|
|
View PDF Version
(329 KB)
Segmental retaining wall (SRW) systems are used commonly and successfully in a range of applications, including highway projects. Their popularity can be attributed to a combination of reduced construction costs, versatility, aesthetic appearance, and ease of installation. Despite these inherent advantages, there have been some reported problems with durability of SRW blocks in cold climates susceptible to freeze-thaw cycles. The premature deterioration of some SRW blocks has led to stricter performance specifications, and in come cases, the restricted use of these walls by some State Highway Agencies.
In response to these concerns, the Federal Highway Administration (FHWA) initiated the Transportation Pool Funded research project, TPF-5(026), "Durability of Segmental Retaining Wall Blocks." The primary objectives project was to determine the cause and extent of SRW block distress and to provide recommendations on the pertinent test methods and specifications to ensure the long-term durability of SRW blocks in highway applications. The report also provides some guidance on producing durable SRW blocks.
Through this research project, it has been confirmed that the vast majority of SRW blocks have performed well and continue to perform well, even in cold climates and when exposed to deicing salts. However, this project also identified cases where SRW blocks showed significant deterioration in both field applications and laboratory evaluations. The factors that most affect frost resistance were identified, and modifications to the standard test methods ASTM C 1262 and specification ASTM C 1372 have been developed for proposed revisions.
Gary Henderson, Director
Office of Infrastructure
This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for its contents or use thereof. This report does not constitute a standard, specification, policy, or regulation.
The U.S. Government does not endorse products or manufacturers. Trade and manufacturers' names appear in this report only because they are considered essential to the object of the document.
The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.
1. Report No. FHWA HRT-07-021 |
2. Government Accession No. |
3. Recipient's Catalog No. |
|
4. Title and Subtitle Durability of Segmental Retaining Wall Blocks: Final Report |
5. Report Date April 2007 |
||
6. Performing Organization Code |
|||
7. Author(s) Cesar Chan, Kenneth C. Hover, Kevin J. Folliard, Randall M. Hance, and David Trejo |
8. Performing Organization Report No. |
||
9. Performing Organization Name and Address Concrete Durability Center |
10. Work Unit No. |
||
11. Contract or Grant No. DTFH61-01-02-R-00078 |
|||
12. Sponsoring Agency Name and Address Office of Infrastructure Research and Development |
13. Type of Report and Period Covered Final Report |
||
14. Sponsoring Agency Code |
|||
15. Supplementary Notes Contracting Officer's Technical Representative (COTR): Michael Adams, HRDI-06 |
|||
16. Abstract Segmental retaining wall (SRW) systems are commonly and successfully used in a range of applications, including highway projects. Their popularity can be attributed to a combination of reduced construction costs, versatility, aesthetic appearance, ease of installation, and an increasing number of proprietary designs available in the market. Despite these inherent advantages, there have been some reported problems with durability of SRW blocks in cold climates. The deterioration of some SRW installations in State highway agency (SHA) applications has resulted in concern over the long-term performance of SRW systems and has led to stricter specifications and, in some cases, restrictions on future use of SRW systems. In response to these concerns, a Federal Highway Administration (FHWA)-funded research project was initiated to determine the cause and extent of SRW block distress, to identify and recommend test methods for improving durability of SRW systems, and to recommend specifications for SHAs to ensure long-term durability and performance of SRW systems in highway applications. This report summarizes the key findings of this project and provides guidance on producing durable SRW blocks to ensure long-term performance of SRW systems in highway applications. |
|||
17. Key Words Segmental retaining wall; SRW; freeze-thaw; salt distress; SRW blocks; frost resistance |
18. Distribution Statement No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161 |
||
19. Security Classif. (of this report) Unclassified |
20. Security Classif. (of this page) Unclassified |
21. No. of Pages 271 |
22. Price |
Form DOT F 1700.7 (8-72) Reproduction of completed page authorized
CHAPTER 1: INTRODUCTION AND SCOPE.
1.3 RESEARCH BACKGROUND AND SCOPE.
2.2.1 Mechanisms of Frost Damage in Concrete.
2.2.2 The Role of Deicing Salts in Frost Damage.
2.3 FREEZE-THAW DURABILITY OF DRY-MIXED CONCRETE PRODUCTS.
2.3.2 Mechanisms of Freeze-Thaw Damage in Dry-Mixed Concretes.
2.3.3 The Role of Salts in Frost Damage in Dry-Mixed Concretes.
2.3.4 Role of Air and Compaction Voids.
2.3.4.1 Air Void Characteristics in Low-Slump Concretes (Whiting, 1985)
2.3.4.2 Frost and Salt Scaling Resistance of RCC (Marchand et al., 1990)
2.3.4.3 Air Entrainment in No-Slump Mixes (Marchand et al., 1998)
2.3.4.4 Air Entrainment in Dry Masonry Concrete (Hazrati and Kerkar, 2000)
2.3.4.5 Other Studies (Pigeon and Pleau, 1995 and SEM, 2001)
2.3.4.6 Summary of Studies on Air Entrainment and Compaction Voids.
CHAPTER 3: FIELD EVALUATION OF SRW BLOCKS.
3.2 FIELD EVALUATIONS OF SRWs IN WISCONSIN AND MINNESOTA.
3.2.1 Types of Distress Observed in SRW blocks.
3.2.2 Laboratory Evaluation of SRW Blocks Procured From Inservice Walls.
3.2.2.1 Test Methods for SRW Blocks Procured From Inservice Walls.
3.2.2.2 Test Results for SRW Blocks Procured From Inservice Walls.
CHAPTER 4: LABORATORY EVALUATIONS.
4.2 SAMPLING CONSIDERATIONS FOR SRW BLOCKS.
4.2.1 Current Sampling Guidelines.
4.2.2 Spatial Variability of Material Properties.
4.2.2.1 Within-Manufacturer Variability.
4.2.2.2 Between-Manufacturer Variability.
4.2.3 Split Face Delamination.
4.2.4 Recommendations for Sampling.
4.2.4.1 Sampling of SRW Units.
4.2.4.2 Extracting Specimens From SRW Units.
4.2.4.3 General Laboratory Practice.
4.3 VARIABILITY IN FREEZE-THAW EQUIPMENT USED IN ASTM C 1262 (2003)
4.3.1 Comparison Between Different Freezers.
4.3.1.2 Walk-in Environmental Chamber.
4.3.1.4 Recommendations To Reduce Freezer Internal Variability.
4.4 CHARACTERISTICS OF THE FREEZE-THAW CYCLE.
4.4.1 Significance of Freeze-Thaw Cycle.
4.4.2.1 Ice Formation and Rates.
4.4.2.2 Changes in Concentration for Saline Solution.
4.4.2.4 Connection to Freeze-Thaw Test Specimens.
4.4.2.5 Rates of Temperature Change.
4.4.3 Other Aspects Relevant to the ASTM C 1262 (2003) Test Method.
4.4.3.1 Concept of Frozen Solid.
4.4.3.2 Temperature Tolerance.
4.4.3.3 Cooling Rates and Target Cold Soak Temperatures.
4.4.4 Summary—Implications for ASTM C 1262 (2003).
4.5.1 Variability Test Series.
4.5.2 Performance Criteria (PC) Test Series.
4.5.3 Significance of NCMA Project Findings.
4.6 FROST DURABILITY INDICES FOR SRW UNITS.
4.6.2 Databases of SRW Block Freeze-Thaw Performance and Material Properties.
4.6.4 Discussion of ASTM C 1262 (2003) (in Water) Results.
4.6.5 Discussion of ASTM C 1262 (2003) (in 3 percent NaCl solution) Results.
4.7 Synopsis of study on effects of alternative deicing salts on SRW block durability.
4.8 RESEARCH ON DEVELOPMENT OF MORE REALISTIC FREEZE-THAW TEST FOR SRW BLOCKS.
CHAPTER 5: CONCLUSIONS AND RECOMMENDATIONS FOR FUTURE WORK.
5.2 Conclusions—Field Performance and Durability of SRW Blocks.
5.3 Conclusions—SRW Material Characterization and Sampling.
5.4 Conclusions—Frost Durability of SRW Units.
5.5 Conclusions—General Freeze-Thaw Testing and Processes.
5.6 Conclusions—ASTM C 1262 (2003) Testing and Specimen Performance.
5.7 Recommendations—ASTM C 1262 (2003) Testing for SRW Units.
5.8 Recommendations—Future Research.
5.8.1 SRW Material Characterization—Between-Unit Variability.
5.8.2 Frost Durability of SRW Units—Frost Index.
5.8.3 Dilation Tests for SRW Specimens.
5.8.4 Acoustic Emission Testing.
5.8.5 Effect of Freeze-Thaw Cycle on Specimen Performance.
5.8.6 Effect of Specimen Preconditioning.
5.8.6.1 Effect of Pretest Exposure.
5.8.6.2 Effect of Saturating Specimens Prior to Freeze-Thaw Testing.
5.8.7 Significance of Mass Loss and 1 Percent Limit on Different Grades of SRW Mixes.
5.8.8 Partial Versus Full Immersion of Specimens.
5.8.9 Database of Mass Loss Prediction Constants.
5.8.10 Efficacy of Silane or Other Coatings/Sealants in Mitigating Damage for Inservice SRW Blocks.
5.8.11 Freeze-Thaw Performance—Field and Laboratory Correlation Based on Critical Moisture.
APPENDIX A: NEWLY PROPOSED VERSIONS OFASTM C 1262 (2003)— FREEZE-THAW TEST FOR SRW BLOCKS)
ANNEX: RECOMMENDED PROCEDURE FOR SURVEY OF INTERNAL TEMPERATURE DISTRIBUTION OF FREEZE-THAW CHAMBER.
APPENDIX B: NEWLY PROPOSED VERSION OF ASTM C 1372 (2003)— SPECIFICATIONS FOR SRW BLOCKS.
Figure 1. Drawing. Conventional forms of SRW construction (NCMA, 2005a).
Figure 2. Drawing. Soil reinforced forms of SRW construction (NCMA, 2005a).
Figure 3. Drawings. Sample sizes and shapes of SRW units for SRW systems (Bathurst, 1993).
Figure 4. Photos. Example applications of SRW systems.
Figure 5. Photo. View of mix during production of SRW units at block plant.
Figure 6. Photo. SRW unit immediately after compaction and demolding.
Figure 7. Photos. Comparison of internal structures between SRW and ordinary concretes.
Figure 8. Photo. Condition of SRW in Ithaca, NY.
Figure 10. Diagram. Powers' rendition of an air bubble and its "sphere of influence" (Powers, 1949).
Figure 11. Photo. Demolding of SRW units during production.
Figure 12. Photo. Typical deterioration of SRW blocks with scaling most pronounced for cap units.
Figure 13. Photo. Severely damaged cap units on otherwise healthy wall.
Figure 14. Photo. Effects of drainage and salt exposure from parking lot above SRW.
Figure 16. Photo. Severe damage of SRW blocks in direct path of drainage from bridge overpass above.
Figure 19. Photo. Deterioration of exposed vertical surfaces of SRW blocks.
Figure 20. Photo. Another example of deterioration of exposed horizontal surfaces of SRW blocks.
Figure 21. Photo. Blocks obtained from SRW in Wisconsin (WI-2).
Figure 22. Photo. Blocks obtained from SRW in Wisconsin (WI-4).
Figure 23. Photo. Blocks obtained from SRW in Minnesota (MN-4).
Figure 27. Diagram. Concentration groups for the evaluation of ASTM C 1262 test method.
Figure 28. Photo. Units immediately after demolding.
Figure 29. Photo. Units prior to entering curing chamber.
Figure 30. Photo. Splitting of conjoined units.
Figure 31. Photo. Split face of units.
Figure 32. Photos. Definition of terms: SRW units (or blocks).
Figure 33. Drawing and photo. Definition of terms: test specimens (or coupons).
Figure 34. Photo. Possible exposure condition of units in winter weather.
Figure 35. Photo. Percentages in spatial distribution of absorption in large wall unit.
Figure 36. Drawing. Distribution of absorption in large wall unit.
Figure 37. Photo. Percentages in spatial distribution of absorption in small wall unit.
Figure 38. Drawing. Distribution of absorption in small wall unit.
Figure 39. Drawings. Simple random versus stratified random sampling from the face of an SRW unit.
Figure 42. Graphs. Spatial distributions of volumetric paste content.
Figure 43. Graphs. Spatial distributions of volumetric compaction void content.
Figure 44. Photo. Sample A of split face delaminations on SRW units.
Figure 45. Photo. Sample B of split face delaminations on SRW units.
Figure 46. Drawings and photo. Suspected cause of split face delaminations.
Figure 48. Photo. Detached split face delamination under frost conditions in field SRW units.
Figure 49. Photo. Freeze-thaw damage on SRW unit in field.
Figure 50. Photos. Section through region containing split face delamination.
Figure 51. Drawing. Sampling of SRW units from pallet.
Figure 52. Drawings. Extraction of freeze-thaw specimens from SRW unit.
Figure 53. Drawing. Extraction of specimens shorter than the unit height (view into back face).
Figure 54. Drawing. Extraction of specimens from middle layer.
Figure 55. Drawing. Solid unit showing recommended sampling locations (red dashed lines).
Figure 56. Photo. Sample of solid unit.
Figure 57. Photo. Second sample of solid unit.
Figure 58. Drawing. Hollow unit showing recommended sampling locations (red dashed lines).
Figure 59. Photo. Sample of hollow unit.
Figure 60. Photo. Second sample of hollow unit.
Figure 61. Photo. Defects along edges of SRW units.
Figure 62. Photo. Scratched surface.
Figure 63. Photo. Example of sound surface.
Figure 64. Drawing. Recommended clearance from edges.
Figure 65. Photo. Specimen before washing, following saw-cutting.
Figure 66. Photo. Specimen after washing, following saw-cutting.
Figure 67. Graph. ASTM C 1262 (2003) freeze-thaw cycle—definitions.
Figure 68. Photo. Closed chest freezer used in study.
Figure 69. Photo. Open chest freezer.
Figure 70. Photo. Walk-in freezer used in the study.
Figure 71. Photo. View of inside of walk-in freezer.
Figure 72. Drawing. Environmental chamber of walk-in freezer.
Figure 73. Photo. Cabinet freezer, closed.
Figure 74. Photo and drawing. Inside of cabinet freezer.
Figure 75. Photo. View of chest freezer with wooden frame and six specimens.
Figure 83. Photo. View of thermocouple (TC) placement with specimens in cabinet.
Figure 87. Drawing. Temperature mapping in cabinet freezer (side view of the freezer cabin).
Figure 89. Graph. T-t curves for freezer air, water surrounding specimen and specimen.
Figure 90. Photo. Water surrounding specimen and specimen (as graphed in figure 89).
Figure 92. Drawing. Location of thermocouples.
Figure 93. Photo. Vials in freezer.
Figure 94. Photo. Broken vials.
Figure 96. Photo. View of open container with specimen.
Figure 99. Graph. Cooling curves comparison for typical cycles in the two freezers.
Figure 100. Graph. Rates of temperature change for curves in figure 99—temperature.
Figure 101. Graph. Rates of temperature change for curves in figure 99-freezer air.
Figure 102. Graph. Rates of temperature change for curves in figure 99—solution.
Figure 103. Graph. Cooling curves and FP-t curves for plain water.
Figure 104. Graph. Cooling curves and FP-t curves for 3 percent NaCl solution.
Figure 105. Graph. Cooling curves and rate of ice formation curves for water.
Figure 106. Graph. Cooling curves and rate of ice formation curves for 3 percent NaCl solution.
Figure 107. Graph. Plots of FP as function of temperature.
Figure 108. Graph. Changes in NaCl concentration in unfrozen solution.
Figure 110. Photo and drawing. Circuit resistance for detecting expansion damage in freezing vials.
Figure 111. Photo. Strain gage for detecting expansion damage in freezing vials.
Figure 112. Drawing and photo. Direct observation for detecting expansion damage in freezing vials.
Figure 113. Graph. Results of water-filled unconfined vial in circular resistance test.
Figure 114. Photo. Water-filled unconfined vial.
Figure 115. Graph. Results of water half-filled unconfined vial in circular resistance test.
Figure 116. Photo. Water half-filled unconfined vial.
Figure 117. Graph. Results from water-filled, mortar-confined vial in circular resistance test.
Figure 118. Photo. Water-filled, mortar-confined vial.
Figure 119. Graph. Results of strain gage method—plain water.
Figure 120. Photo. Vial after test.
Figure 121. Graph. Results of strain gage method— 3 percent NaCl solution.
Figure 122. Photo. Vial after test.
Figure 123. Graph and photos. Results for direct observation method of damage detection (for water).
Figure 125. Drawing. Location of thermocouples (S1, S2, S3) embedded in SRW specimen.
Figure 126. Drawing. Location of thermocouples (Af, Am) and in water (Wu, Wa).
Figure 127. Photo. Container used to hold SRW blocks.
Figure 128. Photo. Varying container sizes.
Figure 129. Graph. Cooling curves for SRW mix A and B.
Figure 133. Graph. Simple approach to estimate length of freezing plateau.
Figure 137. Photo. View of chest freezer used for single-location repeatability tests.
Figure 139. Graph. Freezer air and specimen cooling curves for seven cycles.
Figure 143. Graph. Rates of temperature change for specimen and surrounding water.
Figure 144. Photo. Specimen after 4.5-hour cold soak in walk-in freezer appears frozen solid.
Figure 146. Graph. Results of cooling in chest freezer.
Figure 147. Photo. Half-filled vial after cooling in chest freezer.
Figure 148. Graph. Results of cooling in walk-in freezer.
Figure 149. Photo. Half-filled vial after cooling in walk-in freezer.
Figure 150. Photo. Half-full vial after 30 minutes of exposure in the chest freezer.
Figure 151. Photo. Half-full vial after 40 minutes of exposure in the chest freezer.
Figure 152. Diagram. ASTM C 666 (ASTM 2004), Procedure A specified T-t exposure of control specimen.
Figure 154. Drawing. ASTM C 1262 (2003) partially immersed specimen.
Figure 155. Drawing. Definition of compaction void in ASTM C 457 (2004) testing.
Figure 156. Graph. Relating mass loss to material property for a given SRW unit type.
Figure 159. Graph. ASTM C 140 compressive strength. Data representation by boundary points.
Figure 160. Graph. ASTM C 140 compressive strength. Data representation by centroids.
Figure 161. Graph. ASTM C 140 24-hour water absorption. Data representation by boundary points.
Figure 162. Graph. ASTM C 140 24-hour water absorption. Data representation by centroids.
Figure 163.Graph. ASTM C 140 Unit weight. Data representation by boundary points.
Figure 164. Graph. ASTM C 140 Unit weight. Data representation by centroids.
Figure 165. Graph. NCMA index. Data representation by boundary points.
Figure 166. Graph. NCMA index. Data representation by centroids.
Figure 167. Graph. ASTM C 642 Boiled absorption. Data representation by boundary points.
Figure 168. Graph. ASTM C 642. Bottom graph. Data representation by centroids.
Figure 169. Graph. ASTM C 642. Volume of permeable voids. Data representation by boundary points.
Figure 170. Graph. ASTM C 642 Volume of permeable voids. Data representation by centroids.
Figure 171. Graph. Saturation coefficient. Data representation by boundary points.
Figure 172. Graph. Saturation coefficient. Data representation by centroids.
Figure 173. Graph. Total air and compaction voids content. Data representation by boundary points.
Figure 174. Graph. Total air and compaction voids content. Data representation by centroids.
Figure 175. Graph. Paste content. Data representation by boundary points.
Figure 176. Graph. Paste content. Data representation by centroids.
Figure 177. Graph. Paste-to-total-void ratio. Data representation by boundary points.
Figure 178. Graph. Paste-to-total-voids ratio. Data representation by centroids.
Figure 179. Graph. ASTM C 457 Specific surface. Data representation by boundary points.
Figure 180. Graph. ASTM C 457 Specific surface. Data representation by centroids.
Figure 181. Graph. ASTM C 457 spacing factor. Data representation by boundary points.
Figure 182. Graph. ASTM C 457 Spacing factor. Data representation by centroids.
Figure 183. Graph. Specific surface/total void content. Data representation by boundary points.
Figure 184. Graph. Specific surface/total void content. Data representation by centroids.
Figure 185. Graph. Evaluation of data points for mass loss less than 5 percent only.
Figure 188. Graph. Average ASTM C 1262 (2003) mass loss for all salt solutions evaluated.
Figure 189. Drawing. Exposure chamber.
Figure 190. Photo. Freeze-thaw test setup showing SRW blocks.
Figure 191. Photo. Smaller SRW block testing in Phase I.
Figure 196. Photo. Typical cracking and spalling from freeze-thaw damage from test 1.
Figure 198. Photo. SRW block from manufacturer A.
Figure 199. Photo. SRW block from manufacturer B.
Figure 200. Photo. SRW block from manufacturer C.
Figure 201. Photo. Typical stacking for larger SRW blocks tested in Phase II.
Figure 202. Graph. Typical block temperature data from Phase II investigation.
Figure 203. Photo. SHA-approved block from manufacturer A (water exposure).
Figure 204. Photo. SHA-approved block from manufacturer A (3 percent NaCl solution exposure).
Figure 205. Photo. Non-SHA-approved cap from manufacturer A (water exposure).
Figure 206. Photo. Surface of non-SHA-approved block from manufacturer A (3 percent NaCl solution).
Figure 210. Photo. SHA-approved block from manufacturer B (NaCl Solution).
Figure 213. Photo. SHA-approved C block exposed to fresh water.
Figure 214. Photo. SHA-approved C block exposed to 3 percent NaCl solution.
Figure 219. Graph. Compaction void content versus paste content for all SRW mixes evaluated.
Figure 220. Graph. Mass loss versus cycles.
Figure 223. Graph. Dependence of mass loss prediction constant "a" on paste content (Hance, 2005).
Table 1. Blocks from in situ SRWs obtained for laboratory evaluation.
Table 2. Characteristics of the various freezers investigated (from Hance, 2005).
Table 3. Temperature variations inside a chest freezer.
Table 4. Temperature variations inside the walk-in freezer loaded with 60 specimens.
Table 5. Temperature variations inside the walk-in freezer loaded with varying specimen quantities.
Table 6. Temperature variations inside the cabinet freezer loaded with 28 specimens.
Table 7. Temperature variations inside the cabinet freezer loaded with varying specimen quantities.
Table 8. Comparison of cycle parameters between cabinet and walk-in freezers.
Table 9. Measured differences for conditions of varying volumes of surrounding water.
Table 10. Measured differences for conditions of varying container sizes.
Table 11. Measured differences for conditions of varying specimen quantities.
Table 12. Comparison of cooling curve characteristics for half-full vials in different freezers.
Table 13. Comparison of specimen cooling rates for cooling curves of section 4.4.2.3.
Table 14. Scope of ASTM C 1262 (2003) test program.
Table 15. Standard test methods and material properties evaluated for SRW units.
Table 16. Ranking of material properties using different types of analyses.
Table 17. Threshold values of material properties determined from figures 159 to 184.
Table 18. Phase I experimental program.
Table 19. Experimental plan showing number of blocks tested in Phase II.
Table 20. Chloride diffusion coefficients for larger SRW block samples.
Table 21. Comparison of cold soak requirement in freeze-thaw test methods.
| FHWA-HRT-07-021 |
 |
TFHRC Home | FHWA Home | Feedback United States Department of Transportation - Federal Highway Administration |