مجله مهندسی زیر ساخت های حمل و نقل
سال هفتم شماره 4 (پیاپی 28، زمستان 1400)

Nowadays, regarding the scarcity and non-renewability of natural resources and environmental issues, the use of waste materials in asphalt mixtures has been very popular. Besides, zinc slag has the potential to absorb microwave radiation because of its conductive nature. The main objective of this study is to investigate the feasibility of using zinc slag as a filler in warm mix asphalt (WMA) mixtures to examine the potential of deicing and self-healing. To evaluate de-icing potential, some tests on deicing potential of asphalt mixtures using microwave heating, including Ice-melting capability test, ice falling time, self-healing during deicing, and stability of WMA samples incorporating different contents of zinc slag filler (0, 35%, 70%, and 100% of total filler weight) were carried out. The results show that if 100% zinc slag filler is used in WMA asphalt mixture, the ratio of self-healing during deicing is the best; additionally, the results indicate that the ice melting speed of the WMA mixture containing 100% BOF filler was 68% higher than that of the control mixture.

Roller-Compacted Concrete (RCC) is a kind of dry consistency concrete with zero slump, with two various main applications for dams and pavements. Owing to the benefits such as cost efficiency, low hydration heat, durability, and high speed of execution, RCC is particularly preferred in the construction of airstrips, military sites, and nuclear plants projects. The effects of cement content, the water to cement (W/C) ratio, and the sand to aggregate (S/A) ratio were investigated on Roller-Compacted Concrete Pavement (RCCP) mechanical properties in this paper. Results were obtained through experimental tests and response surface methodology (RSM) analysis. Two cement content, three W/C ratios, and three S/A ratios were implemented, and their effects on Vebe time, modulus of elasticity, and compressive, flexural, and tensile strengths were evaluated. It was found that the most efficient way to decrease the Vebe time was to increase the W/C ratio. The cement content and W/C ratio had an inverse relationship with the Vebe time, while the S/A ratio influences the Vebe time directly. The cement content had the greatest impact on compressive strength and compressive strength increased when the W/C ratio increased due to greater compact-ability. Results indicated that the modulus of elasticity was a function of coarse aggregate content. The flexural strength was governed by cement content and the first cracking strength of paste. However, in the splitting test, it was the S/A ratio had the maximum effect.

Existence of any liquid on asphalt pavement surface causes a decrease in skid resistance. By increasing water film and vehicle velocity, there is a moment in which hydroplaning phenomenon can occur and causes the vehicle linear speed to become disproportionate to wheel rotational speed. In this study, to understand the influence of pavement texture on the hydroplaning speed, a new lab-scale apparatus has been designed and manufactured. The lack of proportion between linear movement of vehicle shaft and the wheel rotation was found to be a good index to determine hydroplaning threshold and hence an important principle in the design of this machine. In order to evaluate this phenomenon, various types of asphalt mixtures with different aggregate grading have been made and the values of mean textures depth have been measured. Then, at various frequencies, using the manufactured device in dry and wet conditions, the surface of the pavement is subjected to hydroplaning test. Based on the measures, a simplified model was developed that is able to predict the hydroplaning speed depending on pavement’s texture characteristics and Coefficient of wheel brake. By comparing the results obtained from the proposed apparatus with the common experimental models for predicting hydroplaning speed, it has been determined that this apparatus can be used as a suitable device for investigating the effects of factors affecting this phenomenon. The results indicated that an increase of 2 and 3 times of 0.5 to 1 mm range, related to the mean texture depth of asphalt pavement, increases 8% and 17% at the hydroplaning threshold speed respectively.