Sulfur-extended Asphalt Research Articles

Reasons for Reduced Moisture Resistance of Sulfur-Extended Asphalt Concrete.

The paper presents the results of a study of the mechanism for reducing the moisture resistance of sulfur-extended asphalt concrete. It is shown that a decrease in moisture resistance occurs due to the occurrence of chemical and physical processes. At the same time, it was found that during the manufacture of sulfur-bitumen composites, toxic gases H2S and SO2 are formed, which are capable of interacting with a mineral filler, as well as the interaction of sulfur with a mineral powder with the formation of sulfur-containing water-soluble salts, the extraction of which leads to a decrease in the moisture resistance of sulfur-bitumen materials. The change in the rate of leaching of these substances from the composite is due to the physical process caused by the crystallization of sulfur and the formation of a capillary structure, which significantly increases the rate of leaching of calcium and magnesium salts, which are products of dissolution or hydrolytic decomposition of water-soluble products of the interaction of sulfur, H2S and SO2 gases with calcium and magnesium carbonates. The intensity of chemical and physical processes intensifies with an increase in the amount of sulfur in sulfur-bitumen materials.

Rheological and environmental evaluation of sulfur extended asphalt binders modified by high- and low-density polyethylene recycled waste

This research evaluates the rheological properties of virgin asphalt and sulfur extended asphalt (SEA) modified with two types of recycled plastic waste (rPW). The investigated plastic wastes are the recycled low-density polyethylene (rLDPE) and recycled high-density polyethylene (rHDPE). It also assesses the environmental and economic benefits of recycling such materials. A total of 16 modified binder samples are produced by adding rLDPE and rHDPE modifiers to virgin asphalt and SEA in four different concentrations of 2%, 4%, 6%, and 8% by weight of asphalt. The basic and rheological properties of the virgin and modified asphalts are explored by conventional tests, and advanced rheological tests at different aging conditions. Finally, cost-effectiveness and environmental analyses are conducted. The environmental benefit analysis is performed by comparing carbon and non-methyl volatile organic compound (NMVOC) emission from the various recycled polyethylene (rPE) with the manufacturing process of the same quantities of virgin LDPE and HDPE when used to modify asphalt. The effect of incorporating sulfur into virgin asphalt on the environment is also determined. Results show that modification yields a higher binder complex shear modulus (G*) and a lower loss tangent (tan δ) at all traffic speeds meaning improved rut resistance behavior under heavy traffic loading and high temperature conditions. About 29% reduction in material cost occurs when rPE-modified SEA is used instead of virgin asphalt. The environmental and economic analyses show that using SEA modified with rPE for road construction is an economic, sustainable, and ecological alternative with better performance compared to virgin asphalt.

A Comparative Study of Different Complex Shear Modulus Master Curve Techniques for Sulfur Extended Asphalt Modified with Recycled Polyethylene Waste

A Comparative Study of Different Complex Shear Modulus Master Curve Techniques for Sulfur Extended Asphalt Modified with Recycled Polyethylene Waste

Evaluation of various factors affecting mix design of sulfur-extended asphalt mixes

Several laboratory and field studies from the last five decades, predominantly from the 1970s and 80s, have demonstrated that elemental sulfur is a viable binding material that can be used to partially or fully replace conventional asphalt binder in pavement construction applications. The main goal of this study was to determine and demonstrate the impact of different mix design factors on the performance of sulfur extended asphalt (SEA). These factors include sulfur content, the use of polymer modified versus unmodified base binder, and the method of sulfur addition to the mix. The Hamburg Wheel Tracking test was used to characterize rutting resistance and the Illinois Flexibility Index Test (I-FIT) was used to characterize the cracking performance at both short and long-term aging conditions. Overall, sulfur was found not to compromise the very good rutting resistance of the mix, and optimum binder and sulfur contents were determined based on long term cracking resistance of the mix. It is notable that the optimum binder content did not change when sulfur was used based on the long-term cracking resistance. Results, although with a limited set of materials, demonstrate the feasibility of replacing 30% of asphalt binder with elemental sulfur to produce SEA mixes.

Phase angle master curves of sulfur-extended asphalt modified with recycled polyethylene waste

Master curves (MC) of mixtures and asphalt binders are typically implemented in the linear viscoelastic range for assessing their rheological behavior. Although there are several theoretical models to represent the MC of mixtures and asphalt binders, their performance is variable. The use of MC to model the binder’s phase angle has received less attention compared to the MC of the complex modulus. Thus, this paper investigates the possibility of using several predictive equations to represent the phase angle (δ) of neat asphalt (virgin asphalt and sulfur-extended asphalt, SEA) and modified asphalt [recycled polyethylene-modified asphalt and recycled polyethylene-modified SEA (PMSEA)]. The investigated models include the standard sigmoidal (SS) model, generalized logistic sigmoidal (GLS) model, Christensen (CA) model, and Anderson and Marasteanu (CAM) model. The viscoelastic properties of these binders are determined through a dynamic shear rheometer spanning a broad variety of temperatures and frequencies using dynamic mechanical analysis (DMA). The results show that most of the investigated models can reasonably predict neat asphalts’ viscoelastic behavior in terms of δ. However, the accuracy of the investigated models becomes relatively lower for the modified binders, especially in the long-term aged condition. The goodness-of-fit statistics of the investigated models show that the GLS model is the most accurate mode, followed by the SS, CAM, and then the CA model.

Moisture Resistance of Sulfur-Extended Asphalt Concrete. Results of the Study and Features of Definition

Moisture Resistance of Sulfur-Extended Asphalt Concrete. Results of the Study and Features of Definition

Rheological properties and aging performance of sulfur extended asphalt modified with recycled polyethylene waste

This study examines the effect of two different recycled plastic waste (RPW) which are high and low-density polyethylene (RHDPE and RLDPE) on the rheological/viscoelastic characteristics and aging performance of virgin asphalt and sulfur extended asphalt (SEA). Four dosages of the RPW additives representing 2%, 4%, 6%, and 8% by weight of the asphalt binder were investigated. The rheological characteristics of the RPW modified binders (virgin and SEA) are characterized at original and short-term aging conditions through the Rotational Viscometer (RV) and dynamic shear rheometer (DSR) tests. Fatigue performance is also characterized at the long-term aging condition. Also, high-temperature performance, dynamic storage stability (DSS), multiple stress creep and recovery (MSCR) are studied. Testing results show that RPWs lead to improved rutting and fatigue performance. Adding RPW to the virgin and SEA binders slows the binder oxidation reactions during the short-term aging. The Aging Index (AI) is found to be dependent on the asphalt rheological properties, amount/type of RPW, binder type, and temperature. RHDPE leads to an unstable modified virgin asphalt. Less than 4% RHDPE or 8% RLDPE with virgin asphalt show good DSS in terms of degradation and separation. The RPW with SEA meets the requirement of time degradation and separation set by the Federal Highway Administration (FHWA). The temperature susceptibility of asphalt binder decreases dramatically with the RPW modification making the asphalt binder more suitable for use at a wider range of temperatures.

Characterisation of rheological properties of sulfur-extended asphalt with/without crumb rubber

ABSTRACT This study is to characterise rheological properties of sulfur-extended asphalts with/without crumb rubber at high, intermediate, and low temperatures using standard asphalt binder tests. Four dosages of sulfur (i.e. 0%, 15%, 30% and 45%) by weight of neat asphalt binder were used. The results indicated that a low level of sulfur addition, such as 15%, softened original asphalt binder. When the sulfur dosage was larger than 15%, the extra sulfur would act as fillers to stiffen asphalt binder. The addition of crumb rubber significantly increased high temperature performance grade. For sulfur-extended asphalts with/without crumb rubber, an increase in the sulfur dosage resulted in an increase of low temperature performance grade. Sulfur-extended asphalt with 15% sulfur exhibited the largest non-recovery creep compliance (Jnr) value, while the 30% and 45% exhibited the lowest values since more extra sulfur acts as fillers to stiffen asphalt binder. The addition of sulfur significantly decreased viscosity. The semi-circular bending fracture test results indicated that the mixture with the addition of 15% sulfur was softer and behaved in a more ductile manner than the others, which is consistent with the asphalt binder test results of high temperature performance grade and non-recovery creep compliance.

The application of sulfur-asphalt concrete with modifiers in the climatic conditions of Vietnam

The paper considers the influence of ambient temperature and other weather factors on the properties of traditional asphalt concrete in Vietnam. The advantages of sulfur-extended asphalt concrete with modifiers containing neutralizers for the emission of toxic gases are presented to increase the quality and life of roads and solve the environmental problem of using sulfur-extended asphalt concrete. For calculating the surface temperature of asphalt concrete from the ambient temperature, the method of Yu. N. Kovalev is used (Russia). The weather data for January and July 2015, taken from the hydrometeorological stations of the cities of the respective zones in Vietnam, are used for calculations. The paper presents an experimental setup for determining the intensity of toxic gases evolution and the effect of neutralizers. The widespread introduction in the practice of building progressive environmentally friendly sulfur-containing materials: sulfur-extended asphalt concrete with modifiers, containing toxic gases emission neutralizers, which have higher physical and mechanical properties (wear resistance, etc.) compared to traditional ones at less or equal cost, can open up opportunities to increase quality and lifetime of roads in Vietnam.

Sulfur-extended asphalt concrete with assessing the surface temperature of roads affecting urban heat island

The Urban Heat Island (UHI) is a phenomenon that affects many millions of people worldwide. The higher temperatures experienced in urban areas compared to the surrounding countryside has enormous consequences for the health and wellbeing of people living in cities. The paper studies the temperature dependence of the surface of the asphalt concrete on the air temperature of Hanoi city with a view to determine the road surface temperature compared to the comfort threshold of Vietnamese people. Research data on microclimate of Hanoi city was taken from hydro-meteorological station in the period 2010yr – 2015yr. The paper selects two most famous methods of calculating the surface temperature of asphalt concrete: The Method of Kovalev Y.N (Russia) and the method of “Superpave” method (USA). This review article outlines the contribution that pavements make to the urban heat island (UHI) effect and analyses localized and citywide mitigation strategies against the UHI. Asphalt concrete is one of the most common pavements surfacing materials and is a significant contributor to the UHI effect. Dense asphalt concrete has low albedo and high volumetric heat capacity, which results in surface temperatures reaching upwards to 60°C on hot summer days. Application of sulfur-extended asphalt concrete with advanced properties instead of asphalt concrete reduces the urban heat island effect and increase the quality and life of roads in Hanoi (Vietnam).

Structure and physical properties of sulfur with nanoscale carbon modifiers

It is known that sulfur-extended asphalt is of improved operational properties. Binders with higher content of polymeric sulfur are characterized by higher operational properties. Unfortunately, many sulfur modifiers are volatile and toxic. The objective of article is to investigate the structure of sulfur with admixtures of saturated aliphatic hydrocarbon and two types of nanoscale carbon modifiers. It was shown that such admixtures lead to formation of the fine-crystalline structure of high uniformity; average size of crystals decreases in order of magnitude. Structural changes are accompanied by notable improvement of compressive strength (the values of compressive strength increases in about 3 times). The practical value of the conducted studies is due to possible application of nanomodified sulfur in road construction.

Characterization of Crack Growth Rate of Sulfur-Extended Asphalt Mixtures Using Cyclic Semicircular Bending Test

AbstractCharacterizing crack propagation of asphalt mixtures is helpful for optimizing mixture design and predicting cracking performance of asphalt pavements. This paper explores a new method base...

USING LARGE-TONNAGE INDUSTRIAL WASTE TO CREATE BITUMEN COMPOSITES WITH IMPROVED FATIGUE LIFE

With the goal of searching effective methods of industrial wastes recycling, filler systems for bituminous binders in road building have been proposed. For the first time in the world, the product of recycled tire rubbers, which is an active powder of discretely devulcanized type of rubber in addition to waste of sulfur produced in technological processes of oil refining, natural gas, etc., have been tested in order to improve the quality of bitumen binders. The rheological properties and fatigue life of the sulfur-bitumen binder have been investigated according to the linear amplitude sweep test (LAS) by using a Smart Pave dynamic shear rheometer (Physica MCR series, Anton Paar, Austria). A technique for preparing samples of sulfur-containing binders has been developed based on the results of photomicrographs analysis obtained by optical microscopy. It has been done to study their fatigue cracking resistance. The analysis of the influence of sulfur and elastic filler on fatigue life has showed that the rise of the quantity of cycles up to fatigue damage of binder samples by the factor of 3-5 (strain of 5% and 2.5%) is due to crumb rubber concentration. The addition of sulfur to ternary systems bitumen/sulfur/elastic filler enables saving energy resources as a result of the possibility of manufacturing sulfur-extended asphalt at lower temperatures.

Improving moisture sensitivity and mechanical properties of sulfur extended asphalt mixture by nano-antistripping agent

Moisture damage and fatigue cracking are the most common defects of Sulfur Extended Asphalts (SEAs). Moisture damage in asphaltic mixtures occurs due to the weak cohesion and adhesion that causes the creation of different forms of pavement defects. Various methods have been employed in order to enhance the asphalt mixture’s resistance to the moisture damage. One of the main methods is the addition of antistriping agents (ASAs) which reinforce the bonding between asphalt binder and aggregates. In this study, a series of laboratory testing has been performed to appraise the mechanical properties and moisture sensitivity of the SEA mixtures modified with ASA. In addition, Googas as a new generation of modified-sulfur-mix additive and ASA (nanotechnology Zycotherm) were employed to make warm-mix asphalt (WMA) specimens, through modification of neat asphalt (PG 64-22). Furthermore, four types of mixtures with different additive proportions, containing ASA and sulfur, were prepared, and the moisture susceptibility, resilient modulus, rutting resistance, and fatigue behavior were measured. Obtained results, demonstrated the improvement of mechanical characteristics due to the implementation of the modified sulfur, exclusively for rutting phenomenon. Moreover, nanotechnology Zycotherm (NZ) as an ASA enhanced the adhesion between aggregates and sulfur-extended asphalt; thus, the resistance of SEAs against moisture damage and fatigue cracking improved.

Viscosity of plasticized sulfur-extended asphalt: two-factor sequential optimization

The compounding properties of construction materials for pavements strongly depend on dynamic viscosity of the binder. The favorable class of binder is plasticized sulfur-extended asphalt. Unfortunately, the viscosity of such a binder has not been studied in detail. In the present work we have performed experimental two-factor sequential constrained optimization of the viscosity. The binders under examination were made of asphalt, sulfur and paraffin. It was revealed that the addition of sulfur and paraffin leads to a significant decrease of the dynamic viscosity. The obtained results allowed us to estimate mixture and temperature that correspond to optimal compounding properties of the sulfur-extended asphalt concrete. In particular, for plasticized asphalt concrete with 30% of sulfur and 5% of paraffin, the optimal processing temperature is 25 °C lower than for ordinary asphalt. Since low preparation temperatures correspond to low emission of toxic gases and low processing costs, we can consider the concretes that will be based on plasticized sulfur-extended asphalt as green paving materials.

Nanoscale study on water damage for different warm mix asphalt binders

In order to analyze the water damage to different warm mix asphalt binders from the micro scale, five kinds of asphalt binders, 70#A base asphalt, sasobit warm mix asphalt, energy champion 120°C (EC120) warm mix asphalt, aspha-min warm mix asphalt, sulfur-extended asphalt modifier (SEAM) warm mix asphalt, under different conditions (dry/wet, original/aging) are prepared for laboratory tests. The atomic force microscope (AFM) is used to observe the surface properties and measure the adhesion force between the asphalt and the mineral aggregate. The obtained results show that under the dry condition aspha-min warm mix asphalt and SEAM warm mix asphalt show stronger adhesive ability with the mineral aggregate compared with other asphalt binders, but also have relatively large dispersion and fluctuation in the tested results; under the wet condition, aspha-min warm mix asphalt and SEAM warm mix asphalt show stronger water damage resistance ability. The EC120 warm mix asphalt and aspha-min warm mix asphalt are less sensitive to moist, and their corresponding adhesion force is less susceptible to the change of external moisture conditions, leading to a better ability to resist water erosion. The aging process significantly lowers the moisture erosion resistance ability, which further impairs the water damage resistance ability. The base asphalt is more sensitive to moisture and more vulnerable to water damage, no matter whether it is under original or aging conditions. The aging aspha-min warm mix asphalt has the least loss of adhesion force, the smallest dispersion of the tested adhesion force, the strongest water damage resistance ability, no matter it is dry or wet.

Structure Formation and Phase Composition of Sulfur-Bitumen Systems

Nowadays, modification of the bitumen by sulfur is considered as an effective way to enhance the properties of materials for road construction. By means of using the sulfur we eliminate the need to reconstruct existing production facilities for asphalt concrete. There is a plenty of research had already been performed for investigation of the sulfur-extended asphalt. Still, formation of new compounds in sulfur-bitumen systems depends on many factors, including mixture and thermal conditions. In the present work we have carried out both experimental and theoretical examination of the specific sulfur-bitumen binder made of grade 60/90 petroleum bitumen and technical sulfur at temperatures that are typical for ordinary asphalt concrete technology. The obtained results indicate that there is no noticeable formation of new chemical products in sulfur-bitumen melts at temperatures below 145 °C. Sulfur is partially dissolved in bitumen during the technological operations; the limiting concentration of dissolved sulfur is near 10%. Later in the course of cooling, the crystallization of the sulfur takes place, accompanied with formation of a separate solid phase.

Characteristics and Preparation Method of Sulfur Extended Asphalt Mixtures

Huge amount of sulfur production as a side product in petrochemical industries and its low application in country has been a challenging issue. In this paper, application of sulfur as a partial substitute for bitumen in process of asphalt mixture production is investigated. According to the results, the characteristics of the sulfur extended asphalt in comparison with the conventional asphalt made from pure bitumen, and the impact of sulfur addition on asphalt performance are expressed and the optimized formula for making the asphalt mixture is obtained. In this content, the modified asphalt was produced in mass production scale and its performance was studied. In this paper, the method of sulfur addition to pure bitumen and then its mixture with aggregate and finally optimized condition of sulfur modified asphalt production regarding pollution and environmental issues are also proposed.

Sulfur-Extended High-Performance Green Paving Materials

Currently, there is a strong need of high-performance and environment-friendly paving materials in Russian Federation. Sulfur dumps near the oil industry enterprises consumes area which otherwise could be occupied by vegetation, contributing to the improvement of the environmental situation. Incorporation of sulfur in bulk building materials contributes to decrease of load to the environment. The results of numerous studies of sulfur-extended asphalt concretes are summarized in the present work. For the suppression of hydrogen sulfide and sulfur dioxide we propose to use the complex nanoscale modifier. The application of such modifier leads to several positive effects. Both amount of sulfur in constructional mix and mobility of the mix can be increased. The values of operational properties, notably compressive strength and resistance to rutting, can also be increased. Due to consumption of industrial by-product, the environmental load decreases in regions near the oil and gas industry enterprises.

The Research on SEAM Modified Asphalt under Low Temperature

Sulfur Extended Asphalt Modified (SEAM) is a newly developed asphalt modifier. The principal purpose of this paper is to study the performance of SEAM modified asphalt under the low temperature. Through the Low-temperature splitting test and the Low-temperature bending test .It indicated that the SEAM enhances the performance of asphalt under the low temperature.