Attachment K - Addendum to Specifications.pdf

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U.S. Fish and Wildlife Service Solicitation 140F0921R002 for Comanche Dam Modifications December 7, 2020

Addendum To Specifications This addendum is issued to update the Technical Specifications to incorporate changes resulting from Schnabel’s RCC mix design report.

SPECIFICATIONS

Bid Tab

1. Delete Item 10 Description and replace with the following:

“Furnishing Cement for RCC (@220 lbs/CY)”

2. Delete Item 10 Quantity and replace with the following:

“295”

3. Delete Item 11 Description and replace with the following:

“Furnishing Flyash for RCC (@330 lbs/CY)”

4. Delete Item 11 Quantity and replace with the following:

“440”

5. Delete Item 12 Quantity and replace with the following:

“4,000”

03 37 23 – Roller-Compacted Concrete

1. Delete Paragraph 1.4D Quality Assurance and replace with the following:

1. The Government Inspector will perform two field density tests per RCC lift by the nuclear method in accordance with ASTM D2922. Compaction of the RCC will be maintained at the average wet density of ten consecutive tests, to the target wet density specified. The moisture content will be measured and recorded for comparison with the moisture content of the batches. The Government Inspector may require adjusting the target wet density in the field based on the results of the test section.

2. The Government will prepare a representative set of five, 6-inch-diameter RCC cylinders for each RCC lift. Compressive test results of each cylinder will be prepared at 3 days, 7 days, 28 days for comparison with test results in the RCC Mix Design Report.

3. The Government will perform air content tests on the fresh RCC near the start of production and at least once more during the work day.

4. The Contractor shall perform a Vebe test of the RCC mix prior to each shift to confirm that Vebe times are in accordance with the Specifications. Adjustments to the RCC mix shall be made to confirm that the Vebe time meets the specifications prior to starting the placement of RCC for each shift.

5. As a minimum, the Contractor shall perform moisture tests of the RCC aggregate stockpile prior to each day’s production and approximately six hours after the start of production.

2. Add the following to the end of Paragraph 1.6A Submittals:

13. Results of the Contractor’s RCC initial set testing performed during the RCC Test Section.

3. Delete Paragraph 2.2A RCC Mix Design and replace with the following:

Solicitation 140F0921R001 for Comanche Dam Modifications December 7, 2020

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A. RCC: The RCC mix design will be similar to the following. The mix may be revised by the Engineer based upon the field mix design performed by Contractor. The mix will have a Vebe time between 8-12 seconds.

Material Batch Weight (SSD) (lb/cy)

Portland Cement 220

Pozzolan 330

Aggregate 3,000

Water (Total water) 270 Set retarder admixture To be determined*

Air entrainment admixture 18 ozs Total 3,830

* Contractor shall determine the admixture dosage rate such that the initial set time will be greater than 16 hours with a RCC mixture temperature equal to or greater than 80 degrees F.

4. Add the following to Paragraph 2.2 RCC Mix Design:

D. The RCC shall have a minimum 90-day compressive strength of 3,000 psi.

5. Delete Paragraph 2.3A Bedding Mortar and replace with the following:

A. Bedding mortar shall have a minimum 28-day compressive strength of 3,000 psi. and shall be a mixture of water and cement with a maximum water cement ratio of 0.45. No coarse aggregate will be allowed in the bedding mortar and set retardant shall be used to set the initial set time at no less than 8 hours at 90° F. Bedding mortar shall have a slump between 9 and 11 inches.

6. Delete Paragraph 2.6E RCC Placement and Compaction Equipment and replace with the following:

E. Compacting Equipment:

1. Self-propelled vibratory rollers shall be used. Rollers shall have a gross weight of 20,000 pounds and shall produce a dynamic force of at least 400 pounds per inch of drum width at the operating frequency of at least 2,000 cycles per minute and shall be operated at speeds not exceeding 1.5 miles per hour. The engine driving the eccentric mass shall have a rating of not less than 125 hp.

2. Small vibratory rollers similar to the Case Model W100 which are capable of operating within a few inches of a vertical face shall be used to compact RCC at areas not possible with the larger equipment or where specified. The dynamic force produced by the small rollers shall be at least 150 pounds per linear inch of drum width of each drum of a double drum unit and at least 300 pounds per linear inch of drum width for a single drum unit.

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3. Tampers shall be of a type similar to the Wacker Model GVR 200Y and shall develop a dynamic force per blow of at least 1,800 pounds.

4. Plate compactors shall be of the type similar to Mikasa Model MBC 77. Contractor should have available during the RCC test section several sizes of plate compactors to test the best size for the IV-RCC mixture.

7. Delete Paragraph 2.6H RCC Placement and Compaction Equipment and replace with the following:

H. Vibrators: Internal immersion-type vibrators shall be used to consolidate the RCC against surfaces and to mix the grout with the uncompacted RCC where grout enriched is called out. The vibrators shall have a head diameter of 3 inches or greater, a minimum frequency of 12,000 vibrations per minute and an amplitude in the range of 0.03 to 0.06 inches.

Selection of vibrators to adequately mix and consolidate the RCC against forms, the existing dam, and abutment contacts shall be confirmed during the test section and be the responsibility of the Contractor, but subject to the approval of the Engineer. At least a backup vibrator shall, be available during RCC placement.

8. Add the following to the end of Paragraph 2.6 RCC Placement and Compaction Equipment:

I. Vibrating Screed: Contractor shall provide a vibrating screed to provide a smooth surface on the downstream RCC steps. Some hand work should be expected. The downstream steps shall have a minimal slope in the downstream direction to prevent ponding of water.

9. Delete text in Section 3.1 RCC Test Section and replace with the following:

A. An RCC Test Section shall be constructed and completed immediately prior to beginning RCC placements. The location of the RCC Test Section is shown on the Approved Drawings and will be included in the RCC buttress. The RCC Test Section will serve as the basis for final acceptance of the Contractor's batching, mixing, transporting, placing, compaction, consolidation, forming, curing, protection, and cleanup methods; suitability of personnel and equipment; and prequalification of vibratory rollers, power tampers, and plate vibrators. It shall also demonstrate the downstream stepped facing forming, vibration and method and procedures for foundation surface preparation and cleanup, procedures for consolidating IV-RCC, step surface finishing, placement of bedding mortar and the installation of contraction joints.

B. The RCC Test Section shall be constructed in accordance with all applicable requirements of this Section for RCC construction. The test section shall include at least one cold joint lift surface exposed longer than three hours old, followed by the required cleanup, placing of bedding mortar, and placing of the RCC lift. RCC shall be placed at the anticipated daily production rate for construction to allow evaluation of the mixture performance.

C. If the RCC Test section is not constructed in accordance with these specifications and to the satisfaction of the Engineer and the Contracting Officer’s Representative, the RCC Test Section will be removed and replaced at the Contractor’s sole expense.

D. All materials removed shall be become the property of the Contractor and shall be removed from the site of the Work and disposed of in accordance with the requirements of these Specifications. Approved, non-blasting excavation methods shall be used for the removal of concrete, when necessary. Blasting will not be allowed as a method of concrete removal.

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E. During placement of the RCC test section, the Engineer will perform nuclear density tests, Vebe time tests, air tests, and will prepare RCC test cylinders for comparison with the RCC Mix Design Report.

F. The Contractor during the RCC test section will have a certified lab onsite to perform initial set tests on the RCC at several different dosage rates.

G. If the Contractor does not meet requirements as specified during the placement of the RCC Test Section, the RCC Test Section shall be removed and additional lifts shall be constructed at no additional cost to the Government.

10. Delete Paragraph 3.2B Preparation and replace with the following:

B. All existing concrete surfaces where RCC will be placed shall be cleaned, roughened, and all laitance removed. Methods of roughening surfaces and removing laitance may include mechanical abrasion or cutting, sandblasting, acid etching, or high-pressure water jetting of hardened (not green) concrete. Water jetting shall be at pressures of at least 6,000 psi.

All methods are subject to the approval of the Government Inspector. Construction joints shall be thoroughly cleaned of loose or defective concrete, coatings, sand, curing compound and other foreign material on the surface. RCC surfaces shall always be in a moist condition. At no time shall the surface to allowed to dry back beyond saturated surface dry conditions.

11. Delete Paragraph 3.2G Preparation and replace with the following:

G. Lift Surface Cleaning and Preparation: Lift surface cleaning operations shall be performed just prior to placing RCC. If deleterious materials are spilled on joint surfaces, the contaminated RCC shall be removed and replaced with fresh RCC. The replacement RCC shall be thoroughly consolidated prior to the next RCC placement. The Contractor shall be entitled to no additional compensation for replacement RCC. Lift surfaces requiring cleaning for removal of deleterious substances shall be cleaned as follows:

1. Standard Cleanup: Standard lift surface cleanup shall be performed on all lift surfaces. Liquids, solids, or combinations of liquids and solids shall be removed with vacuum equipment, air jetting, water jetting, or brushing. Water jetting and brooming shall be followed by vacuuming or air jetting to completely remove standing water or remaining dust. RCC that is damaged by air or water jetting shall be cleaned by vacuum equipment.

2. Cold Joints: All lift surfaces more than 16 hours old or one thousand degree (1000º) hours whichever occurs first and all joint edges greater than two hours old shall be considered a cold joint. Cold joints shall be cleaned by air-water jetting or water jetting to remove all laitance, loose or defective concrete or mortar, other coatings, and other foreign material, followed by vacuuming the surface. The cleaned surface shall be maintained in a moist condition until covered by a bedding mortar as shown on the Approved Drawings.

3. Bedding mortar shall be spread or broomed onto the moist surfaces to which it is to be applied as shown on the Approved Drawings to a thickness of between ¼ and ½ inches. The bedding mortar shall be spread immediately ahead of placed RCC. The bedding mortar shall be covered with RCC while it

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12. Change the title of Section 3.4 to SPREADING

13. Change the title of Section 3.5 to COMPACTION AND CONSOLIDATION

14. Delete Paragraph 3.5C and replace with the following:

C. The RCC shall be consolidated against vertical surfaces, existing dam and abutments as shown on the Drawings within 30 minutes after RCC is spread. Immersion vibrators shall be used to consolidate the RCC. Special attention shall be used to properly consolidate the IV-RCC. Lessons learned during the RCC test section shall be applied. At the downstream steps, after the RCC is consolidated and is at the design grade, a vibratory screen shall be used to create a smooth surface that is sloped in the downstream direction.

15. Add the following to the end of Paragraph 3.10 Tolerances:

D. The top of steps shall be finished to expel water.

16. Delete Paragraph 4.2A Payment and replace with the following:

A. Compensation to the Contractor for all labor, incidental materials, and equipment required for mixing, placing, compacting, consolidating, transporting, spreading, form work, finishing, and curing RCC required in this section shall be included in the unit price bid in the Bid Schedule for Roller Compacted Concrete Mixing, Conveying, and Placement.

Furnishing of cement, flyash, and aggregate materials is not included in this pay item.

END OF ADDENDUM