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Abstract
Thermal cycling, also known as Freeze-Thaw (F-T) cycles is one of the most prevalent types of loads that affect asphalt pavements in cold regions. The type of failure in asphalt material due to the action of thermal loads is known as thermal cracking. Furthermore, the action of F-T cycles in asphalt has a permanent effect on the properties of the material and it may induce and accelerate other types of failure associated with traffic loads such as fatigue cracking. Asphalt mixtures in asphalt pavements are a composite material with three distinct phases: solids or aggregates, binder, and air voids; where the voids can be saturated with water. Thermal cracking of asphalt due to F-T cycles is primarily associated with the interaction between the asphalt composite material and the water present in the pores. However, the exact mechanism of failure is complex and it has not been well understood. Currently, when designing asphalt materials is not being considered the undermining effect of F-T cycles on the structural resistance of the asphalt pavement.
This thesis introduces a mathematical model derived from the Stefan problem to explain the physical phenomena of F-T cycles that occur in the asphalt composite material modeled as a porous media and provides analytical results to quantify the effect of F-T cycles in asphalt based on viscoelastic analysis, finite element analysis, and experimental results. A novel experimental method to simulate F-T cycles in asphalt mixtures is also presented, including analytical results to explain the feasibility of using the Bending Beam Rheometer (BBR) to obtain flexural stiffness and creep compliance in asphalt mixtures after F-T cycles are simulated.
Overall, this thesis presents a wide compendium of numerical and analytical results, as well as testing results and field data to explain and predict the effect of F-T cycles in the mechanical properties of asphalt mixtures at low temperatures.