Amirthalingam Veeraragavan

Abstract: This paper deals with the viability of using reclaimed polyethylene (PE) derived from low-density PE carry bags collected from domestic waste as an additive in asphalt concrete mixtures. Different ratios of PE (2.5, 5.0, 7.5, and 10% by weight of asphalt) were blended with (80/100)-paving grade asphalt. The dynamic creep test (unconfined), indirect tensile test, resilient modulus test, and Hamburg wheel track tests were carried out on asphalt concrete mixtures blended with PE. The analyses of test results show that the performance of PE-modified asphalt mixtures are better when compared to conventional mixtures. The rutting potential and temperature susceptibility can be reduced by the inclusion of PE in the asphalt mixture. A PE content of 5% by weight of asphalt is recommended for the improvement of the performance of asphalt concrete mixtures similar to that investigated in this study.

Abstract: The primary objective of this work is to characterize and compare the dynamic mechanical behavior of asphalt concrete mixes with styrene butadiene styrene (SBS) polymer and crumb rubber modified asphalt binders with the behavior of mixes with unmodified viscosity grade asphalt binders. Asphalt binders are characterized for their physical and rheological properties. Simple performance tests like dynamic modulus, dynamic and static creep tests are carried out at varying temperatures and time. Dynamic modulus master curves constructed using numerical optimization technique is used to explain the time and temperature dependency of modified and unmodified asphalt binder mixes. Creep parameters estimated through regression analysis explained the permanent deformation characteristics of asphalt concrete mixes. From the dynamic mechanical characterization studies, it is found that asphalt concrete mixes with SBS polymer modified asphalt binder showed significantly higher values of dynamic modulus and reduced rate of deformation at higher temperatures when compared to asphalt concrete mixes with crumb rubber and unmodified asphalt binders. From the concept of energy dissipation, it is found that SBS polymer modification substantially reduces the energy loss at higher temperatures. Multi-factorial analysis of variance carried out using generalized liner model showed that temperature, frequency and asphalt binder type significant influences the mechanical response of asphalt concrete mixes. The mechanical response of SBS polymer modified asphalt binders are significantly correlated with the rutting resistance of asphalt concrete mixes.

Abstract: This paper presents the laboratory investigations carried out to determine the various engineering properties such as physical properties of asphalt cement and (polymer modified asphalt binder) PMAB with (styrene-butadiene-styrene triblock copolymer) SBS, Marshall properties using modified Marshall method, static indirect tensile strength at different temperatures, tensile strength ratio, and resilient modulus ratio for asphalt concrete (AC) and polymer modified asphalt concrete mixes (PMAC) with SBS. The temperature susceptibility of PMAB-SBS is lower than asphalt cement. Marshall stability and flow values of PMAC mix are higher when compared to AC mix at optimum binder content. The static indirect tensile strength values for PMAC mixes were higher when compared to AC mixes at different temperatures. Moisture susceptibility of PMAC mixes is low when compared to AC mixes.

Abstract: Traditional pavement design process involves limiting the strain on top of the subgrade layer to ensure that the pavement will not fail by rutting The recently released Mechanistic-Empirical Pavement Design Guide (M-E PDG) and the associated „AASHTOWare Pavement ME Design” software of the United States considers permanent deformations in all the rut- susceptible layers (asphalt concrete and unbound granular material layers) on the overall cumulative rutting in the pavement However, the rutting models incorporated in the design do not consider the influence of reduction of air voids during design life and the effect of confinement pressure This investigation explores the influence of air voids reduction and confinement pressure on the rut depth prediction using AASHTOWare for a typical Indian pavement cross-section An asphalt concrete mixture, Bituminous Concrete (Grade-1) confirming to the Ministry of Road Transport and Highways (MoRTH) specifications was cast at three air voids contents of 7, 4 and 2% The dynamic moduli of these samples were determined at 5, 15, 20, 40 and 55 °C for frequencies ranging from 001 to 25 Hz at 0 and 200 kPa confinement pressure In addition, the dynamic modulus values of Dense Bituminous Macadam (Grade 2) mix at these temperature and frequencies for an air voids content of 4% were determined in the unconfined condition A typical pavement cross-section as given in the Indian Roads Congress guidelines corresponding to 10% CBR and 150 msa traffic was chosen Simulations were carried out for this pavement cross-section using the material properties measured for asphalt layers Air voids and confinement pressure exhibited considerable influence on the rutting predicted for the asphalt layers of the pavement While the AASHTOWare pavement design software may not be directly applicable to Indian conditions due to the use of considerable amount of data pertaining to USA and Canada, such exercise as carried out here, clearly showcases the limitations of the cross-sections used in India and provides guidelines on the directions India should take when it comes to material characterisation

Abstract: A laboratory investigation was conducted to capture the influence of confinement pressure and specimen air voids on the creep and recovery response of asphalt concrete (AC) mixtures. AC specimens were fabricated at 2% and 7% air voids and tested at three temperatures (20, 40 and 55°C) and at unconfined and confined conditions (100 and 200 kPa). A total of 20,000 repetitions of a repeated trapezoidal loading and recovery cycle were applied. The resulting creep curves showed four distinct patterns of the three-stage creep curve depending on the loading condition and specimen density. To quantify the mechanical response during the secondary stage where the response was found to be linear, linear viscoelastic modelling was carried out. Using creep time, energy stored and energy dissipated, which were determined from model parameters; the influence of air voids and confinement pressure was quantified.

Abstract: The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

Abstract: During the last decades, the number of vehicles per citizen as well as the traffic speed and load has dramatically increased. This sudden and somehow unplanned overloading has strongly shortened the life of pavements and increased its cost of maintenance and risks to users. In order to limit the deterioration of road networks, it is necessary to improve the quality and performance of pavements, which was achieved through the addition of a polymer to the bituminous binder. Since their introduction, polymer-modified asphalts have gained in importance during the second half of the twentieth century, and they now play a fundamental role in the field of road paving. With high-temperature and high-shear mixing with asphalt, the polymer incorporates asphalt molecules, thereby forming a swallowed network that involves the entire binder and results in a significant improvement of the viscoelastic properties in comparison with those of the unmodified binder. Such a process encounters the well-known difficulties related to the poor solubility of polymers, which limits the number of macromolecules able to not only form such a structure but also maintain it during high-temperature storage in static conditions, which may be necessary before laying the binder. Therefore, polymer-modified asphalts have been the subject of numerous studies aimed to understand and optimize their structure and storage stability, which gradually attracted polymer scientists into this field that was initially explored by civil engineers. The analytical techniques of polymer science have been applied to polymer-modified asphalts, which resulted in a good understanding of their internal structure. Nevertheless, the complexity and variability of asphalt composition rendered it nearly impossible to generalize the results and univocally predict the properties of a given polymer/asphalt pair. The aim of this paper is to review these aspects of polymer-modified asphalts. Together with a brief description of the specification and techniques proposed to quantify the storage stability, state-of-the-art knowledge about the internal structure and morphology of polymer-modified asphalts is presented. Moreover, the chemical, physical, and processing solutions suggested in the scientific and patent literature to improve storage stability are extensively discussed, with particular attention to an emerging class of asphalt binders in which the technologies of polymer-modified asphalts and polymer nanocomposites are combined. These polymer-modified asphalt nanocomposites have been introduced less than ten years ago and still do not meet the requirements of industrial practice, but they may constitute a solution for both the performance and storage requirements.

Abstract: This work aims to improve the rutting and fatigue cracking resistance of asphalt binders using selected nano- or micro-sized materials and to shed light on the microstructure changes induced by such modification to asphalt binders. The four modifiers (Nanomer I.44P, carbon microfiber, non-modified nanoclay and polymer modified nanoclay) were added into the control asphalt binder (PG 58-34). The Superpave™ tests and Fourier transform infrared spectroscopy (FTIR) measurements were conducted for obtaining the complex shear modulus G * and microstructure distribution of modified asphalt binders. Meanwhile, the short-term and long-term aging processes of asphalt binders are simulated by rolling thin film oven (RTFO) and pressure aging vessel (PAV) tests. From the dynamic shear rheometer (DSR) and FTIR tests results, the complex shear modulus G * values of nano- or micro-materials (Nanomer I.44P, non-modified nanoclay and carbon microfiber) modified asphalt binders increase, and the performance of resistance to rutting is improved compared to the control asphalt binder. The addition of polymer modified nanoclay (PMN) into the control asphalt binder decreases the complex shear modulus, and enhances the resistance to fatigue cracking. Moreover, the addition of four modifiers into the control asphalt binder can delay and weaken the aging and oxidation effect.

Abstract: Asphalt binders play an integral role in the performance and properties of asphalt mixtures. Increased traffic-related factors on the roadways such as heavier loads, higher traffic volume, and higher tire pressure combined with substantial variation in daily and seasonal temperatures of the pavement have been responsible for the asphalt pavements failure. To prevent or mitigate these failures, many attempts have been made by polymer scientists and civil engineers to improve the performance of asphalt pavements by modifying the properties of asphalt binders. A good modifier changes the failure properties such that binder yields more stresses and strains before failure. Modification of asphalt binders through the addition of a polymer to improve their rheological and physical properties has a long history in asphalt industry. Once the polymer is properly mixed with the asphalt binder, a swallowed polymer network is formed, which contributes to the changes in viscoelastic behavior. However, polymer-modified asphalt binders may have some drawbacks related to the poor solubility of polymers. Understanding the internal structure of polymer-modified asphalt binders has been the subject of numerous research studies. Available studies regarding the affecting parameters on the properties of the polymer-modified asphalt binders are reviewed here. Various types of polymers used in asphalt industry and their effects on the rheological, morphological, physical and mechanical properties of polymer-modified asphalt binders are also discussed in this paper. In addition, this paper provides a review on the techniques used to overcome/mitigate the shortcomings of conventional polymer-modified asphalt binders.

Abstract: The present study investigates the potential use of pyrolysis low density polyethylene (LDPE) as a modifier for asphalt paving materials. Five different blends including conventional mix were subjected to binder testing such as rheological tests, as well as to some other tests related to the homogeneity of the system. Further, its effect on the moisture sensitivity and low temperature performance of stone matrix asphalt (SMA) mixtures was studied. Research results indicate that modified binders showed higher softening point, keeping the values of ductility at minimum range of specification of (100+ cm), and caused a reduction in percentage loss of weight due to heat and air (i.e. increase durability of original asphalt). The results indicated that the inclusion of LDPE in SMA mixtures can satisfy the performance requirement of high-temperature, low temperature and much rain zone. In addition, the horizontal tensile strain at the bottom of asphalt concrete layer (Et) and the vertical compressive strain at the top of subgrade layer (Ec) were calculated using multi-layer elastic analysis program, BISAR under 50KN set of dual tires with 106.5 mm contact radius. These responses were used for estimating the improvement in service life of the pavement or reduction in thickness of SMA and base layer for the same service life due to modification the SMA mixtures.