General Info-Concrete Rapids Lake 03300SLAB.docx

A. General

1. The requirements of this section shall govern the supplying of all labor, material and equipment necessary to install a concrete floor slab that is one foot larger on all sides for the 8’ x 16’ Community Safe Room Storm Shelter. The work is located at the Rapids Lake Unit of the Minnesota Valley National Wildlife Refuge, located at Carver MN.

2. Reference Drawing: Refer to drawing for plan and section view dated 3/23/16 for rebar placement and slab information.

Concrete Slab: approximately 10 feet x 18 feet x six inches thick with an 18-inch-wide and 18-inch-deep thicken edge. In the slab place # 4 at 12 inches on center both directions maximum set on chairs and two rows of # 5 typical around the outside edge. Install #3 stirrups 24 inches on center maximum continuous in the thicken edge. Excavate approximately 3 inches below the underside of the slab and install a 4-inch compacted aggregate base, level base as necessary. Install minimum 6 mil vapor barrier on top of aggregate and place 6-inch-thick reinforced concrete slab placed on a vapor barrier with light broom finish. Slab and base shall be installed slightly above existing grade to allow positive drainage away from all sides of slab.

Concrete Aprons: Qty 2 In addition to the slab required for the shelter install on both ends a 10 feet wide x 5 feet deep x 6 inches thick the slab reinforcement shall be continuous through the aprons. Excavate and level base as described supply and 6-inch-thick reinforced concrete slab placed on a vapor barrier with a light broom finish. Slope aprons so they drain 2% away from the slab. Aprons do not require thickened edge.

3. Form work shall conform to ACI Standard Recommended Practice for Concrete Form Work (ACI 347, latest edition).

4. All concrete work not specifically covered by these specifications shall conform to ACI Standard Building Code Requirements for Reinforced Concrete (ACI 318, latest edition).

4. Submittals:

a. Mix Design: The proportions of all components of the concrete mix shall be by weight and shall be submitted to the government for approval prior to placement of any concrete. The approved mix design and supplier shall not be changed throughout concrete placement unless a new mix design and supplier are approved by the government.

DIVISION 3 SECTION 03300

CONCRETE CONCRETE SLAB

Rapids Lake Shelter 8/10/2020

1. Water shall be clean and free from deleterious amounts of acids, alkalis, and organic materials.

2. Portland Cement Concrete shall conform to the following requirements:

a. Cement - Type I, III, IA, or IIIA. Fly ash, if used, shall be Class C or Class F, conforming to ASTM C618, latest revision. Flyash will be limited to no more than 15%, by weight, of the total cementitious material.

b. All aggregates shall conform to the requirements of ASTM C-33. The aggregate particles shall be clean, hard, unweathered, and uncoated.

(1) Fine aggregate shall be natural sand conforming to the requirements of ASTM C-33.

(2) Coarse aggregates shall be crushed stone or washed gravel conforming to the grading requirements of ASTM C-33, size No. 67, 3/4 to No. 4.

c. Water/Cement + Flyash) Ratio (by weight) shall not exceed 0.45.

d. Compressive Strength - 4500 psi @ 28 days (min)(not 3500psi as shown on the drawing).

e. Air Content – 5% to 7%.

f. Air Entraining Admixture - ASTM C-260.

g. Slump - 2 to 4 inches.

3. Reinforcing shall conform to the following requirements:

Steel Reinforcement A. Reinforcing steel bars shall conform to the requirements of ASTM A-615, grade 60, latest revision and set on plastic or metal chairs.

4. Install a minimum 6 mil moisture barrier under entire floor and apron.

5. Liquid membrane-forming compounds shall conform to ASTM Specification C-309, Sealant: Anti-spalling compound shall be commercial grade. Salt Guard by ProSoCo or similar.

C. Execution

1. General

a. All proportioning of aggregate shall be by weight. The proportions of aggregate to cement shall be such as to produce concrete with a slump of 2 to 4 inches by the standard slump test. The combined aggregates shall be of such a composition of sizes that the weight passing a No. 4 screen (fine aggregate) shall not be less than 30 percent nor more than 50 percent of the total. Ready-mixed concrete meeting the above specifications and ASTM C-94 will be acceptable.

b. All concrete work shall be installed to allow for positive drainage away from the building/shelter or as directed by the government. Drain the aprons away from the building doorways.

c. All surfaces which are to receive concrete shall be cleaned of loose material. Pads must have a thoroughly compacted base that is a minimum of 4 inches of granular material and shaped to the required grade.

d. All edges and curves shall be uniform and free from abrupt changes in grade and/or direction. All finished surfaces shall be sloped to provide drainage and to eliminate pockets or depressions which would pocket water.

2. Reinforcing

a. All reinforcement shall be set to proper elevation by the use of chairs. The use of wood blocks, bricks or other materials is prohibited.

b. All reinforcement shall be securely tied in place, supported and spaced so that it will not be displaced while placing concrete.

c. All reinforcement shall be free from loose, flaky rust, mill scale, mud, oil or other coating that will destroy or reduce the bond with the concrete.

3. Concrete Forms

a. Forms shall conform to the shape, lines and dimension as shown, and shall be sufficiently tight to prevent leakage.

b. All 90 corners exposed in the finished work shall have a 1-inch chamfer unless otherwise noted.

c. The surfaces of all forms in contact with concrete that will be exposed shall be smooth.

d. Forms shall be oiled with non-staining form oil before placing concrete.

4. Joints: Provide construction, expansion, and control joints as indicated or required.

a. Expansion joints: Provide expansion joints where concrete slabs abut walls or other fixed structures and across every 30 foot of length. Install expansion joints through full depth or thickness of concrete. Cut-back exposed expansion joint material a minimum of 3/8 in. from surface of concrete; fill with sealant flush to surface; tool smooth.

b. Control joints while finishing surface, every five feet or as approved. Take special care to maintain uniform elevation on both sides of construction joints; correct by grinding if necessary. Control joints may be formed or sawn. Sawing joints shall be properly timed so that shrinkage cracking has not yet occurred, but the concrete has set sufficiently so that the sawing cuts a straight, clean groove.

5. Placing Concrete.

a. General. Concrete shall be placed within 60 minutes after the introduction of water to the cement or shall be removed from the site at the Contractor's expense. Concrete shall be well vibrated, rodded, or spaded into place to fill all voids and angles, and to insure smooth surfaces and dense concrete. Concrete shall be deposited in all cases as nearly as practicable directly in its final position and shall not be allowed to flow in any manner that will cause segregation of the materials.

Before fresh concrete is placed against the portions of concrete which has already set, the contact surface of the concrete already set shall be thoroughly cleaned of all loose material, dirt, and other foreign matter. Immediately prior to placing new concrete, the concrete which has already set shall be soaked with water and covered with a coating of neat cement grout. The fresh concrete shall be placed before the grout has attained its initial set.

b. Cold weather concreting shall meet the requirements of ACI 306, except that the section "Minimum requirements for job taking maximum risk" shall be deleted.

c. Hot weather concreting shall meet the requirements of ACI 305.

5. Finishing.

a. Non-slip Broom Finish: Apply non-slip broom finish to all concrete immediately after trowel finishing, slightly roughen concrete surface by light broom finish with fiber bristle broom perpendicular to main traffic route.

b. Edges shall be neatly trimmed with 1/4 in. radius edging tool. Honeycombed areas shall be pointed with mortar.

6. Curing of concrete shall be for a period of seven (7) days from the time of placing and shall be by one of the following methods:

a. Liquid membrane-forming compounds shall conform to ASTM Specification C-309, revised to date. Compounds shall be sprayed on and dry to touch in not more than four (4) hours from time of application. Entire procedure shall conform to ASTM Specifications.

b. Moist method shall be by covering the concrete surfaces with impermeable sheets of polyethylene material with joints lapped and sealed to make watertight.

(END OF SECTION 03300)