Natural Resources Conservation Service

Conservation Practice CONSTRUCTION Specification

structure for water control - concrete

CODE 587C

1.  SCOPE

> The work shall consist of furnishing, forming, placing, finishing, and
> curing reinforced portland cement concrete as required to build the
> structures shown on the drawings.

2.  **SITE PREPARATION**

Site preparation (mobilization and demobilization, clearing and
grubbing, structure removal, pollution control, and water for
construction) shall be in accordance with Construction Specification
587.

3.  **CLASS OF CONCRETE**

> The minimum class of concrete to be used in the construction of this
> work shall be 3000 unless otherwise specified or as may be shown on
> the drawings.
>
> Concrete shall be classified according to the required compressive
> strength as tabulated below. The strength of the concrete at 28 days
> shall equal or exceed the tabulated Minimum Compressive Strength at 28
> days for the class of concrete specified.

+-------------------------------+--------------------------------------+
| Class of Concrete             | > Minimum Compressive Strength at 28 |
|                               | > days (psi)                         |
+-------------------------------+--------------------------------------+
| 5000                          | 5,000                                |
+-------------------------------+--------------------------------------+
| 4000                          | 4,000                                |
+-------------------------------+--------------------------------------+
| 3000                          | 3,000                                |
+-------------------------------+--------------------------------------+
| 2500                          | 2,500                                |
+-------------------------------+--------------------------------------+

4.  **CONCRETE MIX**

> At least 5 days prior to any placement of concrete, the Contractor
> shall furnish to the Engineer a statement of the mix proportions
> (including admixtures, if any) for each specified class of concrete.
> The statement shall include reports of laboratory tests showing that
> the proportions selected will produce concrete of adequate strength
> and quality. In the event changes become necessary, no concrete
> containing new or altered materials shall be placed until the Engineer
> has approved the revised job mix.
>
> Fly ash shall be substitution for portland cement within the range of
> 20 to 25 percent by weight.
>
> Water-retarding and/or set-retarding admixtures shall be used for any
> concrete placed during the period from May 15 to September 15.
>
> The air content (by volume) of the concrete at the time of placement
> shall be 5% to 7%.
>
> Unless otherwise specified herein or shown on the drawings, the slump
> shall be 2 to 4 inches.

5.  **CONCRETE MATERIALS**

> **Portland Cement.** The cement used shall be a portland cement, Type
> II or Type I/II unless otherwise specified. Only one brand of cement
> and type shall be used throughout the project.
>
> **Fly Ash.** Pozolan (fly ash) shall conform to ASTM Specification C
> 618, Class F, for aggregates obtained within the Rio Grande basin.
> Class C shall be used for aggregates obtained elsewhere.
>
> **Water.** Only clean water, free from acid, alkali, oil, or organic
> impurities, shall be used. Generally, water suitable for drinking may
> be used.
>
> **Admixtures.** Air-entraining admixtures shall conform to the
> requirements of ASTM Specification C 260. Water-retarding and or
> set-retarding admixtures shall conform to the requirements of ASTM
> Specification C 474, Types A, B, D, F or G. Admixtures used as
> accelerators or antifreeze compounds will not be allowed.
>
> **Aggregates.** Aggregates shall be clean, hard, durable particles.
> The maximum size of aggregate shall be ⅜ inch to 1 inch.
>
> **Preformed Expansion Joint Filler.** Preformed expansion joint filler
> shall conform to the requirements of ASTM Specification D 1752, Type
> I.
>
> **Joint Sealant.** Joint sealant shall be a Type S, Grade NS, Use T or
> NT, Class 25 polyurethane-based, elastomeric joint sealant conforming
> to the requirements of ASTM Specification C 290 and shall tolerate
> submergence.
>
> **Waterstops.** Waterstops shall be fabricated of vinyl chloride
> polymer or co-polymer and shall meet the following requirements:
>
> Hardness as determined by the Shore A durometer method shall be a
> minimum of 60.
>
> Specific gravity shall be a maximum of 1.2.
>
> Tensile strength shall be a minimum of 2,500 pounds per square inch.
>
> Ultimate elongation shall be a minimum of 450 percent.
>
> Compression set shall be a maximum of 30 percent.
>
> Water adsorption in weight measurements shall not exceed 5 percent.
>
> Decrease in tensile strength and ultimate elongation after aging shall
> not exceed 20 percent.
>
> There shall be no sign of failure due to brittleness at a temperature
> of minus 35°F.
>
> Unless otherwise specified herein or shown on the drawings, the
> waterstop shall have ribbed anchor flanges and a smooth web containing
> a hollow tubular center bulb having a wall thickness equal to at least
> 3/16 inch, and the inside diameter of ¾ inch. Flanges may be of
> uniform thickness or may have either a converging or a diverging taper
> toward the edges. The overall width of the waterstop shall be 9 inches
> and the web thickness shall be ⅜ inch.
>
> **Curing Compound.** The curing compound shall be Type 1-D translucent
> with fugitive red dye in accordance with ASTM Specification C 309.
>
> **Steel Reinforcement.** Steel bars for concrete reinforcement shall
> be grade 40, 50, or 60 deformed bars conforming to one of the
> following specifications:
>
> Deformed and plain billet-steel bars for concrete reinforcement (ASTM
> Specification A 615).
>
> Rail-steel deformed and plain bars for concrete reinforcement (ASTM
> Specification A 616).
>
> Axle-steel deformed and plain bars for concrete reinforcement (ASTM
> Specification A 617).

6.  **MEASURING CONCRETE MATERIAL**

> **Cement.** Cement shall be measured by weight.
>
> **Aggregates.** Aggregates shall be measured by weight.
>
> **Water.** Water shall be measured by weight or volume.
>
> **Admixtures.** Dry admixtures shall be measured by weight, and paste
> or liquid admixtures shall be by weight or volume.

7.  **MIXING**

> **Ready-mix.** When used, ready-mixed concrete shall be mixed and
> delivered in conformance with ASTM C 94. The concrete shall be
> discharged from the mixer within 1.5 hours after adding the mixing
> water to the cement and aggregates, or cement to aggregates. This time
> shall be reduced to 0.75 hour when the concrete temperature exceeds 85
> °F. The site foreman/superintendent shall obtain statement-of-delivery
> tickets from the driver and furnish those tickets to the engineer. The
> tickets shall document the time of loading, the revolution counter
> readings, and the quantities of materials used for each load of
> concrete.
>
> **Batchmixing at the Site.** For concrete mixed at the site of the
> work with paving mixers or stationary construction mixers, the time of
> mixing after all cement and aggregates are in the mixer drum shall be
> not less than 1.5 minutes.
>
> The batch shall be so charged into the mixer that some water will
> enter in advance of the cement and aggregates and all mixing water
> shall be introduced into the drum before one-fourth of the mixing time
> has elapsed.
>
> **Truck-Mixed Concrete.** When concrete is mixed in a truck mixer
> loaded to its maximum capacity, the number of revolutions of the drum
> or blades at mixing speed shall not be less than 70 nor more than 100.
> If the batch is at least one-half cubic yard less than maximum
> capacity, the number of revolutions at mixing speed may be reduced to
> not less than 50; and mixing in excess of 100 revolutions shall be at
> the speed designated by the manufacturer of the equipment as agitating
> speed.
>
> The mixing operation shall begin within 30 minutes after the cement
> has been added to the aggregates, and the water shall be added during
> mixing. When mixing is begun during or immediately after charging, a
> portion of the mixing water shall be added ahead of or with the other
> ingredients.

8.  **INSPECTING AND TESTING**

> The Engineer shall have free entry to the plant and equipment
> furnishing concrete. Proper facilities shall be provided for the
> Engineer to inspect materials, equipment, and processes and to obtain
> samples of the concrete. All tests and inspections will be conducted
> so as not to interfere unnecessarily with the manufacture and delivery
> of the concrete.
>
> The following tests shall be performed in accordance with the
> specifications indicated:

  --------------------------------------- --------------- ------------------------------
  Test                                    ASTM            
                                          Specification   

  Sampling                                                C 172\*

  Slump Test                                              C 143\*

  Air Content                                             C 231\* or C 173\*

  Compression Test Specimens                              C 31\*\* or C 42\*\*

  Compressive Strength                                    C 39\*\* or C 42\*\*

  Unit Weight                                             C 138
  --------------------------------------- --------------- ------------------------------

> \* Test of a portion of a batch may be made on samples representative
> of that portion for any of the following purposes:

(1) Determining uniformity of the batch.

(2) Checking compliance with requirements for slump and air content when
    the batch is discharged over an extended period of time.

(3) Checking compliance of the concrete with the specifications when the
    whole amount being placed in a small structure, or a distinct
    portion of a larger structure, is less than a full batch.

> \*\* For each strength test of specimens made according to ASTM
> Specification C 31, C 39, or C 42, three standard test specimens shall
> be made. The test result shall be the average of the strengths of the
> three specimens; except that if one specimen in the test group shows
> manifest evidence of improper sampling, molding, or testing, it shall
> be discarded and the strengths of the remaining two specimens shall be
> averaged. Should more than one specimen in a test group show such
> defects, the entire group shall be discarded and additional samples
> shall be taken.

9.  **FOUNDATION WORK**

> Foundation work (diverting surface water, dewatering the construction
> site, dewatering borrow areas, and foundation preparation) shall be in
> accordance with Construction Specification 587.

10. **PLACING CONCRETE**

> No concrete shall be placed until the subgrade, forms, and reinforcing
> steel have been inspected and approved. Placement of concrete on mud,
> dried earth, uncompacted fill, or frozen subgrade will not be
> permitted.
>
> Earth foundations under the structure shall be firm and damp.
>
> Concrete shall be placed and worked into corners of the forms and
> around the reinforcing steel in such a manner as to prevent the
> concrete materials from segregating. Depositing of the concrete shall
> be so regulated that the concrete may be consolidated with a minimum
> of lateral movement.
>
> When conditions are such that the temperature of the concrete may be
> expected to exceed 85 °F at the time of delivery at the work site,
> during placement or during the first 24 hours after placement, the
> contractor shall maintain the temperature of the concrete below 85 °F
> during mixing, conveying, and placing.

11. **PLACEMENT OF CONCRETE ON HDPE OR LLDE LINERS**

> Concrete placement for ramps and other appurtenances shall be in
> accordance to the drawings and specifications. All reinforcement steel
> shall be placed on flat-footed plastic rebar chairs. All rebar splices
> shall be fully tied to avoid loose ends. On slopes, concrete shall be
> placed from the bottom of the slope to the top and have a low slump to
> prevent sloughing down slope during placement. Only plastic shovels
> and internal vibrators shall be used to place concrete. Metal shovels
> and rodding are not allowed. Concrete forms shall be held in place by
> methods that avoid damaging the liner.

12. **CONSTRUCTION JOINTS**

> Construction joints shall be made at locations shown on the drawings.
> If joints are needed which are not shown on the drawings, they shall
> be placed in locations approved by the Engineer.
>
> Surfaces of construction joints shall be cleaned of all unsatisfactory
> concrete, laitance, coatings, stains, curing compound, or debris by
> washing and scrubbing with a wire brush or other means approved by the
> Engineer. The surface shall be kept moist for at least 1 hour prior to
> placing new concrete.

13. **PROTECTION FROM FREEZING**

> Concrete shall not be placed during freezing weather unless adequate
> protection is provided to keep the concrete temperature between 50 °F
> and 90 °F for a period of not less than 7 days.

14. **REMOVAL OF FORMS**

> Forms shall be removed in such a way as to prevent damage to the
> concrete. Supports shall be removed in a manner that will permit the
> concrete to take the stresses due to its own weight uniformly and
> gradually.
>
> Forms shall not be removed sooner than the following minimum times,
> after the concrete is placed. These periods represent cumulative
> number of days and fractions of days, not necessarily consecutive,
> during which the temperature of the air adjacent to the concrete is
> above 50 °F.

  ---------------------------------------------------------- ------------
  Element                                                    Time

  Beams, arches - supporting forms and shoring               14 days

  Conduits, deck slabs -- supporting (inside)forms and       7 days
  shoring                                                    

  Conduits (outside forms), sides of beams, small            24 hours
  structures, gabion capping                                 

  Columns, walls, spillway risers -- with side or vertical   7 days
  load                                                       

  Columns, walls, spillway riser -- with no side or vertical 
  load:                                                      

  Concrete supporting more than 30 feet of wall in place     7 days
  above it                                                   

  Concrete supporting 20 to 30 feet of wall above it\*       3 days

  Concrete supporting not more than 20 feet of wall in place 24 hrs.
  above it\*                                                 
  ---------------------------------------------------------- ------------

> \*Age of stripped concrete shall be at least 7 days before any load is
> applied other than the weight of the column or wall, forms, and
> scaffolds for succeeding lifts.

15. **FINISHING**

> Concrete surfaces shall be true and even and shall be free from open
> or rough spaces. Defective concrete, honeycombed areas, and voids left
> by removal of tie rods shall be repaired immediately after the removal
> of forms. Defective concrete shall be repaired by cutting out
> unsatisfactory material and placing new concrete secured by anchors in
> the repair area. Patching mortar for tie rod holes, et cetera, shall
> be thoroughly compacted into place to form a dense, well-bonded unit.
> All unformed areas of concrete exposed in the complete work shall have
> a float finish.

16. **CURING**

> All concrete shall be cured for a period of not less than 7 days.
> Concrete may be moist-cured by maintaining all surfaces continually
> wet for the duration of the curing period. At the option of the
> Contractor and approval of the Engineer, the concrete may be cured
> using a curing compound conforming to ASTM Specification C 309. The
> curing compound shall be applied at a rate of not less than 1 gallon
> per 150 square feet of surface. Exposed surfaces shall have the
> compound applied as soon as the free water has disappeared. Formed
> surfaces shall have the compound applied immediately after the forms
> are removed and defective areas repaired.

17. **STEEL REINFORCEMENT**

> **Details of Construction.** The reinforcing steel shall be deformed
> reinforcing bars of the size and spacing as shown on the drawings. The
> bars shall have a minimum of 2 inches concrete cover for formed and
> top surfaces and 3 inches for concrete placed against the earth.
>
> **Bending.** Reinforcing steel may be mill or field bent. All bends
> shall be made without heating.
>
> **Splicing.** The splices shall be at least 30 diameters of the
> smaller bar being spliced, but not less than 12 inches.
>
> **Support.** All reinforcing bars must be securely tied and supported
> in their proper location with wire, patented clips, or chair supports
> before concrete placement begins. Bars assembled in place in
> horizontal mats must be tied at each intersection around the periphery
> of the mat and at least at every fourth bar within the mat. Horizontal
> bars placed in the vertical mats should be tied in at least three
> locations for each length or at every third intersection, whichever
> results in closer spaced ties. If mats are preassembled, they should
> be adequately tied so they remain rigid during handling and placement.
> The use of spot welding is not permitted.
>
> **Placing.** All reinforcing steel shall be placed in the structure as
> shown on the drawings (steel details). Bars shall be free of loose,
> flaky rust and scale, oil or grease, or other material that may reduce
> the bond with the concrete.

18. **EARTHWORK**

> Earthwork (common excavation and earthfill) shall be in accordance
> with Construction Specification 587.

19. **MEASUREMENT**

> Concrete is measured to the neat lines shown on the drawings, and
> volume of concrete is computed to the nearest 0.1 cubic yard.
> Measurement of concrete placed against the sides of an excavation
> without using intervening forms is made only to the neatness or pay
> limits shown on the drawings. No deduction in volume is made for
> chamfers, rounded or beveled edges, or any void or embedded item that
> is less than 5 cubic feet in volume.
>
> The weight of steel reinforcement placed in the concrete in accordance
> with the drawings is determined to the nearest pound by computation
> from the placing drawings. Measurement of hooks and bends is based on
> the requirements of ACI Standard 315. Computation of weights of
> reinforcement or welded wire fabric is based on tables in ACI Standard
> 315. The area of welded wire fabric reinforcement placed in the
> concrete in accordance with the drawings is determined to the nearest
> square foot by computation from the placing drawings with no allowance
> for required laps. The weight of steel reinforcing in extra splices or
> extra-length splices approved for the convenience of the contractor or
> the weight of supports and ties is not included in the measurement.
>
> Project Name:
>
> Date:

20. **ITEMS OF WORK AND CONSTRUCTION DETAILS**

> Items of work to be prepared in conformance with this specification
> and the construction details are: