilling in the vicinity of a drilled shaft excavation with freshly placed concrete and curing concrete shall not occur within a 14-foot clear distance from rock socket edge to rock socket edge, until the concrete has attained a minimum compressive strength of 2,000 psi. The compressive strength of the concrete is the in-place strength. Cylinder break testing alone is not adequate to assure that the in-place strength is represented. The in-place concrete compressive strength shall be verified in accordance with Section 03 30 00.60 CONCRETE: PLACEMENT REQUIREMENTS, Paragraph "Determination of In-place Concrete Strength". When the Contractor must use impact methods (i.e. chisel beams) to resolve an obstruction during placement or advancement of casing, or during cleanout of the shaft, such work shall not occur within 24 feet of the rock socket edge of the concrete shaft until the concrete has attained a minimum compressive strength of 3,000 psi. As an alternative to these prescriptive requirements, the Contractor may use a monitoring system to control the progress of the driving/drilling operations in adjacent drilled shafts. The monitoring system would be used to detect operations which create excessive vibrations in the vicinity of drilled shafts with freshly placed and curing concrete. The monitoring equipment would be furnished, installed and operated by the Contractor at no additional expense to the Government. If the Contractor elects this methods, he shall submit a Shaft Vibration Monitoring Plan to the Contracting Officer for review. The plan shall include a description of the monitoring equipment and the installation and monitoring procedure. If the plan is accepted by the Contracting Officer, the Contractor shall install monitoring equipment in accordance with the shaft vibration monitoring plan. The monitoring equipment shall be calibrated to detect a Peak Particle Velocity of 1/4 inch per second occurring anywhere along the drilled shaft. When monitoring detects that the Peak Particle Velocity exceeds 1/4 inch per second, all driving/drilling operations shall cease.

Operations shall not resume until directed by the Contracting Officer.

SECTION 03 31 23 Page 7

3.4.3 Interrupted Concrete Placement

Drilled shaft concrete shall be placed in a continuous, uninterrupted operation. If concrete placement is interrupted for any circumstances, the Contractor shall follow the formal procedure submitted for interrupted concrete placements as described in the Concreting Plan as specified in paragraph "SUBMITTALS". The Contractor's procedure for interrupted concrete placements shall include the following requirements:

a. If concrete placement is interrupted for a period of time such that the slump of the concrete already in place becomes less than 5-inches, concrete placement will not be continued and the following conditions shall be applied:

i. If 10 feet or less of the shaft has been filled, the concrete shall be pumped or augured out of the shaft (after any reinforcing is removed); the shaft shall be cleaned, and prepared; and concrete placement restarted.

ii. If more than 10 feet of the shaft has been filled, immediately remove all scum and contaminated concrete from the top of the green concrete placement, by bucket or airlift, to a minimum depth of 3-feet; allow the concrete to set; and air lift or otherwise reclean the top of the discontinued placement again just prior to restarting concrete placement.

The Contractor's plan for interrupted concrete placement shall be submitted in accordance with paragraph "Submittals".

3.4.4 Time Interval Between Mixing and Placing

Concrete within any drilled shaft shall be completely placed within 3 hours of commencing the concrete placement. The time from which the concrete is mixed (introduction of cement to the water or aggregate) to the time at which it is discharged at the point of placement shall not exceed 60 minutes unless otherwise authorized by the Contracting Officer.

3.5 CONSOLIDATION AND FINISHING

The drilled shaft concrete shall be flowable enough to consolidate by gravity without segregation or excessive bleeding. Tremie concrete will not require finishing. However, the top surface of the shaft concrete shall be prepared as a construction joint in accordance with Section 03 30 00.60 CONCRETE: PLACEMENT REQUIREMENTS, paragraph "Construction Joint Preparation".

3.6 CURING AND PROTECTION

The rate at which cement and cementitious materials hydrate is highly dependent on the temperature of the concrete while it is curing. Drilling operations and other construction sequencing events require the in-place concrete to achieve certain strength requirements. Cold ambient conditions will make it more difficult to determine the in-place strength. Drilling operations shall not occur until the concrete has gained adequate strength in accordance with paragraph Concrete Placement and Driving/Drilling Operations. Construction sequencing events shall be as stated in other sections of the Specifications.

SECTION 03 31 23 Page 8

3.7 TESTING OF DRILLED SHAFT CONCRETE

3.7.1 Nondestructive Testing

Crosshole Sonic Logging (CSL) shall be performed on all drilled shafts, and all drilled shafts shall be provided with CSL tubes. CSL testing shall be conducted after the concrete has reached a given strength that will be determined by the Contracting Officer and will be based upon the results obtained from the Demonstration Drilled Shaft CSL testing as described in Section 03 30 00.20 FIELD DEMONSTRATIONS. Cold weather may delay the rate of concrete strength gain, and may require CSL testing to be delayed. In this case, the 3 to 7 day testing window may need to be modified by the Contracting Officer. The purpose of the CSL testing is to establish the integrity of each concrete shaft and locate any voids or defective areas in the concrete. CSL tests measure the time it takes an ultrasonic pulse to travel from a signal source in one access tube to a receiver located within another access tube and shall calculate the velocity. The results shall be used to assess the integrity of the drilled shaft. In uniform, good quality concrete, the travel time between equidistant tubes will be relatively constant and correspond to a reasonable concrete pulse velocity through the depth of the shaft. In uniform, good quality concrete, the CSL test will also produce records with good signal and amplitude and energy.

Longer travel times and lower amplitude/energy signals indicate the presence of irregularities such as poor quality concrete, voids, honeycombs and soil intrusions. The signal will be completely lost by the receiver and CSL recording system for more severe defects such as voids and soil intrusions. Upon completion of CSL testing, approval of the test results, and as approved by the Contracting Officer, the access tubes shall be filled with neat cement grout to prevent intrusion by subsequent concrete placement. The CSL tests shall be performed by an approved independent testing organization with expertise in performing and interpreting CSL tests. This independent testing organization shall be approved by the Contracting Officer.

3.7.2 CSL Logging Procedures

Before the placement of concrete, CSL access tubes shall be plumbed and the length and spacing of each tube recorded, including a notation of the stickup of the tubes above the theoretical top of the drilled shaft concrete. Information on the shaft bottom and top elevations and/or length, along with construction dates shall be provided to the Contracting Officer and the approved testing organization before the CSL tests are performed.

The drilled shafts shall not be CSL tested until the concrete has reached a given strength that will be determined by the Contracting Officer and will be based upon the results obtained from the Demonstration Drilled Shaft CSL testing as described in Section 03 30 00.20 FIELD DEMONSTRATIONS.CSL tests shall be conducted between pairs of tubes encompassing the perimeter and the major diagonals. Additional logs shall be conducted at no additional cost to the Government in the event that anomalies are detected, and may include minor diagonals and offset testing.

The CSL tests shall be carried out with the source receiver and probes in the same horizontal plane unless test results indicate potential defects, in which case the questionable zone may be further evaluated with angled tests (source and receiver vertically offset in the tubes). CSL measurements shall be made at depth intervals of four inches or less, and shall be done from the bottom to top of the tubes. Probes shall be pulled

SECTION 03 31 23 Page 9 simultaneously, starting from the bottom of the tubes, over the entire depth of tremie concrete.

Any slack shall be removed from the cables prior to pulling to provide for accurate depth measurements of the CSL records. Any defects indicated by longer pulse arrival times and significantly lower amplitude/energy signals shall be reported to the Contracting Officer and further tests shall be conducted as required to evaluate the extent of such defects. Additional NDT methods which may be used to evaluate possible defects include Singlehole Sonic Logging, Gamma-Gamma Nuclear Density Logging, and/or Surface Sonic Echo and Impulse Response tests.

3.7.3 CSL Testing Results

The CSL results shall be presented to the Contracting Officer in a report form. The test results shall include CSL log in tabular form of results showing:

- Profile by elevation

- Rating

- Average velocity in that zone

Where defects are detected, the CSL log shall include:

- Percent reduction

- Velocity range of lowest and highest velocity

The test results shall include CSL graphs showing:

- Initial pulse arrival time versus depth

- Pulse energy/amplitude versus depth

A CSL log and graphs shall be presented for each tube pair tested with any defect zones indicated on the logs and discussed in the test report as appropriate. The report shall include the date concrete was placed, the date the CSL test was conducted, the strength of the concrete as read by the data loggers on the day that the CSL test was conducted, and a diagram depicting the orientation of the numbers and positioning of the CSL tubes as correlates with the test results. .

3.7.4 Evaluation of CSL Test Results

The Contracting Officer shall review the CSL test results and determine if the drilled shaft construction is acceptable. The rating of CSL test results will generally follow the criteria listed below:

NDT RESULTS INDICATIVE OF

RATING DRILLED SHAFT CONCRETE CONDITION

GOOD No signal distortion and decrease in signal velocity of 10% or less are indicative of good quality concrete.

QUESTIONABLE Minor signal distortion and a lower signal amplitude with a decrease in signal velocity

SECTION 03 31 23 Page 10

NDT RESULTS INDICATIVE OF

RATING DRILLED SHAFT CONCRETE CONDITION

between 10 percent and 20 percent. Results indicative of minor contamination or intrusion and/or questionable quality concrete.

POOR/DEFECTIVE Severe signal distortion and much lower signal amplitude with a decrease in signal velocity of 20 percent or more. Results indicative of water contamination or soil intrusion and/or poor quality concrete.

NO SIGNAL No signal was received. Highly probable that a soil intrusion or other severe defect has absorbed the signal.

WATER A measured signal velocity of nominally 1,460 to 1,520 mps. This is indicative of a water intrusion or water-gravel intrusion with few or no fines present.

Ratings other than GOOD, not meeting 90 percent of the required signal at the location in question, will be considered as unacceptable. If the Contracting Officer determines that the drilled shaft is unacceptable based on the CSL tests, the anomalous zone within the shaft shall be studied by alternative testing procedures.

The method of concrete placement and/or the concrete mixture may require revision(s) subject to discovery of defects by CSL testing.

3.7.5 Alternative Testing Procedures

Alternative testing procedures shall be used to further clarify and determine the nature of anomalies found by CSL testing. Alternative methods such as Singlehole Sonic Logging, Gamma-Gamma Nuclear Density Logging, and/or Surface Sonic Echo and Impulse Response tests or coring in accordance with the requirements hereunder are acceptable methods to allow further evaluation of the anomaly detected by CSL testing. Any of these additional procedures shall be performed at the Contractor's expense, except as specified hereunder, at no additional cost to the Government.

The Contractor shall identify the alternative testing method(s) to be used in the Concrete Plan for drilled shafts. If alternative testing and/or coring shows that the interpretation of the CSL testing is incorrect, and that the anomaly is actually sound concrete, the Contractor shall be reimbursed for the cost of the additional testing performed including delays which the Contractor may have experienced during to the alternative testing.

3.7.6 Coring for Defective Drilled Shafts

Production drilled shafts that are determined to be unacceptable by the CSL tests may be cored to determine the quality of concrete within anomalous zones. The number of cores taken from any defective shaft shall be as directed by the Contracting Officer. The core shall be taken from the top of the shaft to at least 3 feet below the irregularity or as directed by the Contracting Officer. The size of the core shall be a minimum diameter of HQ as defined in ASTM D 2113. Drilling shall be completed with rotary

SECTION 03 31 23 Page 11 wash methods. Use of drilling mud will not be permitted. The remainder of the drilled shaft concrete shall be allowed to develop sufficient strength to allow cores of competent concrete to be retrieved. The proposed location of all cores shall be reviewed by the Contracting Officer prior to taking the cores. Equipment to be furnished by the Contractor for core drilling shall include suitable diamond bit core-drilling machinery, complete with all accessories for taking continuous cores of a diameter consistent with the specified bit size to the depths specified. All proposed machinery shall be reviewed by the Contracting Officer. The core drill shall be the product of one of the standard core drill manufacturing companies designed primarily for this type of work. The Contractor shall use a ball-bearing, swivel-type, triple tube core barrel in accordance with ASTM D 2113, or manufacturers' equivalent meeting standards established by DCDMA TM. Capacity of barrels shall not exceed 10 feet of core, and they shall be equipped with diamond-set core bits and standard core lifters.

Supplies for core drilling to be furnished by the Contractor shall include all casing, drill rods, core barrels, diamond-set coring bits, piping, pumps, water, tools, core boxes, and power required for drilling. Bits shall be set with the proper size stones for drilling the concrete. Core samples shall be placed and stored in wooden core boxes similar to those specified in Section 02 32 13.11 EXPLORATORY DRILLING. The Contractor shall deliver the core boxes to the storage location specified by the Contracting Officer. The Contracting Officer reserves the right to direct coring of any shaft regardless of CSL results.

3.7.7 Repair of Unacceptable Concrete

Unacceptable zones of drilled shaft concrete shall be corrected at the Contractor's expense. All repair procedures shall be reviewed by the Contracting Officer and are subject to approval by the Contracting Officer. Corrective measures shall be addressed on an individual basis.

3.7.8 Backfilling Core Holes

Core holes and CSL access tubes shall be filled with neat cement grout once the drilled shaft has been approved by the Contracting Officer. Core holes shall be flushed clean with water and then grouted. The grout shall be pumped into the hole through drill rods or plastic hose set to within 6-inches of the bottom of the hole.

3.8 CONTRACTOR QUALITY CONTROL

Inspections and tests for concrete materials will be the responsibility of the contractor producing the concrete.. Additional tests and inspections for drilled shaft concrete at the time of placement shall be conducted as described in Section 03 30 00.60 CONCRETE; PLACEMENT REQUIREMENTS.

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SECTION 03 31 23 Page 12

3.8 CONTRACTOR QUALITY CONTROL