16 - UFC 3-250-04 Standard Practice For Concrete Pavements With Change 2.pdf

UFC 3-250-04

16 January 2004 including Change 2 - 29 July 2009

UNIFIED FACILITIES CRITERIA (UFC)

STANDARD PRACTICE FOR

CONCRETE PAVEMENTS

APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED

including Change 2 - 29 July 2009

UNIFIED FACILITIES CRITERIA (UFC)

DESIGN: STANDARD PRACTICE FOR CONCRETE PAVEMENTS

Any copyrighted material included in this UFC is identified at its point of use.

Use of the copyrighted material apart from this UFC must have the permission of the copyright holder.

U.S. ARMY CORPS OF ENGINEERS (Preparing Activity)

AIR FORCE CIVIL ENGINEER SUPPORT AGENCY

Record of Changes (changes are indicated by \1\ ... /1/)

Change No. Date Location 2 29 July 2009 Removed FA designation to indicate unification

This UFC supersedes TM 5-822-7, dated 16 August 1987 \2\and UFC 3-250-12N dated 8 June 2005/2/. The format of this UFC does not conform to UFC 1-300-01;

however, the format will be adjusted to conform at the next revision. The body of this UFC is the previous TM 5-822-7, dated 16 August 1987.

FOREWORD including Change 2 - 29 July 2009 \1\ The Unified Facilities Criteria (UFC) system is prescribed by MIL-STD 3007 and provides planning, design, construction, sustainment, restoration, and modernization criteria, and applies to the Military Departments, the Defense Agencies, and the DoD Field Activities in accordance with USD(AT&L) Memorandum dated 29 May 2002. UFC will be used for all DoD projects and work for other customers where appropriate. All construction outside of the United States is also governed by Status of forces Agreements (SOFA), Host Nation Funded Construction Agreements (HNFA), and in some instances, Bilateral Infrastructure Agreements (BIA.)

Therefore, the acquisition team must ensure compliance with the more stringent of the UFC, the SOFA, the HNFA, and the BIA, as applicable.

UFC are living documents and will be periodically reviewed, updated, and made available to users as part of the Services’ responsibility for providing technical criteria for military construction. Headquarters, U.S. Army Corps of Engineers (HQUSACE), Naval Facilities Engineering Command (NAVFAC), and Air Force Civil Engineer Support Agency (AFCESA) are responsible for administration of the UFC system. Defense agencies should contact the preparing service for document interpretation and improvements. Technical content of UFC is the responsibility of the cognizant DoD working group. Recommended changes with supporting rationale should be sent to the respective service proponent office by the following electronic form: Criteria Change Request (CCR). The form is also accessible from the Internet sites listed below.

UFC are effective upon issuance and are distributed only in electronic media from the following source:

• Whole Building Design Guide web site http://dod.wbdg.org/.

Hard copies of UFC p rinted from electronic media should be checked against the current electronic version prior to use to ensure that they are current.

AUTHORIZED BY:

DONALD L. BASHAM, P.E.

Chief, Engineering and Construction U.S. Army Corps of Engineers

DR. JAMES W WRIGHT, P.E.

Chief Engineer Naval Facilities Engineering Command

KATHLEEN I. FERGUSON, P.E.

The Deputy Civil Engineer DCS/Installations & Logistics Department of the Air Force

Dr. GET W. MOY, P.E.

Director, Installations Requirements and Management Office of the Deputy Under Secretary of Defense (Installations and Environment) http://www.wbdg.org/pdfs/ufc_implementation.pdf http://www.wbdg.org/ccb/browse_cat.php?o=29&c=4 http://dod.wbdg.org/

ARMY TM 5-822-7

AIR FORCE AFM 88-6, Chap. 8

DEPARTMENTS OF THE ARMY AND THE

AIR FORCE TECHNICAL MANUAL

STANDARD PRACTICE FOR CONCRETE PAVEMENTS

DEPARTMENTS OF THE ARMY AND THE AIR FORCE

AUGUST 1987

REPRODUCTION AUTHORIZATION/RESTRICTIONS

TECHNICAL MANUAL

No. 5-822-7

AIR FORCE MANUAL

No. 88-6, Chapter 8

HEADQUARTERS

DEPARTMENTS OF THE ARMY

AND THE AIR FORCE

Washington, DC 16 August 1987

STANDARD PRACTICE FOR CONCRETE PAVEMENTS

Paragraph Page

PURPOSE

SCOPE

RESPONSIBILITIES, STRENGTH, AND AIR CONTENT

CEMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ����

AGGREGATES

ADMIXTURES

POZZOLANS

MISCELLANEOUS MATERIALS

WATER

SAMPLING AND TESTING OF MATERIALS

DELIVERY AND STORAGE OF MATERIALS

GRADE CONTROL

PROPORTIONING

SUBGRADE, BASE, FORMS, AND STRING LINES

BATCHING AND MIXING

PLACING

FIELD TEST SPECIMENS

FINISHING

CURING

GRADE AND SURFACE -SMOOTHNESS REQUIREMENTS

TOLERANCES IN PAVEMENT THICKNESS

REPAIRS OF DEFECTIVE PAVEMENT SLABS

JOINTS

PAVEMENT PROTECTION

MEASUREMENTS

APPENDIX A: REFERENCES

APPENDIX B: THIN BONDED RIGID OVERLAYS FOR RIGID PAVEMENTS

APPENDIX C: STEEL-FIBER- REINFORCED CONCRETE

APPENDIX D: ROLLER-COMPACTED CONCRETE PAVEMENTS; DESIGN AND CONSTRUCTION

A-1 B-1 C-1 D-1 i

Figure 1.

2.

3.

D-1.

D-2.

D-3.

D-4.

D-5.

Table 1.

2.

3.

4.

5.

6.

7.

8.

C-1.

C-2.

D-1.

LIST OF FIGURES

Prediction of concrete rate of evaporation.

Air Force runway grooving requirements.

Special joint between new and existing pavement.

Typical layout for RCCP test section.

Compaction of first paving lane.

Compaction of interior paving lanes.

Construction of a cold joint.

Two-lift cold joint preparation.

LIST OF TABLES

Approximate relation between water-cement ratio and strengths of concrete Coarse aggregate size groups Grading of coarse aggregate Deleterious materials in coarse aggregates for airfield and heliport pavements Deleterious materials in coarse aggregates for other pavements Grading of fine aggregate Deleterious substances in fine aggregate Surface smoothness - airfield and heliport pavements Selected characteristics of fiber-reinforced airfield pavements Interim suggested maximum joint spacing for steel-fiber-reinforced concrete Vibratory rollers used in RCCP construction

STANDARD PRACTICE FOR CONCRETE PAVEMENTS

1. Purpose. This manual provides information on the materials and construction procedures for concrete pavements.

2. Scope. This manual describes the constituents to be used in concrete, the procedures to be used in manufacturing concrete, and the equipment and procedures to place, texture, and cure concrete for pavements.

3. Responsibilities, strength, and air content.

a. Responsibility for mixture proportioning. The responsibility for mixture proportioning must be clearly assigned to either the contractor or the contracting officer in the project specifications.

When the contracting officer is responsible for mixture proportioning, he will approve all concrete materials as well as determine and adjust propor-tions of all concrete mixtures as necessary to obtain the strength and quality of concrete required for the pavements. Cement will be a separate pay item in the contract. When the contractor is responsible for mixture proportioning, he will control all proportions of the concrete mixture necessary to obtain the strength and quality of the concrete required for the pavements, and cement will not be a separate pay item in the contract. However, the contracting officer is responsible for approving the quality of all materials the contractor uses in the concrete.

b. Approval responsibility. The contracting officer is responsible for approval of all materials, mixture proportions, plants, construction equipment, and construction procedures proposed for use by the contractor. The contractor must submit proposed mixtures if he is responsible for mixture propor-tioning; samples of all materials; and detailed descriptions of all plants, construction equipment, and proposed construction procedures prior to the start of construction.

c. Flexural strength. Structural designs are based on flexural strengths that the concrete is expected to obtain at 28 days for road pavements and 90 days for airfield pavements. These ages are not adequate for quality control in the field since a large amount of low-strength concrete could be placed before strength tests on samples revealed the problem.

Correlations can be established between a 14-day strength and the 28- or 90–day strength used in design, and this correlated 14-day strength can be used as a strength check for a more timely concrete mixture control in the field.

(l.) Materials and flexural strength. To select suitable flexural strengths for the design of pavements and for inclusion in contract specifica-tions, the contracting officer should have reliable information regarding flexural strengths obtainable with acceptable concrete materials which are available in the vicinity of the project. Typical design values for flexural strength of paving-quality concrete vary from 500 to 750 pounds per square inch (psi).

Numerous tests indicate considerable variation in the flexural strength of concrete when different aggregates or different cements are used. There are some indications that aggregate shape and modulus of elasticity are relatively more important in concrete flexural strength than in compressive strength. Also, after optimum flexural strength is reached, there usually is little increase in strength, even with a large increase in cement content. Mixture proportioning studies will be made in accordance with ACI 211.1 (see app A for referenced publications) to determine the flexural strengths to be used for the design of the project. The water-cement ratio-strength relations for mixture proportioning in ACI

211.1 are given in terms of compressive strength.

Table 1 gives some approximate guidance for relating the concrete modulus of rupture to the compressive strength-water cement ratio relation-ships given in ACI 211.1. All aggregates, cementitious materials, and admixtures used in the mixture proportioning studies will be representative of materials available for use in pavement construction.

In selecting a flexural strength for pavement design, suitable allowance will be made for variations in strength indicated by tests of different combina-tions of aggregate and cement. Pavement design will be based on a realistic and economical strength obtainable with available materials.

Table 1. Approximate relation between water-cement ratio and strengths of concrete (modified from ACI 211.1)

(eq 1)

TM 5-822-7/AFM 88-6, Chap. 8 characteristics of freshly mixed concrete and is required for the freezing and thawing resistance of hardened concrete. The use of entrained air in concrete will reduce strength, but because of the improved workability in the freshly mixed concrete, adjustments in aggregate proportions and reduction of water are normally possible that will negate or at least minimize the loss of strength. Proper propor-tioning and control of the air-entrained concrete mixture are essential in order to derive maximum benefits from improvement in the placability and durability of concrete with a minimum effect on flexural strength.

(2.) Percentage of air content. The specified air content will be 6 ± 1½ percent for concrete pavements located in regions where resistance to freezing and thawing is a prime consideration, and will be 5 ± 1½ percent for concrete pavements located in regions where frost action is not a factor and air entrainment is used primarily to improve the workability and placability of freshly mixed concrete.

Air content will be controlled in the field at the point within the specified range most appropriate for local conditions depending upon the severity of exposure and the quality and maximum size of aggregate. If slag aggregate is used, the air content will be deter-mined by the volumetric method as described in ASTM C 173. Where the aggregate is of compara-tively poor quality or when the maximum size is 1% inches or less, the air content will be controlled at 6 ± 1 percent. In such instances, where resistance to freezing and thawing is not a prime consideration, the air content will be 5 ± 1 percent. If further reduction in the air content or the use of non-air-entrained concrete is necessary, prior approval will be obtained from HQDA (DAEN-ECE-G), Wash-ington, DC 20314-1000 or the appropriate Air Force major command.

e. Cement content. Either the contractor or the contracting officer may be responsible for mixture proportioning. When the contractor is responsible for mixture proportioning, no separate payment will be made for cement. When the contracting officer is responsible for mixture proportioning, no limits for the quantity of cement content will be included in the contract specifications; the quantity of cement used per cubic yard of concrete will be determined by the contracting officer, and cement will be paid for under a separate bid item. When the concrete proposed for use on a paving project has a cement content of less than 470 pounds per cubic yard, prior approval will be obtained from HQDA (DAEN-

ECE-G) or the appropriate Air Force major command.

When concrete proportioning is the responsibility of the contractor and the cement content is less than 470 pounds per cubic yard, the results should be verified by two Corps of Engineers Division laboratories or commercial laboratories prior to submittal. The results of mixture proportioning studies for proposed aggregates and cements and the results of qualitative tests on aggregates and on resulting concretes will be submitted with requests for approval.

4. Cement.

a. Five portland cements designated as Types I through V are marketed today. ASTM C 150 provides a detailed specification for these cements. Type I portland cement is common or ordinary cement that is supplied unless another type is specified. Type II is modified portland cement that provides moderate resistance against sulfate attack and a lower heat of hydration than Type I cement. It is common for cement to be manufactured to meet the physical and chemical requirements of both Type I and II cements.

b. Type III cement is high early-strength cement.

Ultimate strength is about the same as Type I cement, but Type III cement has a 3-day compressive strength approximately equal to the Type I cement’s 7-day strength. The cost of Type III cement in lieu of Types I or II cement can only be justified when early strength gain is needed to open pavements to traffic or the high heat of hydration is needed for cool construction periods. Type IV cement has a low heat of hydration that may be useful in mass concrete but is not likely to be encountered in pavement construction. Type V sulfate-resistant cement should be used when the concrete will be exposed to severe sulfate attack.

The potential for severe sulfate attack exists when the concrete is exposed to water-soluble sulfate in soil or water in excess of 0.20 percent or 1,500 parts per million. The potential for moderate sulfate attack exists for sulfate contents in excess of 0.10, or 150 parts per million.

c. High alumina cement, also known as aluminous or calcium aluminate cement, gains most of its strength in one day, has a high exotherm, is resistant to chemical attack, and is a refractory material.

When exposed to warm, moist conditions, it will undergo a long-term strength loss. High alumina cement may find some specialized applications in pavement construction where its rapid strength gain, high exotherm, or refractory properties outweigh its cost and long-term strength loss.

d. There are also some expansive cements, designated as Types K, M, and S in ASTM C 845, that may find some application where concrete shrinkage needs to be minimized or avoided.

However, there is little experience with these cements, and they will require careful investigation before use in pavement construction.

e. At least one United States manufacturer is actively promoting a slag cement made by grinding iron blast furnace slag. This may be substituted for up to 50 percent of the portland cement in a pavement mixture if tests show the required final properties are achieved in the hardened concrete. Preblended mixes of portland-pozzolan (Type IP), and portland-slag cements (Type IS) are described in ASTM C 595 and are acceptable for use in pavements.

5. Aggregates.

a. Approval of aggregates. The contractor will use aggregates from approved sources. If the contractor proposes to use aggregates from an unapproved source, the Government will be responsible for conducting tests to determine whether the proposed aggregates will meet the requirements of the project.

Sampling and aggregate delivery costs will be borne by the contractor. The contract specifications will state aggregate sample size, delivery location, and required evaluation time for the proposed aggre-gates. For small jobs requiring 1,600 cubic yards or less of concrete, all tests for aggregates from an unapproved source will be done by the contractor.

b. Quality. Aggregates must generally meet the requirements of ASTM C 33, as modified in the following paragraphs. These requirements can be adjusted as necessary to reflect local experience with specific aggregates to insure economical use of aggregates to meet project requirements. The magnesium or sulfate soundness test (ASTM C 88) required in ASTM C 33 has not been consistently successful in identifying frost-resistant aggregate.

Consequently, if an otherwise suitable aggregate fails this test, it should be further investigated using freezing and thawing tests as described in ASTM C 666 or ASTM C 682 before it is finally rejected. Similarly, if an otherwise suitable aggre-gate fails the Los Angeles (LA) abrasion test (ASTM C 131 or C 535), it can be accepted if it has a history of local use showing that it can be processed without unacceptable degradation and that it is durable under weathering and traffic conditions comparable to the project under investigation.

c. Recycled concrete as aggregate. Existing concrete may be taken up, crushed to suitable gradation, and re-used as concrete aggregate. It must meet all the requirements for gradation and quality that conventional aggregates must meet.

All reinforcing steel should be removed. During crushing, hammermill secondary crushers tend to produce excess fines and should not be used. The recycled concrete aggregates will not normally require washing unless they have been contaminated with base or subgrade material. If the original pave-ment that is being recycled is D-cracked, then the concrete should be crushed to a maximum size of ¾ inch. When crushed concrete is being used as fine aggregate, the inclusion of some natural sand may be required to improve the new concrete mixture’s workability.

d. Alkali-aggregate reactions. Minerals in some aggregates can chemically react with the cement alkalis, resulting in an increase in volume that places the concrete under expansive stresses which may result in map cracking, popouts, strength loss, and concrete expansion. Once started, the reaction and the resulting progressive deterioration of the concrete cannot be stopped. These reactions are generally associated with aggregates containing poorly ordered forms of silica, such as opal, chalcedony, chert, or flint (alkali-silica reaction), complex layer-lattice, and silicate minerals such as graywackes, phyllites, siltstones, or argillites (some-times differentiated as alkali-silicate reaction), or argillaceous, dolomitic limestone (alakali-carbonate reaction). A petrographic investigation in conjunction with results of tests in accordance with ASTM C 227 for alkali-silica expansion and ASTM C 586 for alkali-carbonate expansion is the most promising approach for identifying these problems. If possible, reactive aggregates should be avoided. If they cannot be avoided, low-alkali cement should be specified. If low-alkali cement is not available or is overly expen-sive, some pozzolans and slag cements have been successful in countering alkali-silica reactions, or reactive aggregate may be blended with non-reactive aggregate to lessen the effect of the reactions.

e. Coarse aggregate.

(l.) Composition. Coarse aggregate may be natural gravel, crushed gravel, crushed stone, crushed recycled concrete, or iron blast furnace slag. The crushing of gravel tends to improve the quality and the bond characteristics and generally results in a higher flexural strength of concrete than if uncrushed gravel is used. When mixture proportioning studies or local experience indicates that a low flexural strength will be obtained with uncrushed gravel, the possibility of obtaining higher strength by crushing the gravel will be investigated. Elongated particles with a width–to-thickness ratio in excess of 3 may not exceed 20 percent by weight as determined by CRD-C 119. This requirement attempts to avoid introducing structural planes of weakness in the finished concrete, workability problems associated with an excess of particles of these shapes, and durability problems that may develop if air and water are trapped under flat and elongated particles.

(2.) Size and grading. The maximum size of the coarse aggregate used in pavement concrete should not exceed one-fourth of the pavement thickness. In no case will the coarse aggregate exceed a 2-inch maximum size. However, for pavement construction in areas where aggregate popouts have been a problem or may occur, the coarse aggregate will not exceed 1½-inch nominal maximum size. In areas where

“D” line cracking in pavements has been a problem, limestone aggregates should not exceed ½-inch nominal maximum size and should be of low absorp-tion. When the nominal maximum size of coarse aggregate is greater than 1 inch, the aggregates shall be furnished in two size groups as shown in table 2, with gradings within the separated size groups conforming to the requirements of table 3.

Where local practice provides size-group separations other than as shown in table 2, local size gradings may be specified if approximately the same size ranges are obtained and the grading of coarse aggre-gate when combined and batched for concrete is as required by mixture proportioning. For projects requiring 1,600 cubic yards or less of concrete, special grading requirements for coarse aggregate according to local practice may be substituted for the gradings shown. Local State Department of Transportation specifications for gradings may be used for those jobs requiring 1,600 cubic yards or less of concrete.

Table 2. Coarse aggregate size groups L

Nominal Maximum Size Size Groups

1½ in. No. 4 to ¾ in.

¾ in. to 1½ in.

2 in. No. 4 to 1 in.

1 in. to 2 in.

Table 3. Grading of coarse aggregate

S i e v e S i z e U . S . S t a n d a r d

Square Mesh

P e r c e n t a g e b y W e i g h t P a s s i n g I n d i v i d u a l S i e v e s No. 4 to 3 / 4 i n .

No. 4 to 1 in .

3 / 4 i n . t o 1 in. to 2 in .1 - 1 / 2 i n .

2 - 1 / 2 i n .

2 in .

1 - 1 / 2 i n .

1 in .

3 / 4 i n .

1 / 2 i n .

3 / 8 i n .

No. 4

No . 8

9 7 ± 3

50 ± ’20

7 ± 7

100- - - -

9 7 ± 3100

9 5 ± 5 - -

3 ± 3- - - -

(3.) Deleterious substances.

(a) Pavements used by aircraft. Table 4 lists the common deleterious substances and specifies limits for these materials. The performance history waive table 4 requirements for Air Force pavements.

Upon request, the AFRCE and the using command will be furnished available engineering information on local aggregates and behavior records on pave-ments made from them. A copy of the instructions and the revised requirements will be furnished for information to the HQDA (DAEN-ECE-G) or AFESC as applicable. In the case of Air National Guard and Army pavements, the using command will be furnished information on the costs of aggre-gates complying with specification requirements and on less costly local aggregates along with behavior records on pavements made with local aggregates. However, requirements will be waived only if requested by the Air National Guard Base Detachment Commander or the Army Installation Commander with his assurance that operational requirements will be satisfied by a performance that is equal to that of existing pavements constructed with these less costly aggregates. Requests will be submitted for approval to HQDA (DAEN-ECE -G) with proposed specification requirements, compara-tive cost estimates, and evidence that operational requirements will be satisfied.

of local aggregates contributing to pavement defects will be the determining factor in setting the limits for deleterious substances. The limits are intended to eliminate popouts and weatherouts in airfield pavements. Other deleterious substances known to contribute to popouts will be identified by the contracting officer, and suitable limits will be specified. Calcium oxide (CaO) and magnesium oxide (MgO) or a mixture thereof, in lumps, representing the hard burned oxides from fluxing stone or refrac-tory brick should be added to the list of deleterious substances if air-cooled blast furnace slag is used as the aggregate. Since the types of materials producing popouts will vary for different areas, some adjust-ments of the limits may be desirable for individual projects. Reductions in specified limits may be made as necessary, but increases to permit the use of local aggregates that have an acceptable experience record will be governed by the following procedures.

Air Force Regional Civil Engineers (AFRCE) have been authorized to instruct division engineers to

Table 4. Deleterious materials in coarse aggregates for airfield and heliport pavements.

Areas with Areas with Major Popouts Minor Popouts

Severe a Moderate a Severe a Moderate a

Materials Weather Weather Weather Weather

Clay lumps 0.2 0.2 2.0 2.0

Shaleb 0.1 0.2 1.0 1.0

Material finer 0.5 0.5 1.0 1.0 than No. 200 sievec

Lightweight particles 0.2 0.2 0.5 0.5

Clay ironstone 0.1 0.5 1.0 1.0

(Continued) aSevere, moderate, and mild weather are defined as follows:

Air Freez- Average Precipitation for a Single ing Index Month During Period--1 Month Before

Weather for Coldest Average Date of First Killing Frost Severity Year in 30* to Average Date of Last Killing Frost

Moderate 500 or less Any amount

Moderate** 501 or more Less than 1 inch

Severe 501 or more 1 inch or more

* Calculated as described in TM 5-818-2/AFM 88-6, Chapter 4.

** In poorly drained areas, the weather should be considered severe even though the other criteria indicate a rating of moderate.

b Shale is defined as a fine-grained thinly laminated or fissile sedimentary rock.

It is commonly composed of clay or silt or both. It has been indurated by compac-tion or by cementation, but not so much as to have become slate.

cLimit for material finer than No. 200 sieve will be increased to 1.5 percent for crushed aggregates if the fine material consists of crusher dust that is essen-tially free from clay or shale.

d The separation medium shall have a specific gravity of 2.0. This limit does not apply to coarse aggregate manufactured from blast-furnace slag unless contamination is evident.

e Clay ironstone is defined as an impure variety of iron carbonate, iron oxide, hydrous iron oxide, or combinations thereof, commonly mixed with clay, silt, or sand. It commonly occurs as dull, earthy particles, homogeneous concretionary masses, or hard shell particles with soft interiors. Other names commonly used for clay ironstone are “chocolate bars” and limonite concretions.

Areas with Areas with

Materials

Chert and/or cherty stone (less than

2.50 sp. gr. SSD) f

Claystone, mudstone, and/or si ltstone g

Shaly and/or argilla-h ceous limestone

Other soft particles

Total of al l deleteri -ous substances exclusive of mate-rial finer than No. 200 sieve

Major Popouts Minor Popouts

Severe a Moderate a Severe a Moderate a

Weather Weather Weather Weather

0.1 0.5 1.0 5.0

0.1 0.1 1.0 1.0

0.2 0.2 1.0 2.0

1.0

1.0 l .0

2.0

1.0

3.0

2.0

5.0 f Chert is defined as rock composed of quartz, chalcedony, or opal, or any mixture of these forms of silica. It is variable in color . The texture is so fine that the individual mineral grains are too small to be distinguished by the unaided eye.

Its hardness is such that it scratches glass but is not scratched by a knife blade.

It may contain impurities such as clay, carbonates, iron oxides, and other min-erals. Other names commonly applied to varieties of chert are flint, jasper, agate, onyx, hornstone, porcellanite, novaculite, sard, carnelian, plasma, blood-stone, touchstone, chrysoprase, heliotrope, and petrified wood. Cherty stone is defined as any type of rock (generally limestone) which contains chert as lenses and/or nodules or irregular masses partially or completely replacing the original stone. SSD = saturated surface dry.

gClaystone, mudstone, or siltstone is defined as a massive fine-grained sedimentary rock which consists predominately of clay or silt without lamination or fissility.

It may be indurated either by compaction or by cementation.

h Shaly limestone is defined as a limestone in which shale occurs as one or more thin beds of laminae. These laminae may be regular or very irregular and may be spaced from a few inches down to minute fractions of an inch. Argillaceous lime-stone is defined as a limestone in which clay minerals occur disseminated in the stone in the amount of 10 to 50 percent by weight of the rock; when these make up from 50 to 90 percent, the rock is known as calcareous (or dolomitic) shale (or claystone, mudstone, or siltstone).

(b) Other pavements. For other pavements, be identified by the contracting officer, and suitable the limiting amounts of deleterious substances in limits will be specified and materials defined when each size of coarse aggregate will be specified as necessary.

shown in table 5. Other deleterious substances will

Table 5. Deleterious materials in coarse aggregates for other pavements

Material Percentage by Weight

Clay lumps and friable particles 2.0

Material finer than No. 200 sieve a 1.0

L i g h t w e i g h t p a r t i c l e s 1.0

Other soft particles 2.0

Note:

aLimit

The total of all deleterious substances shall not exceed

5.0 percent of the weight of the aggregate. The percentage of material finer than No. 200 sieve shall not be included in th i s t o ta l .

for material finer than No. 200 sieve will be increased to

1.5 percent for crushed aggregates consisting of crusher dust that is essentially free from clay or shale.

b The separation medium shall have a specific gravity of 2.0. This limit does not apply to coarse aggregate manufactured from blast-furnace slag unless contamination is evident.

(4.) Slag aggregate. Iron ore blast-furnace slag aggregates vary widely in properties depending on the manufacturing and cooling processes used. Un-aged blast-furnace slag may contain free lime, but aging reduces this to acceptable levels. Properly aged iron ore blast- furnace aggregate has a good history of performance. Slag from steel mills, however, is not acceptable as concrete aggregate because of the various oxides it contains.

f. Fine Aggregate.

(l.) Composition and shape. Requirements for composition and particle shape of fine aggregate are purely descriptive, for example, natural and/or manufactured sand, spherical or cubical, and no limits are shown. A limit will be included for flat and elongated particles in fine aggregate, comparable with the limit specified for coarse aggregate, when tests indicate that poor particle shape will affect the workability and quality of the concrete. Shape will be determined in accordance with CRD-C 120.

(2.) Grading, uniformity of grading, and deleterious substances. The grading and uniformity of grading specified in table 6 for fine aggregate are desirable for pavement concrete and can generally be met at a reasonable cost within the continental United States. However, if conformance with these requirements will result in undue construction costs and if investigation of the available sources of fine aggregate in the locality indicates that limits other than specified are desirable, a request will be sub-mitted to HQDA (DAEN-ECE-G) giving complete results of all tests conducted to substantiate that concrete of comparable workability, durability, and strength can be produced without an increase in cement content. The amount of deleterious substances in the fine aggregate shall not exceed the limits shown in table 7.

Tabk 6. Gnading of fine aggregate

Sieve Size, Cumulative Percentage by Weight U. S. Standard Square Mesh Passing Individual Sieves

3 /8 in . 100

No. 4 9 7 2 3

No. 8 8 5 2 5

No. 50 20 ± 10

No. 100 6 ± 4

Note: In addition, the fine aggregate, as delivered to the mixer, shall have a fineness modulus of not less than 2.40 nor more than 2.90. The grading of the fine aggregate also shall be controlled so that the fineness moduli of at least nine of ten samples of the fine aggregate as delivered to the mixer will not vary more than 0.15 from the average fineness moduli of all samples previously taken. The fineness modulus shall be determined by CRD-C 104 (Appendix A).

Table 7 Deleterious substances in fine aggregate

Material Percentage by Weight

Clay lumps and friable particles 1 . 0

Material finer than No. 200 sieve 3 . 0

Lightweight particles 0 . 5

Note: The total of all deleterious materials shall not exceed 3.0 percent of the weight of the aggregate.

g. Aggregate for calibration hardstands. To avoid inclusion in the pavement concrete of iron oxides or other iron-rich materials having magnetic properties that will interfere with the operation of the facility, the concrete aggregate proposed for paving calibration hardstands will be subjected to detailed petrographic analyses in accordance with ASTM C 295 prior to acceptance. Special attention will be given to the existence of magnetite in granites, high-iron minerals in traprock, pyrite in limestone, and free iron or iron oxide in slag aggregate. When a list of aggregate sources is included in the contract specifi-cations, the sources not approved for concrete used in calibration hardstands will be indicated.

h. Aggregate for power check pads. Concrete that will be exposed to extended jet engine blast during maintenance can use igneous rocks with a low silica content and a high content of ferromagnesian minerals or slag as aggregate to improve its perfor-mance under high temperature. Aggregates rich in silica such as quartzite or chert should be avoided.

Aggregate with a high silica content such as sand-stone or granite, especially if coarse grained, can cause problems. Calcareous aggregates such as lime-stone or dolomite are acceptable.

6. Admixtures.

a. Admixtures are used to modify properties of fresh or hardened concrete. Admixtures may be used to improve workability, control initial set, reduce heat generation, accelerate strength gain, increase strength, and improve durability. Seven chemical admixtures are listed for use in portland cement concrete in ASTM C 494, as follows: Type A—water-reducing admixture; Type B —retarding admixture;

Type C–accelerating admixture; Type D–water-reducing and retarding admixture; Type E—water-reducing and accelerating admixture; Type F— water-reducing, high-range admixture; and Type G–water-reducing, high-range and retarding admixture.

b. Air-entraining admixtures provide resistance to freezing and thawing and should meet the requirements of ASTM C 260, and will normally be required in all concrete for pavements. For small jobs under 1,600 cubic yards, air-entraining cements may be considered. The use of any other admixture will depend on the economics of its use and site conditions. The effect of an admixture will vary, depending on conditions such as cement type, specific mixture proportions, ambient temperature, or water quality. Furthermore, an admixture may affect several qualities of the concrete, and some desirable properties may be adversely affected.

Consequently, the decision to use an admixture must be based on experience and tests with the cement, aggregates, and admixtures representative of those to be used on the project. It must be demon-strated that the final concrete proposed pavement quality is not adversely affected by the use of any proposed admixture. More extensive guidance on admixtures is provided in ACI 212.lR and ACI 212.2R.

7. Pozzolans.

a. Pozzolans are defined in ASTM C 618 as

“siliceous or siliceous and aluminous materials which in themselves possess little or no cementitious value, but will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties.”

This ASTM specification recognizes three classes of pozzolan and provides detailed requirements for each class. Class N pozzolans are raw or calcined natural pozzolans such as some diatomaceous earths, opaline cherts, tuffs, volcanic ashes, clays, and shales. Fly ash is divided into two classes. Class F is fly ash produced by burning anthracite or bituminous coal, and Class C fly ash is produced by burning lignite or subbituminous coal. Environmental Protection Agency (EPA) guidelines published in 1983 (40 CFR, Part 249) require that the use of fly ash must be allowed on all federal projects unless it can be proven technically unsuitable.

b. Pozzolans may be substituted for a maximum of 25 percent by volume of portland cement in concrete for pavements. If substitution of pozzolan above this limit is contemplated, a thorough test program must show that the proposed substitution limit will not adversely affect workability, admixture perfor-mance strength, and durability of the final concrete.

Pozzolans typically have specific gravities appreciably lower than portland cement, and pozzolan limits are expressed as a percent of the volume of cementitious materials. In general, concrete containing pozzolans has improved workability, lower heat of hydration, and a slower strength gain. When pozzolans are to be used, the required time to gain the design strength may be increased beyond the standard 28 days for roads and streets and 90 days for airfield pavements to the extent that the concrete is not to be exposed to traffic.

c. Class N pozzolans will not generally be encountered in pavement construction. The use of fly ash, however, is becoming increasingly common.

Fly ash produced by industrial burning of coal tends to be highly variable, depending on factors such as emission controls, load, and boiler design. This production variability is compounded further by the natural variability of lignite and subbituminous coal that produce Class C pozzolan. Also, Class C pozzolans have poor resistance to sulfate attack, and some have high alkali contents that may contri-bute to alkali aggregate reaction. Specifications for pozzolans should require that the ASTM C 618 specification be modified to require a maximum loss on ignition of 6 and 8 percent, respectively, for Class F and N pozzolans and a minimum pozzolanic activity index with lime of 900 psi at 7 days. Mixture propor-tioning studies should use the same pozzolans and cements that will be used on the project and must determine that the final concrete characteristics, strength gain, and durability are adequate.

8. Miscellaneous materials.

a. Other materials used in concrete pavement construction including curing materials, dowels, tie bars, reinforcement, and expansion-joint filler are covered by applicable specifications. When concrete is required to be free of magnetic materials, special instructions will be obtained from HQDA (DAEN- ECE-G) for the selection of dowels, tie bars, and reinforcement. Aluminum will not be used in concrete pavements.

b. Field welding of crossing bars (tack welding) is prohibited. All welded splices will conform to the requirements of the American Welding Society (AWS) D 1.4. Selection of the proper welding procedure depends on the actual chemical composition of the steel. A procedure suitable for one chemical compo-sition can be totally unsuited for another composition of the same strength grade. It is essential that the composition of the steel to be welded be determined before the welding procedure is established. Where reinforcing bars are to be ordered for new work, the fabricator should be informed that welded splices are contemplated. The fabricator can provide the chemical composition of the reinforcing bars and in many cases can provide bars that are more suited to welding.

c. Epoxy-coated reinforcing steel and dowel bars are being used more frequently in areas such as bridge decks, coastal areas, and pavements subject to heavy applications of de-icing salts to minimize potential corrosion problems. If these materials are used, they should conform to ASTM A 775. Epoxy-coated dowels and reinforcing steel will rest on epoxy-coated wire bar supports or on bar supports made of dielectric material. Wire bar supports will be coated for a minimum of 2 inches from the point of contact with the epoxy-coated reinforcing bars.

Adequate ventilation to dissipate fumes must be provided if epoxy-coated steel is welded.

d. Appendix C describes the materials and methods used for the construction of steel fiber reinforced concrete.

9. Water. Water for mixing concrete will be free from materials that affect hydration of the cement.

Potable water may be used without testing however, tests will be made in accordance with CRD-C 400 if the water source is a stream or another body of water of unknown quality. Seawater has been used successfully as mixing water, but this should only be done if there is no feasible alternative. There may be up to a 15 percent loss in ultimate strength, set times may be affected, and surface efflorescence may occur. The risk of steel corrosion maybe increased, so the use of coated dowels and reinforcing steel should be considered if seawater is to be used.

10. Sampling and testing of materials.

a. Cement. Cement to be used in pavements for aircraft traffic will be sampled and tested. Cement meeting all other test requirements may be accepted prior to the required 7-day age when the strength is equal to or greater than the 7-day strength require-ment. Cement for pavement projects requiring 1,600 cubic yards or less of concrete may be accepted on the basis of the manufacturer’s certified mill test reports showing compliance with cited cement specifications.

b. Aggregates.

(l.) Listed sources. Listing of aggregate sources will be based on a thorough investigation to determine that suitable aggregates are obtainable for the proposed use. Evaluation of the material will require complete laboratory testing including petrographic examinations, physical tests, durability tests, and alkali-reactivity tests. The service record of aggre-gates will be determined by inspecting structures that have had exposure equivalent to the proposed structure. When an aggregate source has been listed previously for use on the basis of a complete investi-gation, additional similar use of the source within a period of 3 years may be permitted on the basis of petrographic examinations and limited physical tests if the results show no change in the composition and quality of aggregate. For proper design and preparation of plans and specifications, it is necessary to investigate and determine suitable aggregate sources and concrete strengths obtainable with aggregates. It is essential that these investiga-tions be conducted as early as possible during project planning.

(2.) Sources for calibration hardstands. When contract specifications cover the paving of calibration hardstands, the list of sources will indicate which sources are approved for such work.

(3.) Aggregate sources not previously listed.

When the contractor proposes aggregate from a source not previously listed, the evaluation of samples of that aggregate will include all tests necessary to demonstrate that a concrete produced from the materials will have quality and strength comparable with that of concrete made with aggre-gate from the approved sources listed. When the contracting officer is responsible for mixture proportioning and cement is a separate pay item in the contract, aggregates of good quality that require an increase in the quantity of cement over that required by aggregates from listed sources to produce concrete of the specified flexural strength will be approved for use only if the contractor agrees in writing to pay for the additional cement required.

(4.) Unlisted source. When the contract specifications do not include a list of approved aggregate sources, the source(s) proposed by the contractor will be investigated as soon as possible after the award of the contract.

(5.) Aggregates for a small project. Evaluation of aggregates from non-listed sources and concrete mixture proportioning for projects requiring 1,600 cubic yards or less of concrete, except for airfield and heliport paving, will be performed by an approved commercial testing laboratory at no expense to the Government.

11. Delivery and storage of materials.

a. Cement and pozzolan. Separate storage facilities will be provided for each type of cementitious material. Storage facility will be thoroughly cleaned before changing the type of cementitious material stored init. Storage facilities must be weather-tight and must be properly ventilated.

b. Aggregates.

(l.) Control of grading. Aggregate-handling and aggregate-storage facilities may vary greatly for different projects, and only general requirements can be specified. Grading and uniformity of grading requirements will be determined as the aggregates are delivered to the mixer, and the contractor is responsible for meeting these requirements. Careful inspection of storage and handling operations, however, is desirable to assure satisfactory control of the aggregate grading and to prevent contamin-ation by foreign material. Aggregate storage tech-niques that use coned piles or spread truck-dumped aggregate with a bulldozer cause segregation problems. Aggregates delivered by trucks are best dumped and left in individual adjacent piles. A clam shell spreading aggregate in thin layers has also been used to minimize segregation. Aggregate should be handled as little as possible to minimize segregation. Potential sources of contaminants include windblown foundation and adjacent materials and contaminants from equipment used in handling the aggregates.

(2.) Moisture control. Uniformity of free moisture in aggregate is essential for proper control of concrete consistency. A period of free-draining storage is required for fine aggregates and the smaller size of coarse aggregate. Normally, 24 to 48 hours will be sufficient. However, shorter or longer times may be specified if the tests of time to reach an equilibrium so indicate.

12. Grade control. The lines and grades shown for each airfield and heliport pavement category of the contract shall be established and maintained by means of line and grade stakes placed at the jobsite by the contractor. Elevations of all benchmarks used by the contractor for controlling pavement operations at the jobsite will be established and maintained by the Government. The finished pavement grade lines and elevations shown shall be established and controlled at the jobsite in accordance with bench-mark elevations furnished by the contracting officer.

The pavements shall be constructed to the thicknesses and elevations indicated. Provisions for line and grade control for roads, streets, and open storage areas shall be included in the contract specifications.

13. Proportioning.

a. Mixture proportioning. Before any concrete is placed, trial mixtures will be prepared with materials from the sources to be used for production of concrete on the project. When the contractor is responsible for mixture proportioning, trial mixtures will be prepared by a commercial testing laboratory approved by the contracting officer at no expense to the Government, and the results will be submitted to the contracting officer for approval. When the contracting officer is responsible for mixture proportioning, trial mixtures will be prepared by the Government with materials supplied by the contractor from the sources to be used for production of concrete on the project. Mixtures will be made in sufficient number to establish optimum proportions of the aggregates and to represent a wide range in cement contents and water–cement ratios within specified requirements for air content and workability. The water-cement ratio will not exceed 0.45 by weight for pavement mixtures. After the final proportions of the trial mixtures have been established, 6–inch by 6-inch cross-section test/beam specimens from each mixture will be made in accordance with ASTM C 192 and tested as described in ASTM C 78.

A minimum of nine test specimens should be made to establish the flexural strength of each mixture at each test age. From these mixture proportioning studies, the controlling maximum water-cement ratio and hence the cement content required to produce concrete of specified strength will be deter-mined. This same procedure will be used to establish new mixture proportions when necessary because of a change in the source or the character of the concrete ingredients after concrete placement has started.

b. Mixture proportions.

(l.) Contracting officer responsible for mixture proportions. When the contracting officer is respon-sible for the mixture proportions, proportions of all materials used in the concrete mixture will be as directed. The contracting officer will require such changes in the mixture proportions as necessary to maintain the workability, strength, and quality required by the contract specifications. The mixture proportions determined by mixture proportioning studies will be used in starting paving operations.

Adjustments will be made by the contracting officer as necessary to establish the mixture proportions best suited for job conditions and materials used.

Subsequent mixture adjustments will be made when necessary, but usually these adjustments will be of a minor nature as required to compensate for variations in gradings and the moisture content of the aggregate.

(2.) Contractor responsible for mixture propor-tions. When the contractor is responsible for the mixture proportions, proportions of all materials used in the concrete mixture will be as directed by the contractor.