In order to investigate the effect of nylon fibers on the performance of asphaltic mixtures, 12mm long nylon fibers in different contents of 0.1, 0.2 and 0.3% (by the weight of total mixture) were added to a typical asphaltic concrete. After determination of the optimum binder content of the mixtures, the volumetric properties of the mixtures containing different percentages of nylon fibers were analyzed. Then, the fiber reinforced mixtures were subjected to Marshall Stability, flow an indirect tensile strength tests. In addition, in order to evaluate the permanent deformation behavior of the mixtures, using UTM-10, dynamic creep tests were conducted under different stress levels of 200 and 400kPa, and at different temperatures of 40, 50 and 60°C. Dynamic creep curve, flow number and the creep strain slope (CSS) were used for analysis of the results. Then, the creep behavior of the mixtures was modeled using the three-stage model developed by Zhou et al. The resistance against moisture damage of the mixtures were also evaluated using the tensile strength ratio (TSR) and Marshall Stability ratio (MSR). The results showed that the mechanical properties of the mixture such as the Marshall stability, Marshall Quotient and the indirect tensile strength of the mixture can be improved by modifying with 0.1% of nylon fiber. Also, the moisture sensitivity of the mixtures decreases with increasing fiber content, up to the fiber content of 0.1%, after which, increases with increasing fiber content. The results of dynamic creep tests and modelling the creep curve using the three=stage model showed that the mixture containing 0.1% of nylon fiber has the highest length of primary creep region and flow number and the lowest creep stain slope, indicating that its resistance against the permanent deformation is the highest.

Asphalt pavements are damaged continuously due to premature failures and exceeded traffic loads. Among the various failures, moisture damage is the most widely spread failure in asphalt pavements. Sulfur extended polymer is a newly developed additive that is used to increase loading capacity of asphalt pavement designed. However, the role of these additives are purely investigated in term of their effect on moisture resistance of asphalt mixes. In this research by replacing 30, 40 and 50 percent of Googas (a sulfur extended additive produced in Mashhad, Iran), Marshall size specimens were prepared. Modified Lattman testing was performed on mixes and their Tensile Strength Ratio (TSR) parameter was determined on all mixes. The results showed that above additive cannot attributed on moisture resistance of asphalt mixes as its present status. In order to overcome this lack of resistance, a crumb rubber modified containing 20 percent rubber was replaced with the original 60/70 pen bitumen of the mix. repeating all ITS testing on the above mix combination with this new binder, it resulted in improvement of mixes (about 15 percent increase in TSR value). This exceeded the minimum requirement of TSR for asphalt mixes which could not be achieved neither with conventional mix, nor with those containing Googas and 60/70 pen graded bitumen.

The aggregate particles in asphalt mixtures get connected by (bitumen + mineral filler) mastic. The goal of this paper is to study the feasibility of partial and total substitution of Limestone (LS) filler by Barite powder (BP) in Stone matrix asphalt (SMA) mixtures. To evaluate barite powder performance, resilient modulus, indirect tensile strength, freeze-thaw cycles, dynamic creep at two different temperatures, and bitumen draindown tests were used. The obtained values revealed that an increase in barite powder content from 50% to 100% improved the Stone matrix asphalt mixture moisture performance by 4.5% after going through 5 freeze-thaw cycles while on the other hand, it had an 18.5% reverse effect on the permanent deformation in higher temperatures. Also, despite barite powder's positive effect on bitumen draindown compared to the control samples; it could not yet thoroughly control SMA bitumen draindown.

Moisture damage in asphalt mixtures is defined as loss in strength and durability in present of water. Lack of relationship between distress mechanism in the laboratory and field, lack of measurement of effective properties of materials and their role, lack of modification solution, and other deficiencies of these methods have motivated researchers to present more appropriate experimental methods based on the properties of materials and asphalt mixtures, which could have a determining role in the occurrence of moisture-induced distress. Thus, the present research tries to present a model for predicting moisture sensitivity of asphalt mixtures based on thermodynamic parameters and characteristics of mix design of asphalt mixtures, which could predict the performance of an asphalt mixture against moisture based on the mentioned parameters. Results of this study demonstrated that using antistripping additives can generally improve the performance of asphalt mixtures against moisture; but, type and percent of these additives must be determined considering type of aggregate, type of asphalt binder, and properties of asphalt binder-aggregate mixture. Moreover, based on the presented statistical analyses, the results represented that the parameters of cohesion free energy and adhesion free energy of aggregate-asphalt binder in dry conditions, wettability of aggregate by asphalt binder, specific surface area of aggregates, and apparent film thickness of asphalt binder on the aggregate surface as well as free energy of system during antistripping event and permeability of asphalt mixture considerably influenced the occurrence of moisture damage directly and reversely, respectively.

Stripping is one of the asphalt surface distresses that is caused by moisture or by moisture have been intensifying. Stripping cause other distresses damage such a structural cracking and fatigue. Most common methods is coring and destructive test. The ratio of indirect tensile stress saturated to dry is one of them. But these tests are destructive and it takes time and money. In addition that test is suitable for points you core in asphalt surface and we can’ t evaluate this method for widespread paving. Nowadays Ground penetration radar it helps pavement engineering to evaluate continuous and non-destructive test. In this research we have compared dried and conditioned of Bulk Specific Gravity test with TSR. we found Related between ITS and Bulk Specific Gravity with diagrams then، we compare the result of GPR surveys dielectric with destructive test. It has significantly related between The ratio of indirect tensile stress saturated to dry and bulk gravity and dielectric constant. when moisture damage occur، air void percentage goes up and dielectric constant decrease.