Asphalt Rubber Producers Group SP~ALTRUBBERPROWCERSGROUP 3336 NORTH 32ND STREET, SUITE 106 PHOENIX, ARIZONA (602)

Transcription

1 Asphalt Rubber Producers Group - SP~ALTRUBBERPROWCERSGROUP 3336 NORTH 32ND STREET, SUITE 106 PHOENIX, ARIZONA (602)

2 Introduction This is a comparison evaluation of seven construction methods used to extend the life of an old Portland Cement Pavement overlaid in Route 12 between Worcester and in the Sterling-Boylston area in Massachusetts is a Portland Cement Concrete Pavement overlaid using five methods. New interstate off ramps being constructed were included to compare and evaluatecracking on Route 12 usingfull-depth design. The research project was designed by Paul Constantino and inspected by Michael Abraham. After eight years, the test sections obtained variable degrees of success. The 1987 survey indicated major cracking in the control section and the full-depth section, while sections containing Asphalt-Rubber as a Stress Absorbing Membrane Interlayer had the least amount of cracking Conditions This project is four miles in total length on each side of Sterling, Massachusetts. The major portion of the project is an 8-inch reinforced concrete pavement estimatedto have been placed years ago. There are three longitudinal joints at 10-foot intervals across the 40-foot PCCP, with transverse joints every 51 feet. Shoulders are asphalt concrete varying from 2 to 4 feet wide approximately inches thick. A portion of the project Sta to consists of 6 inches of existing asphalt concrete in a swampy subgrade. High plastic index of the soil and variable water content created a very poor surface ride. The surfacing exhibited typical deterioration from age, including transverse thermal crack, alligator cracked areas, longitudinal and random cracks. Some of the PCCP section had been overlaid with 3 inches of asphalt in previous years. Transverse and longitudinal joints reflected through this overlay. All joints had some form of deterioration. Major deteriorated joints were removed and replaced. See photos 1 and 2. Route 12 was being used for traffic until the Interstate could be opened. Engineers knew throughexperienceasimpleoverlaywouldnotpreservethis roadway until I-190opened. Standard overlays consist of 3 inches of asphalt concrete and some cracksealing. It was decided to try five test sections utilizing various methods professed to stop or retard reflective cracking with the least amount of traffic tie-ups and delays to the traveling public. See figure 1 map. The other 3 sections were Section I - New Construction, Section 4 -Control and Section 8 -A railroad crossing repaired at a later date. The Sterling, Massachusetts area has wintertemperatures as low as -19"F, and summer temperatures of as high as 96"F, with annual precipitation ranging from 60 to 70 inches peryear, and degree days of 500. See Figures 1 and 2. Section 1 Test Sections Full-depth asphalt concrete design for 1-190, 9 inches of AC on a prepared native soil, constructed at the same time as test sections on Route

3 Section 2 (Sta to Sta ) A 545-foot-section on PCCP. All joints and cracks were repaired and sealed, followed by an application of Polyguard Band Aid Strips 12 inches wide covering ail transverse and longitudinal joints. The Band Aid surface was then treated with an Asphalt-Rubber Stress Absorbing Membrane lnterlayer (SAMI). Band Aids are defined as the application of an asphalt mastic sprayed or squeegeed over the joint followed by a woven fabric and again followed by an asphalt mastic such as Glass Flex and Road Glas. Other Band Aids are preformed having the woven fabric encapsulated by a rubberized mastic. It is usually placed over the joints after being prepared by a tack coat of asphalt. Asphalt-Rubber was applied at at rate of 0.6 f.05 gal.-per-sq.-yd., followed by 35 ibs. of a precoated 3/8-inch-aggregate. The surface was immediately roiled and swept. All SAM1 sections have the same application rate. The roadway was open to traffic at all times during application of the Asphait-Rubber, providing a constant flow of traffic with minimal delays. A inch thick asphalt concrete bindercourse was then placed followed by a inch asphalt concrete surface course. Thissection wasthen sawcut directlyoverthe existing joints. The sawcutwas318-inch-wide by 1/2-inch-deep. All sawcuts were then filled with a Federal Specification SS-S-164 crack sealant. See photos 8 and 9. At the time of construction the shoulders, being of marginal condition, were also overlaid with a SAMi without preparation of cracks. Section 3 (Sta to Sta ) A 2,955-foot-section on PCCP. All severely deteriorated joints were repaired by sawcutting full-depth and 2 to 3 feet wide on either side of the joint. Material was then removed and replaced with asphalt concrete and compacted. This method of joint repair was used on all sections containing PCCP. Joints were then covered with Band Aids of Bituthene and Owens Corning fabric. The surface including shoulders was then treated with an Asphait-Rubber SAMI. After rolling and sweeping, the surface was overlaid with I-112-inch asphalt concrete binder followed by a inch asphalt concrete surface course. This section was not sawcut or sealed on the surface course. See photos 12 and 13. Section 4 (Sa to Sta ) Control Section 4 is an 800-foot sect ion on PCCP. which was des ianated as t he control section. Severely deteriorated cracks and joints were repaired. All remaining cracks and joints were cleaned and sealed using a Federal Specification SS-S-164 crack sealant. The pavement was then overlaid with a inch asphalt concrete binder course, followed by a l-1/2-inch asphalt concrete surface course. This section did not receive a SAMI, Band Aids, nor was it sawcut. Also, there were no shoulder repairs prior to the overlay. See photos 6 and 7. Section 5 (Sta to Sta ) A foot-section on PCCP. Some of the deteriorated joints and wide cracks were treated with Band Aids, consisting of 18-inch-wide strips of Polyguard. Only longitudinal joints were Band Aid treated, transverse joints were not treated. -4-

4 Asphalt-Rubber as a SAM1 was then applied followed by a inch asphalt concrete binder course and a inch asphalt surface course. It was not sawcut and sealed. Section 6 (Sta to Sta. 5+00) This is a foot sect ion on PCC P. All joints were repaired and covered with a "Band Aid" using 12-inch-wide strips of Polyguard. Section 6 was then overlaid with a inch asphalt concrete binder course followed by a inch asphalt surface course. The surface was sawcut and sealed in the same manner as Section 2. Section 7 (Sta to Sta ) A2.780-foot sect ionofoldasdhaltconcrete. Mostof thecrackswere blown andsealed.this section is in a swamp area with subgrade problems and was alligator cracked, with numerous random cracks and the usual transverse and longitudinal cracks. The profile was very poor with a surface that had been distorted by the poor subgrade and traffic. Athin leveling course of 0-to-314-inch was placed to improve the ride and profile. An Asphalt-Rubber SAM1 was then placed followed by a inch asphalt concrete binder course and inch AC surface course. No sawcut or seal was performed. Section 8 (approx. Sta. O+OO to Sta. 5+00) Bridge approach over a railroad in the center of the project. This section was reconstructed in 1985 using a 9-inch full-depth asphalt concrete on a prepared native soil Condition Survey After eight years of service, the 1980 test sections were evaluated by the authors and the Asphalt Rubber Producers Group Technical Director. This survey indicates the following: Section 1 Random Cracking exists in the full-depth Interstate design and most construction joints are completely open. The ride and profile are good. Section 2 About 5% of the cracks and joints have reflected through the overlay. Some of the reflection is due to loss of "Band Aid"strips underconstruction traffic. These were not replaced. This section became a transition area and did not receive the full 3-inch asphalt concrete overlay. It is performing well with 5% of the sawcut seal lost. Ride and profile are good. Section 3 Less than 1% of the cracking has become evident. One 40 foot-longitudinal crack on the shoulder and one on the main road exists today. It is in very good condition. Section 4 (Control Section) A measured 3,230 feet of cracks have reflected through the overlay or 85% of the underlying joints. Transversecracking isabout 75%ofthetotalwith25% randomcracking. Ride and -5-

5 profile are good, however, water is moving info the cracks andcausing spalling and secondary cracking. See photos 6 and 7. Section 5 Less than 1% of cracks and joints have reflected through the overlay. Thirty feet of longitudinal cracking and 32 feet of transverse cracking on the main road, and 1,511 feet of cracks reflected through the shoulders. Ride and profile are good. Section 6 Materials used in joint filler in sawcuts has lost bond to the asphalt concrete. Most of the longitudinal joints are in good condition. See photos 8,9, 10, and 11. A measured 3,363 feet of cracking with 50% longitudinal and 50% transverse was found. Some pot holing has developed as 90% of the joint sealing is not effective. Secondary cracking has developed at the transverse joints. See photo 10. The ride is fair, however, transverse joints do cause some discomfort during the winter months. Section 7 Less than 1% of cracking has returned. About 95 feet of cracks were measured, of which 80 feet of the cracks were at each end of the section, where it is believed the Asphalt-Rubber application was less than specified. One longitudinal joint crack 15 feet long exists in the shoulder area. This section is performing very well considering swamp water is within 2 feet of the pavement shoulders on both sides of the roadway and this section was in a transition area not receiving the full-depth of 3 inches of overlay. Section 8 This full-depth section has in excess of 2,000 feet of random cracks. The ride and profile are good, however water is moving into the cracks. ********* -6-

6 Observation and Conclusions Asphalt-Rubber is an effective material as a stress absorbing membrane interlayer on Portland Cement Concrete Pavements when used in conjunction with a "Band Aid" strip of some type. The concept of sawcutting was to offer a long term maintenance free surface however, the test section indicates a short term result. Sawcutting causes further deterioration with the loss of its filler and retains water. Secondary cracking and pot holing has developed at some of these sawcuts. The control section had 30 times more pavement distress in the form of cracking as did any other test section. Massachusetts' standard full-depth design had more than 10 times the cracks that the test section had. Increasing the asphalt concrete overlay thickness, does not stop the reflective cracking on PCCP. The use of a Stress Absorbing lnterlayer should be required via Asphalt-Rubber and "Band Aids" when overlaying this type of pavement. Section 7, over the bituminous concrete area is in excellent condition, especially, considering the subgrade problems existing prior to the placement of the SAMI. Some deformation has returned due to moisture and peat in the subgrade. It would have taken nothing short of totalreconstruction(includingremovaland replacementof thesubgrade) tosolve the problem. Funds invested in this type of reconstruction would not have been cost effective since was to be opened inihe near future. The Asphalt-Rubber SAM1 was the most cost effective alternative for this section. Test sections using the Stress Absorbing Membrane Interlayer have performed very well for8 1/2yearsandcontinuestoperform beyondexpectation. Indications in Massachusetts are that most overlays over PCCP last less than 5 years. Three of the test sections should double that and some may triple life expectancy. To date, no maintenance has been performed on this section of Rte. 12 and very little is anticipated, except in sections severely cracked or that have some pot holing. These test sectionswill becontinuallyobservedforfurtherdevelopments and reports. -7-

7 Town of STERLING Maln SecUon Figure 1-8-

8 No. 1 -Typical Concrete Pavement Conditon 1980 prior lo overlay No. 2 - Cracked Pavement with spalling and curling -9-

9 No. 3 - Application of Asphalt-Rubber on Shoulders No. 4 -Application of Aggregate -10-

10 No. 5 - Rolling Surface with Rubber Tire and Steel Wheel -11-

11 No. 6 - Control Section 3 of Asphalt-Concrete No. 7 - Control Section 3 of Asphalt-Concrete - 12-

12 No. 8 -Sawed and Filled Joints over Concrete Joints No. 9 -Joint fill seperated from saw cut sides -13-

13 NO. 10- Secondary cracking on saw joints No Water entering seperated saw joint filler - 14-

14 No. 12 -Typical Longitudinal Joint reflection without longitudinal joint treatment or joint repair No. 13 -Transverse Crack reflection without treatment of joint repair - 15-

15 No Single Crack in Asphalt-Rubber on shoulder - 16-

16 No Single Crack in Asphalt-Rubber center line -17-

17 Route 12 Test Sections Section 1 New Construction 9 Full Depth Asphalt Section " Top Course 1 I/?' Binder Course Course Section 2 Section 6 r Sawcut and Seal Sawcut and Seal7 1 i /z"~op Course " Top Course u i ii3" R~nrl~r Cniir+e Course 1 1/2"nnder course course 1., I ~, L?ss-I I c Seal " " k 4 Band Aid 1 2: Joint -Joint Section /2 Top Course 1 1/2" Binder Course Course 8" Concrete I Section " Top Course Section 4 Control Section 8 New Construction Crack Seal 1 1r2" 8inder tiourse course 8" Concrete LJoint Figure No