A number of completed or ongoing studies on warm mix asphalt (WMA) and steel slag (SS) asphalt mixtures have been conducted all over the world. This paper presents the results of a laboratory study aimed at verifying the damage behavior of WMA mixtures containing electric arc furnace (EAF) steel slag. The SS was used as the fine and coarse portions of aggregate gradation in hot mix asphalt (HMA) mixtures and as the coarse portion of aggregate gradation in a WMA mixture. The physical, chemical, and mechanical properties of aggregates and binders were evaluated to identify their effects on the moisture susceptibility, fatigue, and rutting behavior of asphalt mixtures. The moisture susceptibility of the asphalt mixtures was also evaluated using four different methods, including Marshall stability ratio, resilient modulus ratio, tensile strength ratio, and fracture energy ratio, and the fatigue and rutting behavior of the mixtures was evaluated using four point beam fatigue and dynamic creep tests, respectively. The results generally indicated that the use of coarse SS aggregate in WMA mixtures enhances the resistance of asphalt mixtures to moisture damage and permanent deformation. Also, WMA mixtures containing SS aggregates as the coarse portion of aggregates has better fatigue performance than HMA mixtures. Hence, the WMA mixture containing EAF steel slag aggregates is recommended as an eco-friendly, economical, and suitable mixture for pavement industries.

In recent years, ground vibration has become a popular research topic due to the growing construction close to vibration sources and the attentiveness of people about living conditions. Thus, vibrations caused by the passage of the train near buildings play an important role. In prediction of train-induced vibrations, many experimental and theoretical methods have been proposed. In order to study the vibration near the railway at Qaemshahr, a 2D finite element analysis employed for modeling of the train movement and its effect on the adjacent building. The validation of the numerical model was done by the high-speed train running measurements. The results show that the vibration level decreases by increasing the track centerline to building distance and decreasing train speed. The frequency of vibration up to 12 Hz was present in the incident wave field and the dominating part of the frequency content was between 2.5 and 5.5 Hz. The building foundation bending moment variations caused by train-induced vibrations was negligible. The track centerline to building edge distance of 18 m was seemed to be an acceptable value to reduce the annoyance and environmental effects caused by train-induced vibrations.

Environmental issues of reclaimed asphalt pavement (RAP) production and efforts to preserve natural mines are among the main factors for the use of RAP. Besides, the characteristics of RAP can improve some properties of asphalt mixtures. Since these materials are produced during the maintenance or rehabilitation process, they are better to be consumed in the same procedure. One of the best methods for pavement maintenance is the use of microsurfacing as a surface treatment. In this regard, the use of RAP in the microsurfacing mixture further enhances the application of this method. In the present study, first, the feasibility of using almost 100% RAP instead of virgin aggregate (VA) was studied according to the microsurfacing mix design tests. Then, 69% and 43% RAP contents were also evaluated to determine the preferable RAP content and better analyze the results. The results showed that the design of microsurfacing mixture containing RAP met the criteria of the international slurry surfacing association (ISSA) guideline. RAP-containing mixtures needed about 1% more bitumen than those containing VA to obtain sufficient cohesion within the specified time. Nevertheless, mixtures containing more RAP content would require lower amounts of additive to increase the mixing time and workability, which could reduce the cost of material preparation. The adhesion of bitumen emulsion with the aged bitumen spread over the RAP aggregate surface was less than its adhesion to the VA and was aggravated in a wet environment. RAP-containing mixtures displayed a more appropriate behaviour in association with the flushing distress. Also, RAP aggregate coating prevented the stripping of these materials in the vicinity of water. Among the RAP-containing mixtures, the one with 69% RAP outperformed the other ones.

The main types of distresses in asphalt mixtures are rutting, fatigue, and thermal cracking at various performance temperatures. One of the beneficial approaches for improving their strength related to these failures is modifying the characteristics of bitumen by additives. The use of polymers in modifying bitumen properties is very common now. Thermoplastic elastomers and reactive polymers are a family of polymers that have a tremendous effect on the properties of bitumen. In this study, synthesized polyurethane (PU) with polypropylene glycol (PPG) functionalized by polymeric diphenylmethane diisocyanate (MDI) as an additive in the bitumen modifier is studied. Penetration degree tests, softening point (R&B), rolling thin film oven, pressure aging vessel, dynamic shear rheometer, bending beam rheometer, and Fourier-transform infrared (FTIR) spectroscopy were carried out on the modified samples. The results of these tests showed that the PU reduced the penetration degree and increased the softening point of bitumen, in which modified bitumen had higher stiffness and viscosity with a lower thermal susceptibility. It also increased bitumen resistance to permanent deformation to provide higher performance levels. In the intermediate temperature, bitumen modified with PU had a better performance and more resistant to fatigue compared to the base bitumen. The results of FTIR revealed modified PU bonds in the modified bitumen, which confirmed the formation of bonds in bitumen and determinant of chemical structure. By calculating penetration index represented the bitumen thermal susceptibility, the control bitumen had the lowest penetration indicator and bitumen sample with 7% PU had the maximum penetration indicator −0.62 and 0.91, respectively, and yielded the lowest performance temperature which was equal to −15.04°C.

Asphalt mixtures performance is influenced by its components. Mastic properties and interaction between of filler and bitumen control viscoelastic properties of asphalt mixture. In this research, asphalt mixtures performance containing biomass fillers (Rice Husk Ash (RHA) and Wood Saw Ash (SA)) was evaluated. For this purpose, Marshall stability, Indirect tensile strength, Moisture sensitivity and resilient modulus tests were used. To study more about biomass particles and to have a better analysis of the results of tests, the biomass fillers were photographed by X-ray diffraction. The results of tests show that the combination of 75 per cent RHA and 25 per cent limestone (LS) caused greater Marshall Stability and lower moisture sensitivity compared to the sample containing 100% LS filler, and the combination of 25 per cent SA and 75 per cent LS shows the best tensile performance. Therefore, it is expected that replacing the biomass fillers not only protect the environment and natural resources but also can achieve mixtures with better performance.