Sweep Test Research Articles

Characteristics of Waste Oil-rejuvenated RAP Bitumen: An Experimental Study

In recent years, Reclaimed Asphalt Pavement (RAP) has become very popular in pavement construction due to its benefits to the economy and the environment. The present study investigates the feasibility of employing Waste Cooking Oil (WCO) and Waste Engine Oil (WEO) as rejuvenators blended with reusable asphalt binder through physical and rheological properties at high and intermediate temperatures. Examined conventional properties of WCO-and WEO-modified bitumen include softening point, penetration, ductility and viscosity. In addition to these rheological properties, they also include Amplitude Sweep, Frequency Sweep, Multiple Stress Creep Recovery (MSCR), Linear Amplitude Sweep (LAS) and High-temperature Performance Grading (HTPG) tests carried out by Dynamic Shear Rheometer (DSR). The experimental outcomes revealed that both WCO and WEO could reduce deformation resistance and improve stiffness, workability and viscous behavior of aged bitumen. Moreover, the addition of waste oils improves the fatigue lives of rejuvenated bitumen and enhance fatigue cracking resistance, but at the cost of rutting resistance. Overall, WCO performs better in restoring stiff binder properties than WEO as per rheological testing. KEYWORDS: Dynamic shear rheometer (DSR), Reclaimed asphalt pavement (RAP), Rejuvenators, Waste cooking oil (WCO), Waste engine oil (WEO).

Temperature and Frequency Dependence of the Dynamic Viscoelastic Properties of Silicone Rubber.

Temperature-frequency sweep tests were performed on silicone rubber to investigate the dynamic viscoelastic properties. The test results show that the viscoelasticity of silicone rubber presents significant temperature dependence and frequency dependence. The dynamic viscoelastic test curves at different temperatures can be shifted along the logarithmic frequency coordinate axis to construct smooth master curves at the reference temperature of 20 °C, covering a frequency range of 10 decades, which indicates thermorheological simplicity on a macro level and frequency temperature equivalence of the silicone rubber material in the experimental temperature range. The van Gurp-Palmen plot and Cole-Cole plot for the test data at various temperatures merge into a common curve, which further validates thermorheological simplicity. The temperature dependent shift factors of silicone rubber material were well characterized by the Williams-Landel-Ferry equation. Moreover, the fractional-order differential Kelvin (FDK) model, the fractional-order differential Zener (FDZ) model, and the improved fractional-order differential Zener (iFDZ) model were used to model the asymmetric loss factor master curve. The result shows that the iFDZ model is in good agreement with the test results, indicating that this model is suitable for describing the asymmetry of dynamic viscoelastic properties of silicone rubber.

AGREEMENT BETWEEN FRICTION, ABRASION, AND ROLLING RESISTANCE IN SILICA-FILLED TIRE TREAD COMPOUNDS BY TUNING DEGREE OF SILANIZATION AND LOADING OF CARBON BLACK

ABSTRACT Development of green tires by using silica and silane in tread compounds has emerged as a key technology in the tire industry. One of the most important features of a green tire is its low rolling resistance; however, agreement between other performances of a tire, such as wet grip and wear, along with rolling resistance of tread compounds, is a serious challenge. Properties of tire tread compounds are very sensitive to the silanization of silica and the loading of primary and secondary fillers. This work investigates simultaneous effects of silanization of silica as the primary filler and loading of carbon black as the secondary filler. By performing dynamic-mechanical testing in strain sweep and mechanical testing of tire tread compounds, the degree of silanization of silica and loading of carbon black were tuned to make agreement between friction, abrasion, and rolling resistance of green tire tread compounds. Morphology of the filler, kinetics of vulcanization, and bound rubber content in the tread compounds were used to explain the findings. Other than dynamic-mechanical analyses to predict final performance of tread compounds, direct measurements of friction, abrasion, and rolling resistance of tread compounds showed a 43% increase in the coefficient of friction on wet concrete, a 47% increase in abrasion resistance, and a rolling resistance coefficient of approximately 6.5 by using 10 parts per hundred of rubber (phr) of bis(triethoxysilylpropyl)tetrasulfide and 10 phr of carbon black N330 as the secondary filler.

Linear Viscoelastic Limit Determination and Modeling for Binders with Physical Hardening Effects

Abstract The objective of this research is to study the limit of linear viscoelastic behavior on a common straight-run bituminous binder at different temperatures and frequencies by performing strain amplitude sweep tests. A dynamic shear rheometer was used for the experimental campaign. An increase of complex modulus due to physical hardening was observed during strain amplitude sweep tests at low temperatures and frequencies. A correction method is proposed to consider the effect of physical hardening on complex modulus when evaluating the linear viscoelastic limit.

Rheological Behaviors of Waste Polyethylene Modified Asphalt Binder: Statistical Analysis of Interlaboratory Testing Results

Abstract This article investigated the effect of waste polyethylene (PE) on the modified asphalt binders’ rheological behavior from a statistical point of view. The interlaboratory testing results from the RILEM Technical Committee 279 Valorization of Waste and Secondary Materials for Roads Task Group 1 were used for this purpose. First, an unaged 70/100 penetration graded neat binder was selected as the reference material. Next, a single 5 % content of waste PE additives (PE-pellets and PE-shreds) was mixed with a 95 % neat binder to prepare two PE modified binders. Then, dynamic shear rheometer–based temperature-frequency sweep tests were performed over a wide range of temperatures and frequencies to evaluate the rheological properties of these three binders. Different rheological behaviors were observed in the isochronal plots at high temperatures. Based on a reproducibility precision requirement proposed for phase angle, 28°C was set as the transition temperature across the rheological behaviors. Next, according to the three rheological behaviors defined in a previous study by the authors, statistical analysis was introduced to identify sensitive rheological parameters and determine the thresholds. Results indicate that the phase angle measured above 28°C and 1.59 Hz can be used as a sensitive parameter to discriminate the three rheological behaviors of PE modified binders. The thresholds among different behaviors were also calculated as an example for phase angle measured at the highest common testing temperature of 70°C. Additional experimental evaluations on more types of PE modified binders, especially at intermediate and high temperatures, are recommended to better understand their influence on the rheological behavior of PE modified binders.

Effect of Long-Term Aging on Fatigue and Thermal Cracking Performance of Polyphosphoric Acid and Styrene-Butadiene-Styrene-Modified Bio-Blend Bitumen.

Polyphosphoric acid (PPA) and styrene-butadiene-styrene (SBS) were adopted to produce PPA-SBS-modified bio-blend bitumen, which achieved excellent mechanical performance. However, its long-range performance, such as the fatigue and thermal cracking behavior under long-term thermal oxidation, is not well understood. Therefore, a pressure aging vessel (PAV) system was applied to simulate the aging behavior of the bitumen under the action of thermal oxidation. Then, a linear amplitude sweep (LAS) test combined with a viscoelastic continuum damage (VECD) model was applied to investigate the fatigue properties of the bitumen. Moreover, a bending beam rheometer (BBR) test was conducted to evaluate the thermal cracking resistance of the bitumen before and after PAV aging. Meanwhile, an atomic force microscope (AFM) was applied to observe the microscopic topography. The results show that the original compound-modified bitumen can bear more fatigue damage than that of the control bitumen at the failure point, and it also has excellent fatigue resistance at 2.5%, 5%, 7.5%, and 10% applied strain. Moreover, the VECD model can accurately predict the fatigue life of the bitumen under different applied strains. The variation ratio of stiffness modulus for the compound-modified bitumen is below that of the control bitumen after PAV aging, so it shows a better anti-aging performance. Finally, the AFM test shows that PPA and bio-bitumen decrease the heterogeneity of the bitumen, reducing the difference between phases.

Gelling and rheological properties of a polysaccharide extracted from Ocimum album L. seed

In this study, a new polysaccharide was isolated from Ocimum album L. seed (OA), and its physicochemical and rheological properties were investigated. Ocimum album polysaccharide (OAP) was an acidic heteropolysaccharide with a molecular weight of 1935 kDa, and it was composed of five types of sugars: mannose (32.95 %), glucose (27.57 %), galactose (19.29 %), rhamnose, (15.96 %) and galacturonic acid (4.23 %). According to the results obtained from Huggins and Kraemer equations, the intrinsic viscosity was 6.9 dL/g in distilled water. The OAP solutions at a concentration between 0.1 and 1.5 %, showed shear-thinning behavior, and the Herschel–Bulkley and Cross models exhibited a high ability to describe the flow behavior of OAP solutions. The apparent viscosity of 1 % OAP solution was decreased in the presence of different concentrations of NaCl (0.1, 0.3, and 0.5 M), at different pHs (3−11), and in temperatures between 5 and 100 °C. Also, the pseudoplastic behavior was observed in all samples. In OAP solutions (0.1–1.5 %), the up and down curves in the shear stress-shear rate diagram did not coincide, which indicated time-dependent (thixotropic) behavior. Although, the thixotropic properties of 1 % OAP solution were weakened with adding NaCl (0.1–0.5 M) and at different pH (3–11). The results obtained from the dynamic oscillatory test showed that the OAP solutions at concentrations higher than 0.1 % had a gel-like behavior, and the viscoelastic moduli (G′ and G″) were weakened in the presence of salt and with a change in pH. Also, in the temperature sweep test, the 1 % solution showed the behavior of thermally irreversible gels.

Effect of Atmospheric Pressure Argon Plasma on Physicochemical, Structural and Rheological Properties of Sorghum Starch

AbstractNonthermal plasma is a physical method of starch modification. In this study, sorghum starch is subjected to dielectric barrier discharge (DBD) argon plasma at voltage levels of 21 and 29 kV for 1, 10, and 20 min. Plasma etching creates more pores on the surface of starch granules. Fourier transform infrared spectroscopy shows that low intensity of plasma causes crosslinking of starch molecules, while longer time or higher voltage suppresses crosslinking and increases depolymerization. The plasma treatment of starch for 1 min decreases the clarity, while an increase in the time or voltage rises clarity. The swelling power of treated starch is higher than that of untreated one. By an increase in time or voltage, the solubility of untreated starch (16.95%) increases (up to 33.47%). After 1 min of treating starch, the viscosities of the paste increases, but then decreases with increases in voltage or time. According to the frequency sweep test, the gels of 1–21, 10–21, and 1–29 samples are stronger than those of the other samples and have greater complex viscosities than them. It can be concluded that DBD argon plasma can produce cross‐linked and depolymerized starch depending on different voltage and time of treatment.

Extraction of asphalt mastic from mixture without chemical agent

A mechanical method is presented which helps to recover asphalt mastic from asphalt mixture without any chemical agent. It may be used as a surrogate to the current chemical extraction method when asphalt mastic shall be recovered from the asphalt mixture. The presented approach is based on granulation and sieving techniques. For the purpose of validation, the method is compared to the standard chemical extraction method which uses a chemical agent to recover the asphalt binder from the mineral aggregates. Both methods are compared in terms of recoverable amount of mastic, and of filler/binder ratio, of reproducibility, and of suitability of the recovered mastic sample for subsequent temperature and frequency sweep (T-f sweep) tests using a Dynamic Shear Rheometer (DSR).

Use of Random Forest to Predict Intermediate Temperature SCB Jc Parameter of Long-Term Aged Asphalt Mixtures

With the growing use of reclaimed asphalt pavement (RAP), recycled asphalt shingles (RAS), and other innovative additives in asphalt mixtures, there are concerns about the accuracy of Superpave volumetric-based mixture design. Performance tests in mix design procedures are needed to ensure desirable pavement performance. The Louisiana Department of Transportation and Development (LADOTD) has adopted the semi-circular bend (SCB) critical strain energy release rate parameter, Jc, to evaluate the cracking resistance of asphalt mixtures. To address practical shortcomings, this study aims to develop a predictive model to estimate SCB Jc at intermediate temperature of long-term aged (LTA) asphalt specimens from volumetric properties of plant-produced asphalt mixtures, and rheological and chemical properties of unaged asphalt binder by using a machine-learning model, random forest. Asphalt mixture SCB test and asphalt binder rheological and chemical properties tests were conducted. Stepwise correlation analysis was used to determine the most influential variables to SCB Jc. Random forest model was optimized using grid search with hyperparameter combinations. Results show that the developed random forest model was able to predict the SCB Jc fracture parameter of asphalt mixtures and a good agreement was observed between predicted and measured SCB Jc values. Variable importance scores based on mean decrease in impurity (MDI) showed that the Δ Tc had the most influence on SCB Jc prediction accuracy, and other inputs such as coarse aggregate type, LTA days, Fourier transform infrared spectroscopy test carbonyl index, and linear amplitude sweep test ALas also had significant effects on SCB Jc.

Rheological analyses of binders modified with triple combinations of Crumb-Rubber, Sasobit and Styrene-Butadiene-Styrene

The development of polymer-modified asphalt (PMA) has been a widely used technique by many researchers. Moreover, further modification of PMA binders has generated interest due to possible improvements in performance and cost. In this regard, Sasobit wax has been an alternative to reduce costs in Crumb-Rubber (CR) and Styrene-Butadiene-Styrene Copolymer (SBS) binders. However, there is little detail on the rheological behaviour of CR-SBS-Sasobit triple-modified samples for failure and damage resistance properties. Therefore, this study shows various properties of binders with triple modification of CR-SBS-Sasobit at different dosages. For this purpose, the development of single, double and triple modifications has been proposed to be tested by Multiple Stress Creep Recovery (MSCR) for permanent deformation. In the case of radial cracking and thermal cracking, it is evaluated by linear amplitude sweep test (LAS) and binder creep energy test (BYET). The results indicate that a CR-SBS combination in single or double addition achieves good thermal stability and behaviour. However, a higher elasticity is achieved in the case of a triple modification with CR-SBS-Sasobit. Specifically, Sasobit achieves 67% and 28% reduction in the cumulative deformation of MSCR for a variation of 40–80 °C, respectively. Concerning fatigue life (Nf), it is shown that CR-SBS modifications do not always acquire higher Nf than single modifications. However, adding Sasobit in triple modifications increases these values, generating bitumen with higher strength. It is also shown that adding Sasobit is a viable modifier in yield, even increasing the yield energy (Er) for samples with equal CR-SBS and reducing the percentage of SBS in the sample.

In situ experimental study of vibration reduction using thick concrete slabs with natural and cement-improved subgrade

Thickening the foundation slab and improving the subgrade soil using geo-techniques are effective measures for controlling unwanted vibrations at high-tech facilities. In this study, the vibration-reduction performance of 1-m-thick concrete slabs with natural and cement-improved subgrades was investigated based on in situ frequency sweep tests. One 1-m-thick concrete slab rested on 1-m-thick compacted sandy gravel backfill atop an undisturbed subgrade was constructed on the north side of the experimental site, and another identical concrete slab rested on 1-m-thick compacted sandy gravel backfill atop a cement-improved subgrade was constructed on the south side. The vibration-reduction effect was evaluated by comparing the free-field ground vibrations and surface vibrations of the two slabs at three pairs of evaluation locations. In terms of peak velocity, the 1-m-thick concrete slab with the natural subgrade exhibited a slight vibration amplification effect at low frequencies and a significant reduction effect at middle and high frequencies; the 1-m-thick concrete slab with the cement-improved subgrade exhibited a continuous vibration reduction action at all frequencies. In terms of RMS velocity, the vibration-reduction performance of the 1-m-thick concrete slab with the cement-improved subgrade was better than that with the natural subgrade. The results demonstrated that the vibration-reduction effect of the thick concrete slab was significant and could be increased by improving the subgrade using the cement grouting method.

Rheological properties of cross-linked inulin solutions as a function of cross-linker concentration and temperature

The purpose of this study is to determine the rheological properties of cross-linked inulin solutions in two different polymerization degrees (native and degree of polymerization of >23%). Thus, the effect of cross-linking, a new approach applied to support a specific property (stabilization) of inulin, which has many benefits, has been demonstrated. Sodium hexametaphosphate was used as a cross-linking agent at three different ratios (0.375%, 0.500%, and 0.750%). The cross-linked inulin solutions were lyophilized, and the lyophilized mixture was then reconstituted at 25 °C and 45 °C to obtain cross-linked inulin solutions with 1% and 5% (w/v) concentrations. The control samples (native and with a high degree of polymerization) were treated similarly without a cross-linking agent. The samples were subjected to a dynamic frequency sweep test in the range of 0.01–10 Hz as well as shear viscosity measurements at 1–500/s shear rates for the determination of rheological properties. The thixotropic curves were analyzed as the shear rate increased from 0.1/s to 300/s in the first 120 s (up curve), and then decreased to the same point in the subsequent 120 s. Results indicated that cross-linking increased inulin solution viscosity, particularly at 5% concentration, and solubility. Solutions with 5% inulin containing 0.750% and 0.375% cross-linker yielded the highest viscosities at 45 °C and 25 °C, respectively. Samples with 5% inulin concentration exhibited solid-like behavior in the oscillation test. Thixotropic curves revealed antithixotropy at low shear rates and thixotropy at high shear rates. The study demonstrated the impact of cross-linking on inulin stabilization, providing insights for future applications. Results indicated that cross-linking increased inulin solution viscosity, particularly at 5% concentration, and solubility. Solutions with 5% inulin containing 0.750% and 0.375% cross-linker yielded the highest viscosities at 45 °C and 25 °C, respectively. Samples with 5% inulin concentration exhibited solid-like behavior in the oscillation test. Thixotropic curves revealed antithixotropy at low shear rates and thixotropy at high shear rates. The study demonstrated the impact of cross-linking on inulin stabilization, providing insights for future applications.

Deformation characteristics of hydrogel products based on cross-linked hyaluronic acid.

The cross-linked hyaluronic acid (HA) fillers are the viscoelastic hydrogel with a dominant elasticity rather than a viscosity as a useful medical device in the soft tissue augmentation. These HA fillers undergo deformation to begin the biodegradation by the biochemical and physical environment of the body, and result of deformations are closely related to clinical performance. The specific equation of molding index is newly generated and proved with Collin's equation, which is used for strong elastomers, for selecting optimal product in facial treatment. In this study, the results of amplitude sweep test from five marketed HA fillers were mathematically demonstrated for the proper clinical application. The increment of loss modulus by deformation was evaluated as a useful factor for the maintenance of optimal shape molding performance and resistance to external deformation of the cross-linked HA gel. From this study, the equation of molding index for weak viscoelastic hydrogels like HA products can be applied for choosing which products even in aesthetic plastic field. This molding index equation is compared to Collins' equation that index of deformation as elastomer like rubber and then found the positive correlation between two equations. This study could provide a basic theory that achieve useful clinical performance according to characteristics among many types of medical devices based on the molding index.

Asphalt mixture performance deterioration in the salty environment based on theoretical calculation

In a salty environment, the asphalt mixture is exposed to the effect of sodium chloride which can affect its performance. Using less energy and raw materials, a model was effectively created in this study to predict the influence of sodium chloride on the performance of the asphalt mixture (rutting resistance and fatigue damage) in a salty environment. To ascertain the physical characteristics of the asphalt binder at various salt solution proportions, fundamental tests such as the penetration test, softening point, and ductility test were performed. Additionally, the Dynamic Shear Rheometer (DSR) was used to conduct the temperature sweep test in order to assess the rheological characteristics of asphalt binder samples before and after immersion in different salt solutions. Based on the DSR results and mixture volumetric parameters, the Hirsch model and the Asphalt Institute (ALI) model were used to forecast the performance of the asphalt mixture. The test results indicated that the asphalt mixture with the highest complex modulus (G*), lowest voids in mineral aggregate (VMA), and highest voids filled with asphalt binder (VFA) had the highest value of dynamic modulus, which is preferable to increase the asphalt mixture's resistance to rutting. The maximum rate of deterioration was estimated to be 45% at 15% salt content, followed by that of 10% salt content (26.76%), and 5% salt content (22.8%). However, the findings from the ALI model revealed that the fatigue life of the asphalt mixture in the presence of salt solution significantly decreased when compared to the specimen soaked in plain water, indicating that salt was detrimental to the mixture's resistance to fatigue cracking. The largest rate of deterioration was 37.11% at 15% salt content, and it was followed by rates of 22.35% at 10% salt content and 19.13% at 5% salt content.

Effect of chemical warm-mix additives on asphalt binder rheological and chemical properties in the context of aging

Warm-Mix Asphalt (WMA) has achieved gradually increasing popularity among researchers and agencies because of the environmental and economic benefits associated with lower production temperatures. An ongoing research study sponsored by the Oklahoma Department of Transportation (ODOT) is focusing on evaluating how different chemical WMA additives and the associated lower production temperatures impact asphalt binder and mixture properties and exploring potential relationships between asphalt rheology and chemistry in the context of chemical WMA and various aging conditions. This manuscript presents partial findings from this study that involved testing of two binder types (modified and unmodified binder) and four different WMA additives (chemical additives). Different aging conditions were simulated by changing the Rolling Thin Film Oven (RTFO) temperature, and by subjecting the binder to different cycles of Pressure Aging Vessel (PAV) aging. Frequency and Temperature Sweep tests by a Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) tests were performed for rheological characterization, while Fourier Transform Infrared Spectrometer (FTIR) test was conducted for chemical characterization. Analysis of the test results indicated that while all the WMA additives can improve the rheological and chemical properties of control binders at original and RTFO conditions, two additives cause inferior properties after 20 h, 40 h, and 60 h of PAV aging, indicating possible higher aging susceptibility and long-term performance concerns. Good correlations (R2 greater than 0.8) observed between binder rheological parameters and chemical indices indicate the existence of fundamental relationships between asphalt binder’s engineering properties and chemical make-up, which also supports the possibility of using FTIR as a quick screen or fingerprint tool for binder selection and comparison. Two new rheological parameters have been proposed for evaluation of the polymer-modified binder in this study. This was important to address the presence of multi-transition behavior in modified binders. These two parameters show consistent trends with increasing aging conditions.

Insight into the critical evaluation indicators for fatigue performance recovery of rejuvenated bitumen under different rejuvenation conditions

This study aims to propose critical fatigue indicators for evaluating the restoration effectiveness of various rejuvenators on the fatigue performance of aged bitumen. The influence factors of rejuvenator type/dosage and aging degree of bitumen are involved, and different fatigue parameters from linear viscoelastic (LVE), linear amplitude sweep (LAS), and time sweep (TS) tests are analysed. The results reveal that bio-oil exhibits the greatest rejuvenation efficiency in improving fatigue life of aged bitumen, followed by engine-oil and naphthenic-oil rejuvenators, while aromatic-oil shows the lowest effect. Moreover, the rejuvenation percentages on fatigue parameters of rejuvenated bitumen enhance significantly with increased rejuvenator dosage but weaken as the aging level deepens. The fatigue failure temperature (FFT) from the LVE test, fatigue life (Nf5), peak strain (ɛsr), elastic modulus (E) from the LAS test, and crack width (C500) from the TS test are recommended as critical indicators for fatigue performance evaluation of rejuvenated binders. Further, the crack width greatly correlates with other essential indicators and can be predicted using correlation equations without conducting the time-consuming time sweep test. The difference in these critical fatigue parameters of various rejuvenator-aged bitumen blends provides the macroscale basis for future nanoscale mechanism exploration and superior rejuvenator development.

A generalized model for field assessment of particle settling velocity in a viscoelastic fluid

The accurate prediction of particle settling velocity in viscoelastic fluids is important for the design, analysis, and optimization of various oil-field operations including hole cleaning and cuttings transport in oil and gas well drilling, proppant transport in hydraulic fracturing operations. An experimental study was, therefore, conducted to investigate the effect of fluid viscoelastic properties on the particle settling velocity. The main objectives of the study were to understand the factors that influence the particle settling velocity in shear-thinning viscoelastic fluids and develop a generalized model for the field assessment of particle settling velocity in shear-thinning viscoelastic fluids.We prepared ten different fluids, which were divided into two groups based on their shear viscosity values. In each group, five fluids were having similar shear viscosity and variable elasticity values. Nineteen different spherical particles were used to conduct particle settling experiments with a density range from 2700 kg/m3 to 6000 kg/m3 and a diameter range from 1 mm to 4 mm. Rheological characterizations of the fluids have been conducted by using funnel viscometer, API Rotational viscometer, controlled shear rate, and amplitude sweep test measurements. The fluid elasticity was quantified by using the concept of energy dissipation, which is determined by using standard field measurements of the apparent viscosity (AV) and the funnel viscosity.Finally, based on the experimental results and theory of the particle settling in non-Newtonian fluids, we proposed a model that can be used for predicting particle settling velocity in shear thinning viscoelastic fluids. The statistical analyses have shown that the root means square error and mean absolute percentage error of model predictions were 0.0032 m/s and 4.1%, respectively.

Evaluation of Thermal and Rheological Properties of Phase Change Material-Incorporated Asphalt Mastic with Porous Fillers

Incorporating phase change material (PCM) into paving materials can regulate the pavement temperature, improve the pavement durability, and mitigate the heat-island effects. In this research, porous fillers were used as the PCM carrier, and the thermal and rheological behaviors of the asphalt mastic with the PCM were evaluated. Two different carrier materials (diatomite and expanded perlite) and four types of PCMs were used in the study. The candidate filler, PCM, and proper blending ratios were determined based on the results of scanning electron microscope image analysis, the filter paper test, and the temperature sweep test. The thermal and rheological behaviors of the mastics with PCMs were further evaluated with different filler replacement ratios. Thermal analysis through a differential scanning calorimetry test, thermal conductivity and volumetric heat capacity test, and real-time temperature performance test were performed on the asphalt mastics. Rheological tests, including the complex shear modulus test, the bending beam rheometer test, and the linear amplitude sweep test, were also conducted. The modified mastics were found to have high heat capacity with the latent heat storage ability. The rheological analyses showed that with the addition of polyethylene glycol, while the low-temperature performance of the asphalt mastics was improved, the performance at intermediate and high temperatures was not adversely affected by the PCM.

Melting properties of vegan cheese: Effect of emulsion and protein addition on the thermal behaviour of starch gels

The aim of this study was to understand the effect of emulsion and protein incorporation on the structural and melting properties of starch gels designed as model systems for specific types of vegan cheese, and to explore the potential of using these ingredients to mimic the melting properties of dairy cheese. To characterise the melting properties of the gels, temperature sweep tests were conducted. In addition, pictures were taken to visualise changes in appearance upon increasing temperature. The microstructure of the gels was investigated with confocal laser scanning microscopy (CLSM). Whereas gels of native maize starch did not melt, those made from oxidised potato starch melted completely at temperatures above 70 °C, resulting in a fluid with a viscosity much lower than that of molten dairy cheese. With the addition of a protein-stabilised sunflower oil emulsion, at oil contents >10%, an oil droplet network was formed in the starch matrix, which partly inhibited the melting of the gel. The addition of pea protein that was subsequently heated together with the starch also resulted in the formation of a network that limited melting. However, due to the high degree of pea protein aggregation, an inhomogeneous appearance was obtained. At low protein contents syneresis occurred. When protein was added without heat treatment, the melting degree was inhibited already at low contents, a more homogeneous appearance was obtained, and syneresis was prevented due to the high-water holding capacity of the protein. When emulsion and protein were added together at high contents, the appearance was also more homogeneous, and the melting degree of the composite gels was further limited. When comparing the relative inhibiting effect of oil and protein content on melting, protein was found to be more effective. By changing both oil and protein content, samples with melting properties similar to those of processed cheese were obtained, which shows that the design of multi-component starch-protein-oil gels is a promising approach in optimising the functional properties of dairy cheese substitutes.