• No results found

DEPARTMENT OF THE AIR FORCE HEADQUARTERS AIR FORCE CIVIL ENGINEER SUPPORT AGENCY

N/A
N/A
Protected

Academic year: 2021

Share "DEPARTMENT OF THE AIR FORCE HEADQUARTERS AIR FORCE CIVIL ENGINEER SUPPORT AGENCY"

Copied!
100
0
0

Loading.... (view fulltext now)

Full text

(1)

DEPARTMENT OF THE AIR FORCE

HEADQUARTERS AIR FORCE CIVIL ENGINEER SUPPORT AGENCY

27 JUL 2007

FROM: AFCESA/CEO

139 Barnes Drive, Suite 1 Tyndall AFB, FL 32403-5319

SUBJECT: Engineering Technical Letter (ETL) 07-8: Spall Repair of Portland

Cement Concrete (PCC) Airfield Pavements in Expeditionary Environments

1. Purpose. This ETL supplements guidance provided in Unified Facilities Criteria

(UFC) 3-270-03, Concrete Crack and Partial Depth Spall Repair. This ETL provides standard procedures for repairing spalls on PCC pavements. This ETL focuses on the use of extremely rapid-setting repair materials.

Note: The use of the name or mark of any specific manufacturer, commercial product,

commodity, or service in this ETL does not imply endorsement by the United States Air Force.

1.1. Background. Spall repairs lasting several years are routinely achieved at

primary operating bases. Repairs in expeditionary environments using procedures outlined in the UFCs have achieved life spans in excess of 12 months in apron areas but often last less than eight months on runways and primary taxiways. Some spall repairs constructed at expeditionary locations have failed sooner than would normally be anticipated based upon load test studies. An investigation of spall repair failures was initiated to determine the cause of repair failures in the field, determine why there was a difference as compared to the load test studies, and to develop materials and practices recommendations to minimize these failures.

Many of the repairs at these locations involve large non-uniformly shaped repairs that are loaded shortly (within a few hours) after placement. While many problems can be traced back to problems with the preparation of the spall, there are some problems that arise from curing techniques, material selection, and early loading. The need to use extremely rapid-setting materials and the early loading of repairs

(2)

always fully implemented in the field. In some instances, restricted time on the airfield to perform the repairs has resulted in some recommendations not being followed. This document provides recommendations that will extend the overall life of a repair when time on the airfield is limited. This ETL does not cover full-depth repairs (repairs with a depth greater than one-half of the pavement thickness).

Paragraph 9 provides information on emergency repairs that will allow airfield operations; however, these repairs are not expected to last more than a few passes or days.

2. Application. This document applies specifically to the repair of spalls on PCC airfield

surfaces in expeditionary environments.

2.1. Authority: Air Force Policy Directive (AFPD) 32-10, Installations and Facilities. 2.2. Effective Date: Immediately.

2.3. Intended Users: Air Force base civil engineers (BCE); RED HORSE squadrons,

and other units responsible for the repair of airfield pavements in an expeditionary environment; U.S. Army Corps of Engineers (USACE) and Navy offices responsible for the emergency repair of airfield pavements.

2.4. Coordination: Air Force major command (MAJCOM) pavement engineers; the

Naval Facilities Engineering Service Center (NFESC); the USACE Engineering Research and Development Center (ERDC); and the USACE Transportation Systems Center (TSMCX).

3. Referenced Publications: 3.1. Air Force:

• AFPD 32-10, Installations and Facilities, available at:

http://www.e-publishing.af.mil/pubs/publist.asp?puborg=AF&series=32

3.2. Joint:

• ETL 96-4, Temporary Joint Sealing Details and Procedures for Pavements,

available at: http://www.wbdg.org/ccb/AF/AFETL/etl_96_4.pdf

• ETL 97-2 (Change 1), Maintenance and Repair of Rigid Airfield Pavement

Surfaces, Joints, and Cracks, available at:

http://www.wbdg.org/ccb/AF/AFETL/etl_97_2.pdf

• ETL 02-8, Silicone Joint Sealant Specification for Airfield Pavements, available at: http://www.wbdg.org/ccb/AF/AFETL/etl_02_8.pdf

(3)

• UFC 3-250-08FA, Standard Practice for Sealing Joints and Cracks in Rigid and Flexible Pavements, available at:

http://www.wbdg.org/ccb/DOD/UFC/ufc_3_250_08fa.pdf

• UFC 3-270-03, Concrete Crack and Partial-Depth Spall Repair, available at:

http://www.wbdg.org/ccb/DOD/UFC/ufc_3_270_03.pdf

• UFC 3-270-04, Concrete Repair, available at:

http://www.wbdg.org/ccb/DOD/UFC/ufc_3_270_04.pdf

• UFC 3-270-07, O&M: Airfield Damage Repair, available at:

http://www.wbdg.org/ccb/DOD/UFC/ufc_3_270_07.pdf

3.3. Federal Aviation Administration (FAA):

• Design Guide Supplement: Portland Cement Concrete: Airport Pavements, FAA, Northwest Mountain Region, October 2003, available at:

http://www.faa.gov/airports_airtraffic/airports/regional_guidance/northwest_m ountain/construction/design_resources/media/des_pcc.doc

• FAA Circular 150/5380-6A, Guidelines and Procedures for Maintenance of

Airport Pavements, 14 Jul 2003, available at:

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCirc ular.nsf/0/d64e80527a2b7c3f86256d640063b59a/$FILE/150-5380-6A.pdf

3.4. ASTM International:

• ASTM C309, Standard Specification for Liquid Membrane-Forming Compounds for Curing Concrete, available at:

http://www.astm.org/cgi-bin/SoftCart.exe/index.shtml?E+mystore

• ASTM C882, Standard Test Method for Bond Strength of Epoxy-Resin Systems Used with Concrete by Slab Shear, available at:

http://www.astm.org/cgi-bin/SoftCart.exe/index.shtml?E+mystore

4. Acronyms and Terms.

ASTM – American Society for Testing and Materials ASR – alkali-silica reaction

BASF – Badische Anilin und Soda Fabrik

C – Celsius

CTS – CTS Cement Manufacturing Corporation cu ft – cubic foot

(4)

RED HORSE – Rapid Engineers Deployable Heavy Operations Repair Squadron Engineers

rpm – revolutions per minute SSD – saturated surface dry UFC – Unified Facilities Criteria

USACE – U.S. Army Corps of Engineers

5. Summary of Procedures. See paragraph 8 for detailed descriptions of each

procedure.

5.1. Remove loose debris from the damaged area.

5.2. Mark the outer edge of the repair (2 to 3 inches [50 to 76 millimeters] beyond

the damaged area).

5.2.1. The shape should be a rectangle or pentagon. 5.2.2. The aspect ratio should be less than two.

5.2.3. The largest dimension should be 8 feet (2.4 meters) or less.

5.3. Saw the edges of the repair to a depth of at least 2 inches (50 millimeters). Do

not feather the repair.

5.4. Make additional cuts within the bounds of the repair edges using a concrete

saw.

5.5. Make transverse cuts on each end, 1.5 inches (38 millimeters) from the ends of

the repair.

5.6. Remove the remaining material using a small jack hammer (30 pounds or less).

5.7. A skid steer mounted cold planer can also be used to prepare the repair area. 5.8. Remove loose debris from the repair area.

5.9. Wash the repair area with a high-pressure washer or use water and a scrub

brush.

5.10. Remove any loose material or lodged debris from the joint or crack. 5.11. Place a small bead of caulk over the joint or crack.

(5)

5.13. Place a compressible insert material over any joint or crack in the repair area. 5.14. Mix the materials in accordance with manufacturers’ recommendations.

5.15. A temperature gun (thermometer) should be used to check the temperature of

the water and material before mixing, as well as the temperature of the material during mixing.

5.16. Pour/place the material in the repair.

5.17. Clean mixing and placement equipment immediately after use.

5.18. When using cement repair materials, either wet cure or apply curing

compound.

5.19. Remove the compressible spacer insert after the repair has cured.

5.20. Reseal the joint.

6. Summary of Material Test Data. Based on tests performed by the Air Force

Research Laboratory (AFRL) in the summer of 2007, the following hydraulic cement-based products provided the best performance in several key tests: CTS Cement Rapid Set DOT Repair Mix; Pre-Blend’s Premium Patch; BASF’s Thoroc 10-60; Dayton Superior’s HD-50; and Euclid Chemical’s Versaspeed. These products provided the best performance (comparing cement products; polymers not compared) at early ages (1.5 to 4 hours) in several critical areas. These areas included bond, compressive, tensile and flexural strength, set times and strength consistency. Additional testing is underway. The results of these tests will be included in future updates of this ETL.

7. General Guidance and Information.

7.1. There are four areas that require particular attention to ensure a long-lasting

repair. In general, it is important to identify and address the root cause of the pavement distress or the pavement and repair will continue to deteriorate. Most spalls result from debris that enters a joint or crack; therefore, it is important to clean and seal all cracks and joints.

(6)

7.1.1.2. When making repairs next to joints or cracks, the joint or crack must

be sealed with a small pliable bead of caulk or other equivalent seal material to prevent the intrusion of grout or epoxy into the crack or joint.

7.1.1.3. When making repairs next to joints, the repair material must not be

placed so that it is in direct contact with the adjacent slab. A compressible spacer must be placed in the joint. Tests conducted on spall repairs where such a spacer was not included resulted in failures within 48 hours.

7.1.1.4. Failure to properly clean out and seal the joint or crack will reduce the

life expectancy of the repair.

7.1.2. Ensure that spall repairs rest on clean, sound material.

7.1.3. Allow the repair material enough time to cure. This is at least two hours

when the ambient air temperature is above 75 degrees Fahrenheit (75 °F [24 °C]) when using the materials listed in paragraph 7.3 (check manufacturer’s recommendations). Additional cure time will increase the probability that the patch will last up to and beyond two years. When the temperature is below 75 °F (24 °C), the amount of unloaded cure time (including mix time) will increase. The amount of increase in time varies with the materials, core temperature of the pavement, and curing technique. In general a compressive strength in excess of 2700 psi is desired before loading. See the manufacturer’s recommendations on minimum pavement temperatures for placing repairs.

7.1.4. Maintain a proper geometry and size for the repair. The largest repair

dimension without a joint should be no more than 8 feet (2.4 meters).

7.2. It is important to select the right repair materials and procedures to provide a

long-lasting repair.

7.2.1. Emergency repairs are required when there is insufficient time to properly

repair the airfield using conventional materials/techniques. This type of repair can fail in a short period of time, perhaps after only a few aircraft passes. Therefore, such repairs require constant monitoring and will require replacement with a permanent repair at the earliest possible opportunity.

7.2.2. Full-depth Repairs. Full-depth repairs are required when the unsound

portion of the pavement extends below the mid-height of the slab, or if the spall is located on a section of slab prone to movement due to a lack of base support or lack of dowels for load transfer across a joint or crack. Also, a full-depth repair should be considered when a spall occurs on a corner break.

(7)

7.2.3.1. Partial-depth repairs are placed when repairing an area that is

one-half the thickness of the slab or less, and the remainder of the slab on which the repair is placed is not prone to movement.

7.2.3.2. Partial-depth Repairs on a Crack (Vice a Doweled Joint). When spalls

are located on a crack in a slab, the crack should be treated as a joint. Furthermore, load transfer across the crack should be restored in accordance with Chapter 10 of UFC 3-270-04, Concrete Repair, or the life of the repair will be shortened.

7.3. Materials. The following materials have been tested and have performed well in

several repair environments. The Material Safety Data Sheets (MSDS) for these materials are provided in Attachment 1. The effectiveness of these materials can be increased by storing the materials inside an air-conditioned space for at least 48 hours before use and when any required mixing water is heated or cooled to 72 °F (22 °C) before use.

7.3.1. General Guidance.

7.3.1.1. Some of the materials used to patch spalls are very alkaline;

therefore, care should be taken to ensure these alkaline patch materials are not placed on pavements containing materials that are prone to alkali-silica reaction (ASR). Furthermore, aggregates used to extend patch mixes should be checked to ensure ASR-susceptible materials are not used.

7.3.1.2. It is recommended that full containers be used when preparing a

patch. Many extremely or very rapid-setting materials contain several chemicals that are a small portion of the mix but are extremely vital to the proper performance of the patch.

7.3.1.3. It is recommended that more material than required be ready for use

to ensure you have sufficient material on hand. Owing to the precise nature of the chemistry used in many of these materials, some variability in mix performance can be expected in the field.

(8)

Unfortunately, faster setting materials tend to create more heat during setting and curing and can experience a large amount of dilation and shrinkage over the first few months after placement. Extremely or very rapid-setting materials also tend to be more sensitive to contaminants present during the mixing and placing process.

7.3.2. CTS Cement Rapid Set DOT Repair Mix, no National Stock Number

(NSN), may be used if the ambient air temperature is between 32 °F and 100 °F (0 °C and 38 °C). Work time is approximately 10 to 15 minutes at 72 °F (22 °C). This material may be extended with aggregate. A mortar or concrete drum mixer can be used to mix this material, but is not recommended at temperatures above 70 °F (21 °C) due to rapid setting. This material is trowelable. It can not be poured in lifts.

a. Part Number: 511 655

b. Minimum Order: 1 Pallet (50 each 55-lb bags) c. Cost: $21 per bag (plus shipping)

d. Shelf Life: One year

e. Potential Source POC: Frank Senatore, CTS Cement, 11065 Knott Avenue, Suite A, Cypress, CA 90630, (800) 929-3030 Ext. 130 f. Web Site: http://www.rapidset.com/home.asp

7.3.3. Thoroc 10-60, BASF Building Systems (formerly Degussa Building

Systems), no NSN, may be used if the ambient air temperature is between 40 °F and 110 °F (4 °C and 43 °C) (estimated). For temperatures above 90 °F (32 °C), consider using Thoroc 10-61 which provides a long work time at very high temperatures (10-61 is not recommended for temperatures below 90 °F [32 °C] due to the much longer set times). Work time for Thoroc 10-60 is approximately 15 minutes at 70 °F (21 °C). This material may be extended with aggregate. A mortar or concrete drum mixer can be used to mix this material, but is not recommended at temperatures above 70 °F (21 °C) due to rapid setting. This material is trowelable. It can not be poured in lifts.

a. Minimum Order: 1 Pallet (50 each 50-lb bags) (1 bag yields 0.43 cu ft [0.012 m3])

b. Cost: $21 per 50-lb bag plus shipping c. Shelf Life: One year

d. Potential Source: BASF Building Systems, 889 Valley Park Drive, Shakopee, MN 55379, (800) 243-6739, (800) 433-9517

e. Web Site: http://www.basfbuildingsystems.com

(9)

area, use 90 °F (32 °C) mixing water, and cover with a curing blanket for two hours. This material must be extended with 0.75-inch (19-millimeter) washed pea gravel for patches deeper than 2 inches (50 millimeters). A mortar or concrete drum mixer can not be used to mix this material. This material is trowelable. It can not be poured in lifts.

a. Part Number: Premium Patch

b. Minimum Order: 1 Pallet (50 each 50-lb bags) (1 bag yields 0.43 cu ft [0.012 m3])

c. Cost: $16 per 50-lb bag plus shipping d. Shelf Life: One year

e. Potential Source: Pre-Blend Products Inc., 100 Den Fairless Drive, Fairless Hills, PA 19030, (215) 295-6004

f. Web Site: http://www.preblend.com

7.3.5. Dayton Superior HD-50 is a flowable fiber-reinforced material that may be

used if the ambient air temperature is between 10 °F and 100 °F (-12 °C and 38 °C). Work time is approximately 15 minutes at 72 °F (22 °C). This material may be extended with aggregate. A mortar mixer can be used to mix this material, but is not recommended at temperatures above 70 °F (21 °C) due to rapid setting. This material is trowelable. It can not be poured in lifts.

a. No Minimum Order Required. (Note: 1 pallet contains 60 each 55-lb bags) b. Cost: $28 / bag

c. Shelf Life: One year

d. Potential Source POC: Ram Tool & Supply, 1411 Moylan Road, Panama City Beach, FL 32407, (850) 230-4700

e. Web Site: http://www.daytonsuperior.com/chemical/index.htm

7.3.6. Versaspeed, Euclid Chemical Company, no NSN, may be used if the

ambient air temperature is between 20 °F and 85 °F (-7 °C and 29 °C). Work time is approximately 15 minutes at 72 °F (22 °C). For temperatures above 85 °F (29 °C), use Versaspeed LS. This material must be extended with 0.75-inch (19-millimeter) washed pea gravel for patches deeper than 2 inches (50 millimeters). A mortar mixer can be used to mix this material, but is not recommended at temperatures above 65 °F (18 °C) due to rapid setting. This material is

(10)

7.3.7. Pavemend 15, NSN 6850-01-500-6996, may be used in ambient air

temperatures up to 120 °F (49 °C), but should not be used if the temperature is below 30 °F (-1 °C). Work time is seven to nine minutes at 72 °F (22 °C). This material can not be extended with aggregate. This material should never be mixed in a mortar or concrete drum mixer—it sets up too quickly. This material is self-leveling. This material can be poured in lifts.

a. Minimum Order: 1 Pallet (36 each 5-gallon buckets), 45 lbs / bucket, 0.42 cu ft (0.012 m3) / bucket

b. Cost: $60 / bucket

c. Shelf Life: Three years in original, unopened bucket

d. Potential Source POC: Michelle Crowder, 1500 North Beauregard Street, Suite 320, Alexandria, VA 22311, (804) 556-5159

e. Web Site: http://www.ceratechinc.com/

7.3.8. Pavemend TR, NSN 6850-01-532-9958, should not be used if the ambient

air temperature is above 90 °F (32 °C), and may be used in temperatures down to 0 °F (-18 °C). Work time is three to six minutes at 72 °F (22 °C). This material may be extended with aggregate. This material should never be mixed in a mortar or concrete drum mixer—it sets up too quickly. This material is semi-self-leveling and trowelable. This material can be poured in lifts.

a. Minimum Order: 1 Pallet (36 each 5-gallon buckets), 46 lbs / bucket, 0.42 cu ft (0.012 m3) / bucket

b. Cost: $60 / bucket

c. Shelf Life: Three years in original unopened bucket

d. Potential Source POC: Michelle Crowder, 1500 North Beauregard Street, Suite 320, Alexandria, VA 22311, (804) 556-5159

e. Web Site: http://www.ceratechinc.com/

7.3.9. Pavemend 5.0, no NSN, should not be used if the ambient air temperature

is above 100 °F (38 °C) (this material is not recommended if the temperature is above 90 °F [32 °C]), and may be used in temperatures down to 0 °F (-18 °C). Work time is two to three minutes at 72 °F (22 °C). This material can not be extended with aggregate. This material should never be mixed in a mortar or concrete drum mixer—it sets up too quickly. This material is self-leveling. This material can be poured in lifts.

a. Minimum Order: 1 Pallet (36 each 5-gallon buckets), 45 lbs / bucket, 0.42 cu ft (0.012 m3) / bucket

(11)

7.3.10. FlexPatch, NSN 6850-01-549-0548, is a polymer which requires a dry

surface for placement. This is a three-part mix which must be stored between 50 °F and 90 °F (10 °C and 32 °C). This material may be used in ambient air temperatures from 40 °F to 100 °F (4 °C to 38 °C). The material must be conditioned to a temperature between 65 °F and 80 °F (18 °C and 27 °C) before use. The working time is 20 minutes at 72 °F (22 °C). The cure time increases dramatically as temperature decreases. This material is not recommended for use if the temperature is below 60 °F (16 °C) unless you have more than four hours before the first load application. It can not be extended with aggregate. It can be cleaned before it sets using mineral spirits. A mortar mixer can be used but is not recommended due to the restrictive cleanup requirements. Instead, mix the material in 5-gallon buckets. This material is trowelable. It can not be poured in lifts.

a. No Minimum Order

b. Cost: $80 / Bucket (0.5 cu ft [0.014 m3] Kit) (plus shipping) or $150 / Bucket (1 cu ft [0.028 m3] Kit) (plus shipping)

c. Shelf Life: One year

d. Potential Source POC: Charles Smith, Silicon Specialties, Inc (SSI), 430 South Rockford, Tulsa, OK 74120, (918) 271 – 2210

e. Web Site: http://www.ssicm.com/flexpatch.htm

7.4. Equipment: The following equipment is recommended for repairing spalls:

• Non-contact infrared digital thermometer

• Concrete saw with a 16-inch- (406-millimeter) diameter or larger blade • 30-pound or smaller jack hammer

• Small, single pistol grip, pneumatic chisel

• Mixing drill with paddle (500 rpm minimum, 800 rpm maximum) • Portable air compressor

• Portable generator • Wet/dry vacuum • Utility knife • Caulking gun

(12)

8. Procedures:

8.1. Remove loose debris from the damaged area by hand, broom, compressed air,

and/or with a wet/dry vacuum.

8.2. Mark the outer edge of the repair.

8.2.1. The outer edge should be located 2 to 3 inches (50 to 76 millimeters)

beyond the damaged area (area of scaling, cracking, or spalling). Use a metal rod to “sound” the area around the visibly damaged area to determine the extent of the unsound material. In some instances there is a horizontal crack (delamination) that extends beyond the visible surface damage.

8.2.2. The repair area should be square or rectangular in shape (it may be

pentagonal at a slab corner).

8.2.3. When a repair spans a crack or joint, the repair must be considered as two

repairs—one on each side of the crack or joint.

8.2.4. The length and width of the rectangle must each be larger or equal to 6

inches (152 millimeters).

8.2.5. The ratio of the longer dimension to the shorter dimension of the repair is

called the aspect ratio.

8.2.5.1. The aspect ratio should be less than two.

8.2.5.2. If the aspect ratio is larger than two, the repair must be broken into

two or more individual repairs. These repairs can be accomplished at the same time, but must be separated at the time the material is placed by using a form or insert (backer board), or it must be separated by saw cutting once the material has cured for at least two hours but not more than three days.

(13)
(14)

8.4. Make additional cuts within the bounds of the repair edges using a concrete

saw. The cuts should be made in the longitudinal direction and spaced 1 to 2.5 inches (25 to 64 millimeters) apart.

8.4.1. The cuts should extend 2 inches (50 millimeters) below the pavement

surface or 0.5 inch (13 millimeters) below the bottom of the spall.

8.4.2. Make sure the cuts do not extend beyond the edge of repair or across a

joint or crack.

Figure 3. Longitudinal Cuts

8.5. Once the longitudinal cuts are complete, one or two transverse cuts on each

end should be made 1.5 inches (38 millimeters) from the ends of the repair.

8.5.1. The depth of these cuts should match that of the edge cuts.

8.5.2. Make sure these cuts do not extend beyond the edge of the repair area or

(15)

Figure 4. Transverse Cuts

8.6. Remove the remaining material using a small jack hammer (30 pounds or less).

8.6.1. A small, hand pistol grip chisel can be used to clean up the corners and

avoid extra spalling of the edges.

(16)

8.7. Alternative Preparation Methods.

8.7.1. A skid steer mounted cold planer (i.e., milling machine) can also be used

to remove unsound material and prepare the area for placing the repair material. Ensure that the bits/tips of the planer are designed for use on concrete.

(17)

8.7.2. Use of a jack hammer alone is not recommended. If a jack hammer must

be used, then the hammer should be 30 pounds or smaller in size. Larger hammers can cause damage to the underlying material, as shown in Figure 6, which will lead to a reduced life expectancy of the repair.

(18)

8.8. If necessary, the bottom of the repair may be sloped; however, the slope should

be kept as minimal as possible and there should not be any abrupt changes in slope within the repair.

Figure 7. Repair with Abrupt Slope Change (Not Recommended)

Figure 8. Repair without Abrupt Slope Change (Recommended)

(19)

Compressed air should be filtered to prevent oil and other contaminants from being blown onto the clean surface.

8.10. If a dowel bar or any rebar is exposed, with more than one-fourth of the bar

circumference exposed for 3 inches (76 millimeters) or more of length, remove material 0.5 inch (13 millimeters) to either side and below the dowel/rebar. This should be done with a concrete saw and a small pneumatic chisel, hammer drill, or jack hammer. Typical design standards place dowel bars at the mid-height of a slab; however, they have been found in the top half of the slab at some contingency locations. If you encounter a dowel at mid-height, a full-depth repair should be accomplished.

8.11. Wash the repair area with a high-pressure washer or use water and a scrub

brush. When using a polymer such as FlexPatch, it is best to clean the surface without water by scrubbing the surface with a stiff brush while blowing compressed air over it, or sandblasting the repair area.

8.12. Remove any loose material or lodged debris from the joint or crack. 8.13. Place a small bead of caulk over the joint or crack.

8.14. If the temperature of the pavement is above 90 °F (32 °C) (some materials

require this at temperatures above 80 °F [27 °C]), pour cool or ice water onto the repair area and, if possible, allow it to sit for two to five minutes, or flush cool water over the repair area for two minutes.

8.14.1. Remove the excess water with a wet/dry vacuum or use compressed air

to blow it out.

8.14.2. When using a polymer such as FlexPatch, all excess and surface

moisture must be removed by blowing the surface with compressed air.

8.14.3. For cement-based materials such as Pavemend, CTS Cement Rapid Set

DOT Road Repair Mix, and Dayton Superior HD-50, leave the area SSD.

(20)

8.15.3. Any holes or gaps in the insert must be filled or sealed.

8.15.4. It may be necessary to tape several pieces of backer board together to

meet the repair geometry.

Figure 9. Compressible Insert Placed at Joint Interface Before Placing Repair Material

(21)

8.16. Surface Preparation/Bonding Agents.

8.16.1. One of the primary functions of a bonding agent is to reduce the amount

of water absorbed by the surrounding material.

8.16.2. Polymer materials such as FlexPatch do not require a special bonding

agent. However, they may (as in the case of FlexPatch) require the user to apply some of the liquid portion of the product (i.e., prior to adding aggregate) to the repair area surfaces with a brush or trowel.

Figure 11. Applying FlexPatch Liquid to Repair Area Surfaces

8.16.3. Hydraulic cement materials such as Pavemend, CTS Cement Rapid Set

DOT Road Repair Mix, and Dayton Superior HD-50, normally do not require a bonding agent if the repair area is in SSD condition when the repair material is placed. At high temperatures (above 90 °F [32 °C]), and/or where SSD conditions cannot be maintained before mixing and placing the repair material, a bonding agent such as Dayton Superior’s Ad Bond (J-40) (an acrylic latex material) should be applied to the surfaces of the repair area.

8.17. Mix the materials in accordance with manufacturers’ recommendations.

(22)

8.17.1.2. For polymer materials, all containers, paddles, and trowels should

be kept dry. These types of materials require special materials for cleanup (e.g., mineral spirits for FlexPatch).

8.17.2. A temperature gun (thermometer) should be used to check the

temperature of the water and material before mixing, as well as the temperature of the material during mixing.

8.17.3. The mix times will increase at lower ambient air temperatures and will

decrease in high temperatures. At temperatures above 95 °F (35 °C), some of the recommended materials have been known to flash set.

8.17.4. Store the mortar at approximately 72 °F (22 °C) for at least 48 hours

before use. Combine with water poured at 72 °F (22 °C) to extend workability in hot weather and speed the set time in cold weather. Alternatively, some materials recommend ice water for mixing in hot temperatures or 90 °F (32 °C) water for mixing in temperatures below 40 °F (4 °C). Consult the manufacturer’s recommendations.

8.17.5. Some polymers such as Concrete Welder, Delcrete, and Flexset are very

sensitive to moisture and require surfaces and aggregates (when used) that are absolutely dry.

8.17.6. Extreme care must be taken when using locally obtained aggregates to

extend the materials. In general, the use of these aggregates is discouraged. Many repair materials are very alkaline and can prematurely fail when extended with ASR-susceptible aggregates. Some repair materials cannot be extended with limestone aggregates (consult the manufacturer’s recommendations). However, the use of aggregates can improve dimensional stability (i.e., reduce shrinkage) and reduce thermal problems during the setting and curing. Any aggregates used must be washed before use. Aggregates should be stored in a covered location. They should be dry for use in polymer repairs. Aggregates should be soaked and SSD for use in hydraulic cement repairs. Typically, it is best to use a well-graded aggregate from a crushed material; however, most manufacturers of extremely and very rapid-setting materials recommend the use of a uniformly graded rounded aggregate (0.375-inch [10-millimeter] pea gravel) to ensure the material can be placed quickly enough. Furthermore, the use of aggregates in these materials is used to control shrinkage and heat production, not necessarily for strength and cement reduction.

8.17.6.1. Some materials are shipped with proprietary aggregates.

(23)

8.17.6.3. Test a small batch of the aggregate/material mix before use on the

airfield.

(24)

8.18.3. The other materials recommended in this ETL require some work to

ensure that a complete, compact, level repair is obtained. Rod or vibrate the material briefly after it is placed in the repair area, then level the repair with a screed, float, or trowel.

Figure 14. Filling the Repair Area with Pavemend

8.19. Clean mixing and placement equipment immediately after use.

8.19.1. Polymers will require special materials for cleanup (e.g., mineral spirits for

Flexpatch).

8.19.2. Water may be used for cleaning when using hydraulic cements for

repairs.

8.20. Curing.

8.20.1. Polymer repair materials do not require any special treatment for curing;

however, in cold weather required cure times will increase. Use of a blanket will reduce cure times.

8.20.2. Hydraulic cement materials such as CTS Cement DOT Rapid Set Repair

Mix, Thoroc, Premium Patch, Dayton Superior HD-50, Versaspeed, and Pavemend require a moisture cure for one hour after the material has initially set and when windy or hot (over 80 °F [27 °C]), dry conditions prevail. It is recommended that steps to reduce moisture loss during curing be implemented.

(25)

Compounds for Curing Concrete, such as ChemMasters Safe-Cure 2000 (see

MSDS in Attachment 1), once the repair no longer has a surface sheen. Apply at least two coats of the compound or apply until the surface appears completely white. This compound can be applied as soon as the surface has been worked to the finish grade.

8.21. When possible, remove the spacer insert after the repair has cured for at least

two hours.

8.22. Reseal the joint with backer rod and joint sealant to ensure that incompressible

material and moisture cannot easily enter the joint or crack.

9. Emergency Repair Procedures. When time on the airfield, availability of materials

or equipment, or operational requirements dictate that a spall be repaired in a manner other than as outlined in paragraph 8, the following procedures may be used.

9.1. Remove loose debris from the damaged area by hand, broom, compressed air,

and/or with a wet/dry vacuum.

9.2. Brush the surface vigorously with a stiff brush. Remove all dust /loose debris

with a broom, compressed air, and/or with a wet/dry vacuum.

9.3. If possible, place a section of backer board or other soft insert material over any

joint or crack in the repair area.

9.4. Mix and place patching material in the prepared area until level with or within 0.5

inch (13 millimeters) of the surface.

9.4.1. For temperatures above 90 °F (32 °C), use Pavemend 15.

9.4.2. For temperatures from 40 °F to 90 °F (4 °C to 32 °C), use Pavemend 5.0

or Pavemend SLQ.

9.4.3. Alternatively, an asphalt cold patch material such as Instant Road Repair

(26)

Figure 15. Instant Road Repair Patch

9.4.4. Some polymers, such as Concrete Welder, that are extremely sensitive

(very reactive) to water are the least preferred materials; however, some of these repairs can be opened to traffic within a few minutes of placement. These materials do not work in the presence of water.

9.5. At a minimum, monitor emergency repairs daily. Take steps to re-accomplish

(27)

10. Special Considerations.

10.1. If a spall extends along both a transverse joint and longitudinal joint which

meet at a corner, the spall repair must be accomplished as two repairs: one along the transverse joint and one along the longitudinal joint.

10.1.1. If they must be accomplished at the same time (i.e., in one pour), then a

spacer must be placed or a 2-inch- (51-millimeter) deep cut must be sawed at the junction of the two repairs (preferably in the longitudinal direction).

10.1.2. Saw cuts should be made after final set of the material, usually one to two

hours after the pour.

10.1.3. The cut or joint should be filled with a backer rod and joint sealant.

(28)

Figure 17. The Same Repair with Red Lines Added to Indicate Where Saw Cuts Should Have Been Made

10.2. The repair sections should be square, rectangular, or pentagonal (for corner

spalls) in shape. Many repairs in the field have a complex geometry when seen in plan view. When such repair geometries are necessary, the repair must either be accomplished in several phases/pours or crack control joints must be cut into the resulting repair to control the location and condition of cracks. All joints must be sealed with a sealant. Joints should be aligned in a longitudinal direction whenever possible. Saw cuts must be made no sooner than the final set, which usually occurs one to two hours, and no later than 12 hours, after the material is placed. Delays in making the saw cuts will reduce the life span of the repair.

(29)
(30)

aligned in the longitudinal direction whenever possible. Saw cuts must be made no sooner than the final set, which usually occurs one to two hours, and no later than 24 hours, after the material is placed. Delays in making the saw cuts will reduce the lifespan of the repair. Controlling the size of the repair will reduce stresses on the bond interface and increase the lifespan of the repair.

10.4. Weather conditions during the preparation and placement of a repair can

decrease the life expectancy of the repair. Steps to mitigate weather effects are presented below.

10.4.1. Wind. The biggest effect of wind on the repair—aside from blowing debris

into the prepared spall—is increased evaporation. This can quickly dry the prepared repair surface which can adversely affect the bond and dry the surface of the placed repair material, leading to shrinkage cracks.

Note: Windy conditions do not affect the performance of polymer materials.

10.4.1.1. Use a bonding agent similar to Dayton Superior’s Ad Bond (J-40)

when an SSD condition on the repair surface cannot be maintained. Alternatively, a grout scrub can also be used as a bonding agent, but it must be applied very rapidly, followed by material placement before the grout sets or dries.

10.4.1.2. Moist cure hydraulic cement materials for one hour after the material

has no sheen. This can be done by misting the surface or by placing a wet burlap cloth over the repair. Alternatively, a white curing compound, similar to ChemMasters Safe-Cure 2000, can be applied. Apply the curing compound until the entire repair surface appears completely white (at least two coats).

10.4.2. Rain. Rain can affect the bond by ponding water in the repair area. It can

also adversely affect the material during mixing, placement, and curing by affecting the water/cement ratio or by chemically reacting with the polymers. Use a portable rain fly, similar to an easy-up, to cover the repair area and/or use a box van for mixing the materials. Some materials, such as Concrete Welder, will foam up when exposed to the slightest amount of water and are not recommended for use when it is raining.

10.4.3. Heat. Heat can affect the bond developed between the repair materials

and the existing slab. It can cause flash setting of the repair materials and shrinkage cracking.

(31)

10.4.3.2. If SSD conditions cannot be maintained, use a bonding agent with

hydraulic cement materials (not for Flexpatch, which is a polymer material).

10.4.3.3. Precondition the materials (cement and water) and tools by storing

them in a cool place, 72 °F (22 °C) or cooler, for at least 48 hours before use. When transported to a job site, the materials should be kept in a cooled vehicle cab or in a Styrofoam cooler or insulated box.

10.4.3.4. Use materials designed for high temperatures, such as Thoroc

10-60, Thoroc 10-61, Versaspeed LS, Pavemend 15 or FlexPatch. Some manufacturers sell admixtures that can be combined with their repair products to increase the effective temperature range. CTS sells admixtures that can be used with their DOT repair mix.

10.4.3.5. Moist cure hydraulic cement materials (not polymer materials such

as FlexPatch) for one hour after the material has set (i.e., no sheen). This can be done by misting the surface or by placing a wet burlap cloth over the repair. Alternatively, a white curing compound, similar to ChemMasters Safe-Cure 2000, can be applied. Apply the curing compound until the entire repair surface appears completely white (at least two coats).

10.4.4. Cold, Cold temperatures can affect the bond between repair materials

and the existing slab. It can cause the material reactions to halt, resulting in the material failing to set or cure.

10.4.4.1. Heat the pavement by running hot water or steam over the

pavement for several minutes (until the surface is warm to the touch). Alternatively, aerospace ground equipment (AGE) heaters can be used.

10.4.4.2. Precondition the materials (cement and water) and tools by storing

them in a warm place, 72 °F (22 °C) or warmer (Dayton Superior and Premium Patch recommend 90 °F [32 °C] for HD-50), for at least 48 hours before use. When transported to a job site, the materials should be kept in a warm vehicle cab or in a Styrofoam cooler or insulated box.

(32)

shift the critical resource from time on the airfield to the availability of personnel, equipment, and materials. Several phased repair options are presented below.

11.1. Areas of distressed concrete are identified but major spalls do not yet exist, or

spalls exist in areas not subject to direct tire loads.

Step 1 Saw cut the borders of the spall area and clean loose debris.

Step 2 It may be possible to make additional cuts within these borders, spaced 2 inches (51 millimeters) apart in the longitudinal direction (direction of traffic), to assist with the removal of material within the borders. Refrain from this step if the concrete becomes loose as a result of this additional saw cutting. This step can be done in conjunction with Step 1.

Step 3 a. Remove (jack hammer) the unsound concrete. b. Place a compressible joint spacer insert. c. Fill the spall.

Step 4 If possible, remove the joint spacer and reseal the joint.

11.2. Spall must be immediately filled. Additional areas around the spall may be

unsound, but are not spalled.

Step 1 a. Remove loose debris from the spall.

b. Caulk or otherwise protect the joint from repair material entering the joint or crack.

c. If possible, place a compressible joint spacer insert. d. Fill the spall.

Note: This type of spall repair will rapidly deteriorate and the next phases must

remove and replace this original repair.

Step 2 Saw cut the borders of the spall area and clean loose debris.

Step 3 It may be possible to make additional cuts within these borders, spaced 2 inches (51 millimeters) apart in the longitudinal direction (direction of traffic), to assist with the removal of material within the borders. This can be done in the repair material also, but is difficult to do in some polymer repairs. Refrain from this step if the concrete becomes loose as a result of this additional saw cutting. This may be

(33)

b. If possible, place a compressible joint spacer insert. c. Fill the spall.

Step 5 If possible, remove the joint spacer and reseal the joint.

11.3. Spall must be filled, but there is not enough time to perform all of the

necessary saw cuts in the initial phase/step.

Step 1 a. Remove (jack hammer) the unsound concrete directly below the spall and a few inches on all sides. Remove all debris.

b. If possible, place a compressible joint spacer insert.

c. Fill the spall. This may lead to feathered edges and may leave some unsound material remaining outside of the original spall area—this will be addressed in later steps.

Step 2 Cut the borders of the entire spall area and clean loose debris.

Step 3 Make additional cuts within these borders, spaced 2 inches (51 millimeters) apart in the longitudinal direction, to assist with the removal of material within the borders. This may be done in conjunction with Step 2.

Step 4 a. Saw cut the spall material 1 to 2 inches (25 to 51 millimeters) within the feathered edge on each side of the spall.

b. Remove (jack hammer) the unsound concrete. c. If possible, place a compressible joint spacer insert. d. Fill the spall.

e. Cut the new spall repair in the longitudinal direction along one or two sides of the repair. This will prevent diagonal cracks from forming in the repair. Alternatively, Step 4 may be accomplished in three separate steps, ensuring each time that a rectangular section is poured so as to minimize stress intensities at interior corners and preclude cracking.

(34)

12. Point of Contact. Recommendations for improvements to this ETL are encouraged

and should be furnished to the Pavements Engineer, HQ AFCESA/CEOA, 139 Barnes Drive, Suite 1, Tyndall AFB, FL 32408-5319, DSN 523-6439, commercial (850) 283-6439, e-mail AFCESAReachbackCenter@tyndall.af.mil

JAMES D. FRISHKORN, Col, USAF Attachment

Director, Operations and Program Support 1. Material Safety Data Sheets Air Force Civil Engineer Support Agency 2. Distribution List

(35)
(36)
(37)
(38)
(39)
(40)
(41)
(42)
(43)
(44)
(45)
(46)
(47)
(48)
(49)
(50)
(51)
(52)
(53)
(54)
(55)
(56)
(57)
(58)
(59)
(60)
(61)
(62)
(63)
(64)
(65)
(66)
(67)
(68)
(69)
(70)
(71)
(72)
(73)
(74)
(75)
(76)
(77)
(78)
(79)
(80)
(81)
(82)
(83)
(84)
(85)
(86)
(87)
(88)
(89)
(90)
(91)
(92)
(93)
(94)
(95)
(96)
(97)
(98)
(99)
(100)

DISTRIBUTION LIST

DEPARTMENT OF DEFENSE

Defense Commissary Agency (1) AAFES (1)

Design and Construction Division ATTN: RE-C 2250 Foulois St., Suite 2 PO Box 660202

Lackland AFB, TX 78236 Dallas, TX 75266-0202 SPECIAL INTEREST ORGANIZATIONS

Information Handling Services (1) Construction Criteria Base (1) 15 Inverness Way East National Institute of Bldg Sciences

References

Related documents

Uniting theoretical approaches to fairness to an overview of the empirical literature, we illuminate the salient features of fairness relations in complex

Employers are already helping students develop their employability skills – three quarters (74%) of companies who have university links do so to provide work experience

Whether the issue be which pharmacy model you should adopt, location rules, getting the right tax structure, managing cash flow or buying a pharmacy, RSM can strategically advise

incident management, change management, release management, problem man- agement, and asset management can all make use of key information tracked by configuration management.. As

• The park was following the American culture, offered mostly American food and also didn’t serve wine or any alcohol in their premise as it was not considered ideal for a

Intellectual disabilities, emotional disabilities including mood-disorders, as well as behavioral challenges of special needs communities may be characterized by deficits

A Takagi–Sugeno–Kang PID–fuzzy controller is suggested and implemented as an outer loop controller in the framework of a master–slave control system architecture dedicated to

This automatically calculates a staff members Bradford Point score allowing you to manage your disciplinary for absence and sickness at your discretion. The Bradford Factor