Rheometer Test Research Articles

Physicochemical properties of enzymatic hydrolysis lignin-modified bitumen and its modification mechanism

ABSTRACT Enzymatic hydrolysis lignin (EHL) is a renewable, inexpensive and widely available biomass resource, which has great potentials in improving service performance of bituminous pavement. To develop EHL-modified bitumen and to reveal modification and anti-ageing mechanisms of EHL on bitumen, the impacts of EHL on basic performance, rheological property, micromorphology, chemical compositions, molecular weight distributions and thermal decomposition behaviors of bitumen were studied using basic property tests, dynamic shear rheometer (DSR) test, bending beam rheometer (BBR) test, environmental scanning electron microscope (ESEM) test, Fourier transform infrared spectrometry (FTIR) test, gel permeation chromatography (GPC) test and thermal gravimetric analyzer (TG) test. Results show that bituminous ductility and penetration are decreased, but bituminous viscosity and softening point are increased. Bituminous deformation resistance is improved by EHL. Bituminous cracking resistance is decreased slightly by EHL. Also, the compatibility between EHL and bitumen is satisfactory. Bituminous ageing is delayed owing to abundant phenol hydroxyl groups in EHL, which capture active free radicals produced in bituminous ageing process. Moreover, EHL cross-links with asphaltene to form macromolecular network structures to lower bituminous temperature sensitivity. Finally, EHL dosage of 8% is proposed to prepare EHL-modified bitumen, which effectively reduces energy consumption and increases ecological benefits.

A novel method for determining the wax precipitation temperature in wax-based warm mix asphalt

ABSTRACT To accurately determine the wax precipitation temperature (WPT) of wax-based warm mix asphalt binder, a novel algorithm for WPT calculation was proposed, and the process of wax precipitation in asphalt, as well as the effects of aging, cooling rate, and shear rate on wax precipitation characteristics, were investigated through dynamic shear rheometer (DSR) tests and polarised light microscopy (PLM) experiments. The research findings reveal the following: The refined WPT algorithm exhibits heightened precision compared to the traditional viscosity method, showcasing superior reproducibility and mitigating human-induced errors. During the cooling process, wax molecules become oversaturated, leading to the precipitation of wax crystals and the transformation of asphalt into a solid–liquid two-phase system. The aging of asphalt causes changes in its composition, shifting the phase equilibrium towards favouring wax precipitation. The WPT of asphalt is also influenced by the cooling rate and shear rate, and a larger cooling rate and shear rate will reduce the WPT. Wax crystals are less numerous and more regular in shape at low cooling rates.

A Microsphere-Based Rubber Curing Model for Tire Production Simulation

ABSTRACT In this contribution, a constitutive model for rubber is presented that describes the material in its unvulcanized and vulcanized state as well as during its phase transition. The model is based on the microsphere approach to represent the three-dimensional macroscopic behavior by a set of one-dimensional microscopic chains. When the uncured rubber is exposed to large temperature, the polymer chains build-up crosslinks among each other and the material changes its properties from soft viscoplastic to stiffer viscoelastic behavior. The state of cure over time at different temperatures is identified via a moving die rheometer (MDR) test. Based on this experimental data, a kinetic model is fitted to represent the state of cure in the simulation. The material model changes from the description of an unvulcanized state to a vulcanized state based on the current degree of cure in a thermomechanically consistent manner and fulfills the second law of thermodynamics. The curing model framework is suitable to combine any given material models for uncured and cured rubber. The presented material formulation is applied to an axisymmetric tire production simulation. Therefore, the kinetic state of cure approach is fitted to MDR experimental data. The uncured and cured material model parameters are fitted separately to experiments by a gradient based fitting procedure. The in-molding and curing process of a tire production is simulated by a finite element approach. Subsequently, the simulated footprint of the tire is compared to experimental results. It can be shown that the quality of the footprint could be optimized solely by changing the shape of the green tire.

Rheological and anti-moisture characteristics of rubberized reclaimed asphalt pavement with interfacial bond behavior

The application of recycled materials in terms of reclaimed asphalt pavement (RAP) and crumb rubber, as an environmental-friendly and sustainable strategy, has become an important topic in the pursuit of long-term growth in the pavement construction field. However, the interfacial bonding behaviors of rubberized reclaimed asphalt were still ambiguous, causing the deteriorated life-performance of pavement. This study analyzed the interfacial bonding characteristics of various rubberized RAP binders with binder bond strength (BBS) test, in terms of two crumb rubber with different mesh sizes and contents, and two RAP sources with different age levels and contents. The high-temperature rheological properties were evaluated through Dynamic Shear Rheometer (DSR) test. Additionally, softening point test was also adopted to characterize the high-temperature performances. Moreover, comprehensive mechanical performance tests, including Hamburg wheel track (HWT) test, water boiling test for visual interpretation and indirect tensile strength (ITS) test were conducted to assess the feasibility of rubberized RAP mixture as pavement construction materials. It was reported that the PG temperature of asphalt was increased from 73rom ed thand the stripping of mixture under moisture reduced from 11.98% to 9.20% at least. Finally, a surface interaction model of rubberized RAP binder with colloid structure and statistical analysis were established. This research demonstrated that the reuse of end-of-life materials in pavement was feasible and provided comparable service performance. The surface interpretation with the light components trapping within gel-phase of rubber and the chemical composition oxidization of RAP would ultimately affect the bonding characteristics and properties of rubberized RAP materials, whose interfacial bond mechanism was recommended investigation before application.

Buildability assessment of mortar with fine recycled aggregates for 3D printing

In this paper, the buildability of a mortar incorporated with fine recycled concrete aggregates (recycled sand) for the purpose of 3D printing has been assessed according to the bi-linear thixotropy model. The natural sand from a reference, rheology based mortar for 3D printing, is gradually replaced with recycled sand using replacement rates of 25, 50 and 100 vol%. For each mixture, stress growth tests are performed at resting intervals of 0, 10, 20, 30, 40, 50, 60, 90 and 120 s to determine the re-flocculation rate (Rthix) of the 3D printing concrete. In addition, the flowability, rheology and initial setting time of the mixtures are measured with slump flow tests, stress-growth tests using a rheometer and Vicat tests. The results show that mortar with recycled sand is less flowable and has shorter initial setting time compared to the reference mortar for 3D printing. In addition, it is found that recycled sand improves the static yield stress evolution with time of the mixtures which improves the buildability. With recycled sand replacement rates of 25 and 50 vol%, the buildability of the mortar mixture increases respectively 33% and 83%.

Upscaling of a Mechanochemical Devulcanization Process for EPDM Rubber Waste from a Batch to a Continuous System

The present work is a comparative study of the effects of mechanical shear, temperature, and concentration of a chemical agent on the devulcanization process of post-industrial ethylene propylene diene (EPDM) rubber waste. Devulcanization was carried out in a heating press (no shear), an internal mixer (low shear), and a co-rotating twin screw extruder (high shear) at temperatures ranging from 100 to 200 °C. The efficiency of pure dibenzamido diphenyl disulfide (DBD) and a commercial devulcanizing agent, Struktol A89®, containing DBD were studied. Based on the results, the devulcanization process was upscaled from 40 g per batch to a continuous process with a capacity of 270 g/h. The parameters were fine-tuned regarding flow rate, screw speed, and temperature. Blends of virgin rubber (VR) and 25, 50, and 75 wt% recyclates were compared with blends of VR and 25, 50, and 75 wt% of untreated RWP. The quality of the recyclate was determined by rheometer tests, SEM images, TGA, and mechanical properties. The best results were obtained with 2 wt% DBD in the extruder with a temperature profile of 120 to 80 °C, 50 rpm, and 4.5 g per minute (gpm). The tensile strength and strain at break of the recyclate already met the requirements of DIN EN 681-1:2006 for the production of sealing systems. The compression set and Shore A hardness were restored by mixing recyclate with 25 wt% VR.

Effect of Nano-Cobalt Oxide on the Rheological Behavior of Asphalt Binder and Mechanical Characteristics of Hot Mix Asphalt

In this study, the effects of nano-cobalt oxide (nano-CoO) (1 and 2% by asphalt binder weight) on the rheological behavior of the asphalt binder and mechanical characteristics of asphalt mixtures were examined. To evaluate the behavior of the asphalt binder at moderate and high temperatures, the dynamic shear rheometer (DSR) test was used. Besides, to study asphalt mixtures’ rutting potential and fatigue cracking, the repeated load axial (RLA) test and the indirect tensile fatigue test (ITFT) were conducted, respectively. Based on the rheological tests, adding 1 and 2% of nano-CoO to asphalt binder increases the complex modulus (G∗) and reduces the phase angle (δ) at high temperatures and significantly improves the modified asphalt binder’s rutting parameter. Also, at moderate temperatures, the addition of nano-CoO reduced the fatigue parameter of the modified asphalt binder compared to the control asphalt binder. It was demonstrated that the permanent strain of the modified specimens was decreased by about 35% compared to that of the control specimens. The fatigue tests at two temperatures and five stress levels also showed that incorporating nano-CoO significantly increased (about 90%) the fatigue life of modified samples compared to controlled samples.

Investigations on the rheological and swelling-degradation behavior of crumb rubber within the bituminous matrix

This paper focuses on the rheological and swelling-degradation behavior of crumb rubber within the bituminous matrix. Three different penetration-grade asphalts were modified by crumb rubber in a four-paddle mixer at various curing times and treatment temperatures. Rotational viscosity, dynamic shear rheometer, solubility and gel permeation chromatography tests were conducted to evaluate the viscosity, rheological property, crumb rubber solubility and molecular weight distribution of the rubber-modified asphalts, respectively. Moreover, the microstructure of the rubber-modified asphalts was characterized by fluorescence microscopy and Fourier transform infrared spectroscopy tests. The results reveal that the viscosity and complex modulus of the rubber-modified asphalts decrease and the infiltrating ability of crumb rubber within the bituminous matrix increases with increasing treatment temperature (or curing time). However, serious degradation of crumb rubber and asphalt ageing happen with the increased treatment temperature or prolonged curing time, which causes a noticeable increase in viscosity and stiffness. The increase in asphaltenes content within the bituminous matrix causes an enhancement in viscosity and complex modulus, and releases of the large (or medium) molecules, improving rutting deformation resistance. There is no obvious difference in small molecules, illustrating that asphalt type does not affect the distribution of small molecular size. When the treatment temperature increases from 200 °C to 220 °C, the curing time required to achieve 60 % solubility of crumb rubber in asphalt X is from 25 h to 15 h, which indicates that the higher the treatment temperature, the shorter the curing time required to reach the maximum solubility. Moreover, the swollen crumb rubber molecules are degraded into some small molecule substances dissolving into asphalt binder for modification. It makes the adsorption peaks of typical function groups increase significantly. The outputs from this study can provide the guidance for the selection of preparation conditions and asphalt binders that fabricate the rubber-modified asphalt with desired properties.

Factors Influencing the Low-Temperature Properties of Styrene-Butadiene-Styrene Modified Asphalt Based on Orthogonal Tests.

Styrene-butadiene-styrene (SBS) is widely used in asphalt modification to obtain superior high-temperature performance. Nevertheless, studies on the low-temperature properties of SBS-modified asphalt are not satisfactory. Orthogonal tests are valid in analysing the results. In this paper, the main factors (SBS content, sulfur content, and the addition of rubber processing oil) for improving the low-temperature performance of SBS-modified asphalt were analyzed base on the orthogonal tests. Firstly, the frequency sweep test, bending beam rheometer (BBR) test, and force-ductility test were conducted to evaluate the low-temperature properties of SBS-modified asphalt. Investigation of low-temperature parameters obtained through these tests was conducted base on the orthogonal analysis method. The G-R parameter was abandoned in the analysis of the orthogonal method for the result that the increase of SBS content was negative to the low-temperature properties by the Glover-Rowe (G-R) parameter, which were contrary to the results of BBR and force-ductility tests. Moreover, the other parameters (ΔTc and toughness) sorted according to the orthogonal analysis method indicated the effect on low-temperature performance of the SBS-modified asphalt as SBS content > rubber processing oil > sulfur. As shown above that both SBS and rubber processing oil play a critical role in improving the low-temperature properties of SBS-modified asphalt, for SBS could resist the generation and subsequent propagation of cracks while the rubber processing oil could supplement the maltene loss.

Investigating the Rheological Properties of Styrene-Butadiene-Styrene-Based High-Viscosity Modified Asphalt Using Carbon Nanotubes

Styrene-butadiene-styrene (SBS) is currently the most widely used asphalt modifier. However, high-SBS-concentration high-viscosity modified asphalts (HVMA) are characterized by poor flow and storage instability. To make up for the lack of performance of traditional SBS-HVMA, a nano-based high-viscosity composite modified asphalt with excellent performance was developed. Since carbon nanotubes (CNTs) are nanomaterials, they are prone to agglomeration when added to the modified asphalt, and the dispersion effect is poor, which affects the modifier’s contribution rate. To better disperse CNTs in the modified asphalt, the nanomaterials were modified, and two new CNT additives were prepared by combining two polymers with CNTs. The appropriate ratio of these two new additives was selected to be further combined with SBS to obtain CNTs/SBS-HVMA. The flow characteristics and anti-aging properties of the three kinds of bitumen in different temperature ranges were studied by taking the common SBS-HVMA and Tafpack super (TPS) high-viscosity modified asphalts (TPS/SBS-HVMA) as comparison samples and by evaluating the road performance of a stone mastic asphalt (SMA-13) mixture. The storage stability, workable performance, rheological characteristics, and aging resistance of three high-viscosity asphalts were analyzed through a segregation test, dynamic viscosity analysis, Brookfield viscosity measurements, bending beam rheometer (BBR) tests, dynamic shear rheometer (DSR), and multiple stress creep recovery (MSCR) before and after short-term aging. The experimental results showed that CNT/SBS-HVMA exhibited good storage stability and workability. DSR measurements and other rheological tests revealed that TPS/SBS-HVMA had higher low-temperature flexibility than the other modified asphalts, while CNT/SBS-HVMA exhibited good high-temperature resistance, aging resistance, and deformation resistance. Through the verification of asphalt mixture performance, it was found that the high-temperature rutting resistance of CNTs/SBS-HVMA prepared by new CNT additives was 7% and 28% higher than those of SBS-HVMA and TPS/SBS-HVMA, respectively, but the low-temperature performance of CNT/SBS-HVMA was 5% lower than that of SBS-HVMA. This showed that CNT/SBS addition improved the high-temperature performance of the asphalt without a significant negative impact on the low-temperature performance of the asphalt.

Validation of empirical changes to asphalt specifications based on phase angle and relaxation properties using data from a northern Ontario, Canada pavement trial

Polymer modified asphalt is generally accepted to provide positive benefit/cost outcomes in terms of extending pavement service life. It has recently been claimed that higher modification levels perform better. A 13-year-old pavement trial in Ontario, Canada is providing valuable insights on this issue. Dynamic shear rheometer (DSR) tests were conducted to monitor rheological changes upon oxidative aging. Gelled binders exhibit more solid-like response leading to less ability to relax thermal stress, and hence an accelerated decay in performance. This was further verified from relaxation spectra calculated from stress relaxation data. A test section constructed with a gel-type binder containing 7 % styrene-butadiene-styrene (SBS) modifier has a predicted service life of 23 years, nearly the same as the control which was tainted with recycled engine oil bottoms (REOB). In contrast, sol-type 3.5 % SBS modified binder and straight-run Cold Lake asphalt binder are expected to last around 60 % longer at 36 and 38 years, respectively. Conclusions from this study reiterate that current specifications fail to correlate with field performance. Improved binder grading is possible by limiting the slope of the phase angle master curve between 30° and 45°.

Modification and enhancing effect of SPUA material on asphalt binder: A study of viscoelastic properties and microstructure characterization

In order to significantly improve the viscoelasticity and durability of asphalt materials, Spray polyurea (SPUA) resin modified materials with different particle sizes were obtained by low-temperature fine grinding process in this study, and the corresponding SPUA modified asphalt was prepared. The basic properties of resin modified asphalt were compared and analyzed. The influence of SPUA resin modification materials on the apparent viscosity of asphalt was analyzed. Through dynamic shear rheometer (DSR) and bending beam rheometer (BBR) test, the effect of SPUA resin material on rheological properties of asphalt was systematically investigated. Furthermore, the modifier and asphalt binder were characterized by scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). Results show that decreasing the particle size or increasing the dosage of the SPUA modifier could improve the softening point and apparent viscosity and reduce the ductility, which indicate SPUA modifier could improve the high temperature shear resistance and elastic recovery performance of asphalt binder. The SPUA modifier with smaller particle size has better high temperature rheological modification effect and less negative effect on low temperature performance deterioration. Although part of the functional spherical structure was damaged, the 0.075 mm SPUA modifier could closely interact with the base asphalt perfectly. This study would provide the scientific references for the application of Spray polyurea resin materials in the field of asphalt pavement materials.

Investigation on storage stability and rheological properties of environment-friendly devulcanized rubber modified asphalt

The application of conventional rubber modified asphalt was limited to its high viscosity, poor storage stability, and environmental pollution. This study proposed a preparation process of environment-friendly devulcanized rubber modified asphalt (DRMA) with superior performance. The storage stability and rheological properties of base asphalt, rubber modified asphalt (RMA), and DRMA with different modifier content were evaluated by segregation test, frequency scanning test, multiple stress creep recovery test (MSCR), linear amplitude scanning (LAS) test, and bending beam rheometer (BBR) test. Modification mechanisms of DRMA were detected by scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), and four-component analysis. Test results indicated that interaction between crumb rubber and asphalt was mainly physical and has slight chemical reaction. The swelling process of devulcanized rubber (DVR) was adequate and absorbs more light components, which was crucial to improve rheological properties. The storage stability of DRMA was less susceptible to the content of DVR. Besides the crack resistance of DRMA with 18% DVR dosage, the storage stability, high-temperature performance, fatigue resistance, and low-temperature performance of DRMA were markedly superior to that of RMA if the modifier dosage is the same. The rutting and fatigue resistance of RMA was reinforced and then weakened slightly with the increase of CR content, while that of DRMA was enhanced continuously, implying that more waste crumb rubber can be added to asphalt after devulcanization. DRMA was expected to be widely applied owing to its superior performance and environmental features.

Performance evaluation of aged asphalt rejuvenated with various bio-oils based on rheological property index

This study examines the performance of aged asphalt rejuvenated with various bio-oils based on rheological properties and rejuvenation mechanism. Castor oil, gutter oil, soybean oil, straw oil, and vegetable oil were chosen to explore the effects of bio-oils characteristics on the rejuvenated asphalt properties. The contents of each kind of bio-oil were set at 3%, 6%, 9%, and 12%. The high-speed shear apparatus was first used to prepare the aged asphalt rejuvenated with the bio-oils. The temperature sweep (TS) test was used to evaluate the high-temperature permanent deformation resistance of rejuvenated asphalt, and then its high-temperature elastic resilience was measured by using the multiple stress creep recovery (MSCR) test. The rutting and low-temperature crack resistances of aged asphalt rejuvenated with bio-oils were later evaluated by utilizing the frequency sweep (FS) and bending beam rheometer (BBR) tests, respectively. Finally, the functional groups of asphalt before and after regeneration were observed by conducting Fourier transform infrared reflection (FTIR) test, and the relationship between the chemical components of bio-oils and rheological property index of aged asphalt rejuvenated with bio-oils was analyzed by carrying out gas chromatography-mass spectrometry (GC-MS). The results showed that gutter oil and vegetable oil had an apparently adverse influence on G*/sinδ of aged asphalt. Castor oil, soybean oil, and straw oil better improved the recovery rate of aged asphalt, reduced its non-recoverable creep compliance, and effectively enhanced elastic resilience and resistance to its permanent deformation. Gutter oil and vegetable oil made aged asphalt have better low-frequency sensitivity, and most favorable influenced on the crack resistance; The recommended contents of castor oil, gutter oil, soybean oil, straw oil, and vegetable oil were 6.21%∼6.75%, 4.50%∼4.58%, 5.84%∼6.05%, 6.31%∼6.55%, and 5.17%∼5.68%, respectively. The rejuvenation of aged asphalt by adding bio-oils was a physical process; From the perspective of bio-oil composition, it is meaningful to compare and analyze other indexes to scientifically evaluate the extent of rejuvenation.

Evaluation of the field-aged performance of foamed warm mix asphalt: Comparisons with hot mix asphalt

The foamed warm mix asphalt (FWMA) has been widely used as a sustainable construction technique in pavement engineering, yet has not yet been fully studied for its aging performance or durability. Here we aim to examine and evaluate the performance variation characteristic of FWMA compared with conventional hot mix asphalt (HMA) under long-term service conditions. The performance evolution of FWMA core samples drilled from four highways was compared to that of ordinary HMA, which was simultaneously constructed. Fourier transform infrared (FTIR), dynamic shear rheology (DSR), and bending beam rheometer (BBR) tests were respectively performed to evaluate the aging degree, high-temperature, and low-temperature rheological characteristics. The results demonstrated that the aging resistance of foamed WMA was slightly diminished under construction conditions with no temperature reduction. With increased service time, the rheological characteristics of FWMA were enhanced at high temperatures, while deteriorated at low temperatures. The foaming water and service time were primary determinants of the aging as well as high and low-temperature rheological properties of FWMA without temperature construction reduction. Additionally, the aging degree of FWMA under short-term and long-term service was smaller than HMA when the construction temperature decreased. The rheological characteristics of FWMA were inferior to those of HMA during both short-term and long-term service stages. Under conditions of temperature reduction, foaming water and mixing temperature exhibited a considerable influence on the aging and rheological properties of FWMA at high and low temperatures. Therefore, the amount of water used for foaming and the temperature of production should be strictly control in the foamed warm mix asphalt technology.

Solvent‐free synthesis of phosphate‐containing imidazole fluid for flame retardant one‐component epoxy resin with long pot life, low curing temperature and fast curing rate

AbstractThe design of flame retardant one‐component epoxy resin (EP) with long pot life, low curing temperature and fast curing rate has been challenging in the industry. Herein, we synthesized a phosphate‐containing imidazole fluid (TA) as the thermal latent curing agent of EP. Based on simple structural design, TA endows EP with excellent curing properties, storage properties, and flame retardant properties. According to DSC results, EP/TA systems exhibit low curing temperature and fast curing rate during operation. The rotary rheometer test confirms that the viscosity curve of EP/TA system maintains long‐term stability at 40°C. The X‐ray photoelectron spectroscopy (XPS) data reveals that TA releases imidazole intermediates and phosphorous compounds during curing. The former provides conditions for fast curing of EP, while the latter gives EP intrinsic flame retardant properties. With the addition of 20 wt.% TA, EP/TA‐4 achieves UL‐94 V‐0 rating and 28.5% of LOI value. The study of flame retardant mechanism shows that the flame retardancy of TA mainly comes from the protective effect of phosphorus‐rich char layer, the dilution effect of non‐combustible gas and quenching effect of phosphorous compound. Besides, due to no solvent involved, the synthesis strategy of TA is environmentally friendly, showing a great potential of industrial application.

A comparative study of the effects of calcium alginate capsules on self-healing properties of base and SBS modified asphalt mixtures

Calcium alginate capsules can gradually release healing agent and heal cracks in asphalt mixtures under vehicle loading. However, the current research is focusing on how calcium alginate capsules affect the self-healing abilities of base asphalt mixtures. It is still unclear whether calcium alginate capsules can be utilized to rejuvenate and heal SBS modified asphalt mixture. Through a three-point bending (3 PB)-cyclic compression loading-3 PB test, the effects of calcium alginate capsules on the self-healing characteristics of base and SBS modified asphalt mixtures were examined and compared in this study. Fourier transform infrared spectroscopy (FTIR) and dynamic shear rheometer (DSR) tests were conducted on extracted asphalt binders to study the release behaviors of the capsules within different asphalt mixtures and their regeneration effects on the asphalt binders. The findings demonstrate that under cyclic compression loading, calcium alginate capsules can greatly enhance the strength recovery ratios of base and SBS modified asphalt concretes. The capsules in SBS modified asphalt concrete released the oil more rapidly than in base asphalt concrete probably due to the higher mixing temperature. Both the base and SBS modified asphalts can be rejuvenated by the oil released from the capsules. However, SBS modified asphalt concrete containing the capsules showed lower strength recovery ratios than base asphalt concrete due to lower flow ability of SBS modified asphalt and incapacity of the capsules to repair the broken SBS polymer network.

Research on the Interaction Capability and Microscopic Interfacial Mechanism between Asphalt-Binder and Steel Slag Aggregate-Filler

To explore the applicability of steel slag porous asphalt mixture, the interaction capability and microscopic interfacial mechanism between asphalt-binder and steel slag aggregate-filler were investigated in this laboratory study. These objectives were accomplished by comparing and analyzing the differences between steel slag and basalt aggregates in interacting with the asphalt-binder. The study methodology involved preparing basalt and steel slag asphalt mortar to evaluate the penetration, ductility, softening point, toughness, and tenacity. Thereafter, the interaction capability between the asphalt-binder and aggregates was characterized using the interaction parameters of the asphalt mortar obtained from dynamic shear rheometer (DSR) testing. For studying the functional groups and chemical bonding of the asphalt mortar, the Fourier Transform infrared (FTIR) spectrometer was used, whilst the interfacial bonding between the asphalt-binder and aggregates was analyzed using the scanning electron microscope (SEM). The corresponding test results indicated that the physical and rheological properties of the two asphalt mortars were similar. However, whilst the FTIR analysis indicated domination through chemical reactions, the interaction capability and interfacial bonding between the asphalt-binder and steel slag aggregates exhibited superiority over that between the asphalt-binder and basalt aggregates, with pronounced adsorption peaks appearing in the steel slag asphalt mortar spectrum. On the other hand, the SEM test revealed that, compared with the basalt, the micro-interfacial phases between the steel slag and asphalt-binder were more continuous and uniform, which could potentially enhance the interfacial bond strength between the asphalt-binder and aggregates (filler).

Mechanism of multilayer graphene nanoplatelets and its effects on the rheological properties and thermal stability of styrene–butadiene–styrene modified asphalt

Multilayer graphene nanoplatelets (GNPs) have the potential to become the next generation of asphalt modifiers for developing sustainable asphalt pavements. This study investigated the reaction mechanism, high-temperature rheological properties, and thermal stability of styrene–butadiene–styrene (SBS) asphalt modified with GNPs. The GNP-modified asphalts were prepared by incorporating 0.5, 1.0, 1.5, and 2.0 wt% GNPs into SBS asphalt. X-ray diffraction, Fourier-transform infrared spectroscopy, fluorescence microscopy, and atomic force microscopy were employed to investigate the interaction mechanism between GNPs and SBS asphalt, and the high-temperature rheological properties were systematically evaluated using dynamic shear rheometer tests. Saturate, aromatic, resin, and asphaltene (SARA) analysis was applied to investigate the fraction variation after incorporating the GNPs into the SBS asphalt, and grey relational analysis was performed to determine the relationship between the SARA fractions and rheological properties. Thermogravimetric analysis–differential scanning calorimetry experiments were conducted to characterize the heat absorption, specific heat capacity, combustion characteristics, and kinetic parameters of the GNP-modified asphalt. The asphalt molecules were intercalated between the GNPs sheets. The addition of GNPs promoted the development of a polymer-rich phase in the SBS asphalt and a stable three-dimensional network, which hindered the migration of particles at high temperatures. The GNPs improved the rheological properties of the asphalt and produced a more elastic response. Furthermore, the GNPs reduced the combustion intensity and stability of SBS asphalt by up to 12.6 % and 15 %, respectively. The specific heat capacity increased by 10.8 %–174.8 %, and the heat absorption decreased by 49.6 %–75.87 %. By reducing the energy of the system, GNPs decrease the degree of disorder. The highest activation energy and enthalpy were 102.83 and 96.72 kJ mol −1 , respectively, and the Gibbs free energy decreased by 39.7 % at a GNP content of 1.5 wt%. However, excessive GNPs may lead to agglomeration and uneven dispersion in SBS asphalt. • The multilayer graphene nanoplatelets (GNPs) was used to modify SBS asphalt. • Compatibility between SBS asphalt and GNPs was good due to formation of intercalated structure. • GNPs can improve the elastic response and rutting resistance at high temperature. • Enthalpy increased by 76.6 % and entropy decreased by 39.7 % at GNPs content of 1.5 wt%. • Specific heat capacity by 174.8 % and lower the heat absorption by 75.87 % after adding 1.5 wt% GNPs.

Optimize the design by evaluating the performance of asphalt mastic reinforced with different basalt fiber lengths and contents

The excellent mechanical properties of fibers contribute to the properties of asphalt materials. However, the current research is mainly focused on fiber-modified asphalt mixtures, and there is a lack of understanding of the effect of fibers on the functions of asphalt mastics. This study aims to obtain the optimal design of basalt fiber-modified asphalt mastics based on their rheological properties. Basalt fibers with three lengths (3, 6 and 9 mm) and four proportions (0 %, 3 %, 6 % and 9 % of asphalt mass) were used in this study. Dynamic shear and bending beam rheometer tests were conducted to evaluate their rheological performance. The experimental results showed that basalt fibers enhanced the stiffness, rutting resistance and cracking potential of asphalt mastics while reducing their fatigue performance. However, the S value gradually decreased, and the m value gradually increased as the temperature was changed from −18 °C to −12 °C and then to −6°C, representing that the temperature was favorable to enhancing the low-temperature performance of asphalt mastics. Besides, an analysis of fatigue cracking results showed that the asphalt mastic materials followed a two-phase crack growth model, exhibiting identical crack initiation phases and different crack propagation behavior. Finally, a modification design with the optimal overall performance was obtained through statistical analysis: the fiber length was 6–9 mm, and the fiber content was 3 %–6%.