Environmental factors such as temperature, air, and water can have a profound effect on the durability of asphalt concrete mixtures. In mild climates where good quality aggregates and asphalt cement are available, the major contribution to deterioration may be due to traffic loading and the resultant distress is manifested in the form of fatigue cracking, rutting, and raveling. But, when more severe climates are coupled with poor materials and traffic, premature failure may result. The objectives of this research are twofold and includes: (1) development of a test system to evaluate the most important factors influencing the water sensitivity of asphalt concrete mixtures; and (2) development of laboratory testing procedures that will predict field performance. This research also addresses the hypothesis that much of the water damage in pavements is due to water in the asphalt concrete void system. It is proposed that most of the water problems occur when voids are in the range of about 5% to 12%. Thus, the term "pessimum" voids is used to indicate that range (opposite of optimum). In order to evaluate the hypothesis and the numerous variables, the Environmental Conditioning System (ECS) was designed and fabricated. The ECS consists of three subsystems: (1) fluid conditioning, where the specimen is subjected to predetermined levels of water, air, or vapor and permeability is measured; (2) an environmental cabinet that controls the temperature and humidity and encloses the entire load frame; and (3) the loading system that determines resilient modulus (M[subscript n]) at various times during environmental cycling and also provides continuous repeated loading as needed. The ECS has been used to evaluate four core materials and also to investigate the relative importance of mixture variables thought to be significant. Many details regarding specimen preparation and testing procedures were evaluated during a "shakedown" of the ECS. As minor variables were resolved, a procedure emerged which appears to be reasonable and suitable. An experiment design for the four core mixtures was developed, and the overall experiment design included three ranges of void ( <5% low; 5-12%, pessimum; > 12% high). Six-hour cycles of wet-hot (60° C) and wet-freeze ( -18° C) are the principle conditioning variables, while monitoring MR at 25° C before and between cycling. A conventional testing procedure (AASHTO T-283) was also used on the core mixtures to provide a baseline for comparison. Results to date show that the ECS is capable of discerning the relative differences in "performance" such as MR. Three hot cycles and one freeze cycle appear to be sufficient to determine the projected relative performance when comparing different aggregates, asphalts, void levels, loading, etc. Based on these results, a water conditioning procedure has been recommended and also a procedure for water conditioning specimens prior to testing in fatigue, rutting, and thermal cracking. / Graduation date: 1992

The report presents an evaluation of a modification to an asphalt-debonding test procedure when used with a water debonding apparatus developed at the University of Arizona, the Pore-Water Pressure Debonding Device. The method being modified is that outlined by Jimenez in his report "Testing for Debonding of Asphalt from Aggregates". A regular test specimen, 4 inches in diameter by 2½ inches high, is water-saturated at 122°F and subjected to repeated pore-water pressure varying from 5 to 30 psi. The above factors are kept constant and the following ones are varied: air void content, stress frequency, stress repetition, stress duration and testing temperature. Test results of the modified testing procedure demonstrated the following trend: the higher the value of any of the aforementioned test variables, i.e., the void content, stress frequency, stress repetition, or stress duration, or any combination of these variables, the greater the loss of the mix resistance to stripping.

In this report the influence of several variables including asphalt content, mixing temperature, compaction temperature and compaction energy on void content, voids-in-the-mineral-aggregate (VMA), density and stability of asphaltic concrete mixtures was established. Straight lines were obtained on double logarithmic paper for each asphalt content when the logarithm of Marshall stability values as ordinate were plotted versus the logarithm of the corresponding number of blows of a Marshall compactor as the abscissa. The straight lines were very nearly parallel and therefore, it was possible to develop a single empirical formula expressing the relationship between stability at any compactive effort, within the range of 20 to 110 blows per face, in terms of the standard stability at 75 blows per face of specimen. Results indicate that void content, VMA, density and stability were significantly affected by compaction temperature, asphalt content, compactive effort and mixing temperature.

No description available.

No description available.

The extensively used AASHTO structural design procedures for flexible pavement indicate the required pavement design in terms of a structural number. For a particular pavement thickness design, this structural number can be computed from the sum of each pavement layer's thickness multiplied by its strength parameter, called the structural layer coefficient. The research work reported herein presents methods for determining the structural layer coefficients for asphalt emulsion-aggregate mixtures. A hot plant-mixed asphaltic concrete was evaluated for structural layer coefficient, and the radial stress vs. fatigue failure relationship was developed using circular specimens and the Jimenez deflectometer. Relationships between structural number and load repetitions to failure for different loading conditions were developed. These relationships were used to evaluate the structural numbers of other specimens when tested to failure in flexural fatigue. Three asphalt emulsion-aggregate mixtures were designed using CSS-lh asphalt emulsion. The aggregates used for the three mixtures were: (1) Type I aggregate using dense-graded, crushed, river gravel; (2) Type II aggregate using pit-run, coarse sand; and (3) Type III aggregate using a silty sand. These mixtures were evaluated for Marshall stability, Hveem stability and cohesiometer value, unconfined compressive strength, double punch tensile strength and dynamic modulus of elasticity at various ages from 3 to 28 days. Flexural fatigue life, when tested in the deflectometer, was determined for all mixtures at 7 and 28 days. Structural numbers for the specimens and structural layer coefficients for the mixtures were determined. Relationships were developed between the evaluation tests performed and the structural layer coefficients at various mixture ages by using test results from the three mixtures and a regression analysis procedure. A fourth asphalt emulsion-aggregate mixture using CSS-lh asphalt emulsion and a Type II crusher-run aggregate was designed. Evaluation tests were performed at 3 and 7 days and layer coefficients for the mixture were predicted for 7 and 28 days using the regression equations developed. Layer coefficients at 7 and 28 days were also determined by testing specimens in fatigue in the deflectometer and computing their structural numbers and layer coefficients. Layer coefficients determined in these two manners indicated favorable comparisons. The results of this research provides information about the structural layer coefficients for asphalt emulsion-aggregate mixtures. The relationships between the evaluation tests and structural layer coefficient can be used for determining layer coefficients for other asphalt emulsion-aggregate mixtures. Because the evaluation tests used were tests commonly performed in most asphalt laboratories, these determinations can be made without the necessity of additional equipment or procedures in most cases.

No description available.

No description available.

Testing of asphalt binders and asphalt-aggregate mixtures using dynamic mechanical analysis is becoming popular with improvements in high-speed computers, precision equipment, and computer software. Researchers are trying to describe the behavior of asphalt binders and asphalt-aggregate mixtures in terms of their time- and temperature-dependent linear viscoelastic behavior. The objectives of this thesis were to develop a simplified pneumatic test to perform dynamic mechanical analysis (DMA), to evaluate the performance of the pneumatic and hydraulic test systems using the computer software developed to perform DMA tests, and, to develop a simplified method to evaluate the experimental data obtained from DMA tests on aged asphalt-aggregate mixtures. A simplified pneumatic test system was developed to perform DMA. Computer software was also developed to perform DMA testing on both the simplified pneumatic and hydraulic test systems. DMA was performed on both test systems to compare their performance, and on aged asphalt-aggregate mixtures to evaluate the application of the simplified method. The results from the pneumatic and hydraulic test systems show that there is about a 20 percent difference in the complex modulus, especially at high loading frequencies. This is due to the compressibility of the air used in the pneumatic test system. The compressibility of air is greater at warmer temperatures than at cooler temperatures. Therefore, the application of the pneumatic test system to perform dynamic testing should be limited to low frequencies ( < 2 Hz), low temperatures ( < 25°C), and low load ( < 454 kg (1000 lbs.)) applications unless a modification can be made to increase the pneumatic cylinder's response time to match the hydraulic cylinder's response time. The simplified analysis method developed in this thesis divides the DMA results into four complex modulus and five phase angle parameters. These parameters describe the shapes of the master stiffness and phase angle curves and distinguished between the different asphalt-aggregate mixtures and the aging methods performed on the aged asphalt-aggregate mixtures. The phase angle parameters were reduced into two variables, peak frequency and peak angle, which vary with the aging of each asphalt-aggregate mixture. The peak frequency and peak angle decrease as the aging severity increases and the change of peak frequency and peak angle vary with the asphalt-aggregate mixture and aging treatment. Therefore, the complex modulus parameters and peak frequency and peak angle may be good indicators to describe how a master curve's shape varies with asphalt, aggregate, and aging type. / Graduation date: 1993

In 1987, Congress authorized a 5 year $150 million dollar research program called the Strategic Highway Research Program (SHRP). SHRP was divided into four major areas, including the asphalt research program. The asphalt research program was divided into six major research contracts, one such contract, SHRP-003A was called Performance Related Testing and Measuring of Asphalt Aggregate Interaction and Mixtures. Oregon State University performed the portion of this contract related to the development and validation of accelerated test procedures for aging, low temperature cracking, and moisture sensitivity of asphalt-aggreagte mixtures. This thesis contains five independent papers that discuss elements of the development, validation, and or implementation of these accelerated test procedures. In the first paper, the relationship between field performance and laboratory aging properties of asphalt-aggregate mixtures is discussed, including the relative importance of asphalt binder and aggregate type on the amount of aging experience. Based on this work recommended aging procedures are presented to simulate different environmental conditions and pavement age. The second paper makes use of the large body of resilient modulus data conducted as part of the SHRP research effort to compare data obtain in the diametral and the triaxial mode. It is not possible to give a relationship between triaxial and diametral resilient modulus, without describing specimen geometry and other test conditions. The third paper discusses the effect of aging on the thermal cracking properties of asphalt-aggregate mixtures. The temperature at which aging occurs affects the way cold temperature fracture properties change with time. Low temperatures result in quenching of the aging process, while high temperatures result in continued aging. The fourth paper discusses work conducted in association with the Oregon Department of Transportation to extend the environmental conditioning system (ECS) test procedure for moisture assessment to open graded mixtures. Comparison in the ECS of mixtures with and without anti-strip agents added indicates that they don't always decrease moisture damage potential. The final paper presents a discussion of asphalt chemistry and its relationship to asphalt-aggregate mixture performance. Using the SHRP asphalt model, aging and low temperature performance data collected at Oregon State University is explained. / Graduation date: 1995