جستجوی مقالات مرتبط با کلیدواژه « تراشه آسفالتی » در نشریات گروه « عمران »

Recycling and reusing materials have received much attention from researchers in recent decades. Today, environmental issues have become very important due to the limitation of available resources as well as the increase in the cost of new materials. Since most of the existing roads in Iran have flexible pavements, using reclaimed asphalt pavement (RAP) and using fewer new materials can be considered an environmentally friendly solution. In recycling asphalt pavements, there is a major concern related to low-temperature cracking. The purpose of this research is to investigate the low-temperature cracking properties of asphalt mixtures containing RAP along with other additives to introduce a mixture with performance characteristics equivalent to the new asphalt mixture. For this purpose, asphalt mixtures with two different contents of RAP (25% and 50%) were considered. Also, to improve their adhesion properties, the addition of a rejuvenator (10% by weight of RAP binder as the optimal percentage) and to improve the resistance of the mixture against cracking, crumb rubber (10% by weight of new binder) was considered. An indirect tensile strength test and a semi-circular bending test (SCB) were performed to investigate the properties of the mixtures. Also, the crack mouth opening displacement (CMOD) during the SCB test was measured through imaging. According to the SCB test, adding RAP to the base sample reduces the fracture energy. But adding rejuvenator and crumb rubber to the recycled samples improves the properties of the mixture against crack growth. The results showed that the asphalt mixtures containing RAP and additives, according to the tests used in this research, presented equal or even better performance than the new asphalt mixture. Also, the combined index of fracture energy - CMOD can be used as a suitable criterion to investigate the effect of RAP, rejuvenator and crumb rubber in asphalt mixture.

The non-renewability of natural materials and the prevention of environmental degradation for the production of stone materials, has increased the tendency to use waste materials in asphalt mixtures in recent decades. Several research studies were conducted to assess WMA mixtures' mechanical properties containing Reclaimed Asphalt Pavement (RAP), Electric Arc Furnace Slag (EAFS), and waste plastic (WP) separately. However, very scarce studies assessed the influence of the simultaneous presence of RAP, EAFS, and waste plastic on the mechanical properties and moisture susceptibility of WMA mixtures. This research investigates the effects of simultaneous recycling of RAP, EAFS, and waste plastic into the WMA mixtures to remove these barriers. Mechanical properties of WMA mixtures containing different percentages of RAP (0%, 35%, and 55%, fine aggregate replacement), EAFS (0%, 20%, and 40%, coarse aggregate replacement), and waste plastic (0%, and 10% bitumen weight) were evaluated using compressive strength, resilient modulus, static creep, Marshall quotient, and moisture susceptibility tests. Sasobit uses 1.5% of the total asphalt mass to prepared WMA mixtures. The results of this study were shown to improve the moisture sensitivity, rutting resistance, and resilient modulus by increasing the percentage of RAP and also reduce the resistance to moisture sensitivity and improve the compressive strength of mixtures by increasing the percentage of EAFS and decreasing the compressive strength and resilient modulus by increasing waste plastic. The simultaneous use of EAFS, RAP, and waste plastic seems to produce an environmentally-friendly mixture with minimum mechanical properties.

Recycling waste materials into the roller compacted concrete mixes improves their performance and has been attracted grate attentions recently; in this regard using RAP has been increasingly developed. Since it contains 3 to 4 percent asphalt binder which is valuable as waste material; gained grate demands in road construction as partial replacement of aggregate. The previous researches on manipulating RAP in concrete pavements revealed noticeable decrease in compressive and flexural strength of concrete. However there are not enough investigation in this part and it seems that there is an urgent need for extended research in this area. In this study the influence of utilizing RAP in concrete mixtures on toughness behavior of mixtures has been elaborated. Ignoring the type of waste materials which could be influential itself, the effect of gradation and RAP content (0, 25, 50, 100%) in RCC mix design is considered. Finally 32 different RCC mix design with different RAP and cement (250,300,350,400 kg/m3) content with 2 different gradations were developed. The effect of various parameters on mechanical properties of RCC such as flexural and compressive strength and toughness index of mixes were noticed.

This paper investigates the effect of recycling of steel slag aggregates (SSA) and reclaimed asphalt pavement (RAP) on the rutting properties of the warm mix asphalt. Nine types of asphalt mix with different combination of SSA and RAP were prepared and underwent static and dynamic creep tests as well as strength deformation test developed by Kim et al. Results showed that the inclusion of SSA into the asphalt mixes improves the rutting resistance; however, the improvements were insignificant in statistical point of view. In contrast, the effect of incorporation of RAP found to be significant by all rutting criteria. However, the mix with 40% coarse SSA and 40% fine SSA had the best rutting performance with 18.3, 36.2, 11.6, and 13.8 percent improvements in rutting criteria in static creep at 100 kPa, static creep at 150 kPa, dynamic creep and Kim tests, respectively. Statistical analysis showed that the dynamic creep and Kim tests had the best reproducibility potential as they offered lower coefficient of variation than other tests. Moreover, results signified that the static creep test at 100 kPa led to poor results in ranking the mixes and had weak correlation with other tests. On the contrary, static creep test at 150 kPa and Kim test exhibited good correlation with dynamic creep test and the ranking of the mixes in these test were consistent.

Recycling Steel slag aggregates into the asphalt mixes improves their performance; however, increasing the bitumen consumption as a result of this recycling bridle its wide spread application. To overcome this difficulty, this research investigates feasibility of concurrent recycling of reclaimed asphalt pavement (RAP) and steel slag into the warm mix asphalt. To this end, six types of asphalt mixture with two coarse steel slag aggregate percentages (0 and 40%) and three RAP contents (0, 20, and 40%) were prepared in two states of aging (short- and long term) and their resistance against rutting, cracking, and moisture-induced damages were examined and compared statistically. Results showed that incorporation of steel slag aggregates and RAP enhances the rutting and cracking performance of mixes; however, the former reduces and the latter one increases the moisture susceptibility. On the other hand, inclusion of RAP and steel slag in mixes respectively degrades and promotes the deformation of asphalt mix at the failure in indirect tension test. Overall, it is proven that simultaneous recycling of steel slag and RAP into the WMA not only is beneficial from economic and environmental perspective, but also leads to a mix which performs better or at least comparable to the conventional mixes and also the mixes that are made with one of these waste materials.

Use of Reclaimed Asphalt Pavement in HMA is beneficial by reduction of initial costs. But the higher stiffness of aged binder may lead to workability issues in the field، therefore use of large percentages of RAP impacts the HMA properties. Utilizing Sasobit is a solution to use more RAP at a relatively lower temperature in HMA mixes. This study investigates the effects of 2 percent Sasobit on the reduction of compaction temperature by measuring low shear viscosity and workability of mixtures containing RAP binder. Low and intermediate temperature properties of RAP binder using mix designs were compared to properties of artificially aged binders. Virgin binder was aged in PAV to make artificial RAP binder. Comparison between physical parameters of RAP binder and binder aged in PAV was done and it was found that about 40 hours is sufficient for simulating the aging of RAP binder and making artificially aged binder. Results of this study on artificial RAP show that utilizing Sasobit is a feasible way to make HMA which contain 25% RAP. Utilizing RAP and Sasobit together in a HMA project would lead to select softer virgin asphalt binder with a lower performance grade.