TE 15 - TM 5-624 Maintenance and Repair of Surface Areas.pdf

ARMY TM 5-624

NAVY NAVFAC DM MO-102

AIR FORCE MANUAL AFJMAN 32-1040

MAINTENANCE AND REPAIR

OF SURFACE AREAS

APPROVED FOR PUBLIC RELEASE; DISTRBUTION IS UNLIMITED

D E P A R T M E N T S O F T H E A R M Y , T H E N A V Y , A N D T H E A I R F O R C E

27 OCTOBER 1995

REPRODUCTION AUTHORIZATION/RESTRICTIONS

This manual has been prepared by or for the Government and, except to the extent indicated below, is public property and not subject to copyright.

Copyrighted material included in the manual has been used with the knowledge and permission of the proprietors and is acknowledged as such at point of use. Anyone wishing to make further use of any copyrighted material, by itself and apart from this text, should seek necessary permission directly from the proprietors.

Reprints or republications of this manual should include a credit substantially as follows: "Joint Departments of the Army, Navy and Air Force, TM 5-624/NAVFAC DM MO-102/AFJMAN 321040, Maintenance and Repair of Surface Areas, 27 October 1995."

If the reprint or republication included copyrighted material, the credit should also state:

"Anyone wishing to make further use of copyrighted material, by itself and apart from this text, should seek necessary permission directly from the proprietors."

*TM 5-624/NAVFAC DM MO-102/AFJMAN 32-1040

TECHNICAL MANUAL HEADQUARTERS

No. 5-624 DEPARTMENTS OF THE ARMY

NAVY MANUAL THE NAVY, AND THE AIR FORCE

NAVFAC DM MO-102 WASHINGTON, DC, 27 October 1995

AIR FORCE MANUAL

No. 32-1040

MAINTENANCE AND REPAIR OF SURFACE AREAS

Paragraph Page

CHAPTER 1. GENERAL

Purpose ....................................................................................................................................... 1-1 1-1 Scope ........................................................................................................................................... 1-2 1-1 References ................................................................................................................................... 1-3 1-1 General Principles for Maintenance of Surface Areas .................................................................. 1-4 1-1 Safety............................................................................................................................................ 1-5 1-3

2. SUBGRADES, SUBBASES, AND BASES

Pavement Types .......................................................................................................................... 2-1 2-1 Subgrade ...................................................................................................................................... 2-2 2-1 Subbase ....................................................................................................................................... 2-3 2-3 Base Course................................................................................................................................. 2-4 2-3 Materials for Subbases and Base Courses................................................................................... 2-5 2-3 Construction and Repair Procedures............................................................................................ 2-6 2-5

3. BITUMINOUS PAVEMENTS

Pavement Structure ..................................................................................................................... 3-1 3-1 Types of Bituminous Surfaces...................................................................................................... 3-2 3-1 Causes of Bituminous Pavement Distress.................................................................................... 3-3 3-3 Types of Bituminous Pavement Distress...................................................................................... 3-4 3-7 Bituminous Pavement Materials.................................................................................................... 3-5 3-16 Bituminous Pavement Equipment................................................................................................. 3-6 3-21 Bituminous Repair Methods.......................................................................................................... 3-7 3-32

4. CONCRETE PAVEMENTS

Methods and Procedures ............................................................................................................. 4-1 4-1 Properties and Behavior ............................................................................................................... 4-2 4-1 Causes of Concrete Pavement Distress....................................................................................... 4-3 4-5 Types of Concrete Pavement Distress ......................................................................................... 4-4 4-10 Concrete Pavement Materials....................................................................................................... 4-5 4-20 Concrete Pavement Equipment .................................................................................................... 4-6 4-22 Methods of Concrete Maintenance and Repair............................................................................. 4-7 4-27

5. MISCELLANEOUS SURFACES

Maintenance and Repair ............................................................................................................... 5-1 5-1 Types of Surfaces and Materials .................................................................................................. 5-2 5-1 Causes of Distress ....................................................................................................................... 5-3 5-7 Types of Distress.......................................................................................................................... 5-4 5-7 Methods for Maintenance and Repair ........................................................................................... 5-5 5-7

6. SHOULDERS AND ROADSIDES

Shoulders ..................................................................................................................................... 6 1 6-1 Types of Shoulder Surfaces ......................................................................................................... 6-2 6-1 Geometrics ................................................................................................................................... 6-3 6-1 Types and Causes of Shoulder Distress ...................................................................................... 6-4 6-1 Methods of Shoulder Repair ......................................................................................................... 6-5 6-2 General Maintenance.................................................................................................................... 6-6 6-3

7. DRAINAGE OF PAVEMENTS

Drainage Control........................................................................................................................... 7-1 7-1 Types of Drainage Systems.......................................................................................................... 7-2 7-1

*This manual supersedes TM5624/NAVFAC DM MO-102/AFM 85-8, 31 March 1977, and AFM 88-6, Chap 10, January 1989.

i

TM 5-624/NAVFAC DM MO-102/AFJMAN 32-1040

Paragraph Page CHAPTER 7. Types and Causes of Drainage Related Distress ........................................................................ 7-3 7-4

Methods for Maintenance and Repair of Drainage Structures ...................................................... 7-4 7-5

8. MAINTENANCE AND REPAIR OF BRIDGE SURFACES

Introduction .................................................................................................................................. 8-1 8-1 Types of Bridge Surfaces ............................................................................................................. 8-2 8-1 Types and Causes of Bridge Surface Distress............................................................................. 8-3 8-1 Methods for Maintenance and Repair of Bridge Surfaces ............................................................ 8-4 8-1

9. SNOW AND ICE CONTROL

Trafficked Area Requirements ..................................................................................................... 9-1 9-1 Properties of Snow and Ice........................................................................................................... 9-2 9-1 Equipment for Snow and Ice Control ............................................................................................ 9-3 9-2 Snow Control and Removal........................................................................................................... 9-4 9-4 Ice Control and Removal............................................................................................................... 9-5 9-16

10. PREVENTATIVE MAINTENANCE

Rational for Maintenance .............................................................................................................. 10-1 10-1 Inspection and Records................................................................................................................ 10-2 10-1 Maintenance Strategies and Performance of Paved Roads.......................................................... 10-3 10-2

APPENDIX A. REFERENCES ............................................................................................................................ A-1

GLOSSARY .......................................................................................................................................................................... Glossary-1

INDEX ................................................................................................................................................................................... Index-1

List of Figures Page

FIGURE 1-1. Transmission of Wheel Loading to Subgrade ....................................................................................................... 1-2 1-2. Typical Cross-sections of Surfaced Areas ............................................................................................................ 1-3 3-1. Alligator Cracks ..................................................................................................................................................... 3-7 3-2. Bleeding................................................................................................................................................................. 3-8 3-3. Block Cracking ...................................................................................................................................................... 3-8 3-4. Sag in Asphalt Pavement....................................................................................................................................... 3-9 3-5. Corrugation ................................................................... ........................................................................................ 3-9 3-6. Depression ................................................................... ........................................................................................ 3-10 3-7. Edge Cracking ...................................................................... ................................................................................ 3-10 3-8. Transverse Reflective Crack ................................................................................................................................. 3-11 3-9. Lane/Shoulder Drop-off ......................................................................................................................................... 3-11 3-10. Transverse Crack ................................................................................................................................................. 3-12 3-11. Utility Cut Patching ................................................................. .............................................................................. 3-12 3-12. Polished Aggregate ............................................................................................................................................... 3-13 3-13. Potholes................................................................................................................................................................. 3-13 3-14. Railroad Crossing .................................................................... ............................................................................. 3-14 3-15. Raveling................................................................................................................................................................. 3-14 3-16. Rutting ................................................................................................................................................................... 3-15 3-17. Shoving.................................................................................................................................................................. 3-15 3-18. Slippage Cracks .................................................................................................................................................... 3-16 3-19. Swelling ................................................................................................................................................................. 3-16 3-20. Weathering ............................................................................................................................................................ 3-17 3-21. Raveling from Fuel Spills ....................................................................................................................................... 3-17 3-22. Grooved Asphalt Concrete Pavement.................................................................................................................... 3-18 3-23. Motorized Vacuum Broom ..................................................................................................................................... 3-22 3-24. Motorized Circular Broom ...................................................................................................................................... 3-22 3-25. Applying a Seal Coat with Squeegees ................................................................................................................... 3-23 3-26. Hand-held Saw ...................................................................................................................................................... 3-23 3-27. Cutting Disk ........................................................................................................................................................... 3-24 3-28. Removing Damaged Pavement with a Jack Hammer ............................................................................................ 3-24 3-29. Propane Joint Heater ............................................................................................................................................. 3-25 3-30. Heater Scarifier with Blade and Spreader Attachments......................................................................................... 3-25 3-31. Scarified and Bladed Bituminous Material Being Immediately Respread and Compacted..................................... 3-26 3-32. Heater Remixer for In-place Recycling .................................................................................................................. 3-26 3-33. Cold Milling Machine.............................................................................................................................................. 3-27 3-34. Self-propelled Pavement Milling Machine .............................................................................................................. 3-27 ii

Page FIGURE 3-35. Traveling Hammer Mill ........................................................................................................................................... 3-28

3-36. Closeup of Hammer Mill Breaking Shaft ................................................................................................................ 3-28 3-37. Closeup of Pulverizer Mixing Blades...................................................................................................................... 3-29 3-38. Portable Hot-Mix Plant .......................................................................................................................................... 3-29 3-39. Bituminous Distributor ........................................................................................................................................... 3-30 3-40. Asphalt Kettle......................................................................................................................................................... 3-30 3-41. Self-propelled Aggregate Spreader ....................................................................................................................... 3-31 3-42. Slurry Seal Machines............................................................................................................................................. 3-31 3-43. Asphalt Paving Machine ........................................................................................................................................ 3-32 3-44. Vibratory Plate Compactor ..................................................................................................................................... 3-32 3-45. Steel-wheel Tandem Roller.................................................................................................................................... 3-33 3-46. Rubber-tired Roller ................................................................................................................................................ 3-33 3-47. Steel-wheel Vibratory Roller................................................................................................................................... 3-34 3-48. Hole to be Patched With Tack Applied ................................................................................................................. 3-35 3-49. Placing Asphalt Mix in Patch ................................................................................................................................. 3-35 3-50. Placement of AC Backfill in Deep Depression....................................................................................................... 3-36 3-51. Permanent Repair of Potholes............................................................................................................................... 3-36 3-52. Applying Rejuvenator............................................................................................................................................. 3-37 4-1. Pavement Failures ................................................................................................................................................. 4-2 4-2. Age-strength Relationship ..................................................................................................................................... 4-3 4-3. Approximate Bending Strength .............................................................................................................................. 4-8 4-4. Curling ................................................................................................................................................................... 4-10 4-5. Blowup/Buckling .................................................................................................................................................... 4-11 4-6. Corner Break ......................................................................................................................................................... 4-11 4-7. Divided Slab........................................................................................................................................................... 4-12 4-8. D Cracking............................................................................................................................................................. 4-12 4-9. Faulting.................................................................................................................................................................. 4-13 4-10. Joint Seal Damage, Incompressibles in Joint ........................................................................................................ 4-13 4-11. Lane/Shoulder Dropoff........................................................................................................................................... 4-14 4-12. Linear Cracking...................................................................................................................................................... 4-14 4-13. Utility Cut Patch..................................................................................................................................................... 4-15 4-14. Small Patch ........................................................................................................................................................... 4-15 4-15. Polished Aggregate................................................................................................................................................ 4-16 4-16. Popouts ................................................................................................................................................................. 4-16 4-17. Pumping ................................................................................................................................................................ 4-17 4-18. Punch Out ............................................................................................................................................................. 4-17 4-19. Railroad Crossing .................................................................................................................................................. 4-18 4-20. Scaling................................................................................................................................................................... 4-18 4-21. Crazing .................................................................................................................................................................. 4-19 4-22. Shrinkage Crack .................................................................................................................................................... 4-19 4-23. Corner Spalling...................................................................................................................................................... 4-20 4-24. Joint Spalling ......................................................................................................................................................... 4-21 4-25. Water-cooled Power Saw ...................................................................................................................................... 4-23 4-26. High-pressure Water Hose.................................................................................................................................... 4-23 4-27. Blowing out Dirt from Joints................................................................................................................................... 4-24 4-28. Joint Plow .............................................................................................................................................................. 4-25 4-29. Vertical Router Spindle .......................................................................................................................................... 4-25 4-30. Vertical Impact Routing Device.............................................................................................................................. 4-26 4-31. and Blasting Joints ................................................................................................................................................ 4-26 4-32. Applying Crack Sealer with a Pouring Pot ............................................................................................................. 4-27 4-33. Applying Joint Material........................................................................................................................................... 4-28 4-34. Prepared Partial-depth Patch ................................................................................................................................ 4-28 4-35. Completed Patch .................................................................................................................................................. 4-29 4-36. Patching Near Joint or Pavement Edge ................................................................................................................. 4-30 4-37. Full-depth Patch with Dowel Bars at Edges........................................................................................................... 4-30 4-38. Cleaning Patch Area with Compressed Air............................................................................................................ 4-31 4-39. Placing Reinforcement and Dowels in Area to be Repaired................................................................................... 4-31 4-40. Placing Concrete in Patch Area............................................................................................................................. 4-32 4-41. Finishing Surface of Concrete Patch..................................................................................................................... 4-32 4-42. Proper Location of Holes Depending on Defect to be Corrected ........................................................................... 4-36 5-1. Gradation Triangle for Aid in Selecting a Commercial Stabilizing Agent................................................................ 5-4 5-2. Dust Created by a Passing Vehicle ....................................................................................................................... 5-8 5-3. Cultivator Mixing Soil.............................................................................................................................................. 5-9 5-4. Pulvermixer............................................................................................................................................................ 5-9 5-5. Grader Leveling Road Surface............................................................................................................................... 5-10 5-6. Sheepsfoot Roller .................................................................................................................................................. 5-10 iii

Page FIGURE 5-7. Rubber-tired Roller ............................................................................................................................................... 5-11

5-8. Vibratory Roller ...................................................................................................................................................... 5-11 5-9. Regrading and Rolling Road Surface ................................................................................................................... 5-12 5-10. Hand Spreading Bags of Cement .......................................................................................................................... 5-13 5-11. Spreading Lime with a Harrow............................................................................................................................... 5-13 5-12. Spreading Cement Directly from Bulk Carrier........................................................................................................ 5-14 5-13. Dry Mixing Cement with Pulverizer ........................................................................................................................ 5-14 5-14. Adding Water to the Soil ....................................................................................................................................... 5-15 5-15. Finish Rolling with a Rubber-tired Roller................................................................................................................ 5-15 5-16. Spraying Lime from a Tank Truck and Immediately Mixing Treated Soil ............................................................... 5-16 7-1. Typical Subdrain Installation.................................................................................................................................. 7-2 7-2. Concrete Open Drainage Ditch.............................................................................................................................. 7-3 7-3. Concrete Flume for Discharging Water into Drainage Channel............................................................................. 7-3 7-4. Types of Scour at Culvert Outlets.......................................................................................................................... 7-4 7-5. Ditch Check........................................................................................................................................................... 7-5 7-6. Slide Failure or Collapses of a Steep Slope........................................................................................................... 7-6 7-7. Relatively Mild Side Slopes and Good Vegetative Cover........................................................................................ 7-7 7-8. Headwall at Inlet to Culvert Passing Beneath a Railroad Bed ................................................................................ 7-8 7-9. Barred Concrete Endwall for Conveying Runoff .................................................................................................... 7-8 7-10. Recommended Riprap Sizes ................................................................................................................................. 7-9 7-11. Riprap Placed along a Drainage Channel for Protection Against Erosion.............................................................. 7-10 7-12. Wood and Rock Fencing for Control of Erosion ................................................................................................... 7-11 7-13. Rock Fences for Control of Erosion....................................................................................................................... 7-11 7-14. Grated Inlet ............................................................................................................................................................ 7-12 8-1. Exposed Reinforcing Steel..................................................................................................................................... 8-2 9-1. Reversible Blade Mounted on a '/4-ton Utility Truck............................................................................................... 9-3 9-2. Two-element Rotary Plow with Twin Horizontal-axis Helical Augers...................................................................... 9-4 9-3. Belt Conveyor Unit for Truck Loading Snow .......................................................................................................... 9-5 9-4. Towed Power Rotary Broom with High-Volume Low-pressure Airblast ................................................................. 9-6 9-5. Small Tracked Vehicle with V-blade Towing a Sand Spreader .............................................................................. 9-7 9-6. Combination Applicator.......................................................................................................................................... 9-8 9-7. Simplified Impression of Eddies Formed by Typical Obstructions......................................................................... 9-9 9-8. Snowdrifts Generated by Solid Snow Fences and by Vertical Slant Fences of Various Densities......................... 9-10 9-9. Basic Arrangements of Snow Fences for Protecting Roads or Railroads.............................................................. 9-11 9-10. Vertical Slat Fence................................................................................................................................................. 9-12 9-11. Fence Made by Stapling Strips of Reinforced Paper or Plastic Strips onto Wooden Posts................................... 9-12 9-12. Inclined Slat Fences .............................................................................................................................................. 9-13 9-13. Trellis Fence ......................................................................................................................................................... 9-13 9-14. Old Style Russion Snow Fence ............................................................................................................................. 9-14 9-15. Snow Block Fence ................................................................................................................................................ 9-14 9-16. Shelterbelt or Living Snow Fence........................................................................................................................... 9-15

List of Tables

Page TABLE 2-1. Select Materials and Subbases ............................................................................................................................ 2-3

2-2. Characteristics and Ratings of Unified Soil System Classes for Soil Construction ............................................... 2-6 3-1. Pavement Distress Types and Maintenance and Repair Alternatives.................................................................... 3-4 3-2. Possible Causes and Types of Imperfections in Finished Pavements................................................................... 3-6 3-3. Grade Classification .............................................................................................................................................. 3-20 3-4. Mixing Temperatures ............................................................................................................................................. 3-20 4-1. Approximate Mixing Water Requirements for Different Slumps and Maximum Sizes of Aggregates .................... 4-4 4-2. Recommended Slumps for Various Types of Construction................................................................................... 4-5 4-3. Suggested Trial Mixes for Air-entrained Concrete of Medium Consistency........................................................... 4-6 4-4. Suggested Trial Mixes for Nonair-entrained Concrete of Medium Consistency..................................................... 4-7 4-5. Pavement Distresses and Suggested Maintenance and/or Repair Procedures..................................................... 4-9 9-1. Chemical Application Rates for Roads ................................................................................................................. 9-18 9-2. Ice-dissolving Capacity of Urea, Pounds per Square Yard ................................................................................... 9-19 9-3. Freezing Point of Isopropyl Alcohol-water Mixtures ............................................................................................... 9-20 iv

CHAPTER 1

GENERAL

1-1. Purpose This manual provides guidance for all Army, Navy, and Air Force installation personnel engaged in the maintenance and repair of surfaced areas and related structures. It is intended to be practical and concise and useful to foremen as well as engineers.

1-2. Scope.

This manual provides guidance for effective maintenance and repair of roads, streets, parking and open-storage areas, walks, airfields, and similar traffic areas at Army, Navy, and Air Force installations.

Methods used in accomplishing maintenance and repair work are described. Navy policy in these areas is given in OPNAVINST 11010, 20E. The materials, methods, and equipment cited in this manual represent the most predominate types used in the construction industry.

Locally available materials, methods, or equipment not cited in this manual can be used when experience warrants. The text includes general principles of maintenance and repair for use by all activities designated to maintain pavements in a condition suitable for their intended use. The servicing functions of sweeping, snow removal, and ice control described in this manual are applicable to the Army and Navy activities only.

1-3. References Appendix A contains a list of references used in this document.

1-4. General principles for maintenance of surface areas Pavements are usually classified as flexible (bituminous concrete surface) or rigid (portland cement concrete surface). Natural soils are not usually suitable for heavy vehicular traffic or any great volume of vehicular or pedestrian traffic. The simplest types of surfaced areas are those in which coarse materials are added to fine-grained soils, fine soil binders are added to coarse-grained soils, or a waterproofing agent is applied to the surface of naturally stable soils. Heavy loads require surfaced areas that are strong and thick enough so that the transmitted load does not exceed the load-bearing capacity of the subgrade soil. Figure 1-1 shows the general principle of transmission of wheel loads to the subgrade. Unit pressures transmitted to the surface are approximately equal to the tire pressure. Greater surfaced area thickness is required over subgrades having lower bearing capacity than over subgrades having higher bearing capacity. Figure 1-2 shows typical cross sections of surfaced areas.

a. Surface areas. Surface areas includes all pavements and miscellaneous or stabilized (other than grass) areas used for vehicular, aircraft, or pedestrian traffic (such as roads, streets, service drives, walks, parking areas, open storage, and airfield paved areas).

b. Standards of maintenance and repair. The basic objectives of the standards outlined in this manual are to maintain surfaced areas in an economical manner that will protect the Government's investment, reduce to a minimum the hazards to life and property, and permit continuous use.

The concept of standards of maintenance and repair will vary depending on whether the repairs are of an emergency nature with a short life expectancy, semipermanent, or permanent. The quality of the materials used and the thoroughness of the repair will depend on the nature of the repair. Prompt and adequate maintenance is of paramount importance. The general maintenance principles below shall be observed.

(1) Prompt maintenance. Once deterioration or destruction of a surface has started, it can proceed very rapidly. A minor maintenance job postponed can thus develop into a major job involving base, subbase, and subgrade as well as surface. Therefore, timely and adequate inspection and maintenance are essential.

(2) Priority. Priority in making repairs depends on operational requirements, traffic intensity, and consideration of the hazards that would result from complete failure.

(3) Traffic interference. Maintenance and repair work shall be scheduled to minimize interference with essential traffic. Whenever feasible, the work shall be planned and performed to permit at least partial or limited use of the facility. When it is necessary to completely close a facility, plans shall be made for alternate operational areas, and the work shall be done in the least possible time.

When a facility is to be partially or completely closed, every effort will be made to publicize the closure several days in advance. Media that can be used include base newspapers, daily bulletins, and base radio stations.

(4) Basic causes. Surface repair without correction of a faulty subgrade, subbase, or base only temporarily corrects a poor condition, necessitating further maintenance and repair at a later date.

1-1

a. THICK BASE COURSE b. THIN BASE COURSE

Figure 1-1. Transmission of wheel loading to subgrade.

Explorations to determine the cause of failure and action to eliminate the cause as well as to repair apparent damage are considered basic requirements.

(5) Uniformity. Maintenance and repair of existing surfaces will conform as closely as possible to the original construction in design, material, strength, appearance, and texture. A uniform pavement is easier to maintan.

(6) Overloads. Surface areas subjected to extensive overloading eventually require reconstruction and/or strengthening. Repairs to such areas will involve only minimum work necessary to keep them in operating condition until overall corrective measures are taken.

(7) Usage. The extent of maintenance, repair, and rehabilitation of surfaced areas will be governed by the anticipated use. Routine maintenance will be based on a continuing long-term planned program at each activity. On land that is held under lease, permit, or easement, the terms of such document will be taken into consideration when the extent and type of maintenance, repair, and rehabilitation are determined.

c. Selection and sampling of materials. Proper planning and selection of materials as well as methods of operation will determine to a large extent the efficiency of the methods of pavement maintenance.

(1) Inspection and sampling. Field inspections and tests are generally adequate for the selection of soils and aggregates, control of gradation, and the proportioning of bulk materials during the progress of the work. The inspections also serve as a basis for accepting or rejecting processed or manufactured materials. Laboratory tests are needed to determine the physical and chemical properties of materials. These tests may be performed by laboratories of the

Air Force, Naval Districts Public Works Offices, Corps of Engineers Division and District offices, State highway department, or by commercial firms especially equipped for this purpose.

(2) Material survey. Surveys will be made to determine the location, nature, and cost of all natural and processed materials available locally and/or from nearby commercial sources. Complete information about these materials will be obtained and kept on file for future use.

Frequently, maintenance and repair work may be accomplished with local materials either in their natural state or screened, crushed, or blended. The use of these local materials results in savings in man- and equipment-hours, transportation, and money.

d. Surfaced area inspection. A comprehensive maintenance program will be developed and aggressively executed in order to lengthen pavement life and reduce maintenance and repair problems and costs. Frequent pavement inspections can detect early evidence of defects before actual failure occurs. Frequent inspections should be semiannually or annually depending on the type of surfaces and local climatic or operational conditions.

Seasonal inspections of drainage systems will be made. At least twice a year, subsurface drains will be examined to make sure that they are working properly. Drainage inspections should be made during rainy seasons, spring thaws, and immediately following heavy storms. Most potential failures such as cracking, undermining, poor drainage, pumping of slabs, and progress of weathering action may be found through detailed inspections, examination, and testing. Inspection should be conducted by competent personnel to ensure that deficiencies are properly identified and reported.

1-2

Figure 1-2. 7ypical cross-sections of surfaced areas.

e. Overlay. In areas where surface drainage can be maintained, the use of overlays is often economical and advantageous. An overlay is used to increase the strength of the pavement structure and to improve the quality of the surface.

f. Reconstruct and/or recycle. Reconstruction and/or recycling should be considered when the pavement has deteriorated to a condition where normal repair procedures are no longer feasible. Recycling of pavements as either base or surface materials can be economical when compared to reconstruction with virgin material. The various methods and types of recycling should be considered to determine the most cost effective alternative for a particular pavement.

1-5. Safety Personal protective clothing will be issued at the option of the Base or Post Civil Engineer to ensure the health and safety of Civil Engineering personnel.

1-3

Protective clothing includes, but is not limited to, coveralls, goggles, respirators, protective headgear, and steel-toed shoes that may be required in performing the work addressed in this manual.

a. Equipment. Selected equipment will be used when personnel are engaged in handling or placing hot tar, hot asphalt, acids, caustics, creosoted materials, and other liquids that are hazardous. Selected equipment will also be used in sledging, hammering, or chipping on concrete, stone, or metal; and in handling heavy and sharp-edged or abrasive materials.

Reflective vests should be available for all personnel when working in traffic areas.

b. Signs and markings. Safety signs and markings, such as traffic guides, road and runway markings, safe load limits of bridges and culverts, and maximum clearances of overhead structures will be kept clear and legible. Control devices will be operated to the extent necessitated by the traffic involved.

1-4

CHAPTER 2

SUBGRADES, SUBBASES, AND BASES

2-1. Pavement types There are two basic pavement types discussed in this manual. Subgrade, subbases, and bases are also discussed as they relate to the two types of pavements.

a. Flexible pavement. Flexible pavement consists of the subgrade or natural in-place soil, select material or subbases, the base course, and the asphalt pavement surface. Base courses and subbases for flexible pavements are placed to distribute the surface-induced stresses from the vehicle and aircraft wheel loads so that the resulting stresses on the subgrade do not exceed its strength (fig. 1-1). The subgrade ultimately supports the load placed on the surface of the pavement, and the strength of the subgrade partially determines the thickness of pavement structure (surface, base, and subbase). Information for flexible pavements is provided in TM 5-825-2/AFM 88-6, chapter 2, section A/NAVFAC DM-21.3.

b. Rigid pavement. Rigid pavement consists of the subgrade or natural in-place soil, any aggregate courses, and the portland cement concrete slabs.

Aggregate courses under concrete slabs are not always used but are generally provided to prevent water migration or pumping, or to minimize frost action.

Concrete slabs are designed to distribute the stresses from the wheel loadings over large areas. However, concrete slab stresses (and deflections) at free edges will be higher than stresses in the middle of slabs.

Hence, load transfer is a must. In continuously placed unreinforced concrete, contraction joints are placed at a uniform spacing based on the thickness of the pavement, and load transfer is obtained by interlocking the concrete aggregate. Transfer decides such as dowels or keys are used to transmit loads between slabs at butt or fully formed joints and at construction joints in reinforced concrete. Where transfer devices are not used or strengthening by extra steel along edges is not used, provision for slab edge support is made by using a cement-treated base under slabs or by thickening the concrete at the edges of the slab. Strong foundation materials beneath concrete slabs result in a reduced slab design thickness as compared with the thickness that would be required for a weak foundation.

c. Effects of water on foundation soils. Saturation of pavement bases and subgrades generally decreases their load-carrying capacity. Failures as a result of saturation may be minimized by preventing infiltration of surface water into the base or subgrade and by removing excess moisture or trapped water from beneath the pavement. Infiltration of surface water can be prevented by sealing large cracks and periodic application of surface seals to bituminous pavements, by replacing ineffective sealers in joints of concrete pavements, and by proper drainage of surface water from the pavement area. In areas of high water tables under pavements, properly designed subsurface drainage, stabilized bases, or free-draining materials that are not adversely affected by moisture are required. In areas where frost is a consideration, selected materials, as required by specifications, are needed to limit frost penetration and subsequent frost heave or weakening of materials during the frost melting period.

2-2. Subgrade The subgrade is the natural in-place soil under a pavement.

In general, compaction increases the strength of most soils;

however, there are a few soils (some clays and silts) that decrease in stability when scarified, worked, and rolled.

There are also some soils that shrink excessively during dry periods and expand excessively when allowed to absorb moisture. When these soils are encountered, special treatment is required. Unsuitable soils that will not support equipment used in maintenance or repair operations will be stabilized or removed and replaced with more suitable soils. Unsuitable subgrade soils under a failed pavement will be repaired or removed and replaced prior to other correction action.

a. Clays. The types of clays that show a decrease in strength when scarified and rolled are generally organic and…