دکتر احمد منصوریان

One of the inherent characteristics of asphalt mixtures, related to the viscoelastic properties of bitumen, is called self-healing. Due to the self-healing property, minor damages caused in the asphalt mixture during a loading process can be repaired to some extent during the rest period, and some of the original properties of the mixture can be restored. This study aimed to evaluate the factors affecting the failure characteristics and the self-healing phenomenon in modified asphalt mixtures by conducting tests on semicircular samples (SCB). The results obtained in this research showed that the fracture resistance and fracture energy in modified polymer asphalt mixtures are significantly higher than in the control sample (without modifier). Among the investigated additives, APAO polymer was more effective in increasing strength and failure energy, while SBS polymer showed the least increase in these properties. However, the flexibility index in the sample modified with APAO was lower than in the other investigated mixtures. Investigation of the fatigue behavior and self-healing phenomenon in asphalt mixtures showed that increasing the rest time from 0.8 seconds to 2.5 seconds increased the number of loading cycles until sample failure, indicating the self-healing characteristic of asphalt mixtures. Moreover, among the tested mixtures, the mixture modified with APAO polymer showed the best fatigue performance and self-healing behavior, followed by the mixtures containing SBR and SBS polymers, which performed better than the control mixture.

Appropriate skid resistance is one of the important requirements in road paving; because this factor plays a decisive role in the safety of vehicle traffic, especially in rainy conditions. The fine texture of the asphalt surface, which primarily depends on the characteristics of the aggregates used in the asphalt mixture, plays a fundamental role in creating friction and skid resistance between the pavement and the vehicle tire; Therefore, it is necessary to ensure the proper quality of the aggregates before preparing the asphalt mixture. Because institutions and researchers have proposed various tests for this purpose, in the present study, while introducing each of these tests, the specifications limits for the parameters obtained from each of the tests have also been presented. The investigations show that no single test can indicate the optimal performance of the aggregate in the required skid resistance in the asphalt pavement; Meanwhile, a specific limit cannot be introduced for the output of these experiments. The suggested limits or values obtained from research and experiences can be considered as a primary guide in determining the test criteria related to the performance of aggregates in creating an appropriate skid resistance in asphalt pavement.

Aggregates form the structural skeleton of the asphalt mixture. Thus, the physical, mechanical, and chemical characteristics of the stone play significant role on the performance of the asphalt. By identifying the geological characteristics of the aggregates, vital information could be obtained about the behavior of asphalt during utilization. In this research, 13 carbonate mountain mines with diverse geological formations located in Ardabil, Isfahan, Tehran, Zanjan, Semnan, Qom and Hamadan provinces were sampled. The geological characteristics of the rocks in each mine, including the type of texture, the minerals and its constituent elements, were identified and the influence of the determined geological characteristics on the experiments results of Asphalt samples were investigated and evaluated. These experiments include boiling water, indirect tension, marshall strength ratio of asphalt, as well as bitumen absorption of the aggregates. The results of the investigations show that the type of microscopic texture of carbonate rocks is influential in reducing or increasing bitumen absorption. In addition, the presence of evaporative minerals, even in small amounts, increases the moisture sensitivity of asphalt.

Research on the possibility of using Reclaimed Asphalt Pavement (RAP) as a part of pavement materials is increasingly carried out. Economic and environmental considerations are the most reasons in this regard.  In this process, the reclaimed asphalt pavement replaces some of the aggregates in the concrete or asphalt mixtures. Since the previous studies mainly showed the negative effect of reclaimed asphalt pavement on fracture and compressive strength of concrete and on the other hand some studies indicated the positive effect of fibers on the strength of cement concrete, in the present research study the effect of Polypropylene, Polyolefin and steel fibers on mechanical properties (compressive strength, tensile strength and fracture resistance) of concrete containing reclaimed asphalt pavement was evaluated. For this, three different percentages (2, 5 and 8% by weight of cement) of each type of fiber were added to the concrete containing 15, 30 and 45% reclaimed asphalt pavement, and compressive strength, tensile strength and fracture resistance tests were carried out. The specimens used in the fracture resistance test were semi-circular and had three notch depths of 25, 32 and 38 mm. investigation of the tests results indicated that the addition of the fibers to concrete containing RAP may lead to slight increase in compressive strength (up to 7%), small increase in tensile strength (up to 19%) and considerable effect on fracture resistance (up to 30%).

The use of industrial waste, such as steel slag, in the road construction industry, to reduce the use of stone materials and also the environmental benefits of reusing these materials is very important. Research on the use of steel slag as an alternative to stone materials in asphalt pavements has been carried out for many years due to the improvement of some of the main properties of these mixtures. In these researches, slag in general (including fine-grained and coarse-grained with the same percentage) or coarse-grained has replaced the stone materials. However, since some properties of asphalt mixtures show different effects by changing the fine-grained materials or a different combination of fine-grained and coarse-grained to the simultaneous and equal replacement of fine-grained and coarse-grained, in this research, optimum percentage of using slag materials in fine-grained and coarse-grained size has been investigated using the response surface method. In this regard, different mixing schemes of this substitution have been investigated using modulus of resistance, Marshall resistance, indirect tension and moisture sensitivity tests. Results of the performed experiments and their analysis has determined the type of fine-grained and coarse-grained behavior in asphalt mixtures, and finally, for each experiment, the proposed model has been determined based on the research conditions.

Studies show that of all petroleum products, a significant share (about 30%) is allocated to gasoline consumption; therefore, proper management of vehicle fuel consumption can have positive effects on economic and environmental aspects. In the present study, in order to investigate the effect of the pavement roughness and the longitudinal slope on fuel consumption, the pavement roughness and the longitudinal slope of three freeways including Tehran-Saveh, Tehran-Karaj and Tehran-Qom freeways, were measured in one hundred sections using a road surface profiler. Furthermore, by installing a Bluetooth diagram on the test vehicle, the amount of the fuel consumption was recorded for each section. Statistical analysis of the data showed that the pavement roughness and the longitudinal slope increase the vehicle fuel consumption significantly. In this study, an equation was proposed to predict the fuel consumption of the vehicles on freeways. According to the proposed equation, Fuel consumption increases 2 percent when International roughness index increases 1m/km.

Compared to typical hot-mix asphalt (HMA), Warm-mix asphalt (WMA) is produced at a lower temperature; therefore, it can be a good alternative for pavement located in cold climates. On the other hand, the low-temperature cracking is one of the main concerns of highways agencies in cold climates. Many different additives including fibers have been used for improving hot-mix asphalt performance; however, a few types of research have been conducted to investigate the effects of fibers on warm-mix asphalt performance. In this paper, warm-mix asphalt containing Sasobit and different percentages of natural and synthesis fibers (0.7%, 0.5% and 0.3% by weight of the total warm mix asphalt) were prepared by gyratory compactor. The cylinder specimens were cut to prepare semi-circular bending (SCB) specimens to determine the critical intensity factor (fracture toughness) of the warm-mix asphalt specimens. Using ABAQUS software the finite element analysis was conducted to determine the geometry factors and crack positions for pure tension (mode I), pure shear (mode II) and mixed modes (I/II). The cracked specimens were loaded at a constant rate (3 mm/min) at 0 oC, -10 oC and -20 oC until they were fractured; then the fracture toughness of each specimen was calculated. Analysis of testr esults indicated that the fracture toughness of warm-mix asphalt specimens containing natural or synthesis fibers increased when the temperature test decreased. In addition, the tests results showed that fracture toughness of warm mix specimens containing natural or synthesis fibers in mixed mode (with the same portion of tension and shear) and pure tension mode are higher than that of the control asphalt mixtures. However, this trend was not observed for loading modes with the higher portion of shear, especially for specimens containing natural fibers. Furthermore, in the same percentages of fibers, the effect of synthesis fibers to improve the fracture toughness of the mixtures was higher than that of the natural fibers.

Selection of appropriate pavements deicing materials is one of the main concerns of roads maintenance officials. Investigations show that many researches have been carried out on effects of deicing/anti-icing materials on concrete, however a few researches have evaluated the effects of these materials on asphalt mixtures and these few researches have generally concentrated on moisture susceptibility of asphalt mixtures. In the current study, asphalt mixtures specimens were compacted by gyratory compactor and then were cut into semi-circular specimens. Each of specimens was subjected to water and sodium chloride (NaCl), calcium chloride (CaCl2), calcium magnesium chloride (CMA) and potassium acetate (KA) solutions. Fracture toughness of specimens was measured at three temperatures of 0, -10 and -20 °C using semi-circular bending (SCB) specimen test. Tests results showed that the effects of deicing materials on fracture toughness of asphalt mixture specimens were different at three temperatures. At the temperature of 0 °C, the destructive effect of deicing materials on the fracture toughness of the asphalt mixtures was not observed, while at the temperatures of -10 °C or -20 °C, some of deicing materials could decrease the fracture toughness of the asphalt mixtures. Meanwhile the moisture susceptibility tests results indicated that the deicing materials had no destructive effect on the moisture susceptibility of the asphalt mixtures.        

Porous asphalt is a kind of open-graded asphalt mixture that characterized by containing a large proportion of interconnected air voids. Many countries have used porous asphalt since many years ago¡ but due to unfamiliarity and some ambiguities of contractors and consultants with this kind of asphalt¡ it has not been used appropriately in Iran. In this paper the performance of porous asphalt constructed in a section of Ghaemshahr-Sari road¡ is explained and evaluated. Laboratory and field studies show that porous asphalt containing polymer modified bitumen and cellulose fibers has adequate strength and durability; also it decreases the noise and increases the permeability and skid resistance.