Resilient asphalt is a specific type of asphalt concrete that is used in sports fields and recreation areas to help reduce the aching of feet and joints from walking due to the addition of vulcanized rubber fibers and rubber latex to the mixture of asphalt. It is primarily composed of vulcanized rubber fibers, natural and synthetic rubber latex, and zinc oxide added as a latex modifier. Asphalt can be added in small quantities to assist in extending the life of the latex but, cannot replace substantial amounts of latex because the vulcanized rubber particles would absorb it over time causing its binding properties to be lost. The title, resilient asphalt, originates from the resilient properties of the material under many different environmental conditions such as changes in moisture or temperature. Resilient asphalt has a significantly higher resilient modulus than typical asphalt concrete. Despite the varying weather and traffic conditions, it is still able to function at a high standard and maintain its overall structure. It has been used at the 1939 New York World's Fair and on Main Street, USA in Walt Disney World.
There are two primary types of pavement — flexible and rigid. Resilient asphalt is a type of flexible pavement. Flexible pavement typically consists of a bituminous surface course (asphalt concrete) over a base course and sub-base course. Stress induced by traffic loading is highest at the bituminous surface; therefore, this course must be able to withstand the most stress. The layers below are equally important; however, they are not expected to withstand as much stress as the bituminous surface course. One major benefit of flexible pavement is that changes in atmospheric conditions or variations in temperature do not substantially influence its load-bearing qualities.
Resilient modulus (MR) is a material assessment system used to measure and analyze the stiffness of a material under different conditions such as moisture, density, and stress level. It is primarily used to help characterize unbound pavement materials such as crushed stone, slag, concrete, or slate which are the primary materials used in the construction of pavement. Because this test has the ability to realistically replicate the dynamic traffic loading and weather conditions which pavement must withstand on a daily basis, it is regarded as a fundamental material property in pavement design.
The resilient modulus (MR) of a material is an estimate of its modulus of elasticity (E). While the modulus of elasticity is the ratio of stress to strain for a slowly applied load, resilient modulus is the ratio of applied stress to recoverable strain for rapidly applied loads similar to loads experienced by paved roads. A cyclic version of the test is used to determine the resilient modulus by applying repeated axial cyclic stress of fixed magnitude, load duration and cycle duration to a cylindrical test specimen. The pressure chamber provides the sample with both dynamic cyclic stress and static confining stress. This test is able to accurately simulate traffic through the application of a cyclic load.
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