Stiffness Modulus Behavior in Hot Mix Asphalt

Abstract

This paper is intended to understand hot asphalt mixes behavior, from the point of view of stiffness modulus evolution in time. Stiffness Modulus is used in pavement structural design. Therefore, is important to determine whether this value varies in time. If so, a short term module should be considered for design purposes, and another for long-term design considerations. To verify this hypothesis, different hot asphalt mixes laboratory specimens were produced, and stiffness modulus was periodically measured during two years. The selected test method (EN 12697-26) is according to European Standard, because it is a simple and fast method. Besides, it is less likely test specimen to be damaged using this method than others. Selected Test Temperature is 15 °C (59 °F), to ensure an elastic behavior. From laboratory experience, it can be concluded that asphalt mix stiffness modulus varies on time, and in two years tends to a value between 8000MPa and 10000MPa for conventional mixes. For short term analysis, measuring Stiffness modulus for recently laboratory made specimens is recommended. It has been found that there is a relationship between laboratory made specimen stiffness modulus, and modulus retrieved from pavement core of the same mix, both analyzed in laboratory with the same test method. Therefore it is recommended to consider that stiffness modulus in laboratory does not necessarily correspond to stiffness modulus in the pavement. This implies that for design purposes a correction should be made.