Evaluation The Moisture Sensitivity of Asphalt Mixtures Modified with Waste Tire Rubber

One of the most significant factors for a good transportation system is the quality of the road pavement. As a result, many steps have been made to address the concerns of moisture damage to roadways, including increasing pavement quality and structural design approaches. In the last few years, there has been an increase in the attention of respective engineers to enhance the asphalt performance and provides various types of modifiers and substituting the virgin of asphaltic materials with recyclable products, to attain sustainable while reducing the price of modified pavement mixture. This article discusses the performance of modified asphalt mixes and the most commonly used recycled product, crumbs rubber, which is used as a modifier in asphaltic mixes at various contents (0, 2.5, 5, 7.5, 10, and 15% by asphalt weight), and investigates the impact of the addition rubber particles on a critical characteristic of asphalt mixtures, particularly regarding their resistance to damage of moisture. The results showed that modification of asphalt binder with CR increased Marshall’s Stability, and the inclusion of 10% of CR recorded the highest increment, increasing by 30.25%. According to increased TSR and IRS, the addition of CR improved the asphalt mixture’s moisture resistance. The addition of 7.5 % of CR resulted in the largest values of TSR and IRS, increasing by 8.8% and 12.9% respectively. Additionally, this study aims at understanding the benefits and drawbacks of recycling rubber tires and to build a concept for effectively incorporating waste materials into road pavement.

Study on Conventional and Rheological Properties of Corn Stalk Bioasphalt/PPA Composite Modified Asphalt

As a new type of pavement material, bioasphalt has received more and more attention. However, the high-temperature behavior of bioasphalt is poor after blending with asphalt binder. In order to solve this problem and facilitate the waste utilization and resource conservation, the corn stalk bioasphalt/PPA composite modified asphalt was proposed. The conventional performance tests and rheological tests were conducted to evaluate high-temperature and low-temperature behavior. Fourier transform infrared reflection (FTIR) test was undertaken to analyze the mechanism of modified asphalt. The results indicated that blended asphalt penetration and ductility gradually decrease with the PPA content increasing. The softening point and viscosity of the modified asphalt increased, which led to an improvement of blended asphalt’s rigidity. The PPA increased the rutting index of corn stalk bioasphalt/PPA composite modified asphalt. However, bioasphalt had a negative effect on its high-temperature performance. The corn stalk bioasphalt/PPA composite modified asphalt could meet the specification requirement at −18°C considering the creep rate and stiffness modulus, indicating it had outstanding crack resistance. When the PPA and bioasphalt respect to the weight of neat asphalt were 6%–8% and 10%–16%, respectively, the corn stalk bioasphalt/PPA composite modified asphalt performance was optimal. However, shear time and shear rate merely affected the proposed modified asphalt performance. The bioasphalt did not affect the chemical structure of asphalt. However, PPA generated new functional groups (P-O single bond, phosphate (RO)3P = O, and P=O double bond) causing a chemical modification in the asphalt binder. This study can provide a basis for applying bioasphalt, making road engineering more economical and environmentally friendly.

Aging Characteristics of Asphalt Binder under Strong Ultraviolet Irradiation in Northwest China

Asphalt pavement is significantly affected by ultraviolet (UV) aging. Therefore, the establishment of an asphalt UV aging evaluation system is desirable for highway construction in areas which experience strong UV radiation. In this study, Dunhuang City in Gansu Province (northwest China) was used as the research site. Base and SBS modified asphalts were selected, and their performance changes before and after UV aging were studied. An asphalt UV aging evaluation system was established, including the conditions for an indoor, accelerated UV aging test as well as evaluation indicators. The results showed that the adverse effect of UV aging on asphalt performance was greater than that of RTFOT and PAV, and that the low-temperature performance of asphalt degraded most rapidly. SBS modified asphalt was more resistant to UV aging than base asphalt, while 60/80 pen grade base asphalt was found to be unsuitable for use on pavements which are exposed to strong UV radiation. The residual penetration, penetration attenuation index at 25 °C, and residual ductility of the asphalt were used as indicators to characterize the aging of asphalt, while the fracture energy method was used as a supplementary evaluation method.

Identifying the Long-Term Thermal Storage Stability of SBS-Polymer-Modified Asphalt, including Physical Indexes, Rheological Properties, and Micro-Structures Characteristics

The thermal storage stability of styrene–butadiene–styrene tri-block copolymer modified bitumen (SBSPMB) is the key to avoid performance attenuation during storage and transportation in pavement engineering. However, existing evaluation index softening point difference within 48 h (ΔSP48) cannot effectively distinguish this attenuation of SBSPMB. Thus, conventional physical indexes, rheological properties, and micro-structure characteristics of SBSPMB during a 10-day storage were investigated in this research. Results showed that during long-term thermal storage under 163 °C for 10 days, penetration, ductility, softening point, recovery rate (R%), and anti-rutting factor (G*/sinδ) were decayed with storage time increasing. This outcome was ascribed to the phase separation of SBS, which mainly occurred after a 4-day storage. However, ΔSP48 after a 6-day storage met the specification requirements (i.e., below 2.5 °C). Thus, the attenuation degree of asphalt performance in field storage was not effectively characterized by ΔSP48 alone. Results from network strength (I) and SBS swelling degree tests revealed that the primary cause was SBS degradation and base asphalt aging. Moreover, conventional indexes, including penetration, ductility, and softening point, were used to build a prediction model for rheological properties after long-term storage using partial least squares regression model, which can effectively predict I, R, Jnr, G*/sinδ, and SBS amount. Correlation coefficient is above 0.8. G*/sinδ and I at the top and bottom storage locations had high coefficient with SBS amount. Thus, phase separation of SBSPMB should be evaluated during thermal storage.

Performance of Interstate Rubblization in Illinois

In Illinois, hot-mix asphalt overlaid concrete pavements typically exhibit reflective cracking of joints and cracks from the pavement below, resulting in shortened life and maintenance issues. Over the years, various patching, fabric, and crack and seat techniques were attempted with few positive results. This led to more aggressive techniques to eliminate the slab action of the concrete pavement where the pavement would be broken or rubblized into pieces typically less than 12 inches. Since the first rubblizing project in 1990, policy, procedures, and specifications have evolved to the point that rubblization is the mainstream option in dealing with problematic concrete pavements. This report summarizes the performance of several interstate rubblizing projects in Illinois by analyzing available data in Illinois Department of Transportation’s pavement management system. Condition rating survey data allowed the serviceability of these projects to be evaluated by surface mix types and asphalt performance grades. Traffic in the form of 18,000 lb equivalent single axle loads was determined for the projects to evaluate fatigue and rutting as well as compare section performance to the design procedure. The research team reviewed plans, design procedures, and specifications to determine best practices and identify where improvements might be made. Data showed that the use of stone matrix asphalt surface mixtures and mixes using PGXX-28 asphalt binders provides improved performance. Overall, rubblizing has shown good to excellent performance. To provide additional life with improved performance, recommendations include adopting softer asphalt grades, increasing the use of stone matrix asphalt, and improving procedures for protecting culverts.

Enhancement of Asphalt Performance by Graphene-Based Bitumen Nanocomposites

As the State of California continues to grow, demand for enhanced infrastructure such as roadways and highways escalates. In view of the current average highway lifespan of 15–20 years, the improvement of asphalt binders leads to material sustainability by decreasing required maintenance and increasing the lifespan of roadways. In the present investigation, enhancement of asphalt binder properties was achieved by different methods of mixing varying compositions of graphene nanoparticles with an SBS polymer and asphalt binder. Additionally, experimental evaluation and comparison of the rheological and mechanical properties of each specimen is presented. Graphene nanoparticles have attracted great curiosity in the field of highway materials due to their incredible rigidity, even in small quantities. Addition of as little as 1.0%nanoparticles in combination with polymers in an asphalt binder is expected to increase the rigidity of the material while also maintaining the beneficial polymer characteristics. Evaluation of the effect of the mixing design established that the methods for application of graphene to the polymer-modified asphalt binder are critical in the improvement of a roadway, resulting in resistance to premature aging and strain from constant road operation.

Swelling and Degradation Characteristics of Crumb Rubber Modified Asphalt during Processing

The existence of cross-linked structure in crumb rubber modified asphalt (CRMA) leads to the complexity of its system. According to the preparation test of CRMA under different processing technology, the influence of processing temperature and time on the properties and cross-linking structure of CRMA was analyzed. By analyzing the volume expansion rate of the rubber powder after swelling and the toluene insoluble content attenuation rate, the formation conditions of the macro-level cross-linked structure were determined, and the relationship model between the cross-linked structure and the rubber asphalt performance was established. The results show that the rubber particles can form a continuous phase structure after swelling. At this time, the expansion ratio of the swollen rubber powder was 1.76–2.14. Too high temperature (above 200°C) and too long time (above 60 min) caused serious degradation of rubber. The suitable processing technology was stirring at 180–190°C for 45–60 min.