Investigation of influential factors on the tensile strength of cold recycled mixture with bitumen emulsion due to moisture conditioning

The present study attempts to investigate the effect of moisture conditioning on the indirect tensile strength (ITS) of cold recycled mixture with bitumen emulsion. Firstly, samples were prepared using a Superpave gyratory compactor. They were hence conditioned using moisture induced sensitivity tester (MIST) device. Factorial design was carried out considering four factors each at two different levels. These factors were specimen thickness, air voids content, pressure and number of cycles. In the MIST device, samples are cyclically subjected to water pressure through the sample pores. The MIST conditioned samples were tested for indirect tensile strength. The analysis of two-level full-factorial designed experiments revealed that all four factors have a negative effect on tensile strength of cold recycled mixture with bitumen emulsion. Specimen thickness was the most significant factor affecting the tensile strength followed by air voids content. In two-factor interaction, specimen thickness-number of cycles, air voids content-pressure, and pressure-number of cycles were significant. The most significant three-factor interaction was specimen thickness-pressure-number of cycles. The results from the study suggest that in measuring tensile strength, the appropriate specimen thickness and air voids content should be selected to quantify the representative tensile strength for in-situ conditions.