701-Portland Cement Concrete for Structures

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701
Portland Cement Concrete for Structures
2012 STANDARD SPECIFICATIONS FOR CONSTRUCTION - SECTION 701


GENERAL

Unless otherwise specified, air entrained concrete will be required for structural work.

Defoaming (air-detraining) admixtures will not be permitted. All concrete will be air-entrained.

Sack refers to a 94 pound (42.64 kg) sack of cement. Refer to Division 6 of this manual for equipment requirements for mixing and placing concrete.

The Contractor will provide communication service from the work site to the batching plant that will always be available to the Engineer during the concreting operations.

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MATERIALS

Materials
Specification Reference

Cement

901

Fly Ash

901

Ground Granulated Blast-Furnace Slag (GGBFS)

901

Coarse Aggregate 6A, 6AA

902

Fine Aggregate 2NS, 2SS

902

Concrete Admixtures

903

Water

911

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Stone Sand

Stone sand 2SS will be permitted only in concrete to be used in structure concrete not exposed to vehicular traffic.

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Ground Granulated Blast-Furnace Slag (GGBFS)

GGBFS may be used as part of the cementing material with Type IA or Type I Portland cement, which is reproduced here for reference.

All material must be inspected and approved before being incorporated in the work. Materials should be checked for damage in shipment or storage and to insure conformity to the required dimension, appearance and condition. Following are four main methods of material inspection acceptance:

Material may be tested or sampled at the point of production, manufacture or supplier's storage by the Construction and Technology Support Area or an appointed representative. The project office should receive the resulting test report before using the material. The material should be checked for markings, such as lot number, to identify with the test report.

Material may be certified by the supplier as meeting the specified requirements. The certification should be received in the project office before using.

Material may be sampled at the job site. The sample is tested by Construction and Technology and a report is sent to the resident/project Engineer before using.

The material may be visually inspected at the site by project personnel to insure conformance with specified requirements. Then, a visual inspection report is prepared and submitted. The required method of inspection is listed for all materials in Division 9 of the manual and is to be followed. If in doubt, the Region materials staff should be consulted.

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Stockpiling Aggregate

The following actions will be adhered to when furnishing and handling aggregate:

Fine and Coarse - Will be furnished, stocked piled and handled to prevent segregation.

Aggregate Secured for Stockpiles - The ground area will be firm, reasonably level, and thoroughly cleaned of all foreign materials.

Bottom 1 foot (0.3 m) of the Stockpile - Will not be used if paved areas are not used.

Frozen Aggregate Lumps - Will not be used.

Equipment - Causing contamination or degradation will not be used.

Aggregate Moisture Content - Will be kept uniform for each day's run without evidence of any surplus water.

Slag Stockpiles or Other Highly Absorptive Aggregates - Will be kept continuously wet to maintain uniform moisture content.

MDOT Fine & Coarse Aggregates - Will be stocked in separate piles or bins apart from aggregates to be used in other work.

Coarse Aggregate (Blend of Two or More Gradations) - Will be stockpiled separately for each gradation.

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Cementing Materials

Cement, ground granulated blast furnace slag and fly ash furnished to the project in bulk form will be stored in separate weatherproof bins. Wet or contaminated material will not be used.

If the Contractor changes the cement type or source, fly ash source or class or ground blast furnace slag source or grade, the bin will be emptied to within the quantity used for two concrete batches before refilling with new material. Notice of the material change will be recorded on the first ticket.

The Contractor will furnish the Engineer with a shipment notice (copy) with the following information:

  • the quantities of cement, ground blast furnace slag or fly ash.
  • a certification that the material meets MDOT requirements.
Table 701-1 - Concrete Structure Mixtures
Table 701-1 - Concrete Structure Mixtures (metric)

Footnotes for use with Table 701-1:

(a) Unless otherwise specified, Coarse Aggregate 6AA shall be used for exposed structural concrete used in bridges, retaining walls, and pumphouses.

(b) Concrete mixtures containing Type IS-A, I(SM)-A, IP-A, or I(PM)-A cement, or containing ground granulated blast-furnace slag or fly ash, shall not be used on projects in the Lower Peninsula between October 15 and April 1 nor in the Upper Peninsula between October 1 and April 15, except this restriction does not apply to Grade S1 concrete used in foundation piling below ground level, and Grade T concrete used in tremie construction.

(c) Non-air-entraining cement corresponding to the types of air-entraining cement listed may be used with an approved air-entraining admixture to produce the specified air content.

(d) The quantity of admixture shall be as indicated in the Materials Source Guide to provide reduction in mixing water and is required for Grade D concrete and Grades S1, S2, S3 and T having reduced cement content. The admixture used in Grade D concrete shall be a water-reducing retarder admixture and shall be used in such amounts to provide the necessary retardation of setting. When the air temperature is not expected to exceed 60 of for the day, the Contractor shall have the option of using a water-reducing admixture or a water-reducing retarding admixture. Grade D concrete used in concrete diaphragms shall contain either a water-reducing admixture or a water-reducing retarding admixture.

(e) The mix design basis for bulk volume (dry, loose) of coarse aggregate per unit volume of concrete is 68% for Grade S1; 70% for Grades D, S2, T, and S3.

(f) Flexural strength may be used for determining when to remove forms. Compressive strength shall be used for acceptance in all other situations.

(g) Mid-range.

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Ready-Mixed Concrete

Ready mixed concrete is batched and delivered as central mixed or truck mixed concrete.

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Types of Concrete

Central Mixed - Completely mixed in a central mixer and transported to the delivery point in a truck agitator, a truck mixer or in approved, non-agitating equipment.

Truck Mixed - Completely mixed in a truck mixer with an approved revolution counter, at the plant site.

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Batch Mixing

Functions of Parts:

Drum or blade - Will revolve at the speed or within the speed range recommended by the manufacturer and shown on a metal plate attached to the mixer.

Mixing Time - Equals the time all cement and aggregates are in the drum until beginning of discharging the concrete. For multi-compartment mixers, the mixing time will include the transfer time between drum

Ingredients - Will be charged into the mixer so that some water will enter before cement and aggregate; substantially all the water will be in the drum before one third the specified mixing time has elapsed.

The mixer drum and truck mixers must be completely emptied after each batch before recharging.

The maximum batch size may not exceed the mixer capacity as shown on the attached metal plate. Batch sizes for agitating units and truck mixers used to transport central mixed concrete may not exceed the manufacturer's recommendation for maximum agitating capacity.

Batch Mixing Method
Minimum
Mixing Time

Central Mix-Turbine

45 seconds

Central Mixed-Revolving drums & pugmills

60 seconds

Central Mixed-Revolving drums & pugmills 1 yd3 (0.75 m3)

90 seconds

Truck Mixed Concrete

70 revolutions

If Volumetric Batching and Continuous Mixing these methods are used, the concrete will be proportioned, mixed and discharged according to ASTM C 685.

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Elapsed Time

The time between charging the mixer and concrete discharge completion into the work will not exceed that specified in Table 701-2 of the Standard Specifications for Construction which is reproduced here for reference.

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Charging Time

Charging time is the time the cement contacts the mixing water or damp aggregates.

When the anticipated time between charging and discharge completion exceeds 30 minutes, the concrete will be continuously agitated.


Table 701-2 Maximum Time Between Charging of Mixer and Placing of Concrete, Minutes
Type of Unit
Temperature of Concrete (ASTM C1064)
Below 60°F
(16°C)
60°F to 85°F
(16°C to 30°C)
Above 85°F
(30°C)

Closed Top Agitating Units & Truck Mixers

90
60
45

Closed Top Agitating Units & Truck Mixers with Concrete Containing Water-Reducing Retarding Admixture (a)

120
90
70

Does not apply to superstructure concrete. Superstructure concrete will meet the time limits for closed top agitating units and truck mixers.

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Adding Water

For concrete transported in truck mixers:

If additional mixing water is required to obtain the specified slump and the truck mixer is not loaded to more than its rated mixing capacity, water may be added.

After all water is added, a minimum of 30 revolutions at mixing speed will be required before discharging any concrete. The additional water will be added and the additional mixing completed at the work site within the maximum time specified in Table 701-2.

Except for fog curing, no water will be added to the concrete during discharge or placement. In particular, no water will be added to truck chutes or to pump or slipform hoppers.

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Concrete Temperature and Weather Restrictions

Fresh concrete must be between 45°F and 90°F (7°C & 32°C) when placed. The ingredients will be heated whenever necessary to produce concrete having a temperature of > 45°F (7°C). Heated concrete will be obtained by heating the water or aggregates, or both.

WHEN the ingredients are . . .
THEN the concrete temperature . . .

heated

will not exceed 80°F (26°C).

heated and placed in insulated forms

will not exceed 70°F (21°C).

See subsections 706.03.H.2 and 706.03.J of the Standard Specifications for Construction for additional information on equipment and permissible evaporation rates for paving concrete bridge decks.

Temperature will not be heated over 150°F (65°C). The water will be mixed with the aggregates before the cement is added. Aggregate will be free of ice and frozen lumps at batching time.

Stockpiled aggregate will be heated by steam or hot water coils, live steam or by indirect hot air.

Direct flame heating will not be permitted. Accumulated condensation from heating will be compensated for during batching operations to maintain slump within allowable limits.

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Calcium Chloride

Accelerators containing calcium chloride will not be used in concrete for bridges or where the concrete will contain embedded aluminum or galvanized steel.

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Concrete Mixture Requirements

The Contractor is responsible for determining the concrete mixture proportions (mix design) on projects containing Quality Control/Quality Assurance (QC/QA) provisions. The Engineer will provide the mix design requirements on all other projects based on the Contractor's choice of materials from approved sources. Mixture proportions will be designed to provide concrete that meets the requirements in Table 701-1; however, the Contractor must immediately correct concrete production and placement methods if the requirements are not met.

Mix designs will designate the amounts of:

  • cementitious materials.
  • fine aggregate.
  • coarse aggregate.
  • water required per cubic yard (cubic meter) of concrete.
  • admixtures.

Contractor modifications to MDOT’s mix design are restricted to the following at no cost to MDOT:

  • increased cement content.
  • increased coarse aggregate content.
  • decreased water content.

The Contractor may only use ground blast-furnace slag when permitted by contract documents.

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Mixes Using Fly Ash or Ground Granulated Blast-Furnace Slag (GGBFS)

Fly ash may be used in the concrete mixture according to Table 701-1. A greater quantity of fly ash may be used, subject to the following requirements:

A Contractor mix design, produced by a testing laboratory, conforming to ASTM C 1077, must be submitted for the Engineer’s approval. The submittal must include documentation of the slump, air content and a 28-day compressive strength. The compressive strength in Table 701-1 must be exceeded by at least 500 psi (3.5 MPa).

Concrete will be made and cured according to ASTM C 192, with three batches (minimum) made and tested according to the concrete grade. Any subsequent change in the mixture constituents will require that new laboratory data must be submitted for the Engineer’s reapproval.

Type I or IA Portland cement must be used.

The cement quantity for Type I or Type IA shown in Table 701-1 may be reduced up to a maximum of 25 percent for fly ash or up to a maximum of 40 percent GGBFS substitution.

The fly ash weight on GGBFS weights shall be equal to the weight of the cement removed.

If the fly ash and GGBFS are used in the same mixture, the cement quality shown in Table 701-1 may be reduced up to a maximum of 40 percent of which fly ash quantity shall not exceed 15 percent.

Structural Concrete, including concrete placed in steel shell piles, requires 6.5 ± 1.5 percent entrained air (non-air entrained concrete will be permitted in piles not subject to freezing). The only exceptions are:

Concrete
Air Content (Percent)

Air-Entrained

6.5 +/- 1.5

Exceptions

Containing Type F and G admixtures

7.0 +/- 1.5

Furnished for placement by slipform methods and having a slump of 1-1/2 inches (40mm) or less

4.5

Used for cast-in-place concrete slope paving and related headers

6.5 +/- 3.0

That lies in finished work at least 3 feet (1.0m) below the ground's surface or entirely under water

< 5

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Admixtures

Changes in the amount of air-entrained admixture used should be carefully monitored.

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Air-Entrained Admixtures

When the Contractor adjusts the amount of air entraining admixtures used, the actual amount used per sack of cement or per concrete batch will be recorded on the first delivery ticket following the adjustment.

When concrete having low air content is received at the work site in truck mixers, the Contractor may add additional air entraining admixture at the site, mixed in a small amount of water [quart (liter)], with a minimum of 30 mix revolutions until adjustments can be made at the batching plant.

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Water-Reducing Admixtures

Concrete mixtures containing a water-reducing or water-reducing retarding admixture must meet the requirements for strength, slump and air content required for the respective concrete grade without an admixture.

When a water-reducing admixture is used, it shall be added according to the manufacturer’s recommendations. The dosage used will not be less than the amount shown on the Qualified Products List for Admixtures for Concrete found in the Materials Source Guide. Admixture dosage rates will be based on the total cementitious material (cement plus fly ash or granulated blast furnace slag when used) in the concrete.

When a concrete mixture containing Type A, D, or mid-range (MR) admixture requires retempering due to loss of slump, the consistency may be restored according to subsection 701.03.B.4 of the Standard Specifications for Construction.

When a concrete mixture containing a Type F or G admixture requires retempering due to loss of slump, the consistency shall be restored only by the further addition of Type F or G admixture. The additional admixture may be added by manual methods. The mixing drum must be turned a minimum of 45 revolutions at mixing speed after addition of admixture.

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CONSTRUCTION

-Reserved-

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MEASUREMENT AND PAYMENT

Sampling and Testing Concrete

Samples will be taken according to MTM 207.

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Determining Air Content

Freshly Mixed Concrete determined by - MDOT’s modification of Standard Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method, ASTM C 231, or Standard Test Method for Air Content of Freshly Mixed Concrete by the Volumetric Method, ASTM C 173.

Freshly Mixed Concrete Containing Slag or Other Highly Porous Coarse Aggregate determined by - Standard Test Method for Air Content of Freshly Mixed Concrete by the Volumetric Method, ASTM C 173 or Volumetric method, ASTM C 173.

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Determining Concrete Volume

The Engineer will determine the concrete volume used each day, or for each individual pour based on the number of batches placed in the work and the nominal concrete volume per batch. This quantity will be compared with the estimated concrete volume required based on plan quantities.

If the concrete volume used overruns the plan quantity by 6 percent or more, or underruns the plan quantity, all factors that may affect the concrete quantity will be checked and all irregularities corrected.

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Slump

The concrete slump will:

  • be determined by the ASTM C 143 slump cone test, but the samples will be taken according to MTM 207 at the work site.
  • not exceed the limits shown in Table 701-1 for the grade and usage specified.

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Strength

Concrete test specimens will be made, at frequent intervals, from the concrete being incorporated in the work. Concrete for test specimens and labor for making and transporting them to the appropriate MDOT Region lab will be furnished without charge by the Contractor. Molds and testing equipment for specimens will be furnished by MDOT. Removal of forms may be based on flexural strength. Compressive strength will be used for acceptance.

The Contractor's personnel doing designated sampling and testing will be a certified concrete technician(s) (Michigan Level I or II) through a program certified by the Michigan Concrete Association or through the Michigan Concrete Paving Association (Level I - three-year certification). The Contractor will furnish the name(s) and credentials of the concrete technician(s) to the MDOT Engineer before sampling and testing.

Test specimens will be made according to the Method of Making and Curing Concrete Compressive and Flexural Strength Test Specimens in the Field, AASHTO T 23. Test specimens for determining conformance to the strengths shown in Table 701-1 will be cured according to Section 9.2 of T 23, Curing Specimens as the Basis for Acceptance or Section 9.3 of T 23, Curing Specimens as the Basis for Acceptance at Remote Sites.

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Concrete Cylinders

Concrete cylinders will be compression tested according to AASHTO T 22, Standard Method of Test for Compressive Strength of Cylindrical Concrete Specimens. Unbonded caps allowed in the annex of AASHTO T 22 are acceptable. Use unbonded caps according to MTM 206, Test Method for Use of Unbonded Caps in Determination of Compressive Strength of Hardened Concrete Cylinders.

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Flexural Strength

Flexural strength will be determined according to MDOT procedures that are based on a modification of Test Method for Flexural Strength of Concrete (Using Simple Beams with Center-Point Loading), ASTM C 293. If compressive strength is determined on beam ends according to ASTM C 116, the strength determined by that method will be reduced by 20 percent to provide results comparable to results that would be obtained on a cylinder having a height-to-diameter ratio of two.

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Non-QA Projects

If the average strength from compression tests on two companion cylinders is less than the 28-day strength shown in Table 701-1, the Engineer may:

Require the Contractor to remove and replace the concrete at no cost to MDOT.

Determine if the concrete has sufficient structural strength; if so, prorate the unit price for affected pay items and quantity represented based on the following formula:

Adjusted Unit Price = (Tested Strength / Strength*) X (Unit Price)

*Minimum Concrete Strength shown in Table 701-1

Allow the Contractor to submit, for approval, a plan for corrective action to be done at no cost to MDOT. If the plan for corrective action is not approved, either option (above) may be applied.

Reference Division 6 for pay adjustments on Concrete QC/QA projects.

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Opening to Traffic

The structural strength for opening to construction traffic or regular traffic, for removing shoring and forms or for other similar purposes, will be determined by one or more of the following methods. Refer to subsection 104.11 for requirement for opening to construction traffic.

A series of test cylinders or beams may be made and cured under environmental conditions similar to the pavement or structure for use in monitoring strength gain in the concrete.

Nondestructive tests done according to ASTM C 803 Penetration Resistance of Hardened Concrete or C 805 Rebound Number of Hardened Concrete. Testing for calibration and strength determination will be done in the Engineer’s presence. Nondestructive structure tests will be made by the Contractor at locations the Engineer designates or approves.

Concrete containing ground blast-furnace slag or fly ash may gain strength at a slower rate during early stages (before 28 days) than if only Portland cement was used. The Contractor will adjust operations as necessary for staging activities to conform with the actual strength gained by the concrete.

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