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Asphalt-rubber mixtures have been shown to have useful properties with respect to distresses observed in asphalt concrete pavements. The most notable change in properties is a large increase in viscosity and improved low-temperature cracking resistance. Warm mix additives can lower production and compaction temperatures. Lower temperatures reduce harmful emissions and lower energy consumption, and thus provide environmental benefits and cut costs. In this study, the effects of crumb rubber modification on various asphalts such as California Valley, Boscan, Alaska North Slope, Laguna and Cold Lake were also studied. The materials used for warm mix modification were obtained from various commercial sources. The RAF binder was produced by Imperial Oil in their Nanticoke, Ontario, refinery on Lake Erie. A second commercial PG 52-34 (hereafter denoted as NER) was obtained/sampled during the construction of a northern Ontario MTO contract. Some regular tests such as Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR), Multiple Stress Creep Recovery (MSCR) and some modified new protocols such as the extended BBR test (LS-308) and the Double-Edge Notched Tension (DENT) test (LS-299) are used to study, the effect of warm mix and a host of other additives on rheological, aging and failure properties. A comparison in the properties of RAF and NER asphalts has also been made as RAF is good quality asphalt and NER is bad quality asphalt. From the studies the effect of additives on chemical and physical hardening tendencies was found to be significant. The asphalt samples tested in this study showed a range of tendencies for chemical and physical hardening. / Thesis (Master, Chemistry) -- Queen's University, 2014-01-30 11:56:43.978

As a nation that depends so heavily on its infrastructure, the United Statescontinually seeks to better maintain the investment that it has made in its roadways.Asphalt pavements make up the majority of the paved roadways in the United States andultimately contribute to the bulk of the expense of highway maintenance. The goal ofthis research was to develop a means for taking a simple measurement of pressure atvarious interfaces on and within an asphalt pavement structure in an effort to directlyassess the damaging effects of different wheel loadings. It is well known that everincreasing wheel loads and other unusual wheel loading conditions are detrimental to theeffort of maintaining the roadways. The results of the data can be compared to the classicempiricalistic and mechanistic approaches to asphalt pavement design and analysis, aswell as the more modern finite-element computer modeling programs. The Tekscanmeasurement system, which utilizes a very thin matrix based pressure sensitive sensor,has been deemed applicable for measuring pavement pressures. Various types of wheelloadings have been considered throughout this study. It was determined that the type oftire, tire inflation pressure, applied load, and the asphalt itself all have an effect on theresultant pressures on the surface of and within an asphalt pavement structure. Thisresearch may contribute to the understanding of pressure distributions at the tire/asphaltinterface depending on the type of tire, adjustments in tire inflation pressure, and varyingthe wheel load. The results may lead to a better understanding of pressure distributions atvarying depths within an asphalt pavement structure. The ability to quantify thesevariables could assist designers when analyzing and designing asphalt pavements.

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Thesis (Ph. D.)--University of Rhode Island, 2004. / Typescript. Includes bibliographical references (leaves 180-187).

Zugl.: Berlin, Techn. Univ., Diss., 2001.

Master of Science / Department of Civil Engineering / Mustaque A. Hossain / The use of economical and environmentally friendly recycled asphalt materials has become increasingly popular for asphalt pavement construction. Although reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) are typically used in hot-mix asphalt, increasing the amount of RAP and RAS materials increases the potential for premature pavement distresses, especially cracking. This research evaluated four recycled Superpave mixtures with different RAP and RAS contents from Kansas Department of Transportation projects. Two of the mixtures contained 10% RAP and 5% RAS, while the other two mixtures contained 25% RAP but no RAS. Illinois semicircular bending and Florida indirect tension tests were performed to assess mixture cracking and fracture properties. Results showed that mixtures containing 10% RAP and 5% RAS have relatively low fracture energy, creep compliance, energy ratio, and flexibility index but high resilient modulus. These results indicate that mixtures containing 10% RAP and 5% RAS are stiffer, more prone to cracking, and tend to absorb less fracture energy. Mixtures with 25% RAP and no RAS showed the opposite behavior.

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