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Page 67
Suggested Citation:"Appendix B - Survey Results." National Academies of Sciences, Engineering, and Medicine. 2019. Practices to Mitigate Alkali-Silica Reaction (ASR) Affected Pavements at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25553.
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Page 67
Page 68
Suggested Citation:"Appendix B - Survey Results." National Academies of Sciences, Engineering, and Medicine. 2019. Practices to Mitigate Alkali-Silica Reaction (ASR) Affected Pavements at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25553.
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Page 68
Page 69
Suggested Citation:"Appendix B - Survey Results." National Academies of Sciences, Engineering, and Medicine. 2019. Practices to Mitigate Alkali-Silica Reaction (ASR) Affected Pavements at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25553.
×
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Page 70
Suggested Citation:"Appendix B - Survey Results." National Academies of Sciences, Engineering, and Medicine. 2019. Practices to Mitigate Alkali-Silica Reaction (ASR) Affected Pavements at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25553.
×
Page 70
Page 71
Suggested Citation:"Appendix B - Survey Results." National Academies of Sciences, Engineering, and Medicine. 2019. Practices to Mitigate Alkali-Silica Reaction (ASR) Affected Pavements at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25553.
×
Page 71
Page 72
Suggested Citation:"Appendix B - Survey Results." National Academies of Sciences, Engineering, and Medicine. 2019. Practices to Mitigate Alkali-Silica Reaction (ASR) Affected Pavements at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25553.
×
Page 72
Page 73
Suggested Citation:"Appendix B - Survey Results." National Academies of Sciences, Engineering, and Medicine. 2019. Practices to Mitigate Alkali-Silica Reaction (ASR) Affected Pavements at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25553.
×
Page 73
Page 74
Suggested Citation:"Appendix B - Survey Results." National Academies of Sciences, Engineering, and Medicine. 2019. Practices to Mitigate Alkali-Silica Reaction (ASR) Affected Pavements at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25553.
×
Page 74
Page 75
Suggested Citation:"Appendix B - Survey Results." National Academies of Sciences, Engineering, and Medicine. 2019. Practices to Mitigate Alkali-Silica Reaction (ASR) Affected Pavements at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25553.
×
Page 75
Page 76
Suggested Citation:"Appendix B - Survey Results." National Academies of Sciences, Engineering, and Medicine. 2019. Practices to Mitigate Alkali-Silica Reaction (ASR) Affected Pavements at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25553.
×
Page 76

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B-1 A P P E N D I X B Survey Results

Section 1—General Respondent demographics. Figure B1. Geographical Distribution of Survey Responses. Section 2—Verification of ASR 2.1 Using the fields in 2.2 and 2.3, please list the known airside pavement facilities at your airport that have been affected by suspected ASR within the last 15 years, and indicate some of the characteristics of those facilities and ASR conditions. If you have multiple facilities (runways, taxiways, aircraft parking aprons, etc.) affected by ASR, complete the survey for the two or three that are most relevant to studying ASR mitigation. (continued on next page) 2.2. Facility Characteristics Facility Type Year Facility Built Facility Age When Suspected ASR Appeared (# years old) Approx Area of Facility Afflicted with Suspected ASR (sq. yd) Apron 1965 15 11,000 Apron 1987, 1989, 1991 16 32,000 Apron 1992 5 50,000 Apron 1950s & 1990s 10 100,000 Apron 1998 5 260,000 Apron 1996 8-10 Entire area Apron 1960 20 301,367 Runway 1974 15 150,000 Runway 1978 30 128,400 Runway 2001 6 167,000 Runway Overlay 2000 10 12,300 Runway 1990 15 Runway 1998 6 145,000 Runway 1996 8-10 Entire surface Runway 1960 20 285,000 Runway Overlay 2005 10 18,000 Runway 1950s 30 381,333 Taxiway 1950s & 1990s 30 200,000 Taxiway 2001 6 293,000 B-2 Practices to Mitigate Alkali-Silica Reaction (ASR) Affected Pavements at Airports Survey Results B-3

Figure B2. Airside Facilities Affected by ASR in the Last 15 Years. Taxiway 1990 15 Taxiway 1998 7 140,000 Taxiway 1996 8-10 Entire surface Taxiway 1992 5 30,000 Taxiway 1960 20 201,750 Taxiway Overlay 1997 12 7,200 Facility Type Year Facility Built Facility Age When Suspected ASR Appeared (# years old) Approx Area of Facility Afflicted with Suspected ASR (sq. yd) Figure B4. Facility Age When Suspected ASR Appeared. Figure B3. Year Facilities Built. B-4 Practices to Mitigate Alkali-Silica Reaction (ASR) Affected Pavements at Airports Survey Results B-5

Figure B6. Indicators of ASR. 2.3. Facility ASR Conditions What led you to suspect ASR? (# of respondents) Staining at Joints Cracking at Joints Spalling at Joints Map Cracking Over Slab Area Evidence of Expansion (blowups, Shoving of can lights and other structures, etc.) Other 17 27 25 23 20 2* *Crumbling causing excessive FOD Figure B5. Approximate Area Affected by or with Suspected ASR. Figure B7. Means of ASR Confirmation. Section 3—Use of Corrective Treatments to Address ASR Issues Note: Respondents should note that there are corrective treatments to address the symptoms of the ASR distress and mitigation treatments that are trying to slow or mitigate the effects of the ASR. This survey will address each of these approaches in the next sections of the survey. Section 3 focuses on corrective treatments while Section 4 focuses on mitigation treatments. 3.1. For the pavement facilities identified in Section 2 and reproduced below, please answer the questions on the use of and experience with various corrective treatments to address performance issues associated with ASR. Beyond visible signs, what other means were used to confirm ASR? ((# of respondents) Field Test (e.g., uranyl acetate) Petrographic Analysis 2 18 B-6 Practices to Mitigate Alkali-Silica Reaction (ASR) Affected Pavements at Airports Survey Results B-7

Definitions • PDR = partial-depth repair, the removal and replacement of a small area of deteriorated concrete to a depth of one-half to one-third of the slab thickness • FDR = full-depth repair, the removal and replacement of a section of deteriorated concrete through its entire slab thickness, may also include the complete removal and replacement of an entire slab (referred to as slab replacement) • AC Overlay = asphalt overlay placed on the existing concrete pavement • PCC Overlay = concrete overlay placed on the existing concrete pavement • Total Reconstruction = the deteriorated concrete was removed and replaced with an entirely new pavement • Life Expectation = life expectation is how much additional life in the pavement that you hoped to receive as a result of the treatment Please indicate what corrective treatments you have used (if any) and how they have performed for each of the following facilities your identified. Corrective Treatment Treatment Used (# of respondents) Facility Age When Applied (average years) What was your life expectation for this treatment? How do you rate this treatment in achieving your expectations? 0 – 3 ye ar s 4 – 8 ye ar s 8 – 12 y ea rs 13 o r m or e ye ar s N ot S at is fi ed Pa rt ia lly S at is fi ed L ar ge ly S at is fi ed PDR 10 11 Years 5 3 1 1 0 5 5 FDR/ Slab Replace 11 11 Years 1 4 4 3 2 3 7 AC Overlay 8 29 Years 2 1 0 5 0 2 6 PCC Overlay 1 35 Years 0 0 0 1 0 0 1 Total Reconstruct 15 21 Years 0 0 0 14 0 0 15 No corrective treatments used. (0 responses) B-8 Practices to Mitigate Alkali-Silica Reaction (ASR) Affected Pavements at Airports Survey Results B-9

Figure B8. Corrective Treatments Used. Figure B9. Facility Age When Treatment Applied. Figure B11. Respondent Satisfaction. Figure B10. Life Expectations for Treatments. B-10 Practices to Mitigate Alkali-Silica Reaction (ASR) Affected Pavements at Airports Survey Results B-11

If corrective treatments were used, were any follow-up evaluations conducted by the airport to investigate their effectiveness? Are any reports or documentation available? Please describe. • Taxiway was rehabilitated in sections using various methods, including mill/overlay, crack and seat, break and seat. AC overlay with sawcut control joints over PCC joints performed well. Has lasted and performed well since overlaid in the 1990s and is still in service today. The downfall is the concrete below continues to grow. To mitigate we constructed relief joints constructed out of P-209 and P-401. These need to be milled and maintained as they compress and shove. Have not noticed a clear advantage to straight mill/overlay, crack/seat, etc. • Annual inspections of the runway are performed to identify distress and to monitor repairs. • Airfield-wide pavement condition studies have been conducted every several years. To date, the PCI has remained well into the good range. The runway is now approximately 7 years old and appears to be performing very well. • Our primary arrival Runway 4L/22R and associated taxiways were constructed (new) in 2001. The pavements failed prematurely due to ASR. Reconstruction of the runway complex was bumped up to our highest priority at the end of 2013 due to poor condition of pavement. The runway and associated taxiways were closed daily for significant FOD removal. By the fall of 2014, the pavements were in such bad shape, the complex was closed for 45 days for extensive maintenance. At that time, the reconstruction project was in the design phase, with construction scheduled for 2016. We performed a mill and fill (asphalt overlay) in 2014 and another in 2015 (different areas; total repairs cost approximately $5 million) to keep the runway complex open until the scheduled 2016 reconstruction project. The pavement was in such poor shape that we could not phase the project over 2 years and reconstructed most of the project (445,000 sy of the 460,000 sy total project) in one Michigan construction season. The reconstruction included removal and replacement of all concrete and a portion of the asphalt base; new shoulders; underdrain system; and lights and signs. • Daily inspections watching for cracking, heaving, and spalling. • We have periodically performed visual inspections of pavement that was replaced due to ASR issues. I am not aware that any reports have been made. We used a combination of fly ash, aggregate, and cement adjustments for the new pavement. It is holding up much better than the old pavement did. The aggregate is more thoroughly tested now to make sure it is low silica. We use low alkali cement now. We also use fly ash in the new pavement. Please indicate mitigation treatments (if any) that you have used and how they have performed. Mitigating Treatment Type/Name of Mitigation Treatment Facility Age at First Application (# years old) Number of Applications If More than One, Average Time Between Applications, Months Effectiveness Surface Treatment to Waterproof Surface (i.e., silane, siloxane, HMWM) No responses - - - - Surface Treatment to Mitigate ASR (e.g., Lithium) Lithium 8 2 12 Had no effect Lithium 30 1 - Had no effect Other? (List) Slurry seal 40 1 - Had no effect • AC overlay with sawcut control joints over PCC joints has performed well. The downfall is the concrete below continues to grow. To mitigate we constructed relief joints constructed out of P-209 and P-401. These need to be milled and maintained as they compress and shove. Hardstands were constructed with new PCC containing fly ash where needed for parking. • See comments under runway above. • Daily inspections watching for cracking, heaving, and spalling. • Same as above. • 5-in AC overlay with sawcut control joints over PCC joints has performed well. Applied Pavement Technology performed the Runway 15-33 evaluation and overlay design in 2001. Report is available. • Daily inspections watching for cracking, heaving, and spalling. Section 4—Mitigation Strategies 4.1. For the pavement facilities identified in question 2 and reproduced below, please answer the questions on the use of any mitigation treatments that have been used in an attempt to slow or retard the development of ASR on the existing pavement. B-12 Practices to Mitigate Alkali-Silica Reaction (ASR) Affected Pavements at Airports Survey Results B-13

If mitigation treatments were used, were any follow-up evaluations conducted by the airport to investigate their effectiveness? Are any reports or documentation available? Please describe. • No reports are available. Continued ASR deterioration was visually noted with continued expansion and spalling in the pavement. • There was an application of lithium sprayed on the runway for an IPRF project. I am not aware of any follow-up studies or applications. • I'm not aware of any mitigation treatments used on the original Runway and Taxiways. • We have not treated any ASR pavement. We replace ASR pavement using a concrete mix design that is more resistant to ASR. Section 5—Other 5.1. If you have not experienced any ASR issues on your airport facilities, what factors do you believe are responsible? • 1) expansion problems at joints 2) unsealed joints, water entering joints with underlying asphalt so water cannot drain out of joint, and water going through freeze/thaw cycles. • Not applicable. 5.2. If you have experienced ASR issues on your airport facilities in the past but no longer do, what changes have you made to your previous specifications to address ASR? • Use concrete mixes with little to no alkali-based aggregates. • Significant changes have been made to our mix design and would be happy to share the design. • Fly ash is now being used in the PCC to mitigate ASR. Comments: • Have not used any mitigation on existing concrete with ASR. • No treatments applied. • None applied. • NA. • Use of Type F fly ash, typically in the 20-30 percent by weight of total cementitious material determined by trial mixes. Mortar expansion tests must show less than 0.10% expansion in 28 days (ASTM C1260) seems to have limited the ASR issues. Some concrete pavements using this mitigation method (in accordance with FAA P-501 specifications) have been in service for 24 years and do not exhibit ASR effects on the surface. • The airport ensures that mortar-bar expansion tests are performed on all concrete mix designs prior to construction. • Use of UFGS 32 13 11, with the stringent aggregates properties and testing required. • Airfield concrete pavements have been designed with the FAA P-501 specification, which controls the fly ash type (and largely mitigates the formation of ASR). ASR testing has also been required and verified for each project before concrete was allowed to be placed by the contractor. new concrete mixes are tested and mitigated in accordance with the FAA’s concrete specifications. • Standard Aggregate Reactivity Testing per current FAA P-501 Technical Specification. • We use fly ash now in the concrete mix design. We test the aggregate more thoroughly now to make sure it has low silica. We also use low alkali cement. We use different rock quarries for the aggregate. Our current rock quarries have lower silica than before. We also conduct ASR tests on sample mix designs. These tests are specified in the spec. • Not applicable. • We are still experiencing ASR; however, other areas did not fail as prematurely as Runway 4L and associated taxiways. Approximately 6 miles of airfield runway and taxiway pavement failed in 13 years. Other areas experiencing ASR have been repaired with mill and overlay or capping to extend the life until scheduled reconstruction. All B-14 Practices to Mitigate Alkali-Silica Reaction (ASR) Affected Pavements at Airports Survey Results B-15

5.3. Is there any other information that you would like to convey regarding the treatment of ASR-affected airport pavements? • COS was involved with the ACRP done by IPRF and significant data is available to review in that study. • Contractors have indicated that fly ash is getting hard to find. This could force us to try other mitigation in new PCC in the future. • Northwest Arkansas Regional Airport has found that cutting expansion joints in ASR- afflicted concrete to help minimize damage caused by panels expanding and moving. Two and a half inch wide full-depth joints were cut across aprons and around building foundations adjacent to the apron. The joints were then filled with asphalt. If the joint expands, more asphalt is added. If the joint shrinks, the airport uses a milling machine to mill off the excess asphalt pushed out of the joint. Where the fully reconstructed runway abutted ASR-afflicted taxiways, a six-foot wide joint was cut and filled with asphalt. This prevents the ASR taxiway concrete from damaging the new runway pavement. • Recycling of ASR-affected pavements appears to be a sound engineering choice. Utilizing the P-219 specification, we have successfully recycled ASR-affected concrete pavement for use as base stone courses for new pavements. • They do not have many issues with ASR, but when they do, they use standard testing practices to identify the extent. Once the extent has been established to be severe, they isolate the pavement segment and then remove and reconstruct the slab(s). • Primarily repaving impacted sections, replaced an entire runway. • Our treatment of completing partial-depth and full-depth slab reconstruction was just done in 2017 so it is difficult to predict how good the work will be in regards to life longevity of the runway. • Not applicable. B-16 Practices to Mitigate Alkali-Silica Reaction (ASR) Affected Pavements at Airports

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Practices to Mitigate Alkali-Silica Reaction (ASR) Affected Pavements at Airports Get This Book
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Some concrete pavements commonly used at airports are susceptible to the destructive effects of alkali-silica reaction (ASR). The presence of ASR on concrete pavements can have a devastating effect on pavement performance, not only in terms of reduced functionality, but also in terms of shortened service lives.

The focus of ACRP Synthesis 96: Practices to Mitigate Alkali-Silica Reaction (ASR) Affected Pavements at Airports is on current practices for mitigating ASR in affected pavements at airports. Given the substantial initial investment required for pavement, airports are interested in using mitigations to slow the effects of ASR and prolong the life of airfield concrete pavements.

This synthesis identifies the current state of the practice regarding the mitigation measures used on existing ASR-affected airport pavements that service aircraft and summarizes the experiences and practices of airports in dealing with the distress (including conventional treatments, but also any new or emerging technologies).

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