Quantifying Benefits of Geocomposite Membrane as ...

Paper No. 03-3482

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Title: Quantifying the Benefits of a Geocomposite Membrane as a Pavement Moisture Barrier Using Ground Penetrating Radar and Falling Weight Deflectometer

Authors: Samer Lahouar, Imad L. Al-Qadi, Amara Loulizi, Mostafa Elseifi, John A. Wilkes, Thomas E. Freeman

Transportation Research Board 82nd Annual Meeting January 12-16, 2003 Washington, D.C.

TRB 2003 Annual Meeting CD-ROM

Paper revised from original submittal.

Quantifying the Benefits of a Geocomposite Membrane as a Pavement Moisture Barrier Using Ground Penetrating Radar and Falling Weight Deflectometer Samer Lahouar Graduate Research Assistant Virginia Tech Transportation Institute 3500 Transportation Research Plaza Virginia Tech, Blacksburg, VA 24061-0536 Tel: 540 231-1588, Fax: 540 231-1555 e-mail: [email protected] Imad L. Al-Qadi Charles E. Via, Jr. Professor of Civil and Environmental Engineering Leader of the Roadway Infrastructure Group Virginia Tech Transportation Institute 200 Patton Hall, Virginia Tech, Blacksburg, VA 24061-0105 Tel: 540 231-5262, Fax: 540 231-7532 e-mail: [email protected] Amara Loulizi Research Scientist Virginia Tech Transportation Institute 3500 Transportation Research Plaza Virginia Tech, Blacksburg, VA 24061-0536 Tel: 540 231-1504, Fax: 540 231-1555 e-mail: [email protected] Mostafa Elseifi Graduate Research Assistant Virginia Tech Transportation Institute 3500 Transportation Research Plaza Virginia Tech, Blacksburg, VA 24061-0536 Tel: 540 231-1568, Fax: 540 231-1555 e-mail: [email protected] John A. Wilkes President CARPI USA 3517 Brandon Ave. Suite 100, Roanoke, VA 24018 Tel: 540-345-7582, Fax: 540-344-7154 e-mail: [email protected] Thomas E. Freeman Senior Research Scientist Virginia Transportation Research Council 530 Edgemont Road, Charlottesville, VA 22903 Tel: (804) 293 1957, Fax: (804) 293 1990 e-mail: [email protected]

Virginia Tech Transportation Institute Virginia Tech Blacksburg, Virginia



Lahouar, Al-Qadi, Loulizi, Elseifi, Wilkes, and Freeman

1

ABSTRACT The objective of this study is twofold: (1) quantify the benefits of a specially-designed geocomposite membrane (a low modulus polyvinyl chloride [PVC] layer sandwiched between two nonwoven geotextiles) to act as a moisture barrier in flexible pavement systems; and (2) quantitatively measure moisture content of unbound granular materials nondestructively. The geocomposite membrane was installed over half the length of a pavement test section at the Virginia Smart Road, while the other half of the test section consisted of the same design without the interlayer system. Air-coupled ground penetrating radar (GPR) system with 1 GHz frequency bandwidth was used to monitor and detect the presence of moisture within the pavement system over different periods corresponding to different levels of water accumulation. Results of GPR data analysis indicated that the use of the geocomposite membrane reduced water infiltration to the aggregate base layer by as much as 40% when measurements were performed after rain. It was also found that the moisture content underneath the interlayer was almost constant and therefore independent of the amount of rainwater, which is the primary source of moisture in pavement systems that have a low water table. Impact of moisture in the granular layers is investigated using the results of a deflection monitoring program. Results indicated that the area with the geocomposite membrane always showed less deflection than the area without the interlayer.

Keywords: geocomposite membrane, drainage, ground penetrating radar




2

INTRODUCTION Several problems associated with rapid deterioration and unsatisfactory performance of pavement systems are directly related to the accumulation of excessive moisture in the subgrade and granular layers. Examples of distresses associated with the accumulation of water in pavement layers include stripping in hot-mix asphalt (HMA) layers, loss of subgrade support, reduction of granular layers stiffness, and erosion of cement-treated base layers (1). Nowadays, different solutions have been suggested and implemented in flexible pavement design methods to improve drainage conditions on pavement performance service life prediction (e.g., AASHTO, 1993). Drainage layers and edge drains are examples of common additions to flexible pavement systems that may prevent the detrimental effects of moisture on pavement performance. The use of geosynthetic material has also been recognized as a potentially reliable method to enhance the drainage of aggregate and subgrade layers (1, 2). One of the simplest techniques to measure pavement drainage is to collect water at pavement edges. But, because some pavement layers are unbound in all directions, water would drain vertically to the underlying layers or it would be retained within the material. Such problems might be minimized by adequate design of the lateral slopes, but the technique remains inaccurate. Several techniques have been used to estimate the moisture content in pavement systems. Some techniques that detect the presence of moisture within the layers of a pavement system are based on electromagnetic (EM) energy, either by using Ground Penetrating Radar (GPR) or Time Domain Reflectometry (TDR) probes. In 1999, Al-Qadi and Loulizi demonstrated the use of a GPR system to detect the presence of moisture within pavement systems based on the variations of the reflection amplitude from the different layer interfaces (3). In 2001, Elseifi et al. presented the use of GPR and TDR probes to qualitatively validate the effectiveness of a specially designed geocomposite membrane system to act as a moisture barrier and to prevent the infiltration of water to the underneath layers (2). Although the results of these studies demonstrated the ability to detect the accumulation of water in the pavement system, the quantification of such benefits was yet to be achieved. This paper presents two important issues: the effectiveness of the aforementioned geocomposite membrane as a moisture barrier, and the utilization of GPR data to quantify the moisture infiltration reduction to the granular base layers when using a geocomposite membrane. This study was conducted at the Virginia Smart Road pavement test facility where the geocomposite membrane was installed in two different sections to test its effectiveness as a moisture barrier and as a strain energy absorber. BACKGROUND The Virginia Smart Road The Virginia Smart Road located in Southwest Virginia is a unique, state-of-the-art, full-scale research facility for pavement research and evaluation of Intelligent Transportation Systems (ITS) concepts, technologies, and products. The Virginia Smart Road is one of a few facilities to be built from the ground up with its infrastructure incorporated into the roadway. When completed, the Virginia Smart Road will be a 9.6km connector highway between Blacksburg and I-81 in Southwest Virginia, with the first 3.2km designated as a controlled test facility. The flexible pavement part of the Virginia Smart Road test facility includes 12 (heavily instrumented) different flexible pavement sections. More than 500 instruments were embedded in the road during construction to quantitatively measure the response of pavement systems to vehicular and environmental loading. For successful instrumentation strategy, at least two types of response (stress, strain or deflection) should be compared simultaneously. Therefore, strain and stress are carefully monitored along the depth of the pavement system. Climatic parameters, including temperature, base and subbase moisture, and frost depth, are monitored at different depths along the pavement. The calibration and installation of the instruments at the Virginia Smart Road has been presented elsewhere (4). Ground Penetrating Radar Principles The principle of an impulse GPR system (most common type of GPR system commercially available) is based on sending an EM pulse through the GPR antenna to the ground and then recording the reflected pulses from layer interfaces where there is a contrast in the dielectric properties of the layers. Analysis of the reflected GPR signals allows the estimation of the pavement layer thicknesses and their dielectric properties (5). This represents the main application of GPR for pavement assessment.



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Depending on the way the GPR antenna is deployed, GPR systems can be classified as air-coupled (or launched) or ground-coupled systems. In air-coupled systems, the antennas (usually horn antennas) are typically 150 to 500mm (6 to 20in) above the surface. These systems give a clear radar signal and allow for highway speed surveys. However since part of the EM energy sent by the antenna is reflected back by the pavement surface, they have a low depth of penetration into the pavement structure. In contrast, a ground-coupled system antenna is in full contact with the ground, which gives a higher depth of penetration (at the same frequency) but limits the speed of the data collection survey. The GPR system used in this research was a SIR-10B connected to an air-coupled antenna, manufactured by Geophysical Survey Systems, Inc. (GSSI). The air-coupled antenna was composed of a pair of separate horn antennae (one serves as a transmitter and the other as a receiver) having a frequency bandwidth of 1GHz, which corresponds to a pulse width of 1 nanosecond. As depicted in FIGURE 1, the antenna was mounted behind the survey van, with the control unit set inside of it. To precisely locate the collected data longitudinally on the road, a distance-measuring instrument (DMI) connected to the survey vehicle wheel was used to control the trigger pulses generated by the GPR system. In this case, data was collected as a function of distance (i.e., n scans every meter) rather than as a function of time (i.e., n scans every second). Moisture Content Estimation in Base Layers Using GPR It is possible that the moisture content of a pavement layer can be correlated to its dielectric constant. Indeed, presence of free moisture in a pavement layer will increase its dielectric constant since water has a high dielectric constant (approximately 80) compared to the dielectric constant of the other pavement materials (ranges between 3 and 6 for HMA, between 4 and 9 for aggregate, and between 6 and 15 for concrete) (6). Therefore, moisture accumulation in a pavement layer will cause a higher dielectric contrast at its interface when compared to a normal layer. Consequently, the GPR reflected signal at a layer interface with high moisture content will have greater amplitude. Quantitatively, the bulk dielectric constant of any material can be computed from the individual dielectric constant of its components using a mixture law called the complex refractive index model (7). This model expresses the dielectric constant of a material, εm, as follows:  εm =    i

∑V

i

 εi   

2

(1)

where Vi is the volume fraction of component i, and εi is the dielectric constant of component i. A granular base layer is composed of aggregates, air voids, and water. Therefore the dielectric constant of the base layer could be expressed according to equation (1) as follows:

(

ε b = Vagg ε agg + Vair ε air + Vw ε w

)

2

(2)

where εb the dielectric constant of the base layer, Vagg and εagg fractional volume and dielectric constant of aggregate, Vair and εair fractional volume and dielectric constant of air, εair = 1, and Vw and εw fractional volume and dielectric constant of water, εw ≈ 80. Equation (2) could be transformed to yield the gravimetric moisture content, of the base layer according to the following equation (7):



4


(

)

γd ε agg − 1 γ agg mc = γ εb − 1 − d ε agg − 22.2 γ agg εb −1 −

(

)

(3)

where mc is the gravimetric moisture content in percent, γd is the dry density of the base layer, and γagg is the density of aggregate. In equation (3), the dry density, aggregate density, and aggregate dielectric constant could be estimated from direct measurements on samples extracted from the aggregate base layer. In contrast, the aggregate base dielectric constant is determined from the GPR data using the following equation:    1 −   ε b = ε HMA     1 −     

2

    A1   AP 

A0  A  + 1 AP  AP 2

A0   − AP 

2

(4)

where (as presented in FIGURE 2) A0 and A1 are the amplitudes of the surface and HMA/base interface reflections, respectively, AP is the reflection amplitude collected over a calibration copper plate placed on the pavement surface; thus, AP represents the negative of the incident signal, and εHMA is the HMA layer dielectric constant, which is also determined from the GPR data according to the following equation:  1+ ε HMA =   1− 

A0 AP A0 AP

     

2

(5)

GEOCOMPOSITE MEMBRANE INSTALLATION A geocomposite membrane was installed in two sections of the Virginia Smart Road (8). This membrane consists of a 2mm-thick low modulus polyvinyl chloride (PVC) backed on both sides with polyester nonwoven geotextile. The primary function of the PVC geocomposite membrane is to control water infiltration or fine migration. Typical values of geocomposite membrane permeability were reported between 1×10-13 and 2×10-13 cm/sec, which is close to an absolute impermeable material (9). This special design offers the potential to use this type of interlayer as a multi-purpose system as a moisture barrier and as a strain energy absorber. The latter case was investigated and validated elsewhere (10). In section J of the Virginia Smart Road, the geocomposite membrane was installed along half the section underneath an asphalt-treated drainage layer to evaluate its effectiveness as a moisture barrier (a schematic of this section is shown in FIGURE 3; all designations are in accordance with the Virginia Department of Transportation specifications). Section J is located in a cut with a subgrade material classified as A-1-a based on the AASHTO classification (corresponding to GP-GM in the United Classification System). This describes a material consisting predominantly of stone fragments or gravel. During construction of this project (1999) and based on regular deflection testing, the estimated backcalculated subgrade modulus was 335MPa with the presence of a stiff layer at a depth of 4.6m. In this project, ground water table is low and was not detected in any of the test sections. Therefore, the main source of water in the granular layers originates from the amount of precipitation that infiltrates through the layered system. The section has a 5% longitudinal slope and 2% lateral slope, which is considered ideal for positive




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drainage within the pavement structure. While this geocomposite membrane has been used on two bridge decks in Italy and is widely utilized in dam applications in Europe, it has never been used on any roads or bridges in the United States prior to its installation at the Virginia Smart Road. Since the installation at the Virginia Smart Road in 1999, it was installed in a bridge deck application in Delaware in 2000. Prior to installation, the area to be covered with geocomposite membrane was cleaned of any loose aggregates. The installation of the geocomposite membrane in section J (moisture barrier over a granular material) did not necessitate the use of a prime coat between the geotextile and the underneath layer (21B aggregate base layer). A prime coat is not effective when applied to a granular material (e.g., 21B) due to the nature of the surface, which accumulates a large amount of loose aggregates, and due to the fact that greater friction exists between the geocomposite membrane and the aggregate layer when the prime coat is absent. Five rolls, each 37m-long and 2.05m-wide, were installed over the complete width of the road, and extending 2.15m into the shoulder. Additional rolls were then installed to achieve a 50-meter long installation. Transverse joints between PVC rolls were staggered to prevent the creation of a weak joint across the pavement lane. At the longitudinal joints, a 55mm-length weld was performed by applying hot air to melt the uncovered PVC end; see FIGURE 4a for illustration. The welding was then carefully checked; see FIGURE 4b. The upper surface of the geocomposite membrane was primed using PG 64-22 asphalt binder at an application rate of 1.45kg/m2. FIGURE 5 illustrates the application of prime coat on top of the geocomposite membrane. Seventy-five millimeters of asphalt treated open-graded drainage layer (OGDL) was then placed on top of the geocomposite membrane. The only precaution during installation that is outside normal operations is to avoid sudden application of truck brakes on the geocomposite membrane layer to prevent it from wrinkling. Temperature and moisture sensors were placed on both sides of the geocomposite membrane, while three pressure cells were installed under the geocomposite membrane. More details about the installation have been presented elsewhere (8). DATA COLLECTION Since the geocomposite membrane was installed over half of section J at the Virginia Smart Road, its effectiveness as a moisture barrier was quantified by comparing the moisture content of the two section halves. For that purpose, GPR data was collected over different periods of the year from the same locations. The data was collected from two identical 20m segments from section J. The only difference between the two segments was the presence of the geocomposite membrane on top of the aggregate base layer in one of the segments. The surveys were performed on eight different dates: December 7th, 2001; January 30th, April 24th; May 22nd, June 19th, July 16th, August 22nd, and September 12th, 2002. As Shown in FIGURE 6, the surveys were carried out after different weather conditions varying from dry (i.e., it did not rain or snow for more than a week) to wet (rainfall was recorded in the week preceding the survey but it did not rain at least two days before data collection). Another survey was performed on the 21B aggregate base layer on August 16th, 1999 during the road construction and after the 21B layer was completed. This survey was done the same day as nuclear gauge measurements were taken on the aggregate base layer for density and moisture content estimation for quality control purposes. DATA ANALYSIS AND RESULTS As shown by equation (3), the moisture content of the aggregate base layer is related to four parameters: the aggregate base dielectric constant, the dry density of the layer, and the density and dielectric constant of aggregate material. While the dielectric constant of the aggregate base layer is determined by equation (4), the remaining three parameters should be estimated and assumed constant over the whole section. One technique to determine these parameters is to correlate the dielectric constant (or its square root) to the moisture content measured from the same locations, and then deduce the values of the unknown parameters from the regression equation. To apply this method, the moisture content measured using a nuclear gauge over the 21B layer during the construction of the road can be used. The aggregate base dielectric constant over the locations where the nuclear gauge measurements were taken was determined from GPR data collected the same day. The aggregate base dielectric constant is computed in this case using Equation (5) rather than Equation (4) since the base layer was the top layer at that time. The results found from these measurements are summarized in TABLE 1. FIGURE 7 shows the base layer gravimetric moisture content (measured by nuclear gauge) as a function of the square root of its dielectric constant. According to this graph, a linear relationship (R2 = 0.88) can be established between the moisture content and the dielectric constant. On the other hand, Equation (3) can be linearized using a



6


Taylor series expansion about a point εb0 in the middle of the interval of the expected values of the base dielectric constant, according to the following: mc ≈

2 ε b0 + c1 + c2

(ε

b0

+ c2

)

2

εb −

2c1 ε b0 + c1c2 − ε b0

(ε

b0

+ c2

)

2

= a εb + b

(6)

where c1 and c2 are two constants given by: c1 = 1 +

c2 = −1 −

γd γ agg

γd γ agg

(ε (ε

agg

agg

)

−1

− 22.2

(7)

)

(8)

Using the constants a = 0.0628 and b = -0.1187 (obtained from FIGURE 7), Equation (6) yields the values of the aggregate dielectric constant and the dry density to the aggregate density ratio as follows:

εagg = 5.65 γd = 0.68 γ agg The GPR data collected after completion of the road was analyzed for aggregate base moisture content using the previously outlined procedure. The average dielectric constant and moisture content found for each survey date and for each segment are presented in TABLE 2. The base dielectric constant was found using Equation (4) because the surveys were performed on the wearing surface layer. FIGURE 8 depicts the average gravimetric moisture content for the segments with and without geocomposite membrane. FIGURE 9 shows the average increase in moisture content in the segment without geocomposite membrane compared to the segment with geocomposite membrane. It should be noted that the moisture content values found by this technique may be underestimated because the base dielectric constant (from which the base layer moisture content is computed) is underestimated. In fact, estimating the base dielectric constant using Equation (4) does not account for any material loss occurring in the HMA layer. However, the effect of this error is eliminated when comparing the moisture content of the different sections (such as in FIGURE 9) because the comparison is based on the ratio of moisture contents, which are linear functions of the dielectric constant as shown in Equation (6). Therefore, using GPR for estimating the base layer moisture content might not be very accurate unless calibration cores were taken to estimate the different parameters needed for the analysis along with the material loss occurring in HMA. However, the technique could be used to monitor moisture changes in pavements over time by performing surveys during different periods and comparing the moisture content ratios. The results of such surveys would be more accurate and reliable. According to FIGURE 8, the moisture content in the segment with geocomposite membrane is always lower than the segment without geocomposite membrane. Moreover, the moisture content difference is particularly high for the April 2002 and June 2002 surveys because of the rain recorded during these periods. It is also noted that the moisture content underneath the geocomposite membrane is almost constant and therefore is independent of rainfall. This result is confirmed in FIGURE 6 where the volumetric moisture constant underneath the membrane, measured by Time Domain Reflectometry (TDR) probes, was found constant and independent of rainfall. A comparison between the two segments with and without geocomposite membrane (FIGURE 9) shows that for dry conditions, the moisture content in the segment with geocomposite membrane is comparable to that in the segment without geocomposite membrane (approximately 4.6% to 13% difference). However, after rain the difference between the two segments reached 41.5%. This indicates that the 21B layer will have high moisture content in the event of rain if the geocomposite membrane is absent. This may not be desirable as it may reduce the resilient modulus of that layer and, hence, the structural capacity of the pavement system. It is clear from this analysis that the geocomposite membrane is effective in decreasing moisture infiltrating to the granular base layers. It is also equally important that the presence of an OGDL with significant slopes in both directions may not prevent




7

or significantly reduce the moisture infiltration to underneath unbound layers. This observation may well explain the “less than expected” performance of pavement systems having OGDLs. IMPACT ON PAVEMENT SERVICEABILITY Large moisture content may significantly reduce the bearing capacity of the subbase and the subgrade, causing progressive failure of the pavement system. Cedergren predicted a reduction of 50% in the pavement service life if a pavement base is saturated as little as 10% of the time (11). To evaluate the effect of moisture on the pavement structural integrity, use was made of a deflection monitoring program using the falling weight deflectometer (FWD). From the period between March 2000 and December 2001, FWD measurements were regularly performed on a selected set of points in section J. Two points were located in the area with the geocomposite membrane and three other points were located in the area without the membrane. Within the contest of this study, where the major interest is to detect the variation in the subbase and the subgrade, use was made of the deflection measured away from the center. The last sensor, which was located in this project at a distance of 72mm from the center, is regularly used to diagnosis the integrity of the subgrade by assuming that the higher the deflection the weaker the subgrade (12). FIGURE 10 illustrates the measured deflections with and without geocomposite membrane from the period between March 2000 and December 2001. As noticed from this figure, the area with the geocomposite membrane always showed less deflection than the area without the geocomposite membrane. Assuming the uniformity of the subgrade throughout this section, it may be concluded that the accumulation of moisture in the area without geocomposite membrane will result in a decrease of the bearing capacity of the subbase and the subgrade material. It may also be noticed from this figure that a sharp increase in the deflection is measured during the spring thaw season. This cycle is repeated every year and may be noticed twice during the monitoring period. During the AASHO Road test, it was previously reported that the spring thaw cycle result in a sharp decrease in pavement serviceability (13). It appears that the use of a geocomposite membrane will reduce the detrimental effect of spring thaw cycle on the granular layers. CONCLUSIONS The aggregate base layer moisture content of two identical pavement sections one with and one without geocomposite membrane was estimated using Ground Penetrating Radar (GPR). The technique is based on the fact that moisture accumulation in the aggregate base layer increases its dielectric constant, which can be estimated from GPR data. It was shown that, in general, the moisture content underneath the geocomposite membrane was always lower than that in the section without geocomposite membrane. Moreover, the geocomposite membrane allowed a 40% reduction in the moisture content of the base layer when it was measured a few days after it rained. Based on this research, two main conclusions are made: 1. A method to quantify the moisture content in granular material nondestructively is presented and validated. 2. The benefits of using a geocomposite membrane as a moisture barrier are validated using GPR surveys and FWD deflection measurements.

ACKNOWLEDGMENTS This research has been sponsored by the Virginia Center for Innovative Technology, Virginia Transportation Research Council, Virginia Department of Transportation, Carpi USA, and Atlantic Construction Fabrics, Inc. The authors would like to acknowledge the assistance of B. Diefenderfer, G. Flintsch, W. Nassar, R. Davis, A. Appea, K. Light, and K. Taylor. REFERENCES 1. Christopher, B. C., S. A., Hayden, and A. Zhao. Roadway Base and Subgrade Geocomposite Drainage Layers. In J.S. Baldwin and L.D. Suits (Eds.), Testing and Performance of Geosynthetics in Subsurface Drainage, ASTM STP 1390, American Society for Testing and Materials, West Conshohocken, PA, 1999.




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2. Elseifi, M.A., I. L. Al-Qadi, A. Loulizi, and J. Wilkes. Performance of a Geocomposite Membrane as a Pavement Moisture Barrier. In Journal of the Transportation Research Board 1772, TRB, National Research Council, Washington, DC, 2001. 3. Al-Qadi, I. L. and A. Loulizi. Using GPR to Evaluate the Effectiveness of Moisture Barriers in Pavements. In Structural Faults and Repair 99, 8th International Conference (CD-ROM), M. C. Forde (Ed.) London, England, July 13-15, 1999. 4. Al-Qadi, I. L., G. W. Flintsch, A. Loulizi, S., Lahouar, and W. Nassar. Pavement Instrumentation at the Virginia Smart Road. Paper presented at the 14th IRF Road World Congress, Paris, France, 2001. 5. Lahouar, S., I. L. Al-Qadi, A. Loulizi, C. M. Trenton, and D. T. Lee. Development of an Approach to Determine In-Situ Dielectric Constant of Pavements and Its Successful Implementation at Interstate 81, Paper No. 02-2596, Presented at The 81st Transportation Research Board Annual Meeting, Washington DC, January 13-17, 2002. 6. Daniels, D. J. Surface-Penetrating Radar. The Institution of Electrical Engineers, London, UK, 1996. 7. Maser, K. R. and T. Scullion. Automated Pavement Subsurface Profiling Using Radar: Case Studies of Four Experimental Field Sites, In Transportation Research Record No. 1344, Pavement Design, Management, and Performance, TRB, National Research Council, Washington, DC, 1992, pp. 148-154. 8. Al-Qadi, I. L., M. A. Elseifi, and A. Loulizi. Geocomposite Membrane Effectiveness in Flexible Pavements (Final Report, TRA-00-002). Virginia’s Center for Innovative Technology, Carpi USA, and ACF Inc., 2001. 9. Koerner, R. M. Designing with Geosynthetics. 3rd ed., New Jersey, Prentice Hall, 1994. 10. Al-Qadi, I. L. and M. A. Elseifi. Analytical Modeling and Field Performance Testing of Geocomposite Membrane in Flexible Pavement Systems. Paper presented at the 7th International Conference on Geosynthetics, Nice, France, September 22-27, 2002. 11. Cedergren, H. R. Drainage of Highway and Airfield Pavements. John Wiley & Sons, New York, N.Y., 1974. 12. Chester, H. M., and T. Scullion. MODULUS 5.0: User’s Manual. Research Report 1987-1, Texas Transportation Institute, Austin, TX, 1995. 13. Ullidtz, P., and H. J. Ertman Larsen. State-of-the-art Stress, Strain, and Deflection Measurements. Symposium on the State-of-the-Art of Pavement Response Monitoring Systems for Roads and Airfields, sponsored by U.S. Army Cold Regions Research and Engineering Laboratory, Report 89-23, 148-161.




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List of Tables and Figures

TABLE 1 Moisture Content Found from Nuclear Gauge Measurements. TABLE 2 Average Moisture Content for Sections with and without Geocomposite Membrane for Different Survey Dates. FIGURE 1 GPR Survey Van Showing the Air-Coupled Antenna. FIGURE 2 (a) Reflections from Layer Interfaces in a Typical Pavement System and (b) Radar Scan Obtained from a Typical Pavement Section. FIGURE 3 Section J Pavement Design. FIGURE 4 Welding Process at the Longitudinal Joints. FIGURE 5 Application of Prime Coat on Top of the Geocomposite Membrane. FIGURE 6 Average Daily Rainfall During Survey Period along with Base Layer Moisture Content Measured by TDR under Moisture Barrier FIGURE 7 Correlation between Moisture Content and Dielectric Constant of Base Layer. FIGURE 8 Average Moisture Content for the Sections with and without Geocomposite Membrane for Different Survey Dates. FIGURE 9 Moisture Content Increase between Sections without and with Geocomposite Membrane for Different Survey Dates. FIGURE 10 Measured Deflections by the Last Sensor (D = 72mm) with and without Geocomposite Membrane



10


TABLE 1 Moisture Content Found from Nuclear Gauge Measurements. Station 111+60 111+90 112+15 112+35 Average

Bulk Density kg/m3 pcf 1893 118 2066 129 1961 122 2020 126 1985 124


mc (%) 4.5 5.4 5.7 5.3 5

Dry Density kg/m3 pcf 1812 113 1961 122 1855 116 1918 120 1886 118

εb 6.9 7.6 7.9 7.3 7.4


11


TABLE 2 Average Moisture Content for Sections with and without Geocomposite Membrane for Different Survey Dates. Survey Date MB* 12/7/2001 5.85 1/30/2002 5.96 4/24/2002 5.95 5/22/2002 5.57 6/19/2002 5.09 7/16/2002 5.32 8/22/2002 5.84 9/12/2002 5.37 * MB: Moisture Barrier


εb Normal 6.22 6.62 7.12 6.00 5.80 5.61 6.23 5.46

Moisture Content (%) MB* Normal 3.79 3.31 4.29 3.80 4.89 3.45 3.52 2.96 2.31 3.25 2.61 3.01 3.31 3.80 2.69 2.81

Moisture Increase (%) 14.4 13.8 41.5 19.0 41.1 15.3 15.0 4.6


12


FIGURE 1 GPR Survey Van Showing the Air-Coupled Antenna.



13


R0

R1

R2 Air

HMA

Base

Subgrade

(a)

A0 A1 A2

R0

R1 ∆t1

R2

∆t2

(b) FIGURE 2 (a) Reflections from Layer Interfaces in a Typical Pavement System and (b) Radar Scan Obtained from a Typical Pavement Section.



14


Surface Mix (SM-9.5D – 38mm) Base Mix (BM-25.0 – 225mm)

Asphalt-treated drainage layer (OGDL – 75mm) Geocomposite membrane 21B aggregate layer (21B – 150mm)

FIGURE 3 Section J Pavement Design.



15


(a)

(b) FIGURE 4 Welding Process at the Longitudinal Joints.



16


FIGURE 5 Application of Prime Coat on Top of the Geocomposite Membrane.



17


Precipitation (mm)

70

Precipitation Moisture Content

60

Survey Dates

18 16 14

50

12

40

10

30

8 6

20

4

10

2

0 12/1/01 12/31/01 1/30/02 3/1/02 3/31/02 4/30/02 5/30/02 6/29/02 7/29/02 8/28/02

0

Volumetric Moisture Content (%)

20

80

Date

FIGURE 6 Average Daily Rainfall During Survey Period along with Base Layer Moisture Content Measured by TDR under Moisture Barrier



18


0.06

Moisture Content (ratio)

0.058 0.056 0.054 0.052 0.05 0.048

y = 0.0628x - 0.1187 2 R = 0.876

0.046 0.044 0.042 0.04 2.6

2.65

2.7

2.75

2.8

2.85

Sqrt(εb)

FIGURE 7 Correlation between Moisture Content and Dielectric Constant of Base Layer.



19


Gravimetric Moisture Content (%)

5.00

With geocomposite membrane

4.50

Without geocomposite membrane

4.00 3.50 3.00 2.50 2.00 1.50 1.00 0.50 0.00 12/7/01

1/30/02

4/24/02

5/22/02

6/19/02

7/16/02

8/22/02

9/12/02

Survey Date

FIGURE 8 Average Moisture Content for the Sections with and without Geocomposite Membrane for Different Survey Dates.



20


41.5

45.0

41.1

Moisture Increase (%)

40.0 35.0 30.0 25.0 20.0

19.0 14.4

15.0

15.3 13.8

10.0

15.0

4.6

5.0 0.0 12/7/01 1/30/02 4/24/02 5/22/02 6/19/02 7/16/02 8/22/02 9/12/02 Survey Date

FIGURE 9 Moisture Content Increase between Sections without and with Geocomposite Membrane for Different Survey Dates.



21


14

Deflection (microns)

12 10 8 6 4

with geocomposite

2 0 3/8/00

without geocomposite

6/16/00

9/24/00

1/2/01

4/12/01

7/21/01

10/29/01

2/6/02

Date FIGURE 10 Measured Deflections by the Last Sensor (D = 72mm) with and without Geocomposite Membrane

