Rheological properties of polyacrylates used as synthetic road binders

Most adhesives and binders, including bitumen for asphalt mixture production, are presently produced from petrochemicals after the refining of crude oil. The fact that crude oil reserves are a finite resource means that in the future, it may become necessary to produce these materials from alternative and probably renewable sources. Suitable resources of this kind may include polysaccharides, plant oils and proteins. This paper deals with the synthesis of polymer binders from monomers that could, in future, be derived from renewable resources. These binders consist of polyethyl acrylate (PEA) of different molecular weight, polymethyl acrylate (PMA) and polybutyl acrylate (PBA), which were synthesised from ethyl acrylate, methyl acrylate and butyl acrylate, respectively, by atom transfer radical polymerisation. The rheological properties of these binders were determined by means of oscillatory testing using a dynamic shear rheometer and combinations of stress/strain, temperature and frequency sweeps. The results indicate that PEA can be produced to have rheological properties similar to that of ‘soft’ 100/150 penetration grade bitumen, PMA with similar rheological properties to that of ‘hard’ 10/20 penetration grade bitumen, while PBA, due to its highly viscous nature and low dynamic moduli, cannot be used on its own as a binder. The synthetic polymers were found to be thermo-rheologically simple, and the shift factors, used to produce the dynamic moduli master curves, were found to fit an Arrhenius function.     

Poly(ethylene terephthalate) waste derived chemicals as an antistripping additive for bitumen – An environment friendly approach for disposal of environmentally hazardous material

The increasing accumulation of poly(ethylene terephthalate) polymer and poor recycle/disposal practices have made them omnipresent and a major culprit for environmental pollution. Currently global research efforts are focused on primary and secondary recycling of PET waste or through landfills. Chemical recycling of PET through hydrolytic or aminolytic route has been attempted by many researchers however with limited end applications. In our investigations we have used PET waste as a synthon and chemically converted it through a new non-catalytic route into several benzamide derivatives. We have successfully tested them for antistripping performance in bitumen. Our results as elaborated in the paper indicate a comparable performance of the new chemistry products based on PET, to commercially used antistripping chemicals. Our research work thus opens a new route for the recycling of used PET in bituminous concrete roads which may help in alleviating a major environmental problem and disposal of waste PET polymer in large scale.     

Colloidal forces between bitumen surfaces in aqueous solutions measured with atomic force microscope

Colloidal forces between bitumen surfaces in aqueous solutions were measured with an atomic force microscope (AFM). The results showed a significant impact of solution pH, salinity, calcium and montmorillonite clay addition on both long-range (non-contact) and adhesion (pull-off) forces. Weaker long-range repulsive forces were observed under conditions of lower solution pH, higher salinity and higher calcium concentration. Lower solution pH, salinity and calcium concentration resulted in a stronger adhesion forces. The addition of montmorillonite clays increased long-range repulsive forces and decreased adhesion forces, particularly when co-added with calcium ions. The measured force profiles were fitted with extended DLVO theory to show the repulsive electrostatic double layer and attractive hydrophobic forces being the dominant components in the long-range forces between the bitumen surfaces. At a very short separation distance (less than 4–6 nm), a strong repulsion of steric origin was observed. The findings provide a fundamental understanding of bitumen emulsion stability and a mechanism of bitumen “aeration” in bitumen recovery processes from oil sands.     

Sulfur modified bitumen: A new binder

Summary Bitumen is modified after a treatment with 2% sulfur, at 160°C. It is more plastic consecutive to a variation of the nature of the interactions between asphaltene molecules.Composites prepared with this bitumen and silica present dynamic viscoelastic properties obeying the time-temperature-interfacial parameter equivalence principles, evidenced previously. However, the domains of applicability of these principles are more restricted.With 11 figures     

Identification of viscoelastic properties by means of nanoindentation taking the real tip geometry into account

Motivated by recent progress in viscoelastic indentation analysis, the identification of viscoelastic properties from nanoindentation test data taking the real tip geometry into account is presented in this paper. Based on the elastic solution of the indentation problem, the corresponding viscoelastic solution is obtained by the application of the method of functional equations. This general solution, which accounts for the real geometric properties of the indenter tip, is specialized for the case of a trapezoidal load history, commonly employed in nanoindentation testing. Three deviatoric creep models, the single dash-pot, the Maxwell, and the three-parameter model are considered. The so-obtained expressions allow us to determine viscoelastic model parameters via back calculation from the measured load–penetration history. The presented approach is illustrated by the identification of short-term viscoelastic properties of bitumen. Hereby, the influence of loading rate, maximum load, and temperature on the model parameters is investigated.     

NMR measurement of bitumen at different temperatures

Heavy oil (bitumen) is characterized by its high viscosity and density, which is a major obstacle to both well logging and recovery. Due to the lost information of T2 relaxation time shorter than echo spacing (TE) and interference of water signal, estimation of heavy oil properties from NMR T2 measurements is usually problematic. In this work, a new method has been developed to overcome the echo spacing restriction of NMR spectrometer during the application to heavy oil (bitumen). A FID measurement supplemented the start of CPMG. Constrained by its initial magnetization (M0) estimated from the FID and assuming log normal distribution for bitumen, the corrected T2 relaxation time of bitumen sample can be obtained from the interpretation of CPMG data. This new method successfully overcomes the TE restriction of the NMR spectrometer and is nearly independent on the TE applied in the measurement. This method was applied to the measurement at elevated temperatures (8-90 degrees C). Due to the significant signal-loss within the dead time of FID, the directly extrapolated M0 of bitumen at relatively lower temperatures (<60 degrees C) was found to be underestimated. However, resulting from the remarkably lowered viscosity, the extrapolated M0 of bitumen at over 60 degrees C can be reasonably assumed to be the real value. In this manner, based on the extrapolation at higher temperatures (> or = 60 degrees C), the M0 value of bitumen at lower temperatures (<60 degrees C) can be corrected by Curie's Law. Consequently, some important petrophysical properties of bitumen, such as hydrogen index (HI), fluid content and viscosity were evaluated by using corrected T2.     

Sulfur as a supplementary filler for bitumen-silica composites

Summary Dynamic-mechanical properties of bitumen-sulfur mixtures, containing more than 10% sulfur, change with time up to one month ageing. Composites were prepared by adding silica to these mixtures. In general, the time-temperature-superposition principle applies. Moreover, the viscoelastic properties of the bitumen matrix are not significantly altered by the presence of sulfur. However, the triple time-temperature-interfacial area equivalence principle could not be verified, in this instance, since the interfacial area between sulfur, the new filler, and bitumen could not be established.With 11 figures     

Melting and glass transitions in paraffinic and naphthenic oils

Naphthenic and paraffinic oils were analyzed by modulated differential scanning calorimetry (MDSC). The results showed several improvements in the analysis of thermal properties when compared with standard DSC. The glass transition temperature (T_g), the enthalpy relaxation at T_g, and the melting endotherms could be deconvoluted, and reversible melting could be identified. This allowed for an easier interpretation of the thermal properties of the oils. With MDSC, the T_gs in mineral oils were found to coincide with endothermic enthalpy relaxation, which is generally regarded as a melting endotherm with standard DSC. A decrease in heat capacity after T_g was attributed to the existence of rigid amorphous material. From Δc_p at T_g and the oil molecular weight, the number of repeat units in the oil chains was estimated at less than 20. The T_g of a hypothetical pure aromatic oil was found to be similar to that for petroleum asphaltenes, and that for a naphthenic oil of infinite molecular weight to be similar to that of petroleum resins.     

基于三维荧光光谱的沥青老化行为研究

沥青在服役过程中暴露在自然环境里,受到光、热、氧等的作用,易出现老化从而引起的多种病害,如裂缝、龟裂和坑槽等,严重影响沥青混凝土路面的服役寿命。为了提高沥青混凝土路面的耐久性能,揭示沥青在老化过程中的成分与结构的变化规律,基于荧光光谱技术,从沥青的荧光猝灭现象出发,利用实验室内的紫外老化与热氧老化,针对两种不同沥青进行了老化实验,并研究了沥青在老化前后的性能和组分变化;借助荧光分光光度计采集了沥青的三维荧光光谱,并分析了沥青荧光光谱谱图的特征,获取了沥青荧光光谱的峰值强度坐标,计算了老化前后峰值坐标的偏移向量。实验结果表明,沥青避免出现荧光猝灭的理想浓度是0.1 g·L-1;沥青老化后其软化点增加,针入度与延度减小;其四组分中饱和分基本不变,芳香分减小,胶质与沥青质增加。结合三维荧光光谱发现,沥青的荧光强度峰值坐标出现了“蓝移”,且沥青组成中的芳香分的含量决定了荧光光谱峰值的偏移程度;通过向量计算表明,峰值坐标偏移的向量的模大于36时,沥青已经严重老化。通过对沥青三维荧光光谱特征值的分析,可以有效评价沥青的老化过程,对提高沥青的耐久性具有重要意义。     

Rheology and microstructure of asphalt binders

The viscous and linear viscoelastic properties of different asphalt binders have been analyzed in this paper. Thus, an unmodified bitumen, a polymer-modified (SBS) bitumen, a commercial synthetic binder, and two model synthetic binders with different polymer (SBS) concentrations have been studied. The mechanical spectra of these binders are quite different, mainly influenced by SBS concentration. Thus, up to three regions may be observed for a synthetic binder with high polymer concentration. The temperature dependence of the zero-shear-rate-limiting viscosity is described by an Arrhenius-like equation, in a temperature range that depends on binder composition. These results have been discussed taking into account the development of a polymer-rich phase in SBS-modified bitumen and model synthetic binders. Received: 6 February 2000 Accepted: 8 August 2000