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Bearing Capacity of Roads, Railways and Airfields – Loizos et al. (Eds) © 2017 Taylor & Francis Group, London, ISBN 978-1-138-29595-7

Innovative construction techniques and functional verification on airfield pavements—a Dutch case study

F.R. Bijleveld, A.H. de Bondt & R. KhedoeOoms Civiel, Scharwoude, The Netherlands

M. StetVIA Aperta Verhardingsadviseurs, Deventer, The Netherlands

ABSTRACT: There is a push for improving the on-site pavement construction process. In addition, agencies change their specifications towards functional requirements and increase their guarantee periods. However, there is a gap between the tests in the laboratory design phase (CE-marking) and the properties achieved in the field. Also, the on-site construction process is traditionally not routinely monitored. This makes it hard to relate field properties to properties used in the design and properties declared on the CE-marking. This research addresses this gap as well as the need for a better understanding of the on-site construction processes.

In the Dutch airfield construction project Rotterdam The Hague Airport, mechanical properties (indi-rect tensile cracking resistance and triaxial permanent deformation resistance) were determined on (a) laboratory-mixed, laboratory-compacted specimens, (b) plant-mixed, laboratory-compacted specimens, and (c) plant-mixed, field-compacted specimens. Using this methodology, functional verification became possible and it allowed directly comparing field properties with properties promised in the pavement design and declared on the CE-mark. Additionally, supporting technologies were successfully introduced, such as GPS, laserlinescanners and infrared cameras, to monitor the asphalt temperature variability and the number of roller passes. The results made the on-site process explicit and show a consistent and homogeneous process.

The paper demonstrates that the fracture energy of the CE-marking specimens are a pretty good esti-mator for the final fracture energy achieved in the field. Further, the paper demonstrates how technologies can be used to monitor the on-site construction process. Together, this contributes to a deeper under-standing of the construction process, consistent asphalt quality and functionally verified field properties.

route for determining asphalt properties (CE-marking). As such, mechanistic characteristics are now tested in the laboratory that are more relevant to practice, such as resistance to crack-ing and rutting, rather than specifying a recipe to compose the asphalt mixture, such as the aggre-gate gradation and the percentage of bitumen. An essential element in this transition is understand-ing the relationship between characteristics tested in the laboratory and the performance in the field (Airey & Collop, 2014; Erkens et al. 2014; Sluer & Stigter, 2014; Bijleveld, 2015). As such, a consider-able research effort has been put into determining potential asphalt quality characteristics, in terms of functional and mechanical properties, and corre-sponding laboratory tests. Various laboratory tests have been developed and accepted for determining certain asphalt characteristics, such as the Indirect Tensile Strength test, the triaxial test and the four-point-bending test (EN-12697). However, there

1 INTRODUCTION

The roles of agencies (clients) and contractors in the road construction industry in The Netherlands are changing. Agencies are shifting towards service-level agreements and performance contracts with lengthy guarantee periods and contractors become respon-sible for the pavement design and the selection of the asphalt mixes (Ang et al. 2005; Dorée, 2004). Within these new roles, contractors are directly confronted with any quality shortcomings that emerge during the guarantee period. These market conditions lead to a context aiming for higher asphalt quality and a consistent and homogeneous process (predictable). This encourages contractors to seek for a deeper understanding between laboratory design and per-formance in the field as well as for improved strate-gies for asphalt teams and operators.

Furthermore, the Dutch asphalt construction industry decided in 2008 to adopt the functional

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is limited understanding throughout the industry with regard to the prediction of asphalt mixture performance in the laboratory and how this relates to field performance (NAPA, 1996; van Rooijen & de Bondt, 2003; ter Huerne, 2004; Taufik et al. 2005; de Visscher, 2006; Schmitt et al. 2009; Erkens et al. 2014; Plati et al. 2014). More information on CE-marking and functional testing can be found elsewhere (Mollenhauer & Plachkova-Dzhurova, 2016; Erkens et al. 2014; Sluer & Stigter, 2014).

In addition, there is a shift from empirical pave-ment design principles towards mechanistic-empiri-cal design principles. Traditionally, pavement design is primarily based on empirical observations that generally began in the 1950s. However, these empir-ical observations are currently outdated and less relevant. In recent years, mechanical-empirical pave-ment design principles were developed. The main goal of mechanistic-empirical pavement design is to identify the physical causes of stresses in pave-ment structures and calibrate them with observed pavement performance in practice. These two ele-ments define this approach to pavement design: the focus on physical causes is the ‘mechanistic’ part, and using observed performance to determine relationships is the ‘empirical’ part. More details on mechanistic-empirical design principles can be found elsewhere (NCHRP, 2004). So, with the change towards functional specifications and func-tional testing in the laboratory, also a shift towards mechanistic-empirical pavement design is required.

Moreover, a deeper understanding of the on-site construction process (i.e. transportation, paving and compaction) is required to relate the labora-tory design to the performance in the field. How-ever, this is complex because operational strategies are generally not explicit, contractors do not rou-tinely monitor and map their own operational strategies, decisions are mainly based on experi-ence and craftsmanship, and operators receive little feedback about the quality of their work. As such, contractors have little information on what opera-tions emerged during construction, how these were carried out and, therefore, find it difficult to deter-mine a relationship between laboratory design and performance in the field. However, several tech-nologies have been developed to monitor asphalt temperatures during lay-down and compaction using GPS, thermal cameras, laser-linescanners and thermocouples (Stroup-Gardiner et al. 2000; Ulmgren, 2000; Lavoie, 2007; Miller, 2010; Beainy et al. 2012; Vasenev et al. 2014; Bijleveld, 2015), but the adoption in practice till now has been slow.

Thus, contracts are changing towards per-formance contracting including longer guarantee periods, a transition has been made from empiri-cal testing and design to functional testing and mechanistic-empirical design, and technologies to enhance the on-site construction process are

available. This research addresses the gap between laboratory design and the properties achieved in the field (using functional verification) as well as the need for a better understanding of the on-site construction processes by implementing various technologies in the on-site process.

The objectives of this study are: (1) to increase understanding how the performance in the labora-tory relates to performance in the field and (2) to use innovative technologies monitoring the on-site construction process.

Section two describes the case-study Rotterdam The Hague Airport and section three discusses the background and fundamentals of the pavement design. Section four describes the results of the functional verification, followed by the results of the on-site process control in section five. Finally, section six discusses the most important conclu-sions and recommendations.

2 CASE STUDY: ROTTERDAM THE HAGUE AIRPORT

Rotterdam The Hague Airport has the ambition to remain one of the main regional airports in The Netherlands. The existing concrete platforms are approximately 60 years of age and its techni-cal lifespan has expired. Therefore, the current 12 platforms, including foundation, pipes and cables underneath, had to be replaced. The main goal of the project was that the airfield remained opera-tional during construction. At least seven aircraft stands had to be available during construction. Consequently, the project has been carried out in five phases in approximately one year time (March 2016 – April 2017). This paper discusses the results of the first two phases.

The main project characteristics are:

– Remove concrete pavement and foundation: 55,000 m2;

– Remove asphalt pavement: 30,000 m2;– Construct concrete pavement: 30,000 m2;– Construct asphalt pavement: 65,000 m2;– New sewer pipes: 5,000 m;– New cables: 2,500 m.

In this project, technologies were introduced, such as GPS, laserlinescanners and infrared cam-eras, to monitor the asphalt temperature variabil-ity, the paver speed and the roller passes. These results are used in order to provide proper instruc-tions for next construction phases.

Further, mechanical properties (indirect tensile cracking resistance and triaxial permanent defor-mation resistance) were determined on (a) labo-ratory-mixed, laboratory-compacted specimens, (b) plant-mixed, laboratory-compacted specimens, and (c) plant-mixed, field-compacted specimens.

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Using this methodology, functional verification became possible. Functional verification means that asphalt constructed in the field is also tested using performance tests and related to the func-tional tests in the laboratory design phase. This allows directly comparing field properties with properties promised in the pavement design and declared on the CE-mark.

3 PAVEMENT DESIGN

The new pavements at Rotterdam The Hague Air-port comprise of concrete hard stands and new taxiways enclosing the platform to the parallel tax-iway. The pavements are mainly used by B737-900 aircraft and occasionally by B747 operation on a restricted take-off weight.

The basis of any mechanistic pavement design method is the structural pavement models employed.

The flexible multi-layer model in PAVERS (2016) is a classical linear elastic Burmister multi-layered structure. The layers are isotropic except for the bottom layer where anisotropy is addressed by different moduli in the horizontal and vertical direction. The interface between two adjacent lay-ers can be varied between full friction to full slip using the BISAR or WESLAY definition (van Cauwelaert, 2003).

No matter how good the pavement and load models might be, mechanistic-empirical data is still required to tie the life of a pavement to the com-puted stress or strain response. It is important to carefully calibrate the transfer function so that the predicted distress can match with field applications. Mechanistic-empirical calibration can be done by using calibrated transfer functions which relate criti-cal stresses and strains in a multi-layered pavement structure to an allowable number of load repetitions.

Using typical transfer functions e.g. fatigue rela-tions for cement concrete, asphalt and a Cement Treated Base (CTB), the typical concrete pave-ment comprise of slabs in the dimensions of 0.36  x  5.00  x  5.00  m³ on 50  mm asphalt concrete on 350  mm CTB, strength class C8/10 (according to EN-14227-1). All joints are doweled. The CTB is over 50% of the thickness notched in the slab pattern in order to prevent reflective cracking. The CTB is notched in order to minimize thermal expan-sion effects as to minimize reflective cracking. The CTB is placed over 400 mm sand on a clay subgrade.

The asphaltic taxiways comprise of 220  mm asphalt on 500  mm CTB C8/10 on 500  mm sand. Again the CTB is notched in a 5 × 5 meter pattern to delay reflective cracking. Reflective cracking was also addressed by using polymer modified Sealoflex® bitumen products in four asphalt layers with an extra resistance against

reflective cracking. In the initial pavement design, thickness estimations were made based on an FEM-analysis.

The final asphalt construction on the platform was:

– 70  mm AC 22 base, including 5.2% polymer modified bitumen (Sealoflex® 5–50 (HT));

– 55  mm AC 22 base, including 5.2% polymer modified bitumen (Sealoflex® 5–90 (HS));

– 55 mm AC 22 bin, including 5.2% polymer mod-ified bitumen (Sealoflex® 5–90 (HS));

– 40  mm AC 16 surf, including 5.7% polymer modified bitumen (Sealoflex® 5–50 (HT)).

4 FUNCTIONAL VERIFICATION

4.1 Definition and procedure functional verification

Functional verification is comparing the results of functional tests on laboratory produced specimens for the CE-marking of asphalt with the results of functional tests on asphalt specimens realized on-site (e.g. cores). This research also included the plant-produced specimens as an intermediate step. So, this research compares the results of:

– Laboratory mixed, laboratory compacted speci-mens (CE-marking);

– Plant mixed, laboratory compacted specimens (production control at the asphalt plant);

– Plant mixed, field compacted specimens (field, after realization).

This project focusses on the resistance to reflec-tive cracking and the resistance to rutting. These parameters were chosen because they determine the most critical properties with this kind of mixtures and asphalt construction for an airfield application.

For determining the resistance to cracking Indirect Tensile Strength Tests were carried out according to EN-12697-23. In addition to the CE-marking, where the specimens are conditioned and tested at 15°C, additional tests were conducted at 0°C in order to test the resistance to reflective crack-ing. This paper only discusses the results at 0°C.

Next, the Indirect Tensile Strength (ITS), the work of fracture (Wf) and the fracture energy (Gf) are derived from the test measurements. The fracture energy was calculated according to the RILEM TC 50-FMC specification (1985). The ITS-data were computed according to the EN Standard, and the work of fracture (Wf) was computed as the area under the load-displacement curve (Equation 1) and the fracture energy (Gf) was obtained by dividing the work of fracture by the ligament area (Equation 2), a procedure in line with Wen (2013).

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W P duf = ⋅∞

∫0

(1)

where Wf  =  Work of fracture (N.mm), P  =  load (kN), u = displacement (mm).

GWD Hf

f=⋅

(2)

where Gf  =  fracture energy ((N.mm)/mm2), Wf = work of fracture (N.mm), D = diameter of the specimen (mm), H = height of the specimen (mm).

For determining the resistance to rutting, triaxial tests were carried out according to EN-12697-25. The specimens were conditioned and tested at 50°C and loaded with an haversinusoidal pulse (for surface layers a constant confining pressure of 0.15  MPa was applied and then 10,000 pulses of 400 ms per second of 0.75 MPa were applied and for base/bind layers a confining pressure of 0.05 MPa was applied and then 10,000 pulses of 400  ms per second of 0.45 MPa were applied). To reduce friction, a layer of Teflon-foil and a layer of plastic with Teflon oil between them were placed on both the top and the bottom of the asphalt specimens (Erkens, 2002). The analysis revolves around comparing the creep rate (fc) and the cumulative plastic strain (ε10.000).

The specimen for the ITS tests were compacted using a Marshall hammer (75 blows on every side), both in the CE-marking and the production con-trol. The specimen for triaxial testing were com-pacted using a Gyrator (compacted until 77  mm and polished to 60 mm), both in the CE-marking and the production control.

For the CE-marking of each mixture 4 asphalt cores were tested using ITS tests (at 0°C in order to test reflective cracking) and 4 cores were tested using triaxial tests. For the production control (plant-produced specimens) per 2000 ton or per day-production 6 ITS-tests and 4 triaxial tests were performed. For the field produced specimens 3 cores every 2000 m2 were tested using the ITS test and no cores were tested using the triaxial test (this would lead to too much damage in-situ).

4.2 Comparison between CE-marking, production control and final product

The ITS, fracture energy, creep rate and cumulative plastic strain were compared for the CE-marking, the production control at the asphalt plant, and for the final product in the field (after realization). Figure 1 and Figure 2 show the comparisons of the fracture energy of phase 1 and the ITS of phase 2.

From these comparisons the following conclu-sions were drawn:

– The fracture energy of the CE-marking speci-mens are a pretty good estimator for the final

fracture energy achieved in the field. It is a little bit of a conservative estimator, since the fracture energy achieved in the field is higher (better) than ‘promised’ in the CE-marking.

– The fracture energy of the production control specimens are constantly lower (worse) than the specimens of the CE-marking and the field. So, the specimens of the production control are not such a good estimator for the fracture energy achieved in the field (more conservative than in the CE-marking).

– The ITS of the CE-marking specimens and the production control specimens are systemati-cally higher than the ITS realized in the field (up to 20%). This means that the ITS in the CE-marking is a too positive estimator for the ITS achieved in the field. This is mainly caused by a slightly higher density in the laboratory com-pacted using the Marshall hammer.

Figure 3 and Figure 4 show the comparisons of the creep rate of phase 1 and the cumulative plastic strain of phase 2. From these comparisons the fol-lowing conclusions were drawn:

– No clear trend is visible for the creep rate and the cumulative plastic strain between the CE-marking specimens and the production control specimens. This is mainly caused by the small values of the creep rate and the cumulative strain for these kind of (high quality) asphalt mixtures.

Figure 1. Comparison fracture energy phase 1.

Figure 2. Comparison ITS phase 2.

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– This issue around triaxial testing, of small values and a large variation in permanent deformation values, was similarly raised by de Visscher et al. (2006) and Mollenhauer & Wistuba (2013). A useful aim for future research would be to improve the sample preparation and test pro-cedures (higher and longer loading) to mini-mize experimental variation; a goal achieved by Muraya (2007) for gyratory compaction.

– When the sample preparation and test proce-dures are improved, in future research also triax-ial tests should be conducted on field specimens (after realization).

4.3 Conclusion functional verification

In conclusion, the fracture energy of the CE-mark-ing specimens are a fairly good estimator for the fracture energy in the field. The ITS determined in the CE-marking was in this case-study higher than realized in the field, but this could be explained by a difference in density.

For these kind of mixtures, the creep rate and the cumulative plastic strain is too small to deter-mine reliable and realistic relationships.

The next section describes the variability in the on-site construction process which could be an explana-tion for potential large variability in asphalt quality.

5 ON-SITE PROCESS CONTROL

5.1 Framework and technologies for monitoring the on-site construction process

In collaborative research of eleven Dutch road contractors and the University of Twente (called ASPARi), a framework and technologies to moni-tor the on-site construction process were previously developed. Extensive research has been reported and published about this framework (Miller, 2010; Bijleveld, 2015; Vasenev, 2015). Table  1 summa-rizes the technologies and parameters monitored.

5.2 Results monitoring logistics

Using a mobile device, as shown in Figure 5, the foreman on-site (at Rotterdam The Hague Airport) monitored the asphalt logistics. In doing so, the foreman had insight in the total number of trucks and where they were at a certain point of time, how many tonnes of asphalt was in transportation and what time the next truck would arrive on-site. This information helped to make on-site operational decisions, such as the timing to start paving when there is enough asphalt in transportation in order to reduce the number of paver stops (which are potentially weak points from the lifespan point of

Figure 3. Comparison creep rate phase 1.

Figure  4. Comparison cumulative plastic strain phase 2.

Table 1. Technologies to monitor on-site processes.

Technologies Parameters monitored

Linescanner behind the paver

Asphalt temperature behind the screed of the paver

GPS on rollers Number of roller passesInfrared cameras every 100 m Cooling asphalt surfaceThermocouples every 100 m In-asphalt coolingWeather station on-site Air temperature, wind

speed, precipitation, sun radiation.

GPS on logistics Arrival time, location, asphalt amount of every truck

Figure  5. Mobile device (any tablet) to monitor the logistics.

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view). In addition, this information of the logistics was used in order to make decisions regarding the paver speed on-site, also to reduce paver stops.

5.3 Results temperature variability

Using a laserlinescanner the asphalt surface tem-perature behind the screed of the paver was monitored. Figures 6–8 show the temperature homo-geneity. These figures show that the temperature was extremely homogeneous compared to previous studies (Stroup-Gardiner et al. 2000; Ulmgren, 2000; Lavoie, 2007; Park & Kim, 2011; Cho et al. 2012; Bijleveld, 2015). The surface temperature behind the screed of the paver was for 98% of the time between the temperature limits of 130°C and 160°C.

Figure 9 shows the asphalt cooling of the sur-face temperature and of the in-asphalt tempera-ture. This shows that asphalt cooling until 100°C took 10–15 minutes (which is relevant for the first rolling phase) and cooling until 60°C took approx-imately 35–40 minutes (which is relevant when to stop rolling). Under these specific conditions, this asphalt cooling is in line with previous studies (Miller, 2010; Wang et al. 2014; Bijleveld, 2015).

5.4 Results compaction variability

Using GPS equipment on the rollers, the number of roller passes were determined. Figure 10 shows the number of roller passes for a certain stretch of asphalt of a specific roller. The average number of roller passes on this stretch of asphalt for this 3-drum roller was 12 passes with a standard deviation of 2.9 passes. Compared to previous research efforts (Wise & Lorio, 2004; Leiva & West, 2008; Kassem et al. 2008; Schmitt et al. 2009; Gallivan et al. 2011; Plati et al. 2014; Bijleveld, 2015) this is fairly good and quite homogeneous. These graphs help to show roller operators how they actually performed, learn based on this explicit process and improve their working practices in subsequent phases of the project.

Figure 6. Georeferenced asphalt surface temperatures.

Figure  7. 98% of the asphalt surface temperatures between the limits.

Figure  8. Distribution of the asphalt surface temperatures.

Figure 9. Asphalt cooling.

Figure 10. Number of roller passes 3-drum roller.

5.5 Conclusion on-site process control

To conclude, the monitoring of the logistics lead to no significant paver stops, which resulted in an homogeneous asphalt temperature behind the screed of the paver. Also, the compaction variabil-ity (variation in number of roller passes) was quite good and homogeneous. Together, this on-site proc-ess control leads to a consistent construction proc-ess and an acceptable variation in asphalt quality.

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(2) specimens mixed at the asphalt plant and com-pacted in the laboratory, and (3) specimens con-structed on-site, lead to a deeper understanding of the potential characteristics of the asphalt mix-ture related to the characteristics realized on-site. These tests are a stepping stone towards a func-tional verification on asphalt, not only regarding the potential characteristics of the asphalt mixture (CE-marking), but also regarding the functional characteristics on constructed asphalt in-situ.

Using new sensors and technologies to monitor on-site process parameters leads to deeper insights into the asphalt construction process. These insights help to make on-site operational decisions, such as the timing to start paving to avoid stopping places of the paver. Together, monitoring the on-site con-struction process and learning based on these meas-urements enable a continuous construction process towards a reduction of variability in asphalt quality. In essence, this leads to more consistent and better predictable asphalt performance.

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6 CONCLUSIONS AND RECOMMENDATIONS

6.1 Conclusions and recommendations

The most important conclusions and recommen-dations from the case study Rotterdam The Hague Airport are:

1. The fracture energy of the CE-marking speci-mens are a pretty good estimator for the final fracture energy achieved in the field. It is a lit-tle bit of a conservative estimator, which means that the fracture energy achieved in the field is higher (better) than found (and promised) in the CE-marking. This is good in terms of risk con-trol. The specimens of the production control are not such a good estimator for the fracture energy achieved in the field.

2. The ITS of the CE-marking specimens and the production control specimens are system-atically higher than the ITS realized in the field (up to 20%). This means that the ITS in the CE-marking is a too positive estimator for the ITS achieved in the field. This is mainly caused by a slightly higher density in the laboratory, which directly affects the ITS.

3. Regarding the creep rate and the cumulative plastic strain, no clear trend has become visible between the CE-marking specimens and the pro-duction control specimens. This is mainly caused by the small values of the creep rate and the cumu-lative permanent strain for these kind of asphalt mixtures. A useful aim for future research would be to improve the sample preparation and test pro-cedures of the triaxial test to minimize experimen-tal variation and increase permanent deformation for mixtures that are not very sensitive for rutting. Also in future research, triaxial tests should be conducted on field specimens (after realization) to enable comparison between the CE-marking and the realized quality in the field.

4. The monitoring of the logistics resulted in no significant paver stops. This resulted in an extremely homogeneous asphalt temperature behind the screed of the paver, where 98% was between the targeted temperature limits.

5. The homogeneity of the asphalt compac-tion at this project was fairly good and quite homogeneous. The compaction contour plots (visualizing the number of roller passes at each location) show roller operators how they actu-ally performed, so that they can learn based on this explicit process and improve their working practices in another phase of the project.

6.2 Discussion

Conducting functional tests on (1) specimens mixed and compacted in the laboratory (CE-marking),

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