Civil & Environmental Engineering
Permanent URI for this communityhttp://hdl.handle.net/1903/2221
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Item Large-Scale Controlled-Condition Experiment to Evaluate Light Weight Deflectometers for Modulus Determination and Compaction Quality Assurance of Unbound Pavement Materials(2015) Khosravifar, Sadaf; Schwartz, Charles W; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Compaction control using lightweight deflectometers (LWD) is currently being evaluated in several states and countries and fully implemented for pavement construction quality assurance (QA) by a few. Broader implementation has been hampered by the lack of a widely recognized standard for interpreting the load and deflection data obtained during construction QA testing. More specifically, reliable and practical procedures are required for relating these measurements to the fundamental material property—modulus—used in pavement design. This study presents a unique set of data and analyses for three different LWDs on a large-scale controlled-condition experiment. Three 4.5x4.5 m2 test pits were designed and constructed at target moisture and density conditions simulating acceptable and unacceptable construction quality. LWD testing was performed on the constructed layers along with static plate loading testing, conventional nuclear gauge moisture-density testing, and non-nuclear gravimetric and volumetric water content measurements. Additional material was collected for routine and exploratory tests in the laboratory. These included grain size distributions, soil classification, moisture-density relations, resilient modulus testing at optimum and field conditions, and an advanced experiment of LWD testing on top of the Proctor compaction mold. This unique large-scale controlled-condition experiment provides an excellent high quality resource of data that can be used by future researchers to find a rigorous, theoretically sound, and straightforward technique for standardizing LWD determination of modulus and construction QA for unbound pavement materials.Item DESIGN AND MECHANICAL PROPERTIES OF FOAMED ASPHALT STABILIZED BASE MATERIAL(2012) Khosravifar, Sadaf; Schwartz, Charles W; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Foamed asphalt stabilized base (FASB) combines reclaimed asphalt pavement (RAP) and/or recycled concrete (RC) with a foamed asphalt binder. The pavement structural properties of FASB fall somewhere between conventional graded aggregate base (GAB) and hot mix asphalt (HMA). Therefore, the required thickness of the pavement section can be reduced, resulting in cost savings in addition to recycling benefits. Mix designs were developed for eight different combinations of RAP, RC, and GAB. Details of the mix design procedure and the effects of factors representative of design and field conditions are evaluated. Triaxial test specimens from the weakest and strongest mixtures were tested for dynamic modulus and repeated load permanent deformation resistance, which can be used as inputs to the new AASHTO mechanistic-empirical design procedure. The measured stiffness values were also used to determine an appropriate structural layer coefficient value for use in the AASHTO empirical pavement design method.