Amplitude Sweep Test Research Articles

Rheology and yielding transitions in mixed kaolinite/bentonite suspensions

Kaolinite suspensions are known to have quite fast settling behaviour and Newtonian character, particularly at low concentrations, due to the non-swelling nature of their constitutive particles. On the other hand, bentonite is known for its swelling and interacting nature, which leads to the formation of a network structure, even at low concentrations. Therefore, both these clays are known to have significantly different rheological fingerprint. In this study, the yielding transitions in mixed kaolinite/bentonite suspensions have been investigated by varying the kaolinite/bentonite ratio and the total solid content. The detailed rheological analysis of these suspensions was carried out using amplitude sweep tests, frequency sweep tests, stress ramp-up tests and structural recovery tests.The results showed that the kaolinite suspensions exhibited a two-step yielding behaviour in stress and amplitude sweep tests at higher solid content (≥ 35 wt%). On the other hand, the bentonite suspensions displayed a single-step yielding even at higher concentrations. In mixed kaolinite/bentonite suspensions, a clear transition between a single and two-step yielding behaviour was observed in steady and oscillatory tests as a function of kaolinite/bentonite ratio, for a particular total solid content. The structural recovery experiments showed that for mixed kaolinite/bentonite suspensions at lower total solid content, where two-step yielding was present, the structural recovery was lowest. Furthermore, these results showed that the rheological properties (i.e., moduli) of stable kaolinite/bentonite suspensions were completely recovered to their initial state, even after multiple shearing cycles. The settling column analysis displayed that a very small amount of bentonite was needed to stabilize the kaolinite suspensions, which is necessary for preparing stable clay based formulations.

Comparison and correlation of asphalt binder and mixture cracking parameters incorporating the aging effect

Cracking is one of the primary distresses in asphalt pavements, and aging can significantly affect the cracking properties of asphalt material. The primary objective of this study is to investigate comparisons and correlations between binder and mixture cracking property parameters subjected to different aging conditions, and further evaluate how these relationships would change with aging. Nine plant produced mixtures are conditioned following various conditioning protocols, and the corresponding binders are extracted and recovered from those mixtures. Mixture properties are measured from Complex Modulus (E*), Direct Tension Cyclic Fatigue (DTCF), Semi Circular Bending (SCB) and Disk-shaped Compact Tension (DCT) tests. Binder tests include Complex Shear Modulus (G*) and the Linear Amplitude Sweep (LAS) test. The binder and mixture parameters measured include thermo-rheological parameters, fatigue indices and fracture parameters. Different statistical analysis methods including the Pearson, Kendall and Hoeffding’s D analysis, and frequency curves are used to investigate the comparisons and correlations between the parameters. The results from this study indicate that while considering all the aging conditions, binder parameters evaluated generally correlate well with each other. Mixture parameters also show good correlations with the exception of the fatigue parameters. Mixture rheological and fracture parameters generally show moderate to strong correlations with all the binder parameters, while mixture fatigue parameters only show strong correlations with binder fatigue parameters. Further looking into these relationships with respect to the individual aging condition, the correlations between parameters typically are improved with increase of aging levels. In addition, the distributions of these performance parameters with aging show a close trend with change of asphalt chemical composition over time, indicating the fundamental relationship between asphalt chemistry and its engineering performance. The overall good correlations between binder and mixture parameters reinforce the concept that binders play a significant role in the cracking properties of asphalt mixtures.

The rheological characteristics of soy protein isolate-glucose conjugate gel during simulated gastrointestinal digestion

• Gels were prepared using soy protein isolate-glucose conjugates cross-linked by transglutaminase. • The mechanical properties of gels were increased by glycation with limited reaction time. • The rheological properties of SPI-glc conjugate and mixture gels after in vitro gastrointestinal digestion have been studied. • Conjugate gels had slower gastric digestion kinetics than gel prepared by SPI-glc mixture. • There were no differences in simulated intestinal digestion among SPI-glc conjugate and mixture gels. In this study, soybean protein isolate (SPI) and glucose (glc) were conjugated by wet Maillard reaction at 95 °C for 0–6 h with a mass ratio of 1:2. The degree of grafting and SDS-PAGE of SPI-conjugates were studied and a highest degree of grafting (23.14 %) was achieved at reaction time of 4 h. Gels were then prepared by crosslinking SPI-glc mixture or conjugates using transglutaminase, and their mechanical properties were charactered by hardness and gumminess. To further study the impact of conjugation on the gastrointestinal digestion of gel, rheological properties of gels after in vitro gastric and intestinal digestions were evaluated through amplitude and frequency sweep tests. Compared with SPI and SPI-glc mixture, gels formed by conjugates with 1 h and 4 h reaction time showed significantly higher viscosity, storage modulus (G') and complex modulus (G*) values after gastric digestion, indicating that these conjugate gels had slower gastric digestion kinetics. There were no significant differences among these samples in simulated intestinal digestion. Therefore, the SPI-glc conjugate gels may have great potential to be used for gastric delivery.

Use of linear amplitude sweep test as a damage tolerance or fracture test to determine the optimum content of asphalt rejuvenator

A procedure based on the linear amplitude sweep (LAS) test has been developed to determine the optimum rejuvenator content for restoring the properties of aged asphalt binders. The LAS test was employed to assess the damage tolerance, fatigue resistance, and fracture behavior of rejuvenated aged binders. In case of fracture analysis, a crack-based indicator to govern the stable crack propagation was defined to characterize fracture resistance of asphalt binders. While rejuvenators improved all of these properties, higher contents were required to restore the cracking behavior of the original binder. The linear relationship between the integrated damage-fatigue-fracture indicator and rejuvenator content was used to determine the optimum content. Unlike the similar permissible range based on restoration of the low and high-temperature performance, the LAS-based approach demonstrated superior performance of the aromatic extract rejuvenator over the waste cooking oil at higher contents.

Performance improvement and aging property of oil/SBS modified asphalt

The main objective of this work is to use the oil to improve the low- and intermediate- temperature performance of styrene–butadienestyrene (SBS) modified asphalt, and how long the benefits of adding oils can stay (aging property) was also evaluated. In this study, one bio-oil and one re-refined engine oil bottom (REOB) were selected to blend with two types of SBS modified asphalt to prepare oil/SBS modified asphalt. The performance improvement, rheological and chemical evolution upon aging process were characterized and tracked by performance grading, master curve, Linear Amplitude Sweep (LAS) test, Bending Beam Rheometer (BBR) test and Fourier Transform Infrared (FTIR) scanning, and the aging indices were calculated, subsequently. The results confirm the performance-improving effect of adding oils, while the bio-oil exhibits higher efficiency than REOB in terms of changing performance-related characteristics. BBR test results at various aging states show that the low-temperature performance mostly depended on the ability of relaxing the internal stress (m-value) other than stiffness. The addition of bio-oil was proved to have an effect of slowing down the deteriorating rate of low-temperature performance. FTIR scanning and aging indices results show that performance-related characteristics and chemical changes mostly occurred at the long-term aging period, and the oil addition would not influence the SBS degradation during aging.

Exploiting epoxidized cashew nut shell liquid as a potential bio-additive to improve asphalt binder performance

The objective of this work is to evaluate the potential of cashew nut shell liquid (CNSL) as a renewable resource and low-cost raw material for the synthesis of bio-based epoxy for asphalt binders. The epoxidized material named ECL was synthesized via chemical modifications in alkyl phenols present in CNSL – a good alternative of petrochemicals based on phenols to replace the toxic bisphenol A, currently used to synthetize epoxidized products. The additive was structurally characterized by Nuclear Magnetic Resonance (1H NMR and 13C NMR), and Fourier Transform Infrared Spectroscopy (FTIR), presenting results in accordance with the epoxidation reactions. Testing was conducted on asphalt binder with 10% and 20% of epoxidized CNSL to explore the influence of bio-epoxidized additives on the properties of binder, both unaged and RTFO-aged conditions. The Rotational Viscosity, Dynamic Shear Rheometer (DSR) and Binder bond strength (BBS) tests were utilized. The viscoelastic behaviour of epoxy modifier asphalt presented higher viscosity than neat asphalt binder. The rheological parameters from DSR showed that the epoxy modifiers enhance the elasticity of the binder, suggesting the presence of polymer elastic networks in modified binders. The rutting resistance of epoxidized modified binder at the high temperature was evaluated by Multiple Stress Creep and Recovery (MSCR) test, while the fatigue life was analysed by Linear Amplitude Sweep (LAS) test. The MSCR results indicated that the 10% of the ECL additive, increasing rutting resistance, while the LAS test showed that fatigue resistance of AB-10% ECL was positively affected by epoxidized CNSL additive. BBS results showed that the aged AB-10% ECL has the highest binder bond strength. Furthermore, the use of renewable energy resources is a strong incentive towards the development of less pollutant technologies.

Waste cathode-ray-tube glass powder modified asphalt materials: Preparation and characterization

Cathode-ray-tube (CRT) is the ingredient of glass used in obsolescent televisions or computer monitors. CRT glass contains a considerable amount of heavy metals, and the landfilling of CRT glass is significantly harmful to the environment. In an effort to recycle waste CRT glass instead of landfilling it, recycled CRT glass powders were introduced to asphalt binders as a modifier in this preliminary investigation. The recycled CRT glass was processed to a particle size smaller than 0.075 mm and mixed with asphalt binder (PG 58–28) to produce asphalt mastics with four different concentrations (0, 5, 10, and 15 wt%). The rheological performance was characterized with the rotational viscosity (RV), dynamic shear rheometer (DSR), and multiple stress creep recovery (MSCR) tests. The fatigue performance was evaluated by linear amplitude sweep (LAS) test. Meanwhile, the low-temperature properties were measured by the asphalt binder cracking device (ABCD). The hazard materials leaching test was applied to evaluate the leaching potential of lead content into the external environment due to the high lead content in the modified asphalt. The test results revealed that the increase of CRT glass powder content improved the energy of activation compared with that of virgin binder, as well as the resistance of permanent deformation. Furthermore, the incorporation of CRT glass powder may slightly increase the fatigue life of asphalt because of the improved physicochemical interaction between glass and bitumen. The low-temperature cracking temperature first decreased with the increase of CRT glass powder content and then increased as the CRT content increased further. The leaching test demonstrated that the CRT glass powders incorporated into asphalt binders represented a lower lead leaching content than that of the original CRT glass powder, where the lead leaching amount of CRT glass modified asphalt binder is obviously lower than the specified level of 5 mg/L. Therefore, it is possibly acceptable to recycle CRT glass powders in asphalt binders as an additive as an environmental-friendly recycling method, in which the optimal addition content of CRT glass powders could be up to 10% (wt.).

Use of Recycled Oils as Rejuvenators for Bituminous Binders

The addition of rejuvenators agents (RJ) into bitumen allows increasing the amount of recycled asphalt in new mixtures. In the preliminary part of this study, three different type of oils were tested as potentials RJ: a mineral oil from the automotive industry, a waste domestic cooking vegetable oil (VO), and a biodiesel. Several mixtures were prepared by adding different percentage of oils and VO was individuated as the best RJ. Therefore, VO was used in a further investigation, to better characterize the properties of the rejuvenated binder and its resistance to aging during a second life cycle. Rejuvenated binders with different oil content were prepared and evaluated. The rheological characterization included frequency sweep tests to obtain the binder master curves and linear amplitude sweep test to evaluate the cumulative damage resistance. Moreover, the molecular weight distributions of the binders were investigated by both gel permeation chromatography and rheology by application of the delta-method.

Chemo-Rheological Characterization of the Effect of Iran Rock Asphalt on the Performance of Waste Bio-Oil Modified Asphalts

This study aims to investigate the effect of Iran rock asphalt (IRA) on the rheological performance of waste bio-oil modified asphalt (WBMA). Three kinds of WBMA with bio-oil origins including soybean oil residue, castor oil residue, and waste cooking oil residue were blended with different dosages of IRA. The high-temperature performance of the three blended asphalt binders was evaluated using the temperature sweep test and multiple stress creep recovery (MSCR) test. The effect of IRA on the fatigue performance and low-temperature cracking resistance of the three WBMAs was evaluated using the linear amplitude sweep (LAS) test and the bending beam rheometer (BBR) test. A gel permeation chromatography (GPC) test was conducted to further understand the contribution of IRA to the overall rheological performance of different WBMAs. Results indicated that the high-temperature performance of the three WBMAs was enhanced significantly with the increase of IRA content. The predicted fatigue life from the LAS test showed that the incorporation of IRA extended the fatigue life of the three WBMAs at a lower strain level, while this effect was not profound at a higher strain level. Results from BBR test showed that IRA may increase the risk of low-temperature cracking and that the dosage of IRA should be limited to fulfill the requirements of the low-temperature performance. The GPC analysis revealed that the enhanced high-temperature performance and reduced low-temperature cracking resistance of WBMAs modified with IRA was mainly a result of the increased asphaltene concentration.

Key role of network formation in Rutting, fatigue and brittle performance of bitumen/PEG/MDI/SiO2 composites

The effect of hydrophilic SiO2 content on the rheological property of bitumen (B)/ polyethylene glycol (PEG)/4,4′-diphenylmethane diisocyanate (MDI)/SiO2 composite was investigated. The multiple stress creep and recovery (MSCR) and linear amplitude sweep (LAS) tests were applied to analyze the rutting resistance at high temperature and fatigue life at intermediate temperature of bitumious composites, respectively. The low temperature property was evaluated by glass transition temperature and tensile behavior. All the results suggested that the optimal SiO2 loading for modified bitumen with the best service performance was around 1%. The mechanism for these results was explored by the competitive and coupling effects of SiO2 nanoparticles networking themselves, polyurethane reaction between MDI and PEG, as well as urethane reaction between MDI and SiO2. The intrinsic nature of network structure played a key role in the performance of B/PEG/MDI/SiO2 composite.

Characterization of Fatigue Resistance of Warm Mix Binders Using Linear Amplitude Sweep Test

Fatigue failure in asphalt pavements occur due to the accumulation of damage under repeated traffic loading. Fatigue cracks generally occur within the binder phase of the asphalt mixture. Hence the specifications for properties related to fatigue resistance of asphalt binder become an important screening tool to select binders that are not inherently susceptible to fatigue under given environmental and traffic conditions. The Current Superpave Performance Grading (PG) specifications use parameter |G*|.·sinδ of asphalt binder to assess the fatigue susceptibility of asphalt mixes. These specifications do not accurately characterize the fatigue resistance of asphalt binders because |G*|.·sinδ is determined by applying a cyclic loading in the Dynamic Shear Rheometer (DSR) at a very small strain amplitude (1%). In this study, Linear Amplitude Sweep (LAS) test was considered to characterize the fatigue resistance of asphalt binders with warm mix additives. Warm mix asphalt (WMA) is a developing technology that can allow asphalt concrete to be produced at lower temperatures. This paper presents result of a study carried out to investigate the fatigue characteristics of warm-mix asphalt binders using a linear amplitude sweep test. Three warm-mix additives; Sasobit®, Evotherm™ and Rediset® are considered. Viscosity grade (VG 30), Polymer modified binder (PMB 40) and Crumb rubber modified binder (CRMB 60) were selected as base binders for this investigation. Physical and rheological tests were carried out for the characterization of these binders. The LAS test was carried out at 25 °C in a DSR, and the fatigue parameters were calculated from stress–strain plots. Test results showed that the changing trend in fatigue life of mixes is more related to the fatigue parameter Nf from LAS test than to |G*|. sinδ values of the binders. It was also observed that most of the warm mix binders have improved fatigue resistance at 25 °C in comparison to the control binders. The effect of Rediset® additive was found to be insignificant in the case of VG 30 grade binder only.

Formulation and rheology of bio-grease mixed with h-BN nanoparticles

ABSTRACT The degradation of the environment and depletion of natural resources owing to the continuous use of petroleum-based oils has made researchers to find an alternative solution to the non-sustainable lubricants. In the present study, a novel bio-grease has been prepared by mixing biodegradable oil (sesame oil) with varying concentrations of lithium stearate as a thickener. The thickener is added in different concentrations of 5, 10, and 15 wt.%. Further, the effect of h-BN on the rheological properties of novel bio-grease is investigated. The nanoparticles are added in different concentrations of 1–3 wt.%. The rheological experimentation is carried on Anton Paar Rheometer with parallel plate geometry of diameter 25 mm (PP-25). The experiments are carried out at varying shear rates (0.65 s−1 to 6.77 s−1) and temperature (30°C and 60°C). The addition of nanoparticles resulted in an increment in both viscosity and shear stress of nano grease. Viscosity and shear stress of grease is enhanced by 65% and 72% respectively at 2 wt.% nanoparticle concentration. The increase in thickener concentration also results in an increase in viscosity and shear stress of biogrease.Fromthe Amplitude Sweep test(AST), it is observed that storage modulus(Gˈ), loss modulus (G”), and yield stress of novel bio-grease increases with an increase in the h-BN concentration. An increase in nanoparticle concentration increases the resistance of grease to deformation. Similar results are obtained with an increase in thickener concentration due to dense matrix formation. This is attributed to the increase in interaction among grease fibers.

Characterization of microstructural stability of biochar-amended Planosol under conventional tillage for irrigated lowland rice ecosystem

Soil structural degradation through compression from machine and animal traffic affects soil functioning and threatens environmental sustainability. However, the structural stability of the soil against the external stresses can be enhanced through the addition of organic substances. The study aimed to investigate the efficacy of biochar addition on the microstructural stability of a Gleyic Luvic Planosol under yearly conventional tillage of rice-fallow-rice lowland ecosystem in southern Brazil. Organic amendment consisted of four levels of rice husk biochar rates namely 0 % (Bio0), 2 % (Bio2), 5 % (Bio5) and 10 % (Bio10) by dry mass, corresponding to 0, 20, 50, and 100 g biochar/kg soil. As organic matter is known to closely interact with density, we decided further to investigate the impact of varying density, namely 1.15, 1.33, 1.45, 1.60, and 1.75 g/cm3. Biochar-incubated soil samples were subjected to four levels of matric potentials (0, -3, -6, and -10 kPa). The microstructural stability parameters of strain (γ), shear resistance (τ), storage and loss moduli (G’, G’’), and coefficient of structural rigidity (Iz) of the amended soil samples were evaluated using the amplitude sweep test in a rheometer. Increasing biochar rate significantly (p < 0.05) increased the soil organic matter and, consequently, the water retention capacity of the biochar-amended Planosol. The stabilizing effect of biochar addition was reflected in higher microstructural stability of the amended soil compared to the control (no biochar). Increasing density in the biochar-amended Planosol increased the shear resistance, reduced the strain at linear viscoelasticity and yield point, and decreased the stiffness degradation. Increased strength and quantity of the menisci are the driving forces for the improved microstructural stability of the Planosol and at the nucleus of environmentally sustainable application. This is important when considering potential carbon sequestration and storage effects of biochars.

Rheological evaluation of soil aggregate microstructure and stability across a forested catena

Rheological characteristics of soils, including their deformation and flow behaviors when subjected to external stress, can provide important information on microstructural stability. In this study we used rheological measurements to examine the soil aggregate microstructure and stability of four different soil orders – Alfisol, Mollisol, Inceptisol, and Entisol – along a forested catena in Mazandaran Province, northern Iran. Amplitude sweep tests were used to quantify the initial values of the storage and loss moduli, deformation limit (when the material begins to transition from reversible to irreversible deformation), deformation at flow point (when the material becomes viscous), and integral z (which summarizes the overall visco-elasticity of the material). The deformation limit was significantly higher in subsoil layers than topsoil layers, and was also higher in the Mollisol than the other pedons. The flow point and integral z values, which relate to the structural stiffness of soil matrices, were largest in the Btg horizons of the Alfisol and Mollisol, implying that these soils had more rigid microstructures. In contrast, the Entisol Ckg horizon, which had high sand content and little soil development, had the lowest values for all properties, thus indicating a lack of micro-aggregate stability. Regression analyses revealed that integral z was influenced by soil physicochemical properties, and was higher in soils whose clay fraction was dominated by expansive clay minerals and pedogenic iron and aluminum sesquioxides. Altogether, the rheological parameters indicated that older, more developed soils had greater microstructural stability than their less developed counterparts. As a result, rheological measurements may be useful for identifying the major factors that affect soil aggregation, and can indicate the relative amount of soil development along gradients such as the studied forest catena.

A rheological and microstructural study of two-step yielding in mud samples from a port area

Natural fine-grained suspensions usually exhibit a complex rheological fingerprint – in particular a two-step yielding phenomenon – due to the presence of mineral clay particles and organic matter (often found in a flocculated state). These rheological properties may vary considerably from one location to another due to the differences in mud composition (specifically in organic matter content). In this study, the origin of this two-step yielding behaviour for natural suspensions is discussed with the help of different experimental techniques including rheology, particle sizing, rheo-optics, and video microscopy. The samples were collected from different locations in the Port of Hamburg, Germany. A rheological analysis of the samples was performed with amplitude sweep, frequency sweep, stress ramp-up and structural recovery tests. The shear-induced structural changes of mud samples was studied by using a parallel plate shearing device with a microscope. Mineral clay-organic matter flocs were studied using video microscopy to obtain the floc size, floc density and settling velocity of flocs. Higher values of rheological properties such as cross-over stress, yield stress, and moduli were observed for samples having higher organic matter content. These samples also produced the largest floc sizes. The rheo-optical analysis showed the formation of cylinder-like structures in fine-grained suspensions upon shearing action, which reflect the origin of two-step yielding behaviour in mud samples, observed in stress ramp-up and amplitude sweep tests. • Mud samples with different TOC content were analysed using rheology. • Two-step yielding was observed in mud from amplitude and stress sweep experiments. • Rheo-optical analysis showed the formation of cylinder-like structure during shearing. • Larger and porous flocs were observed for samples with higher TOC content. • This study provides a useful understanding of mud flocs during shearing.

Preparation an Optimal Hydrogel of Water Shutoff for Iranian Oil Field

Presenting a suitable hydrogel for water shutoff in Iranian oil field is based on gelation time and gel strength. Rheological behavior of gel was the main purpose of this research. To determine the gelation time, thermal stability and gel strength a plan of bottle tests were conducted by using the central composite design method with two factors. The hydrogels composed of AN125VLM and chromium triacetate as copolymer and crosslinker, respectively were recorded for 8 weeks. Furthermore, the consistency modulus of the gels was measured by amplitude sweep tests using the Paar-Physica universal spectrometer, model MCR501. A hydrogel with 26,339 ppm concentration of copolymer and 0.12 ratio of crosslinker/copolymer and also gelation time of 2 days was selected as the optimal one. Also, it showed the maximum value of consistency modulus of 31,900 Pa among the other samples, tremendously, which showed the highest resistance against external stress. To ensure the gel strength among different effective parameters on the gel in porous media, a plan of rheological experiments were carried out. A 12 Run Plackett-Burman design was used for screening the eight parameters of NaCl, CaCl2, KCl and MgCl2 concentrations, temperature, pH, sodium lactate and nanoclay while keeping the optimal hydrogel component constant. Finally, it was found that temperature was the most effective parameter to control gelation time and also pH had negligible effect on the gelation time of this optimal gel.

Experimental study on the aging behavior of modified asphalt with different types of fine solid wastes under different aging conditions

Both Fine solid wastes (FSW) and various modified asphalt have been gradually applied in road construction for sustainable development and better performance. However, when considering the aging resistance of modified asphalt, present study on the effect of FSW like red mud and diatomite on the aging behavior of asphalt mortar is poorly documented. This research utilized limestone powder (LSP), fly ash (FA), diatomite, and red mud (RM) to estimate the impacting level of FSW and aging after 0 h PAV aging, 5 h PAV aging, and 25 h PAV aging. Firstly, the variations of chemical groups of modified asphalt/mortar were analyzed by carbonyl index test. Furthermore, the low and high temperature properties of modified asphalt/mortar were investigated based on Performance Grade test (PG), Muti-Stress Creep and Recovery test (MSCR), and Low-temperature Shear Stress Relaxation tests (SSR). Additionally, Binder Bond Strength test (BBS) and Linear Amplitude Sweep test (LAS) were carried out to indicate and evaluate the change of adhesion/cohesion property and the fatigue property of modified asphalt/mortar in the aging process, respectively. The test results showed that red mud and diatomite could enhance the aging resistance of modified asphalt much better than fly ash and limestone powder. And aging resistance was the comprehensive results of oxygen permeating, diffusion, and fusion inside the asphalt mortar, adsorption of porous fillers on light components. Besides, comparing with the variation of the index of elastic damage in MSCR test, different fillers showed weak differences in high-temperature property after short-term aging in PG test. The differences of low-temperature property among the modified asphalt/mortar with different FSW were minor after 5 h PAV aging, but significant after 25 h PAV aging. And the effect of hardening asphalt and filling particle would compete and decide the fatigue property jointly.

Ageing effects on the linear and nonlinear viscoelasticity of bituminous binders

ABSTRACT The paper investigates the effects of ageing on the linear and nonlinear viscoelastic properties of bituminous binders for paving applications. Four neat binders were analysed in their unaged state and after long-term ageing, which was simulated in the laboratory with the Rolling Thin Film Oven (RTFO) and the Pressure Ageing Vessel (PAV). Amplitude sweep tests and frequency sweep tests were performed to explore the response in the linear domain. Repeated strain sweep tests were carried out to isolate nonlinearity from other mechanisms related to damage. The time–temperature superposition principle and the generalised Maxwell model with a Prony series discretization were used to describe the overall viscoelastic response of binders, introducing strain-dependent shift factors to account for nonlinearity. Results indicate that the adopted experimental and modelling approach allows a proper assessment of the effects of ageing on viscoelasticity.

Evaluation of Low- and Intermediate-Temperature Performance of Bio Oil-Modified Asphalt Binders

Fatigue cracking and low-temperature cracking are two major distresses that occur in asphalt pavements. Fatigue cracking is a load-associated distress caused by the tensile stresses at the bottom/top of the asphalt concrete (AC) layer due to repeated traffic loading. On the other hand, low-temperature cracking occurs when tensile stresses built up with in the AC layer at low temperatures exceed the tensile strength of that layer. In this study, the performance of date seeds oil bio-modified asphalt binders (DSO-BMB) is evaluated against fatigue and low-temperature cracking. The DSO-BMBs are prepared using volume ratios of 1.5, 2.5, 3.5, 4.5, and 5.5% date seeds oil-to-asphalt binder. The base asphalt binder used in the study is a 60/70-penetration grade with a Superpave performance grade (PG) of PG 64–16. The dynamic shear rheometer (DSR) standard test was used to assess the fatigue performance of the bio-modified binders (BMBs), while the bending beam rheometer (BBR) test was used to test the BMBs for low-temperature performance. In addition, the DSR linear amplitude sweep (LAS) test was used to evaluate the fatigue tolerance behavior of the DSO-BMBs. The analysis and results of the study showed that the bio-oil enhanced the low-temperature performance. The low PG grade improved from −16 °C for the control asphalt binder to −28 °C for the BMB. Additionally, the fatigue resistance of the BMBs was improved as illustrated by the damage–characteristic curves of the modified asphalt binders from the visco-elastic continuum damage (VECD) analysis and the increase in the number of cycles to fatigue failure (Nf).

Evaluating the fatigue characteristics and healing potential of asphalt binder modified with Sasobit® and polymers using linear amplitude sweep test

Sasobit® can be used not only as a warm mix additive in asphalt mixtures but also to further modify highly viscous polymer-modified asphalt (PMA) to achieve viscosity reduction, energy consumption reduction, and environmentally friendly engineering purposes. This paper demonstrates innovative research to evaluate several properties of asphalt binders modified with Sasobit® and polymers, including the exploration of the modification mechanism, fatigue damage characteristics, and healing potential at intermediate temperatures. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were conducted to explore the effectiveness of Sasobit® on the crystallization performance and chemical structure of styrene–butadienestyrene-modified asphalt (SBSMA), crumb rubber-modified asphalt (CRMA), and SBS/crumb rubber composite modified asphalt (SBS + CRMA). The accelerated fatigue approach, the linear amplitude sweep (LAS) test, was adopted to develop fatigue damage evolution of the Sasobit®/polymer-modified binders. A fatigue failure definition and the corresponding failure criteria based on the pseudo-strain energy (PSE) approach were adopted under the framework of the viscoelastic continuum damage (VECD) theoretical model. Subsequently, a healing process was extended. The LAS-based healing (LASH) step was introduced to assess the effectiveness of Sasobit® on the healing potential and fatigue life of the PMA. The XRD results suggested that Sasobit® weakened the crystallization effect of the PMA to some extent. Sasobit® affected the absorption of the polymers into the lighter components of the binder without creating new chemical components. The Sasobit® additives significantly raised the potential of PMA samples to resist fatigue failure. The LASH test results illustrated that Sasobit® increased the healing capacities of SBSMA and CRMA, but decreased the healing potential of SBS + CRMA. Furthermore, compared to the virgin binder, the Sasobit®/polymer-modified binder exhibited a weakened capacity to resist fatigue damage after short-term aging but a strengthened capability after appropriate long-term ultraviolet aging.