LABORATORY STIFFNESS CHARACTERIZATION OF FOAMED COLD-MIX ASPHALT USING INDIRECT TENSILE STIFFNESS MODULUS TEST

Abstract

The use of foamed cold-mix asphalt (FCMA) can potentially saves energy and fuel consumption and reduces greenhouse gas emission. For these reasons, FCMA has been gaining popularity worldwide. These benefits can be realized because foamed bitumen enables the coating of aggregate particles at ambient temperature. It should be understood that in FCMA not all aggregate particles are coated by binder. The sprayed foamed bitumen is seen distributing on the fine particles only and hence its physical performance is unlike the conventional asphalt. In order to gain better understanding about these unique characteristics, an investigation to the fundamental properties of FCMA is warranted. This paper presents the results from a stiffness investigation of FCMA in laboratory by using ITSM (Indirect Tensile Stiffness Modulus) test. The results show that the ITSM test is suitable to evaluate the stiffness characteristics of FCMA materials. It was found that mixing quality is an important aspect in developing stiffness characteristics. Using a better mixed specimens, parameter of foaming water content (FWC) can be clearly identified affecting the ITSM values. In the tensile mode, the ITSM values decrease with the increase in the applied horizontal deformation (stress) and test temperature. One of the interesting findings from this investigation was that binder distribution played a more important role than binder stiffness in developing the ITSM values at low temperature. At the end of investigation, the water resistance of FCMA specimens with 50/70 pen bitumen was found to be acceptable only when the specimens have FWC higher than 5%.