Bituminous Pavement Mechanics: LVE, LAOS, and Failure

Linear Visco-Elasticity in Bituminous Pavement

The Linear Visco-Elastic (LVE) limits of a range of conventional and modified bituminous binders were investigated using stress/strain sweeps via a Dynamic Shear Rheometer (DSR).

Key Findings on LVE Limits

• Plots of LVE stress and strain limits versus complex modulus and phase angle were produced.
• LVE is primarily used for predicting the response of elastomer-like materials.
• It is also used, to a lesser degree, for the very small strain response of thermoplastic materials.

Characterization of Bituminous Pavement Materials

Understanding Bitumen Composition

Bitumen is a complex mixture of high-boiling or non-boiling components. These components remain unaltered during the crude oil distillation process, meaning they are present in bitumen in their original form, making bitumen a natural product, similar to crude oil.

Essential Pavement Surface Characteristics

Key characteristics used to define pavement surface quality include:

• Skid and Slip Resistance
• Friction
• Unevenness Index
• Light Reflecting Characteristics

Bituminous materials exhibit a complex mechanical response. Understanding this response is paramount in pavement engineering. This framework often includes introductory elementary linear viscoelasticity, which is then used to introduce different grading systems for bitumen.

Large Amplitude Oscillatory Shear (LAOS)

Large Amplitude Oscillatory Shear (LAOS) refers to a viscoelastic region where the response to an applied sinusoidal input is nonlinear—meaning the output is no longer a perfect sinusoid.

LAOS and Dynamic Properties

In this nonlinear regime, viscoelastic dynamic properties are dependent on both deformation and deformation rate.

Dynamic Oscillatory Shear Testing

Dynamic oscillatory shear tests are performed by subjecting a material to a sinusoidal deformation and measuring the resulting mechanical response as a function of time.

Causes of Bituminous Pavement Failure

Primary Variables Leading to Pavement Failure

Pavement failure is caused by several variables, including:

• Water intrusion
• Stress from heavy vehicles
• Expansion and contraction due to seasonal temperature changes
• Sun exposure

It is crucial to maintain proper maintenance, such as crack and asphalt sealing, to prevent cracks from spreading or forming.

Functional Failure Mechanisms

The main reasons behind the functional failure of bituminous pavement structures are:

1. Raveling: Involves stone loss.
2. Fretting: Reduction of surface texture due to high abrasion or polishing effect.

Both raveling and fretting ultimately decrease the skid resistance of the road surface.