Coefficient of thermal expansion of concrete mixes in Hawaiʻi: determination and implications for concrete pavement design

Abstract

For this study, the Coefficient of Thermal Expansion (CTE) will be explored with a focus on mix designs that use aggregates found in Hawaii. "The coefficient of thermal expansion (CTEPCC) is defined as the unit change in length per unit change in temperature and it has significant (practical) influence on the design of joints and temperature-related deformations (expansion/contraction and curling) in jointed concrete pavements (JCPs)" (Jahangirnejad et al. 2009). To date, there are no published studies on the value of the CTE of Hawaiian mixes. The CTE is an important input variable for the design of PCC pavements in the Mechanistic-Empirical Pavement Design Guide (MEPDG), which was developed to "provide the highway community with a state-of-the-practice tool for the design of new and rehabilitated pavement structures, based on mechanistic-empirical principles" (NCHRP 1-37A, 2004). In order to obtain the most accurate results for a specific location, it is important to know the value of CTE for the particular mixes used in that location. The MEPDG has three different levels of input when it comes to pavement design including the input of the CTE (Level 1, Level 2, and Level 3). Level 1 of the program allows for the all of the project inputs to be site specific. This is typically more beneficial for high profile jobs, i.e. Interstate and main freeways, due to the economical impact and extra time need for field studies to determine soil classifications, traffic volumes and characteristics, etc. Level 2 is an intermediate step that involves some of the design inputs to be site specific and some to be industry accepted values. Finally, Level 3 uses solely industry accepted values provided by the program. Level 3 is the least reliable but would be advantageous in the design of low profile jobs, e.g. an access road. Therefore, the increase in levels results in a decrease in site specific input requirements. There was a study performed by the Federal Highway Administration (FHWA) that gives typical values for a variety of geologically different types of aggregates. These values can be utilized in Level 2 and Level 3 of the MEPDG. The meaning and the significance of the three levels in MEPDG and the study completed by the FHWA will be described in greater detail in later chapters.