Effects of Reclaimed Asphalt Pavement on Mechanical Characteristics of Asphaltic Mixtures for Surface Layer

Reclaimed asphalt pavement (RAP) is considered one of the valuable alternatives to raw materials due to reducing the need to use raw materials, which are less in some world regions. It additionally reduces the highly-priced new bitumen required inside the asphaltic mixture manufacturing and contributes to the preservation of natural resources. To achieve maximum benefit from the integration RAP in asphaltic mixture, it is necessary to investigate the advantages and disadvantages of the recycling process on the properties of asphalt pavement. This study examines the effect of adding reclaimed asphalt pavement by different percentages on the mechanical properties of asphaltic mixture for the surface layer in terms of Marshall's stability, Retained Marshall stability, indirect tensile strength, and compressive strength. Two types of asphalt grade (40-50) and (60-70) were used in addition to one type of aggregate gradation of the wearing course to prepare the asphaltic mixture. The Superpave system was applied to select the best aggregate gradation and optimum asphalt content using Superpave Gyratory Compactor (SGC) and to prepare compacted asphaltic specimens of 100 mm diameter for simulating Marshall’s molds. PAP is added by four different percentages of (7, 13, 19, and 25) % by the weight of the total asphalt mixture, and samples are prepared to compare the mechanical properties with conditional ones. The results show that adding RAP to the asphalt mixture improved the measured properties. In contrast, the mix containing RAP showed lower loss of stability, lower loss in indirect tensile strength, higher stripping resistance, and better durability than the mixture without RAP

Effect of Styrene Butadiene Styrene on Properties of Open-Graded Asphalt Concrete Mixtures

Open graded asphalt mixture is becoming more widespread where it is applied for various purposes, e.g. drainage of rainwater effectivity, traffic safety (high skid resistance), and controlling pollution noise. However, it has many other disadvantages, of which low stability, high stripping, and moisture sensitivity. The research aims to study the effect of styrene butadiene styrene SBS addition on the volumetric and mechanical properties of open graded mixture. In this research one type of aggregate with gradation (12.5 mm NMAS), asphalt of penetration grade (40/50), and cement as filler were used. Optimum asphalt content was selected based on the criteria of air voids content, asphalt drain down, permeability, and abrasion resistance (for aged and un-aged) samples. Other properties of open-graded mixtures, such as indirect tensile strength (ITS), moisture susceptibility, Marshall stability and flow were evaluated. The results show that addition of polymer (SBS) leads to an enhancement in the properties of the modified mixtures. There is an improvement in Marshall parameters. Also, a slight decreasing is noticed for permeability and air voids. For Cantabro abrasion loss (aging and un-aging condition), the abrasion resistance is increased, the drain down of asphalt is decreased from original mixture by addition of SBS. Finally, the moisture sensitivity is improved indicating that modified mixes becomes more resistant to water damage

Prediction Models for Modified Pavement Mixtures by Reclaimed Asphalt in Terms of Durability Indicators

The asphaltic pavement is often subjected to various types of distress during the service life caused by excessive load, construction practices, deficient materials, and environmental conditions. A lot of pavements may occur due to moisture damage because of the presence of water on the pavement's surface, which affects the pavement's service life. It needs periodic maintenance, which requires materials and money. So many countries take the economic side by reusing old, damaged pavement and mixed with new materials in addition to its sustainable benefits, the old material called reclaimed asphalt pavement (RAP). This study examines the effect of adding RAP on durability indicators, including tensile strength ratio, retained Marshall Stability, and durability Index, in addition to prediction statistical models for reclaimed asphalt pavement mixtures in terms of durability indicators. To achieve the goals of this study, the asphalt mixtures are designed according to the superpave system; the samples are compacted by a superpave gyratory compactor with a diameter of 100 mm and prepared with (6%, 13%, 19%, and 25%) RAP content with three conditioning periods of (1, 3, and 7) days and two aging periods (short term aging for loose mixture at 135˚C for 4 hours long term aging for 120 hours at 85˚C), and two testing temperature of 25˚C and 60˚C. The results indicated that stability increased as the RAP content increased compared to the control mix, and indirect tensile strength increased with RAP addition for both aging periods. Also, results illustrated that the tensile strength ratio for specimens tested at 25˚C is higher than that tested at 60˚C temperature

Experimental Study of the Effect of Crumb Rubber on Properties of Asphalt Mix by Wet Process

The increase in the number of vehicles during the past twenty years has dramatically increased the traffic density and axial loading. In addition to the construction failures and lack of periodic maintenance, rapid deterioration of the road condition happens. So, it was necessary to find solutions to these problems that have been growing for years. One of these solutions is to improve the asphalt mixture to resist excessive loads and weather fluctuations. This research aims to investigate the addition of crumb rubber derived from recycled tires; to the asphalt mixture for improving performance characteristics and to compare the improved and unimproved samples. It is worth mentioning that crumb rubber addition to the asphalt mixture is considered one of the smart solutions for sustainability that the world is heading towards today, considering that the crumb rubber comes from waste tires, which is difficult to eliminate and pollute the environment. Four different proportions of crumb rubber have been added in this research (6, 9, 12, and 15%); by weight of bitumen to (60-70) asphalt binder, with a particle size passing from sieve no.50 (0.3 mm). The aggregate gradation is designed according to the Marshall method with a (12.5 mm NMAS) wearing course to obtain the optimum asphalt content and to prepare laboratory samples to perform various laboratory tests. Marshall Stability and flow, indirect tensile strength (ITS), moisture susceptibility, and permanent deformation of asphaltic mixes with different contents of crumb rubber were investigated. The results of the tested samples were compared with the original samples. It is shown that the asphaltic mixes performance has been improved when adding a certain amount of crumb rubber. Marshall Stability is increased by 29.2% when adding 9% CR by the weight of bitumen. However, the addition of crumb rubber can increase the stiffness of the asphalt mixture resulting in a more rigid pavement structure that is less prone to moisture damage and rutting under traffic load

Effects of Reclaimed Asphalt Pavement on Mechanical Characteristics of Asphaltic Mixtures for Surface Layer

Reclaimed asphalt pavement (RAP) is considered one of the valuable alternatives to raw materials due to reducing the need to use raw materials, which are less in some world regions. It additionally reduces the highly-priced new bitumen required inside the asphaltic mixture manufacturing and contributes to the preservation of natural resources. To achieve maximum benefit from the integration RAP in asphaltic mixture, it is necessary to investigate the advantages and disadvantages of the recycling process on the properties of asphalt pavement. This study examines the effect of adding reclaimed asphalt pavement by different percentages on the mechanical properties of asphaltic mixture for the surface layer in terms of Marshall's stability, Retained Marshall stability, indirect tensile strength, and compressive strength. Two types of asphalt grade (40-50) and (60-70) were used in addition to one type of aggregate gradation of the wearing course to prepare the asphaltic mixture. The Superpave system was applied to select the best aggregate gradation and optimum asphalt content using Superpave Gyratory Compactor (SGC) and to prepare compacted asphaltic specimens of 100 mm diameter for simulating Marshall’s molds. PAP is added by four different percentages of (7, 13, 19, and 25) % by the weight of the total asphalt mixture, and samples are prepared to compare the mechanical properties with conditional ones. The results show that adding RAP to the asphalt mixture improved the measured properties. In contrast, the mix containing RAP showed lower loss of stability, lower loss in indirect tensile strength, higher stripping resistance, and better durability than the mixture without RAP

TENSILE STRENGTH FOR MIXTURE CONTENT RECLAIMED ASPHALT PAVEMENT

This paper is studying the effect of two different heating temperature of RAP on performance of water sensitivity tests, the Indirect Tensile Strength Ratio (TSR). the best gradation and optimum asphalt content was Selected according to Superpave method. Superpave Gyratory Compactor (SGC) used to compact mixture with 100-mm diameter. Four different percentages (20,30,40 and 50) of RAP used for preparation mixes to compared with virgin mixture. The test results indicated that addition RAP to mixes shows significant increase on resistance of moisture damage (TSR) for 110 cﹾ for all percent. For 140 cﹾ showed (TSR) increase to threshold (20%) of RAP while (TSR) decline for another percent but still above the standard limit of 80%

Experimental Study of the Effect of Crumb Rubber on Properties of Asphalt Mix by Wet Process

The increase in the number of vehicles during the past twenty years has dramatically increased the traffic density and axial loading. In addition to the construction failures and lack of periodic maintenance, rapid deterioration of the road condition happens. So, it was necessary to find solutions to these problems that have been growing for years. One of these solutions is to improve the asphalt mixture to resist excessive loads and weather fluctuations. This research aims to investigate the addition of crumb rubber derived from recycled tires; to the asphalt mixture for improving performance characteristics and to compare the improved and unimproved samples. It is worth mentioning that crumb rubber addition to the asphalt mixture is considered one of the smart solutions for sustainability that the world is heading towards today, considering that the crumb rubber comes from waste tires, which is difficult to eliminate and pollute the environment. Four different proportions of crumb rubber have been added in this research (6, 9, 12, and 15%); by weight of bitumen to (60-70) asphalt binder, with a particle size passing from sieve no.50 (0.3 mm). The aggregate gradation is designed according to the Marshall method with a (12.5 mm NMAS) wearing course to obtain the optimum asphalt content and to prepare laboratory samples to perform various laboratory tests. Marshall Stability and flow, indirect tensile strength (ITS), moisture susceptibility, and permanent deformation of asphaltic mixes with different contents of crumb rubber were investigated. The results of the tested samples were compared with the original samples. It is shown that the asphaltic mixes performance has been improved when adding a certain amount of crumb rubber. Marshall Stability is increased by 29.2% when adding 9% CR by the weight of bitumen. However, the addition of crumb rubber can increase the stiffness of the asphalt mixture resulting in a more rigid pavement structure that is less prone to moisture damage and rutting under traffic load