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Browsing by Author "Marasteanu, Mihai O"

Now showing 1 - 9 of 9
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    Cost/Benefit Study of Spring Load Restrictions
    (2005-03-01) Levinson, David M; Marasteanu, Mihai O; Voller, Vaughan; Margineau, Ioana; Smalkowski, Brian; Hashami, Maryam; Li, Ning; Corbett, Mike; Lukanen, Erland
    Across the state of Minnesota, asphalt roads under the jurisdiction of counties, cities and townships have been controlled by restrictions that limit the total weight of each truck that uses those roads during the spring thaw period. During this time, the pavement weakens and the bearing capacity of the roadway is reduced. These policies vary from county to county and from road to road, depending on the capacity of the roads--typically, 5, 7 and 9 tons. While spring load restrictions serve to extend the useful life of the road, they also add significant burdens to truckers who are forced to re-route their vehicles and/or increase the number of trips in order to adhere to the policies. This study assesses the economic impact of lifting all vehicle restrictions during the spring thaw period. Economic benefits of lifting the bans include reduced cost to carriers; potential cost includes reduced pavement life. Their research concludes that if the policy is changed, the costs of additional damage could be recovered from those who use the roads. Recovering those costs could take the form of annual fees, appropriate fuel taxes and/or user charges paid by vehicle operators.
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    Development of Simple Asphalt Test for Determination of RAP Blending Charts
    (2004-06-01) Zofka, Adam; Marasteanu, Mihai O; Clyne, Timothy R; Li, Xinjun; Hoffmann, Olivier
    There are two main reasons why the use of RAP (reclaimed asphalt pavement) as a construction material is profitable. First, the use of RAP is economical and can reduce material and disposal problems. Second, using RAP conserves natural resources. According to Federal Highway Administration (FHWA) nearly 30 million tons of RAP are recycled into Hot Mix Asphalt (HMA) pavements every year and thus RAP is the most recycled material in the United States. The purpose of this study was to investigate the possibility of developing a simple test that could be used to obtain asphalt binder properties that are required in developing blending charts to select the appropriate percentage of RAP. Based on the laboratory testing and data analysis it was found that Bending Beam Rheometer (BBR) tests performed on thin beams of asphalt mixture can be successfully applied into derivation of the creep compliance (and stiffness) of asphalt mixtures. It was shown that recently proposed Hirsch model can be then used to back-calculate the binder stiffness. The detailed procedure that leads to constructing blending charts and obtaining the critical temperatures was proposed. It was concluded that additional research is needed to further investigate Hirsch model and refine it to obtain reasonable stiffness values and binder m-values. It is recommended to employ the proposed procedure only in low temperature grading since the addition of RAP affects mostly the low temperature PG limit.
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    Dynamic and Resilient Modulus of Mn/DOT Asphalt Mixtures
    (2003-01-01) Marasteanu, Mihai O; Clyne, Timothy R; Li, Xinjun; Skok, Eugene L
    This report presents the results of laboratory testing to determine the complex modulus and phase angle of asphalt mixtures. Laboratory tests were performed on four different asphalt mixtures from the Mn/ROAD site. Testing was performed at six temperatures and five frequencies. Data from the tests were processed through a nonlinear regression curve fit to genereate master curves of dynamic modulus and hpase angle vs. frequency. These master curves were compared to results obtained from Witczak's predictive equations. It was found, as expected, that the dynamic modulus increased with an increase in frequency and a decrease in temperature. The model used to fit dynamic modulus master curves provided a good fit for the experimental data. The modulus values calculated using the 2000 predictive equation fit the test data reasonably well for Cell 21 and 35 mixtures, but the differences for Cells 33 and 34 were more significant. Smooth master curves for phase angle could not be obtained. An exploratory study to use a vibration exciter to measure dynamic modulus proved unsuccessful. This study was done under the framework of NCHRP Projects 1-37A, 9-19, and 9-29 that recommends dynamic modulus both as a design parameter and a simple performance test. Keywords-complex dynamic modulus, asphalt mixtures, phase angle, master curve.
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    Evaluation of Asphalt Binders Used for Emulsions
    (2003-08-01) Marasteanu, Mihai O; Clyne, Timothy R; Basu, Arindam
    This project was an effort to better characterize asphalt emulsions that are typically used in cold in-place recycling (CIR) applications. A simple approach was presented that treated the cured residue as asphalt binder and applied the standard Superpave specifications to the material. A literature review examined methods that have historically been used to produce, characterize, and apply asphalt emulsions. Four emulsions were tested in this project: CRS-2P, CSS-1, EE, and HFMS-2P. The emulsions were cured two ways, the first being allowed to sit overnight in a pan at room temperature, and the second being a modified RTFOT approach. Air cured samples were also aged in the PAV. These residues were then tested with the BBR and DT at low temperatures and with the DSR at high and intermediate temperatures. AASHTO MP1 specifications were applied in order to characterize the emulsions by PG grade. Following this, AASHTO MP1a specifications were followed in order to find the critical cracking temperature of the emulsions. Master curves were constructed from the DSR tests of complex shear modulus vs. frequency. Finally, a sample mix design was presented using these emulsions and an empirical equation to predict the dynamic modulus of the mixture.
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    Inventory of Properties of Minnesota Certified Asphalt Binders
    (2004-04-04) Clyne, Timothy R; Marasteanu, Mihai O
    The objective of this study was to create an inventory of the rheological properties of certified asphalt binders used in Minnesota. A literature search was performed to identify existing databases as well as more complex test methods for asphalt binder characterization that have been proposed recently. Nine different asphalt binders were studied. The binders were aged according to standard aging procedures and subject to a number of tests. The Bending Beam Rheometer (BBR) and Direct Tension Tester (DTT) were used together to determine the critical cracking temperature of the binders at low temperatures. The Dynamic Shear Rheometer (DSR) was used to test frequency sweeps (to generate master curves and to calculate zero shear viscosity), strain sweeps (to verify linear viscoelasticity), repeated creep (to measure the permanent strain accumulated after 100 cycles), and fatigue tests (to test for fatigue cracking at intermediate temperatures). A database was created in Microsoft Access , which is easy to use and readily available to most users. Test results, along with some model parameters, were stored in tables inside the database. As more test results become available, the can easily be imported to the database.
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    Low Temperature Cracking of Asphalt Concrete Pavement
    (2004-03-01) Marasteanu, Mihai O; Li, Xue; Clyne, Timothy R; Voller, Vaughan; Timm, David H; Newcomb, Dave
    This report investigates the low temperature behavior of asphalt pavements based on experimental results obtained for three mixtures used in the construction of cells 33, 34, and 35 at Mn/ROAD facility as well as field information acquired over the years at Mn/ROAD. As a result of this research, a new test method was developed to determine the low temperature fracture properties of asphalt mixtures based on tests performed on semi-circular specimens tested in bending. This method can be used to select materials with better fracture resistance and therefore better performance in the field. Two models were developed to predict the low temperature cracking performance of asphalt pavements. The first model predicts the crack spacing in asphalt pavements exposed to low temperatures based on continuum mechanics and the frictional restraint provided by the aggregate base. The second model predicts the accumulation of damage and the propagation of the crack through the asphalt layer as temperature drops based on cohesive zone model.
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    Preliminary Laboratory Investigation of Enzyme Solutions as a Soil Stabilizer
    (2005-06-01) Marasteanu, Mihai O; Hozalski, Raymond M.; Clyne, Timothy R.; Velasquez, Raul
    This research studied the effect of two enzymes as soil stabilizers on two soil types to determine how and under what conditions they function. Researchers evaluated the chemical composition, mode of action, resilient modulus, and shear strength to determine the effects of the enzymes A and B on the soils I and II. The enzymes produced a high concentration of protein and observations suggest the enzymes behave like a surfactant, which effects its stabilization performance. The specimens were subjected to testing of varying lengths of time to determine their performance. Researchers observed an increase in the resilient modulus as the curing time increased but that an increase in application rate, as suggested by manufacturers, did not improve the performance of the enzymes. The study also suggests noticeable differences between the two enzymes and their effects on the soils in terms of resilient modulus and the stiffness of the soil.
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    Recycled Asphalt Pavement (RAP) Effects on Binder and Mixture Quality
    (2004-07-01) Li, Xinjun; Clyne, Timothy R; Marasteanu, Mihai O
    This report looks at how Recycled Asphalt Pavement (RAP) has been used in Minnesota for over 25 years. The most commonly used method is to mill material from an existing pavement and incorporate it into a new asphalt mix. Previous experience and specifications allow various RAP percentages depending on the traffic level. Past research has also shown the effects of RAP on both the high- and low-temperature properties of asphalt cement and the asphalt mixtures. Therefore, it becomes an important priority to study and determine the effects various types and percentages of RAP have on the asphalt cement and mixture quality. This will result in a rational design for asphalt mixture that contain RAP and could change Mn/DOT's asphalt specification.
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    Validation of Superpave Fine Aggregate Angularity Values
    (2004-03-01) Johnson, Eddie N; Marasteanu, Mihai O; Clyne, Timothy R; Li, Xinjun
    This report presents the results of laboratory testing to validate the use of Fine Aggregate Angularity (FAA) measurements with the Superpave method of Hot Mix Asphalt (HMA) design. A search of literature and Minnesota FAA data was conducted in preparation for FAA testing of aggregates and HMA design. Laboratory tests of aggregates included sieve analysis, specific gravity and FAA. Additional work was also performed by acquiring digital imaging data for the aggregates. Testing of asphalt mixtures included dynamic modulus tests and asphalt pavement analyzer tests. Testing was performed on four asphalt mixtures representing a range of Minnesota FAA values. Dynamic modulus testing was performed at three temperatures and five frequencies. Data from the dynamic modulus tests were processed using nonlinear regression. The resulting master curves of dynamic modulus vs. frequency were referenced to test temperature 54C. Asphalt pavement analyzer data at 54C was analyzed with respect to rutting curve. Laboratory test results for aggregates and mixtures were analyzed together using statistical methods to develop correlation coefficients and linear trends. It was found that dynamic modulus and rut resistance values are strongly related to aggregate blend FAA. Some additional parameters from digital imaging also predicted modulus and rut resistance very well and should be included in future reference.