Abstract
Moisture sensitivity of asphalt mixtures may cause damage due to cohesion in asphalt binder membrane and adhesion between aggregate and asphalt binder that result in considerable damage to the pavements. Therefore, by determining the adhesion quality in a modified aggregate‐asphalt binder system, one can choose the suitable material compositions to decrease the moisture sensitivity of mixtures. In this study, the effects of modified asphalt binder with carbon nanofiber and modified aggregates with carbon nanotube on the moisture sensitivity of asphalt mixtures were simultaneously explored. For investigating the moisture sensitivity, the indirect tensile strength test and surface free energy concept were implemented. The results of the indirect tensile strength test revealed that modification of asphalt binder and aggregates with carbon nanofiber and carbon nanotube, respectively, increased the indirect tensile strength and tensile strength ratio values of mixtures. The results of surface free energy indicated that using carbon nanofiber and carbon nanotube enhanced the adhesion free energy of the aggregate‐asphalt binder system. Moreover, utilizing carbon nanofiber to modify asphalt binder enhanced the cohesion free energy values in the asphalt binder membrane. Also, carbon nanofiber and carbon nanotube brought detachment energy of the system toward zero, indicating less desire for the mixtures to be stripped. Generally, investigations performed by the two methods showed that covering aggregates by carbon nanotube as well as utilizing carbon nanofiber as an asphalt binder modifier had a positive impact on decreasing moisture sensitivity of asphalt mixtures.
Highlights
Moisture sensitivity improvement of asphalt mixtures has always been one of the most significant concerns of researchers in the field of pavement engineering science
carbon nanofiber (CNF) decreased the penetration degree and increased the softening point of the asphalt binder. 11.67% and 17.72% of the penetration reduced by the addition of 1% and 2% CNF to the base asphalt binder, respectively
The results indicated that the single utilization of additives could not conclude the significant effects, and it is better to use the additive materials in all asphalt mixture compositions such as asphalt binder and aggregates
Summary
Moisture sensitivity improvement of asphalt mixtures has always been one of the most significant concerns of researchers in the field of pavement engineering science. With the increasing advancement of science and impressive expansion of the use of nanomaterials and other additives in various fields of civil engineering [1,2,3,4], pavement engineers were present in this scientific competition and made extensive attempts to improve the performance of asphalt mixtures [5,6,7,8]. Researchers have always sought to apply any kind of additive for improving the primary engineering properties and find an optimal and economical solution [9, 10]. Moisture sensitivity can generally be classified into two categories, including adhesion and cohesion losses.
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