The existing quicksands in the desert are among the problematic soils whose stabilization has been considered by experts. Emulsion bitumen is one of the environmentally friendly stabilizers of these sands. Also, the method of reinforcement with (fibers) has many advantages due to the increase in soilstrength in the same way and the formation of thickness in the soil mass. The aim of this study was to investigate the effect of polypropylene fibers and emulsion bitumen on improving sandy soil properties and the effect of freeze-thaw cycles on the behavior of soils stabilized by these two substances; For this purpose, samples of aeolian sand soil with 0%, 0.25%, 0.5%, 0.75% and 1% waste polypropylene fibers of 0, 5, 10, 15% bitumen emulsion were made and tested for California load-bearing capacity and uniaxial compressive strength. Also, to evaluate the effect of freeze-thaw cycle, the samples were subjected to uniaxial resistance test after enduring 3 and 7 freeze-thaw cycle. The results show that the addition of fibers and bitumen to the sand first increases the specific gravity and CBR and decreases from one percent onwards by increasing the fibers of these two parameters; It has compressive strength and ultimate strain with increasing fiber percentage; In general, increasing the percentage of fibers from 0to 1% on average increases the compressive strength by 91% and the final strain by 54% and increasing the percentage of bitumen from 5 to 15% on average increases the compressive strength by 4% and the final strain by 13%. In addition, the results show that the compressive strength of the samples decreases by an average of 15% and 19% after withstanding 3 and 7 freeze-thaw cycle, respectively; However, after enduring 3 and 7 freeze-thaw cycle, the compressive strength increases with increasing the percentage of fibers to 75%.
Mathematical optimization, also called mathematical programming, is the process by which the best answer (according to a set of criteria) is selected from a set of possible answers to a particular problem. Today, optimization problems are used in all quantitative fields such as computer science, engineering, operations research, economics, and more; one of the engineering disciplines in which optimization is very important is road and transportation engineering. Road repair is one of the most important componentsof pavement management that requires regular road inspection by road specialists. One of the most important measures to prevent failure is maintenance inspection; Assessment of the condition of road surfaces to ensure their performance, while the road still provides maximum safety for existing traffic, should be done to ensure timely and effective repair and reconstruction operations. But exactly when these inspections should take place and when they are effective is an issue that is addressed in this study. The aim of this study is to optimize the frequency of maintenance inspections for a high-traffic suburban road by optimizing the frequency of inspections with a certain degree of reliability; so, the breakage function was considered as a pavement condition index (PCI). The results show that in order to pave the suburban road with high traffic in order to perform the desired pavement with 95% reliability, 218 inspections should be carried out annually (on average once every two days).
The use of raw resources is increasing due to the continuous increase of world population and rapid industrialization; while natural resources are being depleted day by day. The use of waste or manufactured materials in road construction has significant environmental and economic benefits. In this study, the use of ceramic powder as mineral filler in hot asphalt mix as an alter- native method to traditional crushed stone was investigated. The optimal amount of bitumen was determined using Marshall Mix Design method or using four different amounts of bitumen 4.5%, 5% and 5.5%. With the optimal amount of bitumen, two different types of corroded mineral fillers, ceramic and stone powder with three different filler ratios (4%, 6%, and 8%) were used to prepare asphalt mixture samples. The samples were subjected to Marshall Resistance Test, flow, determination of empty space percentage and percentage of empty space filled with bitumen and the results were compared. Also, to evaluate the type and amount of filler on the performance of bitumen, penetration degree test, softening point and ductility test of pure bitumen and bitumen containing two materials of calcareous filler and ceramic powder with different percentages were performed. The results show that the Marshall and flow strength of mixtures containing calcareous filler is about 5% higher and 12% less than the mixture containing the waste filler, respectively, and with increasing the percentage of filler in asphalt samples, the average degree of penetration and elasticity are about 30% and 4.5%, respectively decreases and softening point increases 7%; These changes are more severe in asphalt samples containing calcareous fillers. In general, it can be concluded that ceramic waste powder can be used in asphalt mixture as a mineral filler to replace crushed rock dust, because the use of this material as filler in road construction is appropriate in terms of economic and environmental factors.
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