Concrete Mixture Properties Affecting the Aggregate Interlock Mechanism of Joints and Cracks for Rigid Pavement Systems

The load transfer efficiency (LTE) of joints and cracks is responsible in a large extent for the long-term performance of a concrete pavement system. One of the most important factors affecting the LTE of non-doweled joints and cracks is the natural but complex mechanism of aggregate interlock which is characterized by an aggregate interlock factor or joint stiffness (AGG). This mechanism has been found to be extensively controlled by the crack width and the surface texture of the cracked face. This surface texture is significantly influenced by critical concrete mixture properties such as water-to-cementitious material ratio, and the type, top size, and hardness of the coarse aggregate. Determination of the aggregate interlock factor, AGG, can be an intricate procedure. Obtaining this factor is commonly performed through iteration in a finite element model, through back-calculation using field data, through constitutive models, or through the use of empirical models that have been obtained based on laboratory test results. In a similar manner, determination of the LTE of joints and cracks exhibits some level of complexity. LTE can only be determined for in-service pavements or large-scale slabs through the use of specialized equipment such as the falling weight deflectometer (FWD). Consequently, it is imperative to develop relationships that allow an estimation of these important parameters, LTE and AGG, as a function of critical concrete properties and known pavement characteristics. The main focus of this study is to develop a relationship between key concrete mixture properties and the parameters LTE and AGG for different geometric and structural pavement conditions. In order to achieve this goal, first, different concrete mixtures were evaluated in the laboratory on their strength, fracture properties and surface texture characteristics. These results were then combined with laboratory and field data from other existent studies, and a regression analysis for the complete data set was performed. As a result, an empirical model relating the critical concrete properties and the aforementioned surface texture of the transverse joints/cracks was created. Lastly, this model was incorporated into existent equations to establish a relationship between key concrete properties and the aggregate interlock parameters LTE and AGG