The semi-circular bend (SCB) test configuration has been favored by many researchers due to the ease of sample preparation, including cores removed from the field and the quick and simple testing procedure. It offers the potential of assessing the cracking resistance of asphalt mixes in the laboratory in the design phase as well as in QA (quality assurance) testing activities. The objective of this study was to conduct a comprehensive evaluation of the SCB test and to utilize this test to evaluate a number of asphalt mixtures against cracking failure. Results of the experimental program were used to validate a three-dimensional (3D) finite element (FE) model, which was used to interpret and to analyze the failure mechanisms in the SCB test. Results of the experimental program showed that the SCB test results successfully predicted the fracture performance of the evaluated mixes and was able to differentiate between them in terms of cracking resistance. Mixtures prepared with polymer-modified binders were the best performers in this test against fracture. Results of the SCB test were in agreement with the DCSE (Dissipated Creep Strain Energy) test and identified the mixtures with high RAP content and the one prepared with unmodified binder as possible poor cracking performers in the field. The SCB test process as well as the propagation of damage were successfully simulated using 3D FE and cohesive elements. The presented modeling approach was in good agreement with measured test results for all mixtures. Based on the results of the FE model, damage that propagates in the vicinity of the notch is mainly caused by a combination of vertical and horizontal stresses in the specimen. The effect of shear was negligible in progressing damage in the specimen.

Non-structural parameters such as surface distresses and ride quality have commonly been used as functional indicators in the treatment selection process. However, transportation agencies have considered in recent years implementing structural capacity indicators into their pavement management system (PMS) and decision-making processes. The objective of this study was to develop a structural condition index for Louisiana, known as the Structural Health Index (SHI), on a scale from 0 to 100 that describes the structural integrity of the pavement structure based on the backcalculated layer moduli of in-service pavements as predicted from FWD testing. Based on the developed methodology, the SHI is estimated by first backcalculating the layer moduli using a backcalculation software. Then, a sigmodal function is used to calculate the SHI. Evaluation and validation of the SHI was successful and demonstrated that the new index responded realistically to sections in poor and in good structural conditions. Furthermore, it was shown that the new index provided additional information that complements existing functional indices in PMS by successfully identifying structurally deficient sections. The implementation of the SHI into the LADOTD decision matrix is demonstrated.

The Rolling Wheel Deflectometer (RWD) offers the benefit to measure pavement deflection without causing any traffic interruption or compromising safety along the tested road segments. This paper presents a detailed field evaluation of the RWD system in Louisiana, in which 16 sites representing a wide array of pavement conditions were tested. Measurements were used to assess the repeatability of RWD measurements, the effect of truck speeds, and the relationship between RWD and (FWD) deflection measurements and pavement conditions. On the basis of the results of the experimental program, it was determined that the repeatability of RWD measurements was acceptable, with an average coefficient of variation at all test speeds of 15%. In addition, the influence of the testing speed on the measured deflections was minimal. The scattering and uniformity of the FWD and RWD data appear to follow closely the conditions of the roadway. Both test methods appear to properly reflect pavement conditions and struct...

Cracking is a major failure mechanism that directly affects the functionality and performance of flexible pavements. The objective of this study is to present the state of knowledge on the use of finite element method (FEM) including cohesive zone model (CZM) to simulate cracking failure mechanisms in flexible pavements under field conditions. Based on this review, a knowledge base is established on how FEM can be effectively applied to predict pavement performance against cracking failure mechanisms. Two main approaches are presented in this study. In the first approach, focused finite element (FE) meshes are used to simulate the crack initiation and propagation phases. Focused meshes allow for estimating the J-integral and the stress intensity factor (SIF) through different contour lines. Since the SIF is a measure of the stress and strain environment around the crack tip (a greater SIF indicates a faster rate of propagation), the rate of crack propagation per cycle can be estimated based on empirical equations such as Paris’ Law. In the second approach, the propagation of damage is simulated using FE and CZM. This approach allows one to study the loading mechanisms responsible for progressing cracking damage in the pavement structure. In summary, both approaches have merits in modelling cracking in flexible pavements. While focused meshes may be used to predict the number of cycles for crack propagation, CZM may be used to study the controlling stresses and mechanisms responsible for crack propagation.

Nonstructural factors, such as surface distresses and ride quality, have been commonly used as the main indicators of in-service pavement conditions. In the last decade, the concept of implementing a structural condition index in pavement management system (PMS) to complement functional condition indices has become an important goal for many highway agencies. The rolling wheel deflectometer (RWD) provides the ability to measure pavement deflection while operating at the posted speed limits causing no user delays. The objective of this study was to develop a model to predict pavement structural capacity at a length interval of 0.16 km (0.1 mi) based on RWD measurements and to assess its effectiveness in identifying structurally deficient pavement sections. Rolling wheel deflectometer data collected from 153 road sections (more than 1,600 km) in District 05 of Louisiana were used in this study. The predicted structural number (SNRWD0.16) showed an acceptable accuracy with a root-mean square error (R...