Adrian Archilla - Academia.edu (original) (raw)

Papers by Adrian Archilla

arXiv (Cornell University), May 2, 2022

This paper presents a new procedure for evaluating the goodness of fit of Generalized Linear Mode... more This paper presents a new procedure for evaluating the goodness of fit of Generalized Linear Models (GLM) estimated with Roadway Departure (RwD) crash frequency data for the State of Hawaii on two-lane two-way (TLTW) state roads. The procedure is analyzed using ten years of RwD crash data (including all severity levels) and roadway characteristics (e.g., traffic, geometry, and inventory databases) that can be aggregated at the section level. The three estimation methods evaluated using the proposed procedure include: Negative Binomial (NB), Zero-Inflated Negative Binomial (ZINB), and Generalized Linear Mixed Model-Negative Binomial (GLMM-NB). The procedure shows that the three methodologies can provide very good fits in terms of the distributions of crashes within narrow ranges of the predicted mean frequency of crashes and in terms of observed vs. predicted average crash frequencies for those data segments. The proposed procedure complements other statistics such as Akaike Information Criterion, Bayesian Information Criterion, and Log-likelihood used for model selection. It is consistent with those statistics for models without random effects, but it diverges for GLMM-NB models. The procedure can aid model selection by providing a clear visualization of the fit of crash frequency models and allowing the computation of a pseudo R 2 similar the one used in linear regression. It is recommended to evaluate its use for evaluating the trade-off between the number of random effects in GLMM-NB models and their goodness of fit using more appropriate datasets that do not lead to convergence problems.

Airfield and Highway Pavements 2019, Jul 18, 2019

Journal of Infrastructure Systems, Jun 1, 1999

Hawaii. Dept. of Transportation, Mar 25, 2014

2014PDFTech ReportArchilla, Adrian RicardoOoi, Phillip S. K.Vasquez, Luis G DiazUniversity of Haw... more 2014PDFTech ReportArchilla, Adrian RicardoOoi, Phillip S. K.Vasquez, Luis G DiazUniversity of Hawaii at Manoa. Department of Civil and Environmental EngineeringHawaii. Dept. of Transportation. Highways DivisionUnited States. Department of Transportation. Federal Highway AdministrationHawaii. Dept. of TransportationHawaiiUnited StatesCalibrationCrackingDynamic modulus of elasticityMechanistic-empirical pavement designModulus of resiliencePavement management systemsRoughnessSoftwareFatigue (Mechanics)DeformationPavement ManagementResilient ModulusDynamic ModulusPermanent DeformationFHWA/HI-15-53463Final 8/1/2005 to 8/1/2012The Hawaii Department of Transportation (HDOT) needs to update its pavement design procedure and pavement management system (PMS). For new pavement sections, calibration of the Mechanistic-Empirical Pavement Design Guide (MEPDG) was performed with the help of tools developed for development of Historical Pavement Structural Information (HPSI); development of axle load spectra (ALS), number of axles per vehicle, and lane distribution factors; and processing of roughness. Testing of material characteristics was performed, including dynamic modulus (|E*|) of Hot Mix Asphalt (HMA), HMA permanent deformation and fatigue cracking, resilient modulus (Mr), binder testing, permeability of permeable base material, and coefficient of thermal expansion of Portland Cement Concrete (PCC). Local models of |E*| and Mr are examined and the difficulties for selecting Mr, created by non-linearities and environmental effects, are analyzed. Simple rules are presented to select Mr input values. A procedure is presented to limit the number of simulations needed for calibration of the MEPDG for cracking and roughness. In addition, a mechanism for top-down fatigue cracking is postulated. Overall, it is shown that the MEPDG can produce reasonable results for Hawaiian conditions. For implementation, after personnel training, it is recommended to use the MEPDG for a few years in tandem with the current procedure to develop calibration data and getting experience with it. Changes to the HDOT design procedure (e.g., traffic loading) are proposed. For the PMS, it is found that although pavement condition has been collected for years, there has been a lack of consistency in terms of the protocols used, the length and location of the pavement segments, and the calculation of the Pavement Condition Index (PCI). The capabilities of StreetSaver\ua9, RoadSoft\ua9, and PAVER\u2122 were analyzed in detail. It is found that any of these programs (and others) can satisfy HDOT needs if some data issues discussed are overcome. This research advanced the most with PAVER\u2122, for which a network of almost 2,000 pavement sections for Oahu was created and populated. Guidelines for the use of PAVER\u2122 that complement the Users\u2019 Manual have been created as well as a program to prepare the data for import into PAVER\u2122. Consequently, if HDOT select a low cost software for its PMS, the suggested order or preference for adoption is (1) PAVER\u2122, (2) StreetSaver\uae, and (3) RoadSoft\uae. Recommendations are provided for solving many PMS and MEPDG issues.104

Sustainable and Resilient Infrastructure, 2020

ABSTRACT One would expect the service life to be treated as an endogenous variable to be optimize... more ABSTRACT One would expect the service life to be treated as an endogenous variable to be optimized in design procedures, but this is often not the case. This article provides a solution to the net-benefit maximizing choice of the design service life as a closed form equation. Using the 1993 AASHTO Design Equation, it is shown that for real discount rates under 4%, design service lives over 72 years are net-benefit maximizing given constant traffic loads. For lower discount rates, optimal service lives are considerably longer. This finding is consistent with perpetual pavement design as well as with optimal maintenance strategies involving multiple resurfacing cycles. Discounting is shown to be a key driver of the solution. Additionally, a simple method is shown on how to calculate an economically maximum pavement thickness that is independent of physical parameters. A methodology to simplify the AASHTO equation for use in analytic modelling is shown.

Journal of Materials in Civil Engineering, 2016

A key step in mix design is the selection of an appropriate aggregate structure since this affect... more A key step in mix design is the selection of an appropriate aggregate structure since this affects mix performance and the amount of asphalt in the mix. This paper explores the effects that fines adhered to larger particles have on the batch gradation and the resulting optimum binder content and dust proportion. It shows that conventional batching procedures can produce gradations with a substantially larger percent passing the sieve No. 200 relative to the target gradation. A batching procedure that corrects for fines adhered to larger particles and trapped moisture is proposed and shown to replicate the target gradation. Asphalt content was determined using the superpave method for both a gradation batched conventionally and a gradation batched with the corrected procedure. It is shown that the asphalt content and volumetrics obtained in both cases are substantially different. To obtain more-representative batch gradations, the corrected procedure is recommended for routine batching of specimens. Further research is recommended to assess potential changes in mix design criteria and effects on performance tests.

Due to their good performance reported in the field, there has been increased popularity in polym... more Due to their good performance reported in the field, there has been increased popularity in polymer modified binder mixtures. In the new Mechanistic-Empirical Pavement Design Guide (MEPDG), however, design procedures appear to attribute only moderate performance improvements to them, particularly for permanent deformation. A relationship is utilized in the MEPDG for permanent deformation in layers of hot mix asphalt (HMA) that include mix characteristics effects only through asphalt concrete mix dynamic modulus. It is suggested, however, through evidence in the literature that dynamic modulus use alone may be insufficient for complete HMA permanent deformation behavior characterization. The authors present permanent deformation analysis of mixes prepared under different conditions with modified and virgin binders using confined axial permanent and dynamic modulus deformation tests. Test results are used for modified binder and other mix characteristic effect evaluation in regard to permanent deformation model parameters. For potential improvement evaluation in performances of modified binder mixes over those with unmodified binders, the MEPDG is then run with field condition-adjusted modified parameters. That laboratory test-based permanent deformation model parameters adjustment provides prediction of modified mix performance improvements over unmodified mixes more in line with literature-reported improvements is shown in this work. How other mix characteristic may offset or complement modified binder improvement is also explored. It is suggested by the study that for proper HMA permanent deformation behavior modeling, modeling needs to be complemented by either permanent deformation model parameters or permanent deformation tests that are a function of binder types and other mix characteristics.

One of the critical inputs for mechanistic-empirical pavement design and analysis is the Hot Mix ... more One of the critical inputs for mechanistic-empirical pavement design and analysis is the Hot Mix Asphalt (HMA) stiffness, which is needed to compute the strains used in different transfer functions to predict damage and pavement distresses. The recently developed Mechanistic-Empirical Pavement Design Guide (MEPDG) uses the dynamic modulus (|E*|) as the design stiffness parameter. In the MEPDG, three input levels are available for determining the input values for most of the material parameters. In general, the input parameters are measured directly for level 1, estimated from correlations or regression equations for level 2, or estimated based on best estimate or default values for level 3. In the case of |E*| for new HMA materials, the MEPDG makes use of either Witczak’s model (NCHRP 1-37A) or the enhanced Witczak’s model (NCHRP 1-40D) for input levels 2 and 3. These models were developed with extensive databases and provide a good fit to the data used in their development and use information about gradation, mixture volumetrics, and binder characteristics. To obtain more representative results, it is still desirable that states develop their own libraries and models representative of their respective mixes. That information can then be used to provide pseudo input level 1 |E*| data. A potential challenge to accomplish this in the short term, however, is that there may not be enough variation in the local databases to estimate many of the parameters of the models if only a few gradations and binders are studied comprehensively. This paper presents a case study with this situation. The paper first compares the predictions of the Witczak model adopted in NCHRP 1-37A with measurements of dynamic modulus for a few Hawaiian mixes. Most of the data is from 79 Superpave mix specimens with 12.5 mm Nominal Maximum Aggregate Size (NMAS) that were prepared with two different gradations and three binder types (one unmodified and two polymer modified) at different asphalt content and air voids levels. The database also contains information from five additional field specimens. It is found that although Witczak’s model provides reasonable values, it provides biased predictions for the mixes analyzed. The paper also describes the statistical estimation of model parameters of a master curve model similar to the Witczak’s models but considering the limited variation in the dataset of gradation and binder characteristics. A total of 2,447 valid observations were used to estimate the model parameters. Some of the model explanatory variables are indicator or dummy variables (i.e., equal to 0 or 1) used to account for unobserved differences in gradation and binder type. It is shown that an excellent fit can be obtained using this type of variable combined with mixture volumetric and other binder information. A detailed analysis is also made of the effects of mix volumetrics on |E*|.

Transportation Research Record, 2011

Journal of transportation engineering, Nov 1, 2007

Researchers report the number of cycles corresponding to the lower strain rate in a permanent def... more Researchers report the number of cycles corresponding to the lower strain rate in a permanent deformation test, known as flow number (FN), as a good asphalt mix stability indicator; however, its variability has limited its implementation. Current procedures for ...

Journal of Infrastructure Systems, Jun 1, 1999

Method for Estimating Transition Probability in Bridge Deterioration Models. [Journal of Infrastr... more Method for Estimating Transition Probability in Bridge Deterioration Models. [Journal of Infrastructure Systems 5, 87 (1999)]. Adrián Ricardo Archilla, Paul D. DeStefano, Dimitri Grivas.

Despite recent developments, two primary challenges associated with fatigue testing of asphalt co... more Despite recent developments, two primary challenges associated with fatigue testing of asphalt concrete cylinders remain: end failures and applicability to in-situ samples. End failures, or failure regions developing outside the strain gauge length, occur frequently and significantly reduce the value of the test. Samples cored from the field are often made up of several construction lifts ranging from 38-150 mm, rendering it incompatible with standard test cylinder dimensions. This study proposes a modified specimen geometry for use in fatigue testing of asphalt concrete mixtures which addresses these two challenges. The proposed configuration is a prismatic specimen which can be sliced horizontally from a cylinder with a diameter of 150 mm. The dimensions of the specimen are 110 mm long by 100 mm wide with variable thickness. The specimen width is tapered along the longitudinal axis to encourage middle failures. Constant crosshead fatigue tests are performed on test specimens as a proof of concept. iv

Infraestructura vial, Dec 31, 1969

Implementación de un procedimiento de bacheo en laboratorio con correción por finos y humedad

Transportation Research Board 95th Annual MeetingTransportation Research Board, 2016

Dynamic modulus (|E*|) is used to evaluate the response of asphalt concrete in mechanistic-empiri... more Dynamic modulus (|E*|) is used to evaluate the response of asphalt concrete in mechanistic-empirical pavement design. Test values measured at different temperature/frequency combinations are used to create a mastercurve, which allows interpolating |E*| for any other condition. Tests are usually performed unconfined even though confined conditions may be more representative of field conditions. This paper describes test results for 4 mixes with a dense gradation used at the Honolulu International Airport. The different mixes were obtained by using two different asphalt binders, a PG64-22 and a polymer modified PG76-22, with and without the addition of a synthetic fibers for each binder. The synthetic fibers used consist of a mix of polyolefin and aramid fibers. The objective is to study the effects on the mastercurve of these different mixtures at different confinement levels (0, 69, 138, and 207 kPa) and different air voids levels (4%, 7%, and 9%). The benefits of confinement varied with the combination of binder type and air voids. For modified mixtures, |E*| was observed to increase significantly with confinement (normally at a decreasing rate) at high temperatures and low frequencies. These benefits are observed for all air voids. For unmodified mixtures, confinement increases substantially at lower and intermediate air voids but the benefits practically disappear at higher air voids. At low temperatures/high frequencies, the confinement effects are minimal. At high temperature/low frequencies, the modified binder increases the confined |E*| significantly but the fibers tend to reduce it slightly with respect to the control mix

arXiv (Cornell University), May 2, 2022

This paper presents a new procedure for evaluating the goodness of fit of Generalized Linear Mode... more This paper presents a new procedure for evaluating the goodness of fit of Generalized Linear Models (GLM) estimated with Roadway Departure (RwD) crash frequency data for the State of Hawaii on two-lane two-way (TLTW) state roads. The procedure is analyzed using ten years of RwD crash data (including all severity levels) and roadway characteristics (e.g., traffic, geometry, and inventory databases) that can be aggregated at the section level. The three estimation methods evaluated using the proposed procedure include: Negative Binomial (NB), Zero-Inflated Negative Binomial (ZINB), and Generalized Linear Mixed Model-Negative Binomial (GLMM-NB). The procedure shows that the three methodologies can provide very good fits in terms of the distributions of crashes within narrow ranges of the predicted mean frequency of crashes and in terms of observed vs. predicted average crash frequencies for those data segments. The proposed procedure complements other statistics such as Akaike Information Criterion, Bayesian Information Criterion, and Log-likelihood used for model selection. It is consistent with those statistics for models without random effects, but it diverges for GLMM-NB models. The procedure can aid model selection by providing a clear visualization of the fit of crash frequency models and allowing the computation of a pseudo R 2 similar the one used in linear regression. It is recommended to evaluate its use for evaluating the trade-off between the number of random effects in GLMM-NB models and their goodness of fit using more appropriate datasets that do not lead to convergence problems.

Airfield and Highway Pavements 2019, Jul 18, 2019

Journal of Infrastructure Systems, Jun 1, 1999

Hawaii. Dept. of Transportation, Mar 25, 2014

2014PDFTech ReportArchilla, Adrian RicardoOoi, Phillip S. K.Vasquez, Luis G DiazUniversity of Haw... more 2014PDFTech ReportArchilla, Adrian RicardoOoi, Phillip S. K.Vasquez, Luis G DiazUniversity of Hawaii at Manoa. Department of Civil and Environmental EngineeringHawaii. Dept. of Transportation. Highways DivisionUnited States. Department of Transportation. Federal Highway AdministrationHawaii. Dept. of TransportationHawaiiUnited StatesCalibrationCrackingDynamic modulus of elasticityMechanistic-empirical pavement designModulus of resiliencePavement management systemsRoughnessSoftwareFatigue (Mechanics)DeformationPavement ManagementResilient ModulusDynamic ModulusPermanent DeformationFHWA/HI-15-53463Final 8/1/2005 to 8/1/2012The Hawaii Department of Transportation (HDOT) needs to update its pavement design procedure and pavement management system (PMS). For new pavement sections, calibration of the Mechanistic-Empirical Pavement Design Guide (MEPDG) was performed with the help of tools developed for development of Historical Pavement Structural Information (HPSI); development of axle load spectra (ALS), number of axles per vehicle, and lane distribution factors; and processing of roughness. Testing of material characteristics was performed, including dynamic modulus (|E*|) of Hot Mix Asphalt (HMA), HMA permanent deformation and fatigue cracking, resilient modulus (Mr), binder testing, permeability of permeable base material, and coefficient of thermal expansion of Portland Cement Concrete (PCC). Local models of |E*| and Mr are examined and the difficulties for selecting Mr, created by non-linearities and environmental effects, are analyzed. Simple rules are presented to select Mr input values. A procedure is presented to limit the number of simulations needed for calibration of the MEPDG for cracking and roughness. In addition, a mechanism for top-down fatigue cracking is postulated. Overall, it is shown that the MEPDG can produce reasonable results for Hawaiian conditions. For implementation, after personnel training, it is recommended to use the MEPDG for a few years in tandem with the current procedure to develop calibration data and getting experience with it. Changes to the HDOT design procedure (e.g., traffic loading) are proposed. For the PMS, it is found that although pavement condition has been collected for years, there has been a lack of consistency in terms of the protocols used, the length and location of the pavement segments, and the calculation of the Pavement Condition Index (PCI). The capabilities of StreetSaver\ua9, RoadSoft\ua9, and PAVER\u2122 were analyzed in detail. It is found that any of these programs (and others) can satisfy HDOT needs if some data issues discussed are overcome. This research advanced the most with PAVER\u2122, for which a network of almost 2,000 pavement sections for Oahu was created and populated. Guidelines for the use of PAVER\u2122 that complement the Users\u2019 Manual have been created as well as a program to prepare the data for import into PAVER\u2122. Consequently, if HDOT select a low cost software for its PMS, the suggested order or preference for adoption is (1) PAVER\u2122, (2) StreetSaver\uae, and (3) RoadSoft\uae. Recommendations are provided for solving many PMS and MEPDG issues.104

Sustainable and Resilient Infrastructure, 2020

ABSTRACT One would expect the service life to be treated as an endogenous variable to be optimize... more ABSTRACT One would expect the service life to be treated as an endogenous variable to be optimized in design procedures, but this is often not the case. This article provides a solution to the net-benefit maximizing choice of the design service life as a closed form equation. Using the 1993 AASHTO Design Equation, it is shown that for real discount rates under 4%, design service lives over 72 years are net-benefit maximizing given constant traffic loads. For lower discount rates, optimal service lives are considerably longer. This finding is consistent with perpetual pavement design as well as with optimal maintenance strategies involving multiple resurfacing cycles. Discounting is shown to be a key driver of the solution. Additionally, a simple method is shown on how to calculate an economically maximum pavement thickness that is independent of physical parameters. A methodology to simplify the AASHTO equation for use in analytic modelling is shown.

Journal of Materials in Civil Engineering, 2016

A key step in mix design is the selection of an appropriate aggregate structure since this affect... more A key step in mix design is the selection of an appropriate aggregate structure since this affects mix performance and the amount of asphalt in the mix. This paper explores the effects that fines adhered to larger particles have on the batch gradation and the resulting optimum binder content and dust proportion. It shows that conventional batching procedures can produce gradations with a substantially larger percent passing the sieve No. 200 relative to the target gradation. A batching procedure that corrects for fines adhered to larger particles and trapped moisture is proposed and shown to replicate the target gradation. Asphalt content was determined using the superpave method for both a gradation batched conventionally and a gradation batched with the corrected procedure. It is shown that the asphalt content and volumetrics obtained in both cases are substantially different. To obtain more-representative batch gradations, the corrected procedure is recommended for routine batching of specimens. Further research is recommended to assess potential changes in mix design criteria and effects on performance tests.

Due to their good performance reported in the field, there has been increased popularity in polym... more Due to their good performance reported in the field, there has been increased popularity in polymer modified binder mixtures. In the new Mechanistic-Empirical Pavement Design Guide (MEPDG), however, design procedures appear to attribute only moderate performance improvements to them, particularly for permanent deformation. A relationship is utilized in the MEPDG for permanent deformation in layers of hot mix asphalt (HMA) that include mix characteristics effects only through asphalt concrete mix dynamic modulus. It is suggested, however, through evidence in the literature that dynamic modulus use alone may be insufficient for complete HMA permanent deformation behavior characterization. The authors present permanent deformation analysis of mixes prepared under different conditions with modified and virgin binders using confined axial permanent and dynamic modulus deformation tests. Test results are used for modified binder and other mix characteristic effect evaluation in regard to permanent deformation model parameters. For potential improvement evaluation in performances of modified binder mixes over those with unmodified binders, the MEPDG is then run with field condition-adjusted modified parameters. That laboratory test-based permanent deformation model parameters adjustment provides prediction of modified mix performance improvements over unmodified mixes more in line with literature-reported improvements is shown in this work. How other mix characteristic may offset or complement modified binder improvement is also explored. It is suggested by the study that for proper HMA permanent deformation behavior modeling, modeling needs to be complemented by either permanent deformation model parameters or permanent deformation tests that are a function of binder types and other mix characteristics.

One of the critical inputs for mechanistic-empirical pavement design and analysis is the Hot Mix ... more One of the critical inputs for mechanistic-empirical pavement design and analysis is the Hot Mix Asphalt (HMA) stiffness, which is needed to compute the strains used in different transfer functions to predict damage and pavement distresses. The recently developed Mechanistic-Empirical Pavement Design Guide (MEPDG) uses the dynamic modulus (|E*|) as the design stiffness parameter. In the MEPDG, three input levels are available for determining the input values for most of the material parameters. In general, the input parameters are measured directly for level 1, estimated from correlations or regression equations for level 2, or estimated based on best estimate or default values for level 3. In the case of |E*| for new HMA materials, the MEPDG makes use of either Witczak’s model (NCHRP 1-37A) or the enhanced Witczak’s model (NCHRP 1-40D) for input levels 2 and 3. These models were developed with extensive databases and provide a good fit to the data used in their development and use information about gradation, mixture volumetrics, and binder characteristics. To obtain more representative results, it is still desirable that states develop their own libraries and models representative of their respective mixes. That information can then be used to provide pseudo input level 1 |E*| data. A potential challenge to accomplish this in the short term, however, is that there may not be enough variation in the local databases to estimate many of the parameters of the models if only a few gradations and binders are studied comprehensively. This paper presents a case study with this situation. The paper first compares the predictions of the Witczak model adopted in NCHRP 1-37A with measurements of dynamic modulus for a few Hawaiian mixes. Most of the data is from 79 Superpave mix specimens with 12.5 mm Nominal Maximum Aggregate Size (NMAS) that were prepared with two different gradations and three binder types (one unmodified and two polymer modified) at different asphalt content and air voids levels. The database also contains information from five additional field specimens. It is found that although Witczak’s model provides reasonable values, it provides biased predictions for the mixes analyzed. The paper also describes the statistical estimation of model parameters of a master curve model similar to the Witczak’s models but considering the limited variation in the dataset of gradation and binder characteristics. A total of 2,447 valid observations were used to estimate the model parameters. Some of the model explanatory variables are indicator or dummy variables (i.e., equal to 0 or 1) used to account for unobserved differences in gradation and binder type. It is shown that an excellent fit can be obtained using this type of variable combined with mixture volumetric and other binder information. A detailed analysis is also made of the effects of mix volumetrics on |E*|.

Transportation Research Record, 2011

Journal of transportation engineering, Nov 1, 2007

Researchers report the number of cycles corresponding to the lower strain rate in a permanent def... more Researchers report the number of cycles corresponding to the lower strain rate in a permanent deformation test, known as flow number (FN), as a good asphalt mix stability indicator; however, its variability has limited its implementation. Current procedures for ...

Journal of Infrastructure Systems, Jun 1, 1999

Method for Estimating Transition Probability in Bridge Deterioration Models. [Journal of Infrastr... more Method for Estimating Transition Probability in Bridge Deterioration Models. [Journal of Infrastructure Systems 5, 87 (1999)]. Adrián Ricardo Archilla, Paul D. DeStefano, Dimitri Grivas.

Despite recent developments, two primary challenges associated with fatigue testing of asphalt co... more Despite recent developments, two primary challenges associated with fatigue testing of asphalt concrete cylinders remain: end failures and applicability to in-situ samples. End failures, or failure regions developing outside the strain gauge length, occur frequently and significantly reduce the value of the test. Samples cored from the field are often made up of several construction lifts ranging from 38-150 mm, rendering it incompatible with standard test cylinder dimensions. This study proposes a modified specimen geometry for use in fatigue testing of asphalt concrete mixtures which addresses these two challenges. The proposed configuration is a prismatic specimen which can be sliced horizontally from a cylinder with a diameter of 150 mm. The dimensions of the specimen are 110 mm long by 100 mm wide with variable thickness. The specimen width is tapered along the longitudinal axis to encourage middle failures. Constant crosshead fatigue tests are performed on test specimens as a proof of concept. iv

Infraestructura vial, Dec 31, 1969

Implementación de un procedimiento de bacheo en laboratorio con correción por finos y humedad

Transportation Research Board 95th Annual MeetingTransportation Research Board, 2016

Dynamic modulus (|E*|) is used to evaluate the response of asphalt concrete in mechanistic-empiri... more Dynamic modulus (|E*|) is used to evaluate the response of asphalt concrete in mechanistic-empirical pavement design. Test values measured at different temperature/frequency combinations are used to create a mastercurve, which allows interpolating |E*| for any other condition. Tests are usually performed unconfined even though confined conditions may be more representative of field conditions. This paper describes test results for 4 mixes with a dense gradation used at the Honolulu International Airport. The different mixes were obtained by using two different asphalt binders, a PG64-22 and a polymer modified PG76-22, with and without the addition of a synthetic fibers for each binder. The synthetic fibers used consist of a mix of polyolefin and aramid fibers. The objective is to study the effects on the mastercurve of these different mixtures at different confinement levels (0, 69, 138, and 207 kPa) and different air voids levels (4%, 7%, and 9%). The benefits of confinement varied with the combination of binder type and air voids. For modified mixtures, |E*| was observed to increase significantly with confinement (normally at a decreasing rate) at high temperatures and low frequencies. These benefits are observed for all air voids. For unmodified mixtures, confinement increases substantially at lower and intermediate air voids but the benefits practically disappear at higher air voids. At low temperatures/high frequencies, the confinement effects are minimal. At high temperature/low frequencies, the modified binder increases the confined |E*| significantly but the fibers tend to reduce it slightly with respect to the control mix