04_SECTION C SpecificationsCATTLEGUARDSbases.pdf

SECTION C

SPECIFICATIONS

CONCRETE CATTLEGUARD BASES

A. General Requirements

The contractor shall furnish concrete cattle guard bases in accordance with these specifications and drawings.

B. References

The most current edition of the referenced standards shall apply.

1. American Society for Testing and Materials:

ASTM A 615 Deformed and Plain Billet Steel Bars for Concrete Reinforcement

ASTM C 33 Concrete Aggregates

ASTM C 39 Compressive Strength of Cylindrical Concrete Specimens

ASTM C 94 Ready-Mixed Concrete

ASTM C 143 Slump of Portland Cement Concrete

ASTM C 150 Portland Cement

ASTM C 260 Air-Entraining Admixtures for Concrete

ASTM C 309 Liquid Membrane-Forming Compounds for Curing Concrete

ASTM C 231 Rev. B Test Method for Ai r Content of Freshly Mixed Concrete by the

Pressure Method

2. American Association of State Highway and Transportation Officials

AASHTO T 26 Test for Quality of Water to be Used in Concrete

3. American Concrete Institute

ACI 304R Guide for Measuring, Mixing, Transporting, and Placing Concrete

ACI 305R Hot Weather Concreting

ACI 306R Cold Weather Concreting

ACI 315 Details and Detailing of Concrete Reinforcement

ACT 318 Building Code Requirements for Reinforced Concrete

ACI 347 Recommended Practice for concrete Formwork

C. Concrete Materials

1. Cement: Portland Cement, Type V; ASTM C 150 for bases. The use of caked or hardened cement will not be permitted.

2. Water: Water shall be clean and free form harmful amounts of acids, alkalis, and organic materials in accordance with AASHTO T 26. Potable water is acceptable without testing.

3. Aggregates: Fine aggregates shall be natural sand in accordance with ASTM C 33, with fineness modulus of not less than 2.5 nor more than 3.0. Coarse aggregates shall be crushed stone or gravel in accordance with ASTM C 33, with maximum size of 1-1/2 inches.

4. Air-Entraining Admixture: Admixture; ASTM C 260.

5. Forming: Design and construct formwork for exposed concrete surfaces with plywood, metal-framed plywood-face, or other panel type materials to provide continuous, straight, smooth as-cast surfaces. Furnish formwork in largest practicable lengths to minimize the number of joints. Form material shall be of sufficient thickness to withstand pressure of newly placed concrete without bowing or deflection.

6. Reinforcing Steel: Reinforcing steel shall not exceed No. 4 bars in size and shall meet the requirements of ASTM A 615, 616, or 617 Grade 40. Rust, scale, mill, or other coating that will destroy or reduce bond is not acceptable. Steel reinforcing shall be furnished in full lengths where practicable. Where splices occur, provide a minimum of 24 inches lap and stagger splices. Metal chairs shall be galvanized or plastic-coated. Design, materials, fabrications, and installation shall comply with the requirements of ACI 318, Chapter 7 and Part 4.

D. Mixes

1. Concrete Design Mix: Design the mix to provide concrete with the following properties:

a. Type A Concrete: 4000 psi, 28-day compressive strength. The water-cement ratio shall not exceed 5 gallons per sack of cement, inclusive of water in the aggregate. The proportions of aggregate to cement shall produce concrete with a slump of 2 to 4 inches in accordance with

ASTM C 143.

b. Air Content: Air content of concrete at the point of placement shall be 4 to 6%.

c. Ready-Mixed Concrete: Ready-mixed concrete that meets the above specifications will be permitted when approved by the Contracting

Officer. The Contracting Officer shall have access to the mix in plant during concrete mixing operations.

E. Installation

1. Forms Construction: Construct forms in accordance with ACI 347, Chapters 1 through 4 to the exact sizes, shapes, lines, and dimensions shown and as required to obtain accurate alignment, location, grades, and level and plumb work in finished structures. Provide required detail work construction aids and embedded items. Use selected materials to obtain required finishes. Fabricate forms for easy removal without hammering or prying against concrete surfaces. Provide crush plates or wrecking plates if stripping may damage cast concrete surfaces.

Kerf wood inserts for forming keyways, reglets, and recesses to prevent swelling and assure ease of removal.

2. Forms Removal: Form oil may be applied to facilitate removal of forms.

Formwork not supporting concrete, such as sides of walls and similar parts of the work, may be removed after curing at not less than 50˚ F for 24 hours after placing concrete, when the concrete is sufficiently hard so as not to be damaged by form removal, and when curing and protection operations are maintained as specified.

3. Reinforcing Steel: Reinforcing steel shall be placed in accordance with the drawings. Reinforcement shall be held securely by steel wire, mortar blocks, or metal chairs during the placement of concrete. Reinforcement shall be securely wired in proper position and shall be adequately supported before concrete is placed.

F. Concrete Mixing

1. Mix materials for concrete in a drum-type batch machine mixer. For mixers of one cubic yard or smaller capacity, mix concrete for a minimum of 1-1/2 minutes, but not more than 5 minutes after ingredients are in the mixer before the batch is released. For mixers with a capacity larger than one cubic yard, increase the minimum mixing time by 15 seconds for each additional cubic yard (or portion thereof).

2. Comply with the requirements of ASTM C 94 and as herein specified for ready-mixed concrete. During hot weather or under conditions contributing to rapid setting of concrete, a shorter mixing time than is specified in ASTM C 94 may be required. When air temperature is between 85˚ and 90˚ F, reduce the mixing and delivery time form 90 minutes to 75 minutes. When air temperature is above

90˚ F, reduce the mixing and delivery time to 60 minutes.

G. Placing Concrete

1. When concrete cannot be placed within the time frame specified above, it shall not be placed and shall be removed from the jobsite.

2. Water shall be removed from within forms and excavation before and during placement of concrete.

3. Concrete shall be placed in maximum lifts of 18 inches, and shall be well vibrated, rodded, or spaded into place to fill voids and angles, and to ensure smooth surfaces and dense concrete. Concrete shall be deposited as nearly as is practicable to its final position, and shall not be permitted to flow in a manner that will cause segregation of the materials. Concrete must not be dropped more than 5 feet vertically without use of a tremie or similar device.

4. Hot weather concreting: ACI 305R.

5. Cold Weather Concreting: ACI 306R. Materials needed for protection shall be on the jobsite before concrete work is started. Do not place concrete on a frozen subgrade or against surfaces having deposits of frost, snow, or ice.

H. Finishing

1. Immediately after the removal of the forms, remove bulges and projections on exposed concrete by chipping or tooling. Chip honeycombed or other defective areas to solid concrete; cut edges to right angles with the surface. Brush cavities with a grout of cement and water, and point with a mortar of cement, sand and water similar to that used in the concrete. Keep the concrete thoroughly saturated with water during the finishing.

I. Curing:

Cure concrete for a period of 7 days from time of placement by use of one of the following methods:

1. The liquid membrane forming compound shall be sprayed on a shall be dry to the touch in not more than four hours from time of application, in accordance with

Paragraph 7.1, ASTM C 309. This method of curing shall not be used where additional concrete, mortar, or joint sealant will be placed against the cured concrete.

2. Cover the damp concrete surfaces with impermeable sheets of polyethylene material with joints lapped and sealed to watertight.

3. Concrete forms left in place may provide proper curing of concrete in contact with the forms. Curing of unformed concrete surfaces shall be by one of the methods shown above, and shall begin as soon as the concrete is hard enough to allow application of the curing material. If forms are removed before the end of the 7 day period, curing by use of the liquid membrane forming compound or sheets of polyethylene material shall begin immediately, and shall continue for the remainder of the 7 day curing period.

J. Protection

1. Damaged or Defective Concrete: Concrete that has been damaged by freezing or by any other cause shall be removed and replaced with acceptable concrete at no additional cost to the Government.

K. Delivery

1. Minimum 2 working days advance notice on delivery is required.

2. Materials not meeting specifications can be rejected. Rejected items will not be accepted for delivery and will be replaced with acceptable items at no additional cost to the government.