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Go to Editorial ManagerReclaimed (recycled) asphalt pavement (RAP), the most recycled material worldwide, is the mostly reclaimed material utilized in hot mix asphalt. Polymer (Crumb rubber) incorporation frequently leads to enhanced durability and resistance to heat cracking and rutting, two forms of permanent deformation. It also relieves stiffness and minimizes fatigue damage. This study aims to gather all previous RAP-related research and crumb rubber CR, so that the impact of using these materials on mechanical, physical properties of asphalt pavement, environmental effect and cost effective are clarify and explained. The finding of this research proved that the use of RAP and CR provide considerable structural and financial enhancements to the construction.
Rutting is the most common distress that most Iraqi asphalt pavements suffer from it. Asphalt binders are modified by using additives and polymers to enhance their physical qualities and fulfill the performance demands. Polyphosphoric acid (PPA) has been used in many countries to enhance the physical and mechanical characteristics of asphalt binders and mixtures that can improve the performance of asphalt pavements. In this paper, evaluation of the Iraqi asphalt binder and mixtures performance by using three percentages of Polyphosphoric acid (PPA) (0.4, 0.8, and 1.2) percent by asphalt binder weight and added to (60-70) penetration grade asphalt binder to show the applicability and suitability of using PPA in asphalt pavement in Iraq. Original asphalt binder and modified are subjected to traditional tests which are penetration, ductility, softening point, and viscosity. Results show better performance and enhancement of the physical properties of the modified binder. Other tests are Marshall Stability and wheel track tests. The results of the addition of PPA to the asphalt mixture show increases in the Marshall Stability and enhance the performance of the asphalt pavement mixtures. The wheel track test is applied to the original and modified mixture at two test temperatures 40 ?C and 50 ?C and the results show a decrease in the rut depth when the percentages of PPA increase. It is concluded that %PPA addition will enhance the performance of the Iraqi asphalt pavement and the mixture will be more rutting resistant, especially in high-temperature weather.
Moisture-induced damage in asphalt pavements, is defined by adhesive failure at the binder-aggregate interface and decreased mechanical integrity, severely reduce pavement durability. The research examines the mechanical properties and moisture sensitivity of hot mix asphalt (HMA) enhanced with styrene-butadiene-styrene (SBS) polymer and including reclaimed asphalt pavement (RAP). Laboratory assessments, including indirect tensile strength (ITS) and tensile strength ratio (TSR) tests, were performed on conventional HMA, SBS-modified HMA (4% SBS), and SBS-modified HMA contained 20% RAP. The results indicated that SBS modification significantly improved mechanical and moisture resistance properties, where unconditioned ITS specimens increased by 37.1% and TSR value enhanced by 13.5%. The incorporation of RAP decreased ITS value by about 21 % relative to pure SBS-modified HMA; nevertheless, the SBS+RAP combination still show higher ITS and TSR values than conventional HMA.
Improving the ability of asphalt pavement to survive the heavily repeated axle loads and weathering challenges in Iraq has been the subject of research for many years. The critical need for such data in the design and construction of more durable flexible pavement in bridge deck material is paramount. One of new possible steps is the epoxy asphalt concrete, which is classified as a superior asphalt concrete in roads and greatly imparts the level of design and construction. This paper describes a study on 40-50 penetration graded asphalt cement mixed with epoxy to produce asphalt concrete mixtures. The tests carried out are the Marshall properties, permanent deformation, flexural fatigue cracking and moisture damage. Epoxy asphalt mixes performed better on resistance to fatigue and permanent deformation. They also performed significantly better on low-temperature properties and resistance to moisture damage. The addition of 30 percent of epoxy (by weight of asphalt cement) resulted in increase of Marshall stability by 39.8 percent, improve the tensile strength ratio by 22.9 percent, lowering both the rate of permanent deformation by 26.8 percent and the fatigue accumulation coefficient by 53.5 percent, in comparison with control HMA. Based on the above findings, it is recommended to use epoxy asphalt mixes as an optimal material for paving bridges deck in Iraq since it showed good prospects for this application due to the valuable performance and durability improvement.
In Iraq some pavements of the newly constructed highway appear precocious distresses with unfavorable implications especially on the safety and the frugality. Cracking and permanent deformation are main types of these failures. The filler is doubtful to be a master contributor to these failures where its content has a significance effect on the mixture stiffness, and thereby affect the HMA pavement performance. The main objective of this research is to appreciate the influence of different contents of filler on the volumetric properties of asphaltic mixtures thus performance of asphalt mixtures through Comparative Evaluation between conventional Marshall Method and Super pave system. The implementation of a detailed experimental work is carried out to achieve the study objectives through the preparation of asphalt concrete samples using aggregate from Al-Nebaie quarry, (40-50) asphalt cement from Dourah refinery and limestone dust filler with four different contents of (0%, 4%, 8%, and 12%) by weight of the total aggregate. The volumetric properties for each mix design method are evaluated using Marshall Test and the Super pave Gyratory Compacter. The influence of filler contents on the rendering of these mixtures was evaluated.
Hot mix asphalt embedded on "Reclaimed asphalt pavement"(RAP) has the advantages of high technology. Moisture damage is a concern in these mixtures at all service temperatures. Therefore, the performance of this mixture against moisture at all service temperatures was considered a target of this research study. In this way, the effects of humidity on the performance of varieties were investigated using experimental methods including tensile strength ratio (TSR). In the framework of this study, Four different ratios of RAP for each of the surface and bonding layers (10%, 15%, 20%, 25%) and (30,40,50,60)% were added to the hot asphalt mix (HMA) for the two layers respectively to study and find the content Optimal RAP for both layers RAP through Marshall stability and hygroscopic resistance of asphalt mixtures through moisture damage is examined. The ratio (TSR) of the mixtures containing the optimal RAP content is compared with the asphalt mixture without RAP for three fillers and for both layers. The results showed a slight decrease in the tensile strength of the (HMA) that does not contain RAP compared to the asphalt control mixtures containing the reclaimed pavement, where it was found that the percentages were slightly higher and still higher than 80%. The results indicate that in general, Although there are old materials in the hot asphalt mix (HMA) produced from RAP, which include aggregates and bitumen binder surrounding the aggregate particles, the performance of these mixtures and integrations against moisture damage. Because it contains this, it can have results with “hot asphalt mixtures” containing RAP for areas with damage without worry in addition to good natural curbs.
The main objective of this study is to design the asphalt pavement structure for the Alkut-Mayssan highway in Iraq as a case study by using PCASE application to determine the necessary thickness of CR-modified asphaltic layers. Additionally, Marshall tests were used to investigate the effect of the dry process crumb rubber modifier on the thickness of the binder coarse layer based on various variables, such as the crumb rubber modifier with different content (1, 2, 3, 4, 5)% and sizes (0.3mm, 2.36mm , 4.75mm, and mix gradation). The test results show that while pavement thickness reduced as crumb rubber gradation increases, MR values increase. Additionally, as compared to the control mixture, the addition of 1% of CR in various gradations could decrease the thickness of the asphalt binder layer.