Micro-Surface Premature Distress SH 19 Hopkins County, Paris District

Transcription

1 Micro-Surface Premature Distress SH 19 Hopkins County, Paris District Research Report RR Prepared for Texas Department of Transportation Maintenance Division Prepared by Texas A&M Transportation Institute Jon Epps Executive Associate Director Charles Gurganus Associate Research Engineer TxDOT Contract No 47-4PV1A007 TTI Contract No December, 2016

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3 TABLE OF CONTENTS LIST OF FIGURES... ii LIST OF TABLES... iii INTRODUCTION... 1 BACKGROUND... 6 TRAFFIC... 6 CLIMATE... 6 PRECONSTRUCTION... 7 MIXTURE DESIGN... 7 ASPHALT BINDER PROPERTIES... 8 AGGREGATE PROPERTIES... 8 MIXTURE PROPERTIES... 9 CONSTRUCTION EQUIPMENT CALIBRATION CONTRACTORS CONSTRUCTION RECORDS ASPHALT BINDER PROPERTIES AGGREGATE PROPERTIES MIXTURE PROPERTIES POST CONSTRUCTION CLIMATE VISUAL CONDITION SURVEY CORES LABORATORY TESTING Air Void Content Asphalt Binder Properties Asphalt Binder Content Aggregate Gradation Hamburg Test SUMMARY ASPHALT BINDER AGGREGATE MIXTURE CONSTRUCTION OTHER REFERENCES Page RR Page i

4 LIST OF FIGURES Page Figure 1. Premature Distress on SH Figure 2. Premature Distress on SH Figure 3. Premature Distress on SH Figure 4. Premature Distress on SH RR Page ii

5 LIST OF TABLES Page Table 1. Construction Date, Location and Yield... 1 Table 2. Traffic Volumes on SH 71 (2013)... 6 Table 3. Historic Daily Climate Data during Construction (1)... 6 Table 4. Monthly Climate History for 2016-Sulphur Springs, Texas (1)... 7 Table 5. Preconstruction Asphalt Binder Properties-CSS-1 (CSS-1P) Emulsion... 8 Table 6. Preconstruction Aggregate Gradation-Accumulative Passing... 9 Table 7. Core Location and Condition Table 8. Air Void Content of Micro-Surface Table 9. Gradation of Micro-Surface RR Page iii

6 INTRODUCTION A micro-surface (Item 350) was placed on State Highway (SH) 19 in Hopkins County during the period April 14, 2016 to May 5, 2016 at the locations shown on Table 1. Premature distress in the form of shoving was experienced on this project within a few months of construction. Samples of the pavement materials were obtained from the project by the Texas Department of Transportation (TxDOT) and sent to the Texas A&M Transportation Institute (TTI) Laboratory for testing and evaluation. Date Table 1. Construction Date, Location and Yield Location Layer Direction X-section From To RR Page 1 Tons Placed Amount Yield, lbs./sq. yds. 04/14/2016 First SB Travel /15/2016 First SB Travel /22/2016 First NB Travel /23/2016 First NB Travel /23/2016 Second NB Shoulder /24/2016 Second NB Shoulder /24/2016 Second SB Shoulder /25/2016 Second NB Shoulder /25/2016 Second SB Shoulder /27/2016 Second NB* Travel /28/2016 Second NB* Travel /03/2016 Second SB* Travel /03/2016 Second NB* Travel /04/2016 Second NB* Travel /05/2016 Second NB* Travel Data from contractor daily report *NB/SB lane information not correct on contractor daily report The project is 12.2 miles in length and starts just north of Sulphur Springs (junction of SH 19 and Loop (LP) 301) to the Hopkins/Delta County Line at the Sulphur River Bridge north of Sulphur Springs. The project is located in the Paris District of TxDOT and has a CSJ designation of The TRM limits are from to Plans were completed and signed by the Engineer on February 13, The project was let for construction on May 5, The existing typical section is generally two 12 ft. lanes with 10 ft. paved shoulders. The microsurface was placed in two applications. The first application is 26 ft. in width at the rate of 30 lbs. per sq. yd. This application covers the two travel lanes (24 ft.) and 1 ft. on each of the two shoulders. The second application is 44 ft. in width at the rate of 25 lbs. per sq. yd.. This application covers the two travel lanes (24 ft.) and the two, 10 ft. shoulders. The alternative pavement section for this project was a ¾ inch overlay of hot mix asphalt. The project estimated

7 the use of 6,731 tons of micro-surfacing with 288,000 sq. yds. of flexible pavement structure repair (Item 351). The pavement section prior to placement of the micro-surfacing was 4 inches of hot mix asphalt on top of 6 inches of Portland cement concrete pavement. Google Earth photos indicated that a chip seal had been placed on the hot mix asphalt material. Aggregate loss of the chip seal cover stone was evident along the centerline of the pavement. Some areas of level-up patching and what appeared to be utility service patching was also evident. Some transverse cracking and longitudinal cracking in the shoulder area was also evident. Premature distress was experienced on the project within months of completing construction. Figures 1 to 4 show typical distress along the project. Shoving or plastic deformation is evident along the roadway as well as some bleeding or flushing in the wheel paths. Cracking was not evident. Figure 1. Premature Distress on SH 19 RR Page 2

8 Figure 2. Premature Distress on SH 19 RR Page 3

9 Figure 3. Premature Distress on SH 19 RR Page 4

10 Figure 4. Premature Distress on SH 19 RR Page 5

11 The purpose of this report is to document the testing and evaluation that was performed on the project to determine the likely cause of the premature distress. A limited study was performed that consisted of information gathering, coring to obtain field samples and laboratory testing. This information is provided below. TRAFFIC BACKGROUND Average daily traffic along the project ranged from 4,000 to 7,600 (Table 2) based on 2013 traffic measurements. The current 18-kip ESALs along the project ranges from 4,214 to 7,436. CLIMATE Table 2. Traffic Volumes on SH 19 (2013) Location Average Daily Traffic So. Of FM ,628 So. of SH 71 5,424 No. of SH 71 4,312 No. of FM ,026 Temperature and rainfall climatic data for Sulphur Springs, Texas are shown on Table 3 during the period of construction. High temperatures were in the 70 s and 80 s with low temperatures in the 50 s and 60 s. Several high rainfall events occurred during the construction periods. Almost half of the days experienced rainfall. Five days during this period experienced over 1.25 inches of rainfall. One day had a rainfall of 4.73 inches. Table 3. Historic Daily Climate Data during Construction (1) Date High Temp., F Low Temp., F Precipitation, inches April 10, April 11, April 12, April 13, April 14, April 15, April 16, April 17, April 18, April 19, April 20, April 21, April 22, April 23, RR Page 6

12 Table 3. Historic Daily Climate Data during Construction (1) (Continued) Date High Temp., F Low Temp., F Precipitation, inches April 24, April 25, April 26, April 27, April 28, April 29, April 30, May 1, May 2, May 3, May 4, May 5, May 6, May 7, May 8, May 9, May 10, Monthly climate summary information is shown on Table 4. The months of March, April and May all experienced over six inches or rainfall with the month of April nearly 11 inches. The spring of 2016 was a wet period at the project site. Table 4. Monthly Climate History for 2016-Sulphur Springs, Texas (1) Month Precipitation, inches High Temperature, F Low Temperature, F Actual Average Actual Average Actual Average January February March April May June July August MIXTURE DESIGN PRECONSTRUCTION The contractor mixture design for the micro-surfacing was provided on the Contractor Daily Report. The mixture designs indicate the emulsion content to be 13 percent by dry weight of the RR Page 7

13 aggregate and the portland cement content to be 1.5 percent by dry weight of the aggregate. A review of the Contractor Daily Report log indicates that the portland cement was typically 0.3 percentage points above the design quantity (typically 1.8 percent in the field versus 1.5 percent in the design). ASPHALT BINDER PROPERTIES Table 5 shows the asphalt binder properties as reported by the TxDOT s Central Laboratory in Austin. The test result summary property sheet indicates a CSS-1 emulsion. Not all specification tests for Item 300 were performed for the emulsion. Table 5. Preconstruction Asphalt Binder Properties-CSS-1 (CSS-1P) Emulsion Property Test No. Test Result Specific 60 F Saybolt 77 F, S. sec. Distillation Penetration of Distillation Residue. 0.1 mm Tex-514-C Specification Minimum Maximum Tex-513-C (20) 100 (100) Tex-521-C Residue, % (62) Oil Portion, % (0.5) Tex-502-C (55) 160 (90) Specification Item 350 for Micro-surfacing requires a CSS-1P. The emulsion was sampled on March 22, 2016 prior to project construction and represents the asphalt emulsion binder used during the mixture design phase of the project. Reported test values for the binder meet the criteria for CSS-1P asphalt emulsion specification. AGGREGATE PROPERTIES Aggregates were sampled prior to construction and 6 gradations were performed and reported (Table 6). These aggregate samples are probably from project stockpiles. The information presented on Table 6 indicates that the minus No. 200 sieve fraction was near the minimum specification limit of 5 percent. This indicates that relatively small quantities of the No. 200 fraction of the aggregate was present in the micro-surface aggregate stockpile. RR Page 8

14 Sieve Size Table 6. Preconstruction Aggregate Gradation-Accumulative Passing Date Sampled Specification Limits 02/22/16 02/22/16 02/23/16 02/25/16 02/26/16 02/29/16 Min Max 3/ No No No. 16 No. 30 No. 50 No. 100 No The sieve analysis data for the No. 8 to No. 50 sieve aggregate fraction indicated a material that was finer than many of the specification limits. The aggregate has relatively large percentages of material that were smaller than the indicated sieves and out of the specification. Compared to the specification the aggregate has a relatively small amount of materials from the No. 4 to the No. 8 sieve and a relatively large amount of materials between the No. 50 and 100 sieves. The impact of this type of gradation (about 75 percent of the gradation results are out of specification) on performance is not known. Increased percentages of No. 200 material typically help the stability or plastic flow of asphalt bound materials. A good coarse aggregate structure (No. 4 to No. 8 sieve for this micro-surface aggregate) that provides aggregate to aggregate contact also provided improved stability or resistance to plastic flow for asphalt bound materials. MIXTURE PROPERTIES The mixture design was developed by the contractor and submitted to TxDOT for approval. Based on the Contractor Daily Report, the mixture contained 13 percent asphalt emulsion with 1.5 percent portland cement by dry weight of aggregate. The residual asphalt binder content is 8.5 percent based on a residual asphalt binder content of in the asphalt emulsion (Table 5). The residual asphalt binder content is between the 6 and 9 percent by dry weight of aggregate as specified in Item 350 of the standard specification. The portland cement content of 1.5 percent by dry weight of aggregate is within the specification limits of Item 350 of 0.5 to 3.0 percent) A wet track abrasion test was performed on the micro-surfacing material prior to construction. The materials were sampled on March 22, 2016 prior to construction. The maximum amount of mixture loss in this test is 75 g/sq. ft.. The test result from Tex-240-F was 3.5 which represents the average of 2.4 and 4.5 g/sq. ft. reported for the two measurements. RR Page 9

15 CONSTRUCTION EQUIPMENT CALIBRATION The micro-surfacing equipment was calibrated for aggregate, asphalt emulsion and portland cement quantities on April 13, The scales used for this calibration were certified on April 13, CONTRACTORS CONSTRUCTION RECORDS Copies of the Contractors Daily Report were provided and are summarized on Table 1. Two layers were constructed as shown on the plan sheets. The first layer was constructed on the main lanes and on 1 ft. of the shoulder on April 14, 15, 22 and 23 of 2016 (Table 1). The second lift was placed on the shoulder areas on April 23, 24 and 25 of 2016 (Table 1). The second lift was placed on the main or travel lanes on April 27 and 28 and May 3, 4 and 5 of 2016 (Table 1). Note that the direction of placement of the second lift on the main lanes or travel lanes was not properly recorded on these records. It is likely that the entries for April 28 and May 3 (stations 0+00 to 68+50) and May 5 are for the south bound lanes (SB). The correct description of the micro-surfacing placement needs to be resolved with the contractor. This is important as the center portion of the project on the SB lane performed at a higher level than the remainder of the project. Station 0+00 is at the north end of the project and Station is at the south end of the project. ASPHALT BINDER PROPERTIES Asphalt binder properties were not reported for samples taken during construction. AGGREGATE PROPERTIES Aggregate properties were not reported for samples taken during construction. MIXTURE PROPERTIES Mixture properties were not reported for samples taken during construction. CLIMATE POST CONSTRUCTION Tables 3 and 4 provide a summary of climate data obtained from Sulphur Springs weather station (1). As identified above a considerable number of heavy rainfall events occurred just prior to and during the construction of the micro-surface (Table 1). These rainfall events likely caused high moisture content aggregate stockpiles and difficult curing conditions for the asphalt emulsion. Above average rainfall occurred during the construction, after construction and during the early performance period (Tables 3 and 4). RR Page 10

16 Moisture content information is supplied on the Contractor Daily Report. It is not clear if this is total moisture content in the mixture or aggregate. It appears as if the reported moisture content is for the total mixture. The reported values for moisture content ranged from 5.4 to 8.4 percent. Some of the higher moisture contents follow rainfall events. VISUAL CONDITION SURVEY A visual condition survey was performed on July 21, A summary of the observations are provided below. 1. Shoving or plastic flow is in the direction of travel 2. More shoving on inside wheel path than outside wheel path 3. Shoving was not continuous 4. Shoving caused rough ride (short amplitude) on a relatively large part of the project 5. About same amount of shoving in NBL and SBL south of SH FM 1536 north more shoving in NBL with edge stripe displaced in some locations 7. Intersections (in general) had more shoving and bleeding 8. Little to no shoving in the SBL from approximately FM 1536 to SH Some transverse construction joints were evident and were rough 10. Bleeding was evident on a portion of the project 11. No transverse, longitudinal or alligator cracking 12. Shoving does not appear to be related to shade from trees or elevation above creek/river bottoms CORES TxDOT obtained 19 cores from the project on July 26, The location and condition of the core samples are identified on Table 7. Latitude and Longitude data is available for the core locations in project files. Table 7. Core Location and Condition Core No. Location Condition of Pavement Laboratory Test Wheel Comments Direction Station Path 1 NBL IWP Plastic Flow Air Voids Broken core, not full depth 2 NBL IWP Plastic Flow Poor core condition Core disintegrated 3 NBL IWP Plastic Flow Extraction Recovery Core disintegrated 4 NBL IWP Plastic Flow Extraction Recovery Core disintegrated 5 NBL IWP Plastic Flow Air Voids Core disintegrated 6 NBL IWP Plastic Flow Hamburg 7 NBL OWP No Plastic Flow Air Voids 8 NBL OWP No Plastic Flow Air Voids RR Page 11

17 Core No. Table 7. Core Location and Condition (Continued) Location Direction Station Wheel Path 9 NBL OWP 10 NBL OWP 11 NBL OWP 12 NBL OWP Condition of Pavement No Plastic Flow No Plastic Flow No Plastic Flow No Plastic Flow 13 NBL OWP Plastic Flow RR Page 12 Laboratory Test Air Voids Extraction Recovery Extraction Recovery Hamburg Comments Poor core condition Solvent used to remove core from barrel 14 NBL BWP Plastic Flow Air Voids 15 NBL IWP Plastic Flow Poor core condition 16 SBL OWP Plastic Flow Hamburg 17 SBL OWP Plastic Flow Poor core condition 18 SBL BWP No Plastic Flow Hamburg 19 SBL OWP No Plastic Flow Air Voids IWP-Inside Wheel Path OWP-Outside Wheel Path BWP-Between Wheel Path NBL-North Bound Lane SBL-South Bound Lane LABORATORY TESTING The air void content of the micro-surface cut from the top of the cores was determined and reported in Table 8. The asphalt binder was extracted and recovered from the micro-surfacing materials to allow for asphalt binder properties, asphalt binder content and gradation of the aggregate to be determined. Hamburg tests were performed on core samples that had both the asphalt concrete mixture and micro-surface. Table 8. Air Void Content of Micro-Surface Core No. General Condition Air Void Content, Percent Individual Sample Average 7 No plastic flow No plastic flow No plastic flow Plastic flow Plastic flow Plastic flow 1.5

18 Air Void Content The air void content of the micro-surface removed from the core samples is shown on Table 8. The air void content was obtained on three samples from areas without plastic flow and from three samples with plastic flow. The average air void content in areas with no plastic flow was 2.8 and the average air void content from areas with plastic flow was 1.7. Asphalt Binder Properties Asphalt binder PG high temperature grade was determined from the asphalt binder extracted and recovered from the micro-surface in areas of without and with plastic flow. The high temperature grade for both locations was PG 58. This appears to be low considering that the penetration of the asphalt binder tested used for mixture design had a penetration of 65. Asphalt Binder Content The asphalt binder content was obtained on the micro-surfaces removed from the cores. The asphalt binder content from cores 10 and 11 that did not have plastic flow was 7.5 percent. The asphalt binder content from cores 3 and 4 with plastic flow were 7.6 percent. Aggregate Gradation Aggregate gradation test results for the micro-surface are shown on Table 9. The gradations reported from the cores without and with plastic flow are within the project specification limits. Note that the gradations for aggregates obtained prior to construction and likely from stockpiles did not meet specification for the majority of the samples (Table 6). The results obtained from the core samples contained more coarse sizes of aggregate (plus No. 8 and plus No. 16). Table 9. Gradation of Micro-Surface Sieve Size No Plastic Flow Plastic Flow Specification Limits Samples 10 & 11 Samples 3 & 4 Min. Max 3/ No No No No No No No Hamburg Test The Hamburg test was performed on cores containing both the hot mix asphalt underneath the micro-surface and the micro-surfacing material. Samples 12 and 18 from areas with not plastic flow had a rut depth of 12.5 mm after 3,400 cycles. Samples 6 and 16 from areas with plastic flow had a rut depth of 12.5 mm after 5,152 cycles. These test results indicate that the hot mix asphalt is water susceptible. RR Page 13

19 Note that rutting was not evident during the visual condition survey performed in July Rutting can be expected if the micro-surface remains on the pavements and seals the moisture in the hot mix asphalt. SUMMARY Premature distress that occurs in a pavement is usually the result of several factors. While the cause cannot be established for certain with this limited investigation, the likely cause is due to several factors including those identified below. ASPHALT BINDER According to the specification a CSS-1P emulsion is to be utilized for micro-surfacing (Item 350). TxDOT test results on the asphalt emulsion used for the project and sampled during mixture design indicated a CSS-1 emulsion test report with properties that meet a CSS-1P (Table 5). Asphalt binder properties of the micro-surface after being in service for a few months indicate a PG 58 base binder in the emulsion for samples obtained from areas with and without plastic flow. This is a soft grade of asphalt cement for this type of highway in this climate. Soft asphalt cement binder in the micro-surface can cause the plastic flow. Additional asphalt binder testing would be useful. AGGREGATE Aggregates obtained and tested prior to construction indicated relatively low quantities of the coarser fractions specified in Item 350. Two gradations obtained after construction from the placed micro-surface (in areas with and without plastic flow) indicated gradation specification compliance. The amount of No. 200 materials in the micro-surface is on the low side of the specification requirements as determined by both preconstruction and post construction gradations (Tables 6 and 9). A lower percent retained on the No. 200 sieve was noted for the samples with plastic flow as compared to those samples without plastic flow (Table 9). Low minus No. 200 material can contribute to plastic flow. MIXTURE The mixture design indicated a residual asphalt binder content of 8.5 percent. Field core samples indicated a residual asphalt binder content of 7.5 percent. No difference in asphalt content was noted between the samples with no plastic deformation versus samples with plastic deformation. Wet track abrasion test indicate that the micro-surfacing mixture design is not highly water susceptible. Portland cement contents recorded in the field slightly exceeded the design quantity. Air void content obtained for the micro-surface after construction are relatively low (Table 8). Air voids in the plastic flow areas averaged 1.7 percent for three samples and in the non-plastic flow areas 2.8 percent for three samples. Plastic flow in hot mix asphalt mixtures is likely with air voids below about 2.5 percent. RR Page 14

20 CONSTRUCTION Climate data collected during and after construction indicates that construction and early trafficking was during a wet period (Table 2, 3 and 4). Aggregate stockpiles were likely wet and the mixtures were likely at elevated water contents during part of the construction. Curing of the mixture after placement with wet conditions and high humidity s likely resulted in a mixture that had low shear strength during early trafficking. This would cause the plastic flow in the microsurfacing. The amount of micro-surfacing place in lift one and two (Table 1) meet the specification of 30 lbs./sq. yd. for the first lift and 25 lbs./sq. yd. for the second lift. OTHER Hamburg wheel track testing in the laboratory indicated that the hot mix asphalt below the micro-surface is likely water sensitive. While this property could contribute to the plastic flow in the micro-surface, it is not likely. No rutting was evident in the pavement at the time of the visual condition survey in July. The micro-surface appeared to be the only material that was shoving. REFERENCES 1. Monthly Climate Data for Sulphur Springs, Texas, US. Climate Data RR Page 15