AASHTO Specs for Minor Structure Concrete, Reinforcing Steel etc.

CONCRETE

Description. This work consists of constructing minor concrete structures such as pipe culvert headwalls, wingwalls and aprons, spillways, slope paving, sidewalks, curbs and other minor concrete structures.

Materials.

Concrete Composition. Concrete shall conform to the requirements of Table below. Before batching concrete, the Contractor shall submit the proposed concrete proportions for approval. As a minimum, the following shall be submitted:

1. Type and source(s) of all material proposed for use.
2. Material certification for all material proposed for use including cement.
3. Saturated surface dry weight of the fine and coarse aggregate per cubic yard of concrete.
4. Gradation of fine and coarse aggregate.
5. Weight of mixing water per cubic meter of concrete.
6. Weight of cement per cubic meter of concrete.
7. Maximum slump of plastic concrete in millimeters.?

Table - Composition of Minor Structure Concrete

Construction Requirements

General. The Contractor shall perform the preparatory work. He shall design and construct forms that are free of bulge and warp and allow for removal without injuring the concrete. When concrete contains a retarding admixture, fly ash, or other pozzolan replacement for cement, forms shall be designed for a lateral pressure equal to that exerted by a fluid weighing twenty-four hundred kilograms per cubic meter (2400 kg/m3).

Wood, metal, or other suitable material shall be used. Forms shall be kept clean and coated with a form release agent or form oil before placing concrete.

Placing Concrete. The forms and foundation shall be moistened immediately before placing concrete.

Concrete shall be handled and placed to avoid segregation. Aluminum pipe for transporting or placing concrete shall not be used. The intervals between delivery of batches for a single pour on a structure shall not exceed thirty (30) minutes.

Placement shall be done when there is a forecast of air temperatures below an atmospheric temperature of two degrees Celsius (2 C) or above twenty-five degrees Celsius (25 C).

Water shall not be supplied to plastic concrete finishes during finishing operations.

Curing Concrete. Minor concrete shall be cured a minimum of seven (7) days. If high early strength cement is used, cure concrete a minimum of three (3) days.

Acceptance. Concrete for minor structures will be subject to acceptance or rejection by visual inspection and review of the load certification at the placement site. Re-tempering of concrete will not be permitted. The Engineer will take or supervise the taking of slump tests, test cylinders or cores for strength determination checks.

REINFORCING STEEL

Materials. Reinforcing steel shall be manufactured for the type and grade specified on the plans as follows:

• High Tensile Steel reinforcing bars shall conform to AASHTO M31 (ASTM A 615) Grade 60 or BS 4449.
• Epoxy Coated Reinforcing bars shall conform to AASHTO M 284(1)
• Welded Steel Wire Fabric shall conform to AASHTO M55 or BS 4483.
• Cold Drawn Steel Wire shall conform to the requirements of AASHTO M32 or BS 4482 in the case of hard drawn steel wire.

Note (1): Inspect the reinforcing bars after the near white blast cleaning has been performed. Reject all bars that exhibit steel slivers or scabs. Selective sorting and rejection at the fabricator's shop may avoid unnecessary delays and subsequent rejection of bars determined unacceptable during the pre-coating inspection at the coating applicator's shop.

The Engineer reserves the right to observe the preparation, coating and testing of the reinforcing bars. The Engineer or his authorized representative shall have free access to the plant and any work done when access has been requested and denied shall be automatically rejected.

Construction Requirements

Bending Diagrams. Before fabricating bars, all bending diagrams shall be furnished by the Contractor for the approval of the Engineer, and no materials shall be fabricated until such bending diagrams have been approved. Vertical reinforcement in columns, walls, piers, and shafts shall not be fabricated until footing elevations are established in the field. Approval of bending diagrams will in no way relieve the Contractor of his responsibility for ascertaining accuracy of such diagrams. Revision of materials furnished in accordance with such diagrams to meet compliance with design drawings shall be at the expense of the Contractor.

Protection and Storage. Reinforcing steel shall be protected at all times from damage. Reinforcing steel shall be stored above the ground on platforms, skids or other supports. It shall be stored in such a manner and adequately marked to facilitate inspection and checking. Before and after placement, reinforcing steel shall be free from detrimental dirt, mill scale, rust, paint, grease, oil or other foreign substances, fins, or tears. The Contractor will not be required to remove slight rusting which discolors the metal but he shall remove all loose mill scale and scaly rust. Brushing to clean blue metal will not be required.

Cutting and Bending. All cutting and bending of reinforcement bars shall be done by competent workmen and with equipment approved by the Engineer. Unless shown otherwise on the plans or unless written approval is obtained from the Engineer, all reinforcement bars shall be cut and bent in a fabrication shop accessible to the Engineer according to the following procedures:

• Fabricate reinforcing bars to conform to required shapes and dimensions, with fabrication tolerance complying with CRSI Manual of Standard Practice. Reinforcement with any of the following defects will not be permitted in the Work:

1. Bar lengths, depths, and bends exceeding specified fabrication tolerances.
2. Bends or kinks not indicated on the drawings or the final shop drawings.
3. Bars with reduced cross-section due to excessive rusting or other cause.
4. Epoxy coating not meeting the requirements of this section.

• Cold worked bars and hot rolled high yield bars shall not be straightened or bent again once having been bent. Where it is necessary to bend mild steel reinforcement projecting from the concrete, the internal radius of bend shall not be less than twice the diameter of the bar.
• Reinforcement bars shall be bent to the dimensions given in the Bar Bending Schedule. All reinforcement shall be cold bent at the temperature range of five degrees Celsius (5o C. ) and one hundred degrees Celsius (100o C.). The minimum bending radii for high tensile steel and mild steel bars shall be not less than three (3) times and two (2) times, respectively, of the nominal bar diameter.
• Bends shall conform to the following requirements:

1. D = 6d for six (6) millimeter through twenty-two (22) millimeter bar sizes.
2. D = 8d for twenty-four (24) millimeter through twenty-eight (28) millimeter bar sizes. D = 10d for thirty (30) millimeter and over bar sizes.
3. Where (D) is the minimum pin diameter around which a bar may be bent and (d) is the bar diameter.
4. The overall height or Drop Bending Tolerance for deck truss bars shall be limited to plus 0 mm or minus six (6) millimeters.

Placing, Supporting and Fastening. Comply with the CRSI recommended practice for placing reinforcing bars, for details and methods of reinforcement placement and supports, and as herein specified.

All reinforcing steel shall be accurately placed and, during the placing of concrete, firmly held by approved supports in the position shown on the plans. Reinforcing bars shall be securely fastened together. Reinforcement placed in any member shall be inspected and approved before any concrete is placed. Laying or driving bars into the concrete after placement will not be permitted.

Bar supports shall be precast mortar blocks, plastic, or metal supports. Mortar blocks shall be constructed and cured in accordance with the requirements in Section, "Portland Cement Concrete" in the Specifications as related to "Mortar" and "Curing." The minimum compressive strength of mortar used for blocks shall equal the minimum compressive strength of concrete for the structure in which they are used. Mortar block supports shall be attached to the supported bar by means of 16-gauge wire cast in the center of each block. Other supports shall be positively attached to the reinforcing steel. Over waterproofing membranes, the use of precast mortar blocks shall be encouraged, to prevent penetration of the membrane.

Cover supports in contact with exposed concrete surfaces shall be buff-colored plastic spacers or plastic protected. Bar supports shall not be used directly or indirectly to support runways for concrete buggies or other similar construction loads.

If supports indent the forms appreciably or deform due to the weight of the reinforcing steel, spacing shall be decreased or heavier duty supports shall be substituted. Reinforcement shall be placed and maintained in the position shown on the drawings. Unless otherwise permitted by the Engineer, all bar intersections shall be securely tied together with the ends of the tying wire turned into the main body of the concrete. Minimum one and two-tenths (1.2) millimeter diameter stainless steel wire shall be used for in-situ members having exposed soffits. Minimum one and six-tenths (1.6) millimeter diameter softer annealed iron wire may be used elsewhere.

In bridge decks, reinforcing bars shall be tied together at all intersections except where spacing is less than three hundred (300) millimeters in both directions, in which case alternate intersections may be tied securely to prevent displacement during concrete placement.

The supports for reinforcing steel shall not be spaced more than one and two-tenths (1.2) meters apart transversely or longitudinally. The placement of deck reinforcing steel shall not deviate more than ten (10) millimeters in the vertical direction or fifty (50) millimeters in the horizontal direction from the position shown on the plans.

Prior to the placement of bridge deck concrete, the Contractor, using the approved screed or finishing machine shall check and verify, in the presence of the Engineer, the minimum cover over reinforcing steel and total thickness of the deck. The verification process shall cover the entire surface of the deck with maximum intervals between checkpoints of three (3) meters in both the lateral and longitudinal direction.

All reinforcement shall have a concrete coverage of fifty (50) millimeters or more except as shown otherwise on the plans or specified herein.

Splicing. Splicing, except where shown on the plans, will not be permitted without the approval of the Engineer. Lap lengths shall be as shown on the plans. Proprietary mechanical splicing devices shall be used only with the prior approval of the Engineer in writing.

No measurement or payment shall be made for additional reinforcement steel used for splices not shown on the plans. Splices shall be avoided at points of maximum stress. They shall, where possible, be staggered, and shall be designed to develop the strength of the bar without exceeding the allowable unit bond stress. Unless otherwise shown on the plans, all bars shall be lapped a minimum of fifty (50) diameters. Unless otherwise shown on the plans, splices in adjacent lines of reinforcing bars shall be staggered.

Welded Wire Mesh Reinforcement for Structures. Welded wire mesh reinforcement shall be of the sizes and spacing of bars and sheets as shown on the plans. Welded wire fabric furnished under this specification shall conform to the requirements of AASHTO M55. If mesh is shipped in rolls, the Contractor shall straighten them into flat sheets before placing. He shall splice sheets of mesh by overlapping not less than one mesh wide plus fifty (50) millimeters and shall securely fasten them at the ends and edges.

Drilled Shaft Reinforcing. The reinforcing steel unit for the shaft consisting of longitudinal bars and spiral hooping or lateral ties shall be completely assembled and placed into position as a unit for shafts of seven hundred fifty (750) millimeters in diameter and less. The longitudinal bars shall be tied to the spiral reinforcement at intervals, not to exceed four hundred fifty (450) millimeters on centers, and such tying shall be staggered on the various bars in order to provide a rigid unit. Bars shall be tied to lateral tie bars at all intersections. The lower end of each vertical bar shall be supported upon a suitable precast concrete spacer block. Side spacer blocks of concrete shall be used at suitable intervals along the unit to insure adequate spacing for the entire length of the shaft.

Welding of Reinforcement. Reinforcement in structures shall not be welded except where indicated on the drawings or by written approval of the Engineer. All welding of reinforcing steel where approved by the Engineer, shall conform to AWS D12.1, "Recommended Practices for Welding Reinforced Steel, Metal Inserts and Connections in Reinforced Concrete Construction." However, do not weld reinforcing steel if the chemical composition of the steel exceeds the percentages in Table below.

?TABLE - REINFORCING STEEL COMPONENTS

Use welders that are currently certified. When required in the contract, test each weld using magnetic particle, radiography or other non-destructive inspection techniques.

Mechanical couplers may be used in lieu of welding if approved. Use couplers with a yield strength that is at least one hundred twenty-five percent (125%) of the required yield strength of the reinforcing steel.

Epoxy Coated Reinforcing Steel. Support coated bars on padded contact areas. Pad all bundled bands. Lift with a strong back, multiple supports or a platform bridge. Prevent bar to bar abrasion. Do not drop or drag bundles.

Before placement, inspect coated bars for damage to the coating. Patch all defects in the coating that are discernible to the unaided eye with a prequalified patching/repair material according to AASHTO M 284. Clean areas to be patched by removing all surface contaminants and damaged coating. Roughen the area to be patched before applying the patching material. Where rust is present, remove the rust by blast cleaning or power tool cleaning immediately before applying the patching material.

Promptly treat the bar according to the resin manufacturer's recommendations and before detrimental oxidation occurs. Overlap the patching material onto the original coating for fifty (50) millimeters or as recommended by the manufacturer. Provide a minimum 8 mil (200 mm) dry film thickness on the patched areas.

Take necessary steps to minimize damage to the epoxy coating of installed bars. Clean and patch any damage to the coating noted after installation as described above.

Field repairs will not be allowed on bars that have severely damaged coatings. Replace bars with severely damaged coatings. A severely damaged coating is defined as a coating with a total damaged area in any three hundred (300) millimeter length of bar that exceeds five percent (5%) of the surface area of that portion of the bar. Coat mechanical splices after splice installation according to AASHTO M 284 for patching damaged epoxy coatings.

QUALITY ASSURANCE PROCEDURES. Reinforcing steel and epoxy coating material shall be evaluated and accepted under "Certification of Compliance," as outlined in the following procedures:

Three (3) copies of a mill test report shall be furnished to the Engineer for each lot of billet- steel reinforcement bars proposed for use on the project. The mill test report shall be sworn to for the manufacturer of the steel by a person having legal authority to bind the manufacturer and shall show the following information:

1. The process or processes used in the manufacture of the steel from which the bars were rolled.
2. Identification of each heat of open hearth, basic oxygen, or electric furnace and/or each lot of acid bessemer steel from which the bars are rolled.
3. Chemical and physical properties of the heat from which the bars were rolled.

The bars in each lot shall be legibly tagged by the manufacturer and/or fabricator before the lot is offered for inspection. The tag shall show the manufacturer's test number and lot number or other designation that will identify the material with the certificate issued for that lot of steel.

The fabricator shall furnish three (3) copies of a certification which shows the heat number or numbers from which each size of bar in the shipment was fabricated.

The sampling and testing of reinforcement bars may be made at the source of supply when the quantity to be shipped or other conditions warrant such inspection. Bars not inspected before shipment will be inspected after arrival on the Work. Sample bars shall be a minimum of one (1) meter in length. Bars sampled at the Work site shall be replaced by the Contractor without additional compensation. The Engineer reserves the right to resample and inspect all reinforcement steel upon its arrival at the Work site.

CONCRETE MATERIALS

Portland Cement. Cement shall be either Types I, II M, III or V conforming to the requirements specified in ASTM C150 or Type IP(MS) conforming to AASHTO M240. Only one type and brand of cement shall be used in any individual structural member. Mixing of types or brands shall not be permitted.

Cement shall originate from manufacturers approved by the Engineer and shall be accompanied by a Certificate of Compliance and/or a laboratory test certificate furnished by the manufacturer. Portland cement shall be tested as stated in MRDTM 504 and shall have a compressive strength of standard cement mortar samples in accordance with ASTM C-150 or AASHTO M-240. The Engineer reserves the right to order a retest of the cement at any time.

Approval of cement quality shall not relieve the contractor of the responsibility to fabricate concrete of the specified strength. The Contractor shall bear all costs in connection with the Certificates of Compliance and laboratory tests. When factory tests or field tests, completed subsequent to the original approval tests, show that the cement does not comply with the specifications, the entire lot from which the sample was taken will be rejected and the Contractor shall immediately remove the rejected material from the site and replace it with cement which meets the required specifications.

Storage capacity shall be sufficient to meet the concrete production requirements for thirty (30) working days unless in the opinion of the Engineer, the supply from the manufacturer is so limited that more storage capacity is necessary. Cement shall be stored in moistureproof storage sheds. Sacked cement shall be piled to permit access for tally, inspection and identification. Neither stale, caked, nor reclaimed or resacked cement shall be used. The Contractor shall not store cement in areas subject to flooding.

Cement remaining in bulk storage at the mill, prior to shipment, for more than six (6) months or cement stored in bags in local storage by the Contractor or a vendor for more than three (3) months after shipment from the mill, may be retested before use and will be rejected if it fails to meet any of the requirements of these specifications.

Aggregate: Aggregate shall be free from clay coating, clay balls and other extraneous materials. Aggregate shall be of such character that it is possible to produce workable concrete meeting all specified requirements. It shall not contain materials which may adversely attack the reinforcement or materials in such a form or quantity to reduce the strength and durability of the concrete. If aggregate is found to be deleterious or potentially deleterious, as the terms are used in ASTM C 289, the Contractor may offer to furnish a mineral admixture in an attempt to utilize the aggregate source, and the performance of the selected mineral admixture shall be tested following the ASTM C441 prior to the final approval of the Engineer.

Fine Aggregate. Fine concrete aggregate shall conform to AASHTO M 6 and shall consist of natural, manufactured, or combinations of sand. Fine aggregate shall be thoroughly and uniformly washed unless otherwise approved by the Engineer.

Fine concrete aggregate shall meet the following requirements. Deleterious substances such as, but not limit to, pyrites, coal, or micas shall not exceed two percent (2%) by weight.

Fine aggregate shall meet the following requirements when tested by MRDTM 204:

TABLE - CONCRETE FINE AGGREGATE GRADATIONS

If the fineness modulus varies by more than two-tenths (0.2) from the value assumed in the concrete mix design, the use of such fine aggregate shall be discontinued until suitable adjustments can be made in the mix proportions to compensate for the difference in gradation.

In addition to the above and when directed by the Engineer, fine aggregate shall be tested in accordance with MRDTM 303 for determination of Total Moisture Content and MRDTM 306 for Surface Moisture.

Coarse Aggregate. Coarse concrete aggregate shall conform to AASHTO M 80 and shall consist of gravel, crushed gravel or crushed stone. Coarse aggregate shall not contain materials such as iron pyrites, coal, mica, laminated materials, or other materials which may adversely affect the strength and durability of the concrete.

Coarse concrete aggregate shall meet the following requirements:

Coarse concrete aggregate shall meet the following gradation requirements when tested in accordance with MRDTM 204 and shall be uniformly graded within the following limits:

?CONCRETE COARSE AGGREGATE GRADATIONS

?Percent Passing

In addition to the above an when directed by the Engineer, coarse aggregate shall be tested in accordance with MRDTM 303 for determination of Total Moisture Content, MRDTM 304 for Specific Gravity and Absorption and MRDTM 308 for Unit Mass and Voids in Aggregates.

Combined Aggregate. Approved coarse aggregate and fine concrete aggregate in each batch of concrete shall be combined in proportions as approved by the Engineer.

The combined concrete aggregate gradation used in the Work shall be as specified, except that when approved by the Engineer, a Size C coarse aggregate shall be used for curbs, handrails, parapets, posts and other similar sections or members with reinforcement spacing too close to permit proper placement and consolidation of the concrete. Changes from one gradation to another shall not be made during the progress of the work unless approved by the Engineer; and shall meet the following requirements for the combined aggregates:

The water-soluble chlorides and sulfates limits specified for the fine and coarse aggregate individually, are subject to the following overriding requirement:

?The total water-soluble chloride content (AASHTO T260) in any mix from all sources, including any chloride present in other materials and the mixing water, shall not exceed the following limits as a percentage of the weight of cement in the mix.

In case of any likeliness of alkali reactivity the following further tests shall be conducted, as soon as practicable after the Contract is awarded to the Contractor.

• Potential Reactivity Tests.

1. Gel Pat Test (National Building Studies, Research Paper No. 14).
2. ASTM Test C 289 - Standard Test Method for Potential Alkali-Silica Reactivity of Aggregates (Chemical Method).
3. ASTM Test C 227 - Standard Test Method for Potential Alkali-Silica Reactivity of Aggregates (Mortar Bar Method).

• ?Shrinkage.

1. The properties of the aggregates shall be such that the Drying Shrinkage of concrete prepared and tested in accordance with the United Kingdom Building Research Station Digest No. 35 (Second Series) shall not exceed forty five thousandths percent (0.045%).
2. The initial Drying Shrinkage of all the proposed concrete mixes prepared and tested in accordance with BS 1881 shall not exceed six hundredths percent (0.06%).

• Reactivity.

1. Aggregates for use in concrete or mortar that will be subject to wetting, extended exposure to humid atmosphere, or contact with moist ground, shall not contain any materials that are deleteriously reactive with the alkalis in the cement, or any which may be additionally present in the aggregates and mixing water or water incontact with the concrete or mortar, in amounts sufficient to cause excessive localized or general expansion of concrete or mortar.
2. Under no circumstances shall the Contractor use Dacite Andesite, hyolites, Opal Cherts, or Tuffs.
3. Coarse and fine aggregates shall be tested for reactivity potential in accordance with the methods listed above and shall satisfy the various criteria given for innocuous aggregates in the foregoing standards.
4. It shall be noted that the above involve a testing period of eight (8) to twenty one (21) weeks.

• Petrographic examination and description, including approximate composition, ASTM C295.

The above additional tests may be waived only with the written approval of the Materials and Research Department of the Ministry, where evidence can be produced that satisfactory test results are already available for materials originating from the same sources with those to be used.

Water. All sources of water for use with cement shall be approved by the Engineer. If at any time during construction the water from an approved source becomes unsatisfactory, the Contractor will be required to provide satisfactory water from some other source.

Water shall be free from injurious quantities of oil, alkali, vegetable matter and salt. The water shall be reasonably clear and shall contain not more than twenty-five hundredths percent (0.25%) total solids and organic matter when tested in accordance with MRDTM 514.

If the specific conductance is less than fifteen hundred (1500) microhms per centimeter, the total solids content requirement may be waived. Water for washing aggregates, mixing, and curing shall contain no chlorides as Cl, nor sulfates as exceeding the values for the type of work as follows:

Mortar prepared with water submitted by the Contractor for test shall show no marked change in time of set, no indication of unsoundness and a reduction of not more than ten (10) percent in mortar strength when compared with mortar made with water of known satisfactory quality.

Admixtures. Admixtures to be used in concrete shall conform to the requirements specified in these specifications, the special specifications and as approved by the Engineer. The Contractor may offer to furnish admixtures at his own expense when admixtures are not specified. The Engineer shall consider the offer and approve or disapprove the use.

Chemical and air entraining admixtures containing chlorides as determined by ASTM Designation C 1152 shall not be used in reinforced or prestressed concrete.

Calcium chloride shall not be used in concrete containing any embedded metals, including reinforcing steel, unless otherwise specified.

If more than one admixture is to be used, such admixtures shall be compatible in combination as used in the concrete.

Admixture shall conform to the following requirements

Mineral Admixtures?ASTM Designation C618 Loss on ignition shall not exceed four percent (4%).

All admixtures to be used in the work shall be accompanied by a Certificate of Compliance signed by a responsible representative of the manufacturer.

The contractor will be permitted to use admixtures conforming to the requirements in AASHTO M194 for Type A - Water reducing, Type B - Set-retarding, or Type D - Water reducing and retarding Type F - water-reducing, high range and Type G - Water-reducing, high range and retarding to facilitate the work, subject to the following:

• When concrete is designated by compressive strength, no reduction in the minimum required cement will be allowed.
• When the required use of air entraining admixture is specified or ordered by the Engineer, the air entraining agent shall be used in amounts required to produce a concrete having the specified air content as determined by MRDTM 519 or MRDTM 521.

Optional use of air entraining admixture will be permitted in the amounts which will result in concrete with an air content not exceeding four percent (4%). The contractor shall include the air entraining admixture and air content as specified in these Specifications.

When the use of mineral admixtures is specified or their use is approved by the Engineer, the minimum amount of admixture and amount and type of Portland cement will be specified or ordered. If the minimum amounts are not specified, the concrete shall be proportioned to conform to the following criteria based on a series of trial mixes:

1. Concrete shall contain the specified cement content using Type IP(MS) conforming to Subsection 5.01.2, "Materials" in these General Specifications.
2. The concrete shall contain the specified cement content consisting of not less than eighty-five percent (85%) Type II M in addition to not less than fifteen percent (15%) by weight of approved mineral admixture conforming to the requirements of ASTM C618, except Type C mineral admixture will not be permitted in conjunction with alkali-silica reactive aggregate, as determined in Paragraph 5.01.2.2 "Aggregate" in these General Specifications.
3. High range admixtures shall comply with the special procedures contained in these Specifications.