Investigation of Bonding Condition in Concrete Overlay by Laboratory Testing, Finite Element Modeling, and Field Evaluation

Abstract

To evaluate the effect of bonded versus unbonded condition in concrete overlay structure, a field evaluation, laboratory experiment, and 3-D finite element analysis (FEA) model were carried out. First, a field evaluation of bonded and unbonded pavement test sections in Iowa was performed. Cores were extracted from existing pavements and tested for their bond strengths with shear testing equipment. The bond strength between an overlay and the existing pavement gradually increased over time, regardless of the initial bond strength. In some cases, an insufficient bond shear strength at the interface between the concrete overlay and the existing pavement seemed to have contributed to increased distress on the overlay surface. Second, a laboratory experiment was conducted to investigate an effect of bonding in pavement structure. Concrete cylinder specimens that were one-half regular concrete and one-half polymer concrete were fabricated, and their indirect tensile strength was measured at the bonding interface. The experiment results indicated that polymer concrete samples exhibited higher indirect tensile strength than regular concrete samples at the interface. Finally, a 3-D FEA model using eight-node solid elements and a spring element was developed to quantify the bonding level. This model can simulate various bond levels from fully bonded to unbonded by a change of the stiffness of the spring element. The most appropriate spring stiffness was identified for different bonding conditions of overlaid pavements. A parametric study was conducted with spring stiffness changed to develop a matrix that can be used to quantify different levels of bonding. This matrix can help pavement engineers select the most appropriate spring stiffness for a given bonding condition and overlay thickness.

Characterization of Load Transfer Behavior for Bonded Concrete Overlays on Asphalt

“…To consider bonding between the overlay and asphalt layer, translational springs were used in the x, y, and z directions to connect the pair of nodes at the bottom of the overlay and at the top of the asphalt layer. Similar types of translational springs were used in previous studies (4,7,16). The interface spring constant for the bonded case was assumed as 20,000 lbf/in.…”

“…The asphalt layer is a continuous layer beneath the overlay, and therefore, it is expected that a significant portion of the wheel load will be transferred through the asphalt layer. Other researchers believe that the thin concrete slabs transfer a significant amount of load as well (7,8). To further examine the contribution of each layer, LTE data collected for several BCOAs constructed at the Minnesota Road Research Facility (MnROAD) were evaluated.…”

Analytical modelling of ultra-thin white topping cement concrete overlay on bituminous concrete pavement using ANSYS

“…Another author has developed a 3D finite element model to quantify the bond level of the thin concrete overlay by introducing springs between the two concrete and asphalt layers with varying stiffness measured by the strains. The validation of the model was done by comparing results against the actual strain data available in the literature (Nishiyama et al , 2005). To Investigate the interface debonding, a study was made by F. Mu and J. Vandenbossche regarding the interface between the asphalt and concrete overlays and developed a superimposed cohesive zone model (Mu and Vandenbossche, 2007).…”