Investigation of Moisture Susceptibility of Warm Mix Asphalt (WMA) Mixes Through Laboratory Mechanical Testing PDF Download
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Author: Wenyi Gong
Publisher:
ISBN:
Category :
Languages : en
Pages : 148
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Book Description
Abstract: The presence of moisture can lead to serious damage in Hot Mix Asphalt mixes and failures of HMA pavements. This is of an even greater concern for Warm Mix Asphalt (WMA) due to the use of much lower production temperatures which may not be high enough to completely dry the aggregates. In this Maine DOT study, the use of fracture energy parameters was evaluated to determine the influence of incomplete drying of mixes on their mechanical properties. Fracture energy based parameters (ER: energy ratio; RER: ratio of energy ratio) were determined from the following indirect tensile testing on mixes with fully and partially dried aggregates, some of which were subjected to moisture conditioning: Resilient modulus (Mr), creep compliance, and indirect tensile strength (ITS) strength at 5°C. The results indicate that: i. resilient modulus, creep compliance, and indirect tensile strength were all affected by the presence of moisture in mixes; ii. the trend and degree of influence by moisture for the different mechanical parameters are different; iii. The moisture conditioning process has caused larger decreases in resilient modulus and ITS values than incomplete drying of aggregates; however, the same moisture conditioning process has caused much larger decreases in modulus and ITS in asphalt mixes prepared with incompletely dried aggregates than the counterparts prepared with fully dried aggregates; and iv. fracture energy-based parameters (ER and RER) appear to be more distinctive moisture effect/damage indicators than the other parameters.
Author: Wenyi Gong
Publisher:
ISBN:
Category :
Languages : en
Pages : 148
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Book Description
Abstract: The presence of moisture can lead to serious damage in Hot Mix Asphalt mixes and failures of HMA pavements. This is of an even greater concern for Warm Mix Asphalt (WMA) due to the use of much lower production temperatures which may not be high enough to completely dry the aggregates. In this Maine DOT study, the use of fracture energy parameters was evaluated to determine the influence of incomplete drying of mixes on their mechanical properties. Fracture energy based parameters (ER: energy ratio; RER: ratio of energy ratio) were determined from the following indirect tensile testing on mixes with fully and partially dried aggregates, some of which were subjected to moisture conditioning: Resilient modulus (Mr), creep compliance, and indirect tensile strength (ITS) strength at 5°C. The results indicate that: i. resilient modulus, creep compliance, and indirect tensile strength were all affected by the presence of moisture in mixes; ii. the trend and degree of influence by moisture for the different mechanical parameters are different; iii. The moisture conditioning process has caused larger decreases in resilient modulus and ITS values than incomplete drying of aggregates; however, the same moisture conditioning process has caused much larger decreases in modulus and ITS in asphalt mixes prepared with incompletely dried aggregates than the counterparts prepared with fully dried aggregates; and iv. fracture energy-based parameters (ER and RER) appear to be more distinctive moisture effect/damage indicators than the other parameters.
Author: Emily Dawn Shrum
Publisher:
ISBN:
Category :
Languages : en
Pages : 79
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Book Description
Warm mix asphalt (WMA) has been used worldwide for many years, primarily in Europe. The National Asphalt Pavement Association first brought WMA to the United States in 2002. By using warm mix technology, the temperature of an asphalt mixture during production, transportation, and compaction decreases dramatically. Several concerns about WMA arise due to the reduced mixing temperature. One of the primary concerns in asphalt pavement is the moisture damage. The lower mixing temperature may not be high enough to vaporize all the moisture absorbed in the aggregate, and part of the moisture may be entrapped in the pavements during compaction. This thesis presents a laboratory study to evaluate the moisture susceptibility of warm mix asphalt (WMA) produced through plant foaming procedure. Two types of mixtures were evaluated. A base mixture meeting the state of Tennessee "BM-2" mix criteria was evaluated at 0, 30, 40, and 50 percent fractionated recycled asphalt pavement (RAP), and a surface mixture meeting the state of Tennessee "411-D" mix criteria was evaluated at 15, 20, 30, 40 percent fractionated RAP. WMA mixture specimens were obtained and compacted at the asphalt plant. The WMA specimens were compared to hot-mix asphalt (HMA) specimens through a set of laboratory mixture performance tests. In addition to traditional AASHTO T283 freeze and thaw (F-T) tensile strength ratio (TSR), Superpave indirect tensile test (IDT) with F-T and MIST conditioning, and Asphalt Pavement Analyzer (APA) Hamburg wheel tracking tests were utilized to evaluate asphalt mixtures. Moisture tests indicated that with the higher inclusions of RAP, specimens exhibited lower rut depths and higher tensile strength retention. Tensile strength ratio tests indicated that HMA specimens had higher tensile strength retention when freeze thaw conditioned. Dynamic modulus conditioned specimens indicated that simple performance tests can show the difference between conditioned and unconditioned specimens. HMA specimens showed lower susceptibility to moisture compared to WMA specimens for both BM-2 and 411-D mixtures. The higher percentages of RAP in WMA and HMA in both BM-2 and 411-D mixtures showed a reduction to moisture susceptibility.
Author: Amy Epps Martin
Publisher: Transportation Research Board
ISBN: 030928368X
Category : Technology & Engineering
Languages : en
Pages : 109
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Book Description
"TRB's National Cooperative Highway Research Program (NCHRP) Report 763: Evaluation of the Moisture Susceptibility of WMA Technologies presents proposed guidelines for identifying potential moisture susceptibility in warm mix asphalt (WMA). The report also suggests potential revisions to the Appendix to AASHTO R 35, "Special Mixture Design Considerations and Methods for WMA" as a means to implement the guidelines."--publisher's description
Author: Abdulaziz Alossta
Publisher:
ISBN:
Category : Asphalt concrete
Languages : en
Pages : 98
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Book Description
A recent joint study by Arizona State University and the Arizona Department of Transportation (ADOT) was conducted to evaluate certain Warm Mix Asphalt (WMA) properties in the laboratory. WMA material was taken from an actual ADOT project that involved two WMA sections. The first section used a foamed-based WMA admixture, and the second section used a chemical-based WMA admixture. The rest of the project included control hot mix asphalt (HMA) mixture. The evaluation included testing of field-core specimens and laboratory compacted specimens. The laboratory specimens were compacted at two different temperatures; 270 °F (132 °C) and 310 °F (154 °C). The experimental plan included four laboratory tests: the dynamic modulus (E*), indirect tensile strength (IDT), moisture damage evaluation using AASHTO T-283 test, and the Hamburg Wheel-track Test. The dynamic modulus E* results of the field cores at 70 °F showed similar E* values for control HMA and foaming-based WMA mixtures; the E* values of the chemical-based WMA mixture were relatively higher. IDT test results of the field cores had comparable finding as the E* results. For the laboratory compacted specimens, both E* and IDT results indicated that decreasing the compaction temperatures from 310 °F to 270 °F did not have any negative effect on the material strength for both WMA mixtures; while the control HMA strength was affected to some extent. It was noticed that E* and IDT results of the chemical-based WMA field cores were high; however, the laboratory compacted specimens results didn't show the same tendency. The moisture sensitivity findings from TSR test disagreed with those of Hamburg test; while TSR results indicated relatively low values of about 60% for all three mixtures, Hamburg test results were quite excellent. In general, the results of this study indicated that both WMA mixes can be best evaluated through field compacted mixes/cores; the results of the laboratory compacted specimens were helpful to a certain extent. The dynamic moduli for the field-core specimens were higher than for those compacted in the laboratory. The moisture damage findings indicated that more investigations are needed to evaluate moisture damage susceptibility in field.
Author: Rouzbeh Ghabchi
Publisher:
ISBN:
Category : Mix design
Languages : en
Pages : 10
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Book Description
This study used a mechanistic framework (i.e., surface free energy) to evaluate the moisture susceptibility of warm mix asphalt (WMA) with three different WMA additives, namely, Sasobit, Advera, and Evotherm. The surface free energy (SFE) components of modified PG64-22 asphalt binder with different percentages of WMA additives and selected aggregates were measured in the laboratory. The wettability, the work of adhesion, the work of debonding, and energy ratios were estimated in order to assess the moisture-induced damage potential of combinations of modified asphalt binders and different aggregates. The results indicate that Sasobit and Advera are able to reduce the moisture susceptibility potential of the mixes, but their use is not recommended with highly acidic aggregates such as granite. Evotherm resulted in the highest increases in wettability, total surface free energy, and increased work of adhesion and a reduction in the work of debonding, resulting in a better possible aggregate coating with asphalt binder and lower moisture susceptibility with all types of tested aggregates relative to those of other WMA additives. Furthermore, tensile strength ratio (TSR) tests were conducted on Advera and Evotherm-modified and neat (unmodified) asphalt mixes, and the results were compared with those from the SFE test. It was found that the SFE approach is a better indicator of moisture susceptibility than the traditional TSR test. The findings of the present study would help the highway engineers and agencies to better understand the moisture damage potential of flexible pavements constructed with WMA technologies.
Author: Maria Lorena Garcia Cucalon
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Economic, environmental and engineering benefits promote the rapid implementation of WMA technologies. However, concerns remain based on changes in the production process that may lead to moisture susceptibility in the early life as compared to HMA. To evaluate WMA moisture susceptibility during this critical period, standard laboratory tests were used for three field projects each with an HMA control mixtures and multiple WMA mixtures. Different specimen types were also evaluated to capture differences in mix design, quality control/quality assurance, and field performance. Specimens were evaluated for moisture susceptibility by Indirect Tensile (IDT) Strength, Resilient Modulus (MR) and Hamburg Wheel-Track Testing (HWTT). Specimens for IDT and MR were tested dry and then tested wet after conditioning as described in AASHTO T283 with one freeze-thaw cycle. HWTT was used to assess both moisture susceptibility and rutting potential under repeated loads in the presence of water at elevated temperatures (i.e., 122°F [50°C]), and the output parameters used for evaluation were the calculated Stripping Inflection Point (SIP) and the rut depth at 5000 load cycles. Based on the results of the laboratory tests performed on PMFC cores acquired at construction and with time, WMA during its early life exhibited inferior moisture resistance when compared to HMA. However, with time, specifically after one summer, the dry and wet properties of WMA became equivalent to those of HMA. For WMA constructed in the fall, the results from this study suggest that the inclusion of recycled asphalt pavement (RAP) or an anti-stripping agent may alleviate possible moisture susceptibility issues in the early life during wet, winter weather conditions. While some laboratory test results demonstrated that WMA is more moisture susceptible than HMA, field performance reported to date from the three projects used in this study shows no evidence of moisture damage. Therefore the search for a laboratory test to screen mixtures for moisture susceptibility continues. An alternative approach, applying Griffith crack growth theory and utilizing IDT, MR and air voids% the adhesive bond energy of asphalt mixtures was calculated for Texas field project. This value holds promise for characterizing performance of asphalt mixtures by considering basic properties and grouping into one representative value. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/149392
Author: Amy Epps Martin
Publisher:
ISBN: 9780309375061
Category : Pavements, Asphalt
Languages : en
Pages : 48
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Book Description
TRB's National Cooperative Highway Research Program (NCHRP) Report 817: Validation of Guidelines for Evaluating the Moisture Susceptibility of WMA Technologies presents validated guidelines proposed for identifying potential moisture susceptibility in warm mix asphalt (WMA) during mix design. The report further corroborates the moisture susceptibility thresholds described in NCHRP Report 763: Evaluation of the Moisture Susceptibility of WMA Technologies.
Author: Thomas Glueckert
Publisher:
ISBN:
Category : Pavements, Asphalt
Languages : en
Pages : 143
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Book Description
The implementation of warm-mix asphalt (WMA) is becoming more widespread in the United States of America with a growing number of contractors choosing to utilize various WMA technologies. WMA technologies were developed in order to reduce mixing and compaction temperatures of hot mix asphalt (HMA) without affecting the quality of the pavement. Research into the effects of WMA additives suggests that it may be more susceptible to rutting and moisture damage than traditional HMA pavements. The objective of this research is to evaluate the effects of a single WMA additive on resistance to rutting and moisture damage on lab mixed and field mixed pavements. This objective was completed by conducting extensive laboratory experiments to determine and assess the performance of both WMA and HMA mixtures produced using Iowa aggregates. The conclusions of this study are as follow: * Reduced mixing and compaction temperatures were achieved using the selected additive. * The selected WMA additive was successfully used and samples were taken during a local resurfacing project. * Moisture sensitivity of both field mixed WMA and field mixed HMA were comparable although both failed to meet Iowa DOT standards. * Dry Indirect Tensile Strength values of lab mixed WMA and HMA samples were nearly the same. * TSR values of lab mixed HMA surpassed those of lab mixed WMA although both failed to meet Iowa DOT standards. * The aged field mixed HMA successfully passed the Hamburg Wheel Tracker Test and provided the best creep and stripping values compared to all other field mixed specimens. * Lab mixed HMA using a PG 64-22 binder performed the best compared to all other lab mixed specimens although none of the lab mixed specimens successfully passed the Hamburg Wheel Tracker Test.
Author: Yichao Xu
Publisher:
ISBN:
Category :
Languages : en
Pages : 158
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Book Description
Abstract: Residual moisture from incompletely dried aggregates would most likely remain in the Warm Mix Asphalt (WMA) due to its lower production and compaction temperature, resulting in harmful effects on field performance. Dynamic modulus has been recognized as a parameter that reflects the overall behavior of asphalt mixtures and possesses promising correlations with field performance. This study aims to investigate the effects of moisture susceptibility of WMA on dynamic modulus and simulate the field performance with the aid of Mechanistic-Empirical Pavement Design Guide (MEPDG) software. Four distinct sets of WMA specimens were prepared as follows: 1. fully dried aggregates without moisture conditioning; 2. fully dried aggregates with moisture conditioning; 3. incompletely dried aggregates without moisture conditioning; and 4. incompletely dried aggregates with moisture conditioning. Simple Performance Test (SPT) was employed to collect the raw data of dynamic modulus tests and master curves were constructed from the reduced data using Hirsch model. The results show that moisture can negatively influence the dynamic modulus values and moisture conditioning had more effect than residual moisture from incompletely dried aggregates. Two types of distress, fatigue cracking and rutting, were analyzed in the simulation. Moisture can significantly decrease the resistance against rutting and to a lesser extent, the resistance against fatigue cracking.
Author: Mansour Solaimanian
Publisher: Transportation Research Board
ISBN: 0309099064
Category : Bituminous materials
Languages : en
Pages : 79
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Book Description
Explores whether combining the environmental conditioning system with the simple performance test would provide a superior procedure for determining the moisture susceptibility of hot-mix asphalt (HMA).
