Meizhu Chen

Effect of Rejuvenator Sealer Materials on the Properties of Aged Asphalt Binder

AbstractThe maintenance of asphalt pavement has become recognized as a critical issue in China. The objective of this study is to investigate the influence of using rejuvenator sealer materials on aged asphalt by means of laboratory analysis. First, asphalt binder first aged by rolling thin-film oven test and ultraviolet light. This aged asphalt was treated by two kinds of rejuvenator sealer materials. The performances of both aged binder and rejuvenator treated binder were evaluated by means of viscosity, temperature sweep, creep recovery, fatigue, and component analysis tests. The results indicated that both rejuvenator sealer materials can significantly decrease the viscosity and complex modulus of aged asphalt. Moreover, applying rejuvenator sealer materials can balance the asphaltene–maltene ratio of aged asphalt to some degree. Aged asphalt can be efficiently softened with the rejuvenator materials, which proves that rejuvenator sealer materials can be used for maintenance to improve the performance...

Thermal performances of asphalt mixtures using recycled tyre rubber as mineral filler

As the global temperature rises in the summer, researchers are paying more attention to cool pavements. Rubberised asphalt, made by mixing shredded crumb rubber into asphalt and used on road and highway pavements, is being regarded as one of the potential cool pavements. This research aims to investigate the thermal performances of asphalt binders and mixtures containing recycled tyre rubber (RTR) powder. The experimental design for this research included asphalt binders and mixtures with different contents of RTR powder. The thermal conductivity coefficients and heat capacities of asphalt binders and mixtures were measured besides vertical temperature distributions of mixtures; meanwhile, water sensitivity and high-temperature properties of mixtures were also investigated in this study. The experimental results show that the addition of RTR powder is helpful in reducing the thermal conductivity coefficient of asphalt binders and mixtures, while it has an opposite effect on volumetric heat capacity for asphalt binders and mixtures. With an increasing content of RTR powder, the heat capacity of the binder is decreased but that of the mixture is increased. And the surface temperature of an asphalt mixture containing RTR powder as mineral filler is higher than that of a control sample in solar heating simulation tests, while the inner temperature is reverse. The use of RTR as mineral filler in an asphalt mixture is helpful in improving the thermal stability of the asphalt mixture, but it slightly reduced the moisture resistance in this study.

Analysis of the Relationships between Waste Cooking Oil Qualities and Rejuvenated Asphalt Properties

Waste cooking oil (WCO), in many cases, can rejuvenate aged asphalt and restore its properties. However, the influence of WCO qualities on rejuvenation behaviors of aged asphalt has not been investigated in detail. The objective of this paper was to evaluate the effects of WCO viscosity and acid value on the basic, rheological, and chemical properties of a typical rejuvenated asphalt. Penetration, ring and ball (R and B) softening point, and ductility were tested to evaluate the influence of WCO qualities on basic properties of rejuvenated asphalts. Then, the rheological properties of rejuvenated asphalt were characterized based on rotational viscometer (RV), dynamic shear rheometer (DSR), and bending beam rheometer (BBR) test results. Further, SARA (saturates, aromatics, resins, and asphaltenes) fraction analysis and Fourier transform infrared spectroscopy (FTIR) tests were performed to investigate the effects of WCO qualities on asphalt chemical composition. Finally, grey correlation coefficients were calculated and the relationships between WCO qualities and rejuvenated asphalt properties were quantitatively evaluated. The experimental results indicated that WCO qualities influence the rejuvenation behaviors of aged asphalt significantly, and the WCO with higher qualities (low acid value and viscosity, as defined in this research) tends to achieve better rejuvenation effects. Based on the results of grey correlation analyses, the acid value is, relatively, a better indicator than viscosity in predicting the rejuvenation efficiency of WCO. The rejuvenation thresholds of WCO are varied with the categories of properties of rejuvenated asphalts, and WCO with an acid value of 0.4–0.7 mg KOH/g, or a viscosity of 140–540 mm2/s, can meet all of the performance requirements for asphalt rejuvenation used in this research.

Preparation and Thermal Properties of Molecular-Bridged Expanded Graphite/Polyethylene Glycol Composite Phase Change Materials for Building Energy Conservation

Using phase change materials (PCMs) in building envelopes became a reliable method to improve indoor comfort and reduce buildings’ energy consumption. This research developed molecular-bridged expanded graphite (EG)/polyethylene glycol (PEG) composite PCMs (m-EPs) to conserve energy in buildings. The m-EPs were prepared through a vacuum absorption technique, and a titanate coupling agent was used to build a molecular bridge between EG and PEG. SEM, mercury intrusion porosimetry (MIP), the leakage test, microcalorimetry, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR) were conducted to characterize the morphology, pore structure, absorbability, and modifying effects of the m-EPs. The phase change temperature, latent heat, thermal stability, and thermal conductivity of the m-EPs were determined by a differential scanning calorimeter (DSC), TGA, and a thermal constants analyzer. Results showed that the maximum mass ratio of PEG to EG without leakage was 1:7, and a stable connection was established in the m-EPs after modification. Compared with the unmodified EPs, the supercooling degree of the m-EPs reduced by about 3 °C, but the latent heats and initial decomposition temperatures increased by approximately 10% and 20 °C, respectively, which indicated an improvement in the thermal energy storage efficiency. The thermal conductivities of the m-EPs were 10 times higher than those of the pristine PEGs, which ensured a rapid responding to building temperature fluctuations.

Effect of ground steel slag powder on cement properties

Abstract The work aims to evaluate the influences of steel slags fineness and particle-size distribution on the properties of cement-based materials. The materials used for this study included Portland cement and steel slag powder with seven different specific surface areas. The properties of cement pastes and mortars with steel slag powder were tested including water requirement of normal consistency, setting time, fluidity, soundness, compressive and flexural strength. The experimental results show that the influence of steel slag powder on water requirement of normal consistency of cement is in relation to its specific surface area, and the value of decreases for steel slag powder with a lower-specific surface area while increases with a higher-specific surface area. The partial replacement of cement by steel slag powder decreases the strength of cement, but increases the ratio of flexural to compressive strength and thus improves the ductility of cement-based materials.

Effects of Aluminum Hydroxide and Layered Double Hydroxide on Asphalt Fire Resistance

When a fire occurs in a tunnel, the instantaneous high temperature and smoke cause great danger to people. Therefore, the asphalt pavement material in the tunnel must have sufficient fire resistance. In this study, the effects of aluminum hydroxide and layered double hydroxide on the fire resistance of styrene-butadiene-styrene (SBS) polymer-modified asphalt was investigated. The fire resistance of the asphalt was evaluated by using a limiting oxygen index (LOI). The impact of aluminum hydroxide (ATH), layered double hydroxide (LDHs), and mixed flame retardant (MFR) on LOI was studied. The synergistic fire resistance mechanism of ATH and LDHs in asphalt binder was analyzed by using an integrated thermal analyzer‒mass spectrometry combined system (TG-DSC-MS) and Fourier transform infrared spectrometer (FTIR). The experimental results indicated that the main active temperature range of these flame retardants was 221–483 °C. The main components of smoke were methane, hydroxyl, water, carbon monoxide, aldehyde, carbon dioxide, etc. The addition of flame retardants could inhibit the production of methane, carbon monoxide, and aldehyde. Moreover, due to the good synergistic effects of ATH and LDHs, 20 wt % MFR had the best fire resistance.

Effect of Waste Cooking Oil Viscosity on Basic and Rheological Properties of Aged Asphalt

Waste cooking oil (WCO) can be used to rejuvenate aged asphalt and restore its properties. However, the influence of WCO properties on rejuvenating behavior of aged asphalt is still unknown. The objective of this study is to investigate the effect of WCO viscosity on basic and rheological properties of aged asphalt. The materials used for this study included eight kinds of WCO (fabricated by fresh soybean oil in the laboratory) and one aged asphalt (AH-90). The basic properties of rejuvenated asphalt were characterized by penetration value, softening point and ductility, then the influence of WCO viscosity on rheological properties of rejuvenated asphalts were evaluated by rotational viscosity, rutting parameter, complex modulus and phase angle master curves, and creep recovery ratio. The experimental results indicate that WCO viscosity has a great influence on the properties of rejuvenated asphalt, and different aged asphalts require WCOs with different viscosity to achieve the desirable rejuvenation effects. Basic and rheological properties of aged asphalt can be restored to some extent but there are still gaps between the basic performances of WCO rejuvenated asphalts and virgin asphalt. WCOs with too high or too low viscosity values would have an adverse impact on the performance recovery of rejuvenated asphalt. WCO with viscosity ranging from 420–700 mm2/s are preferable to restore the properties of rejuvenated asphalt in this research.

Physical and Chemical Properties of Rejuvenating Aged Binder with Waste Cooking Oil and Its Bioasphalt

WCO-based bioasphalt is prepared from waste cooking oil (WCO) by filter, deodorant, viscosity reduction, methyl ester and distillation. The objective of this study was to investigate the properties of rejuvenating aged asphalt binder with WCO-based bioasphalt and waste cooking oil. The materials used for this study included one virgin asphalt, aged asphalt (from virgin asphalt by thin film oven test and pressure aging vessel), waste cooking oil and its bioasphalt with five percentages (0, 3, 5, 7 and 9% of aged asphalt). The physical and rheological properties of these rejuvenated asphalts were tested including penetration, softening point, ductility, rotational viscosity, complex modulus and phase angle, creep stiffness (S) and creep rate (m-value). The chemical characteristics were evaluated using Fourier Transforms Infrared Spectroscopy (FTIR). The results indicate the physical and rheological properties of rejuvenate asphalts are closed to that of virgin asphalt with the dosages increased. Besides, the low temperature performance of rejuvenated asphalts is better compared with the aged asphalt while the high temperature anti-rutting performance need to be further improved. The carbonyl and sulfoxide indexes of rejuvenated asphalts are significantly lower than that of aged asphalt. In addition, the regenerated asphalts containing waste cooking oil show better performance than the ones containing WCO-based bioasphalt at the same condition. Thus, the light components can be separated from the waste cooking oil and used for other purposes, which makes the waste cooking oil have a reasonable use and broaden the application way.

Effect of superfine blast furnace slag powder on properties of cement-based materials

Abstract Industrial waste-like slag has caused serious problems all over the world. In this paper, blast furnace slag was ground to be superfine powder and partial replacement of cement. Multiple contents of slag powder used in cement were studied by cement paste, cement mortar and cement concrete experiment. Water requirement of normal consistency, setting time, soundness, fluidity, compressive and flexural strength were chosen to evaluate the performance of cement-based with different contents of slag powder. The results show that superfine blast furnace slag powder can be effectively used in cement with high contents. The strength of cement mortar with 70% superfine blast furnace slag powder still can meet the requirements of Portland cement P•O 32·5. Meanwhile, superfine blast furnace slag powder can improve fluidity of cement-based materials.