2013 Session: 657

• Influence of Thermal Segregation on Asphalt Pavement Compaction
  Abstract: Both aggregate and thermal segregation during asphalt compaction can cause premature failures in asphalt pavements. Whilst aggregate segregation is easier to identify by visual observation, thermal segregation is impossible to locate in this manner. To evaluate thermal segregation, a thermal imaging technique was employed in this investigation. Continuous profiles of the mat temperature were recorded during field compaction to identify possible locations of cold spots and the rate of temperature loss. The temperature difference was found approximately 14oC immediately after laying the material with scattered cold spots as well as faster heat loss at the lane interface and edges compared to the centre of mat. Laboratory investigations on roller compacted asphalt slabs showed that this temperature difference results in 5-7% higher voids at the edge compared to the centre, indicating inferior compaction. The effect of layer interface was also evaluated in the laboratory and were found 6-10% higher air void contents at the interface. The compaction level in these places was improved when the slabs were produced in a heated moulds (simulating a heated adjoining layer), indicating that better compaction can be achieved if temperatures at the interface are at elevated temperature whilst laying the material. Finally, 3D finite element modelling was conducted for transient thermal analysis to evaluate heat loss at the interface when a hot mixture (150oC) is laid on a cold layer (5oC) and on a layer at ambient temperature 22oC. The temperature at the contact path between new and existing layer showed that the inner part of the adjoining layer had considerably lower temperature compared to the upper part, resulting in non-uniform compaction between top and bottom of the layer.
  Authors: Rahman, Mujib; Grenfell, James; Arulanandam, Steve; Ianakiev, Anton
  Authors: Rahman, Mujib; Grenfell, James; Arulanandam, Steve; Ianakiev, Anton
  Year: 2013
  Document Type: Paper
  Subject: Construction; Pavements
  Session: 657
  Paper Number: 13-1471
• Permanent Deformation of Flexible Pavements: Laboratory and Field Performance Comparisons
  Abstract: Permanent deformation (rutting) is a major distress in asphalt pavements that needs to be minimized for the safety of the driving public. Laboratory rutting performance tests, namely, loaded wheel tracking (LWT) test, flow number (Fn), and rut factor (|E*|/sinƒÔ@54C,5Hz) computed from dynamic modulus test are among common indicators that have been used to predict the rutting performance of asphalt mixtures in the field by many highway agencies. However, the correlations of these laboratory rutting performance indicators with field rutting performance have not been thoroughly evaluated. The primary objective of this study was to identify the correlations of the laboratory rutting performance indicators to the measured field rutting. Through this analysis, laboratory test criteria were evaluated to ensure acceptable rutting resistance of asphalt mixtures in the field. Results of this study showed that field rut measurements and the laboratory LWT rut depth have a considerably high correlation with a R2 value of 0.80. The current LWT rut depth criterion of 6.0 mm @20,000 passes used in Louisiana appears reasonable with a predicted field rutting of 7.5 mm at the end of the service life. On the other hand, there was poor correlations between the field rutting and the laboratory measured flow number, and rut factor (RF).
  Authors: Kim, Minkyum; Mohammad, Louay N.; Elseifi, Mostafa A.; Challa, Harshavardhan
  Authors: Kim, Minkyum; Mohammad, Louay N.; Elseifi, Mostafa A.; Challa, Harshavardhan
  Year: 2013
  Document Type: Paper
  Subject: Construction; Pavements
  Session: 657
  Paper Number: 13-3715
• Thermal Segregation: Causes and Effects on In-Place Density and Fatigue Performance of Asphalt Mixtures
  Abstract: Previous research has demonstrated that an excessive loss of mix temperature during hauling and paving operations can cause significant reductions in the mix consistency and therefore, in its ability to be compacted appropriately. This construction-related problem has been called thermal segregation. Twenty-eight asphalt paving projects were evaluated in the state of Alabama. Thermal profiles of the mat prior to its compaction were obtained by using an infrared bar attached to the paver. Based on the results, it was found that remixing operations of a materials transfer device were a key factor in the reduction of high temperature differentials.Field cores were taken from each ALDOT Division in order to evaluate the effect of thermal segregation on in-place densities. The results indicated a negative effect of thermal segregation on mat in-place densities. Additionally, samples were collected in order to compare the laboratory fatigue performance between cold and hot spots in terms of fatigue cycles, initial stiffness and fracture energy. The mix initial stiffness was determined to be the unique parameter affected by excessive air voids leading to the conclusion that cold spots can be more susceptible to fatigue cracking than hot spots.
  Authors: Fernández Cerdas, Sergio; Watson, Donald E.; Maghsoodloo, Saeed
  Authors: Fernández Cerdas, Sergio; Watson, Donald E.; Maghsoodloo, Saeed
  Year: 2013
  Document Type: Paper
  Subject: Construction; Pavements
  Session: 657
  Paper Number: 13-3948
• Creep and Repeated Creep-Recovery as Rutting Performance Tests for Airport Hot-Mix Asphalt Mix Design
  Abstract: ABSTRACTA performance test to evaluate rutting susceptibility is needed to accompany current volumetric property requirements of airport hot mix asphalt (HMA) designed using a Superpave Gyratory Compactor. The new performance test will provide a level of confidence that pavement constructed using a selected HMA mixture will function according to its design. This paper presents results from a laboratory study to identify a performance test for accepting hot asphalt mixtures for constructing airport pavements designed for high tire pressure traffic. Performance tests intended to indicate rutting susceptibility were performed on twenty-six HMA mixtures. Twenty-two of these mixtures met all aggregate and volumetric property requirements for airport pavement construction; the remaining four mixtures were designed with excessive percentage of natural sand (30%) as rut-susceptible mixtures. Results from asphalt pavement analyzer, triaxial creep, and triaxial repeated creep-recovery tests are presented. Statistical analyses performed on the results indicate the rate of increase in permanent strain and the flow time value determined from triaxial creep testing provide the strongest correlation to Asphalt Pavement Analyzer (APA) simulated traffic rutting.
  Authors: Rushing, John F.; Little, Dallas N.
  Authors: Rushing, John F.; Little, Dallas N.
  Year: 2013
  Document Type: Paper
  Subject: Construction; Pavements
  Session: 657
  Paper Number: 13-3708
  Practice-Ready: Yes
• Permanent Deformation of Flexible Pavements: Laboratory and Field Performance Comparisons
  Authors: Kim, Minkyum
  Authors: Kim, Minkyum
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Construction; Pavements
  Session: 657
  Paper Number: 13-3715
• Thermal Segregation: Causes and Effects on In-Place Density and Fatigue Performance of Asphalt Mixtures
  Authors: Fernandez Cerdas, Sergio
  Authors: Fernandez Cerdas, Sergio
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Construction; Pavements
  Session: 657
  Paper Number: 13-3948
• Creep and Repeated Creep-Recovery as Rutting Performance Tests for Airport Hot-Mix Asphalt Mix Design
  Authors: Rushing, John
  Authors: Rushing, John
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Construction; Pavements
  Session: 657
  Paper Number: 13-3708