Investigating the effect of filler types on thermodynamic parameters and their relationship with moisture sensitivity of asphalt mixes

Filler plays a significant role in mastic cohesion and adhesion between aggregate–asphalt binder in asphalt mixes. In the majority of research on investigating moisture damage based on thermodynamic concepts, little attention has been given to the role of filler. In the present study, 20 different combinations of asphalt mixes made with 4 filler types (stone powder, hydrated lime, calcium carbonate and portland cement), with two types of asphalt binder (60–70 and 85–100), and two types of aggregate (limestone and granite) were used. Then thermodynamic parameters (with and without considering the effect of filler) were calculated and the relationship between these parameters and test results of moisture sensitivity of asphalt mixes was investigated using statistical analyses. Results obtained by thermodynamic parameters show that only stone powder filler caused an increase in free energy of adhesion between base asphalt binder and aggregates, and other fillers reduced free energy of adhesion. The maximum amount of debonding energy in samples made by asphalt binder 60–70, was related to mastics containing calcium carbonate and hydrated lime fillers, and in asphalt binder 85–100, mastics containing portland cement and calcium carbonate had the maximum amount of debonding energy. However, the minimum amount of debonding energy was related to the mastic containing stone powder. In addition, the results of moisture sensitivity mechanical tests show that samples containing calcium carbonate and hydrated lime fillers had the maximum amount of tensile strength ratio. Finally, the amount of adjusted coefficient of correlation between debonding energy and modified Lottman test results increased from 0.553 in 4 base compounds (without filler) to 0.701 in 16 compounds with filler. The difference in correlation coefficients show the necessity to use the effect of filler on calculating thermodynamic parameters in investigating moisture sensitivity of various asphalt mixes.     

Numerical and experimental evaluation of the influence of the filler–bitumen interface in mastics

The successful use of additives in modified asphalt mixtures, such as warm mix asphalt, depends largely on the effect such modification has on the mastic. Previous research indicated that such modifiers do not simply change the bitumen properties, but can also change the interaction between the filler and the bitumen matrix. Understanding the effect of the properties of the fillers, the bitumen and their interaction is thus important for future asphalt mix design. In order to investigate this and to define the dominant relationships, this paper combines a numerical and experimental approach. In the experiments, the viscosities of modified and unmodified mastics with different filler concentrations and types were systematically investigated utilizing a novel testing protocol. In the numerical analyses, the Finite Element Method was utilized for a micro-mechanical analysis, in which the shape and size of the filler particles were varied in the bitumen matrix. Combining the experimental and numerical results allowed for a detailed investigation of the effect of the interface properties, with and without modifiers. The research further indicated that the effect of the shape and size of the fillers varied, depending on the interface properties. From the research relationships were established between the overall mastic viscosity and the influence of the filler–bitumen interface, considering shape and size. The conclusion of this paper can thus be useful for the effective development of modified asphalt mixtures and gives strong indications towards future research directions.     

Fatigue and healing properties of bituminous mastics reinforced with nano-sized additives

The research work described in the paper focused on fatigue and healing properties of bituminous mastics reinforced with nano-sized additives.Commercially available multiwall carbon nanotubes (CNTs) and montmorillonite nanoclay (NC) were combined with a single base bitumen and a standard mineral filler to produce bituminous mastics. These blends were prepared in the laboratory by making use of a technique consisting in simple shear mixing followed by sonication.Fatigue behaviour of mastics under repeated loading was investigated by means of time sweeps performed in the strain-controlled mode at various amplitudes. Healing potential was assessed by adopting a testing protocol specifically conceived to discriminate between recovery of damage induced by fatigue loading and other artefact phenomena which may affect material response. All rheological measurements were carried out with a dynamic shear rheometer in the parallel plates geometry.Outcomes of the experimental investigation were found to be highly dependent on the nature of additive type, as a result of the key role played by interaction mechanisms that nano-particles can establish within the bituminous mastic.     

Influence of natural fillers on the properties of starch-based biocomposite films

Starch microparticles (SMs) were prepared by delivering ethanol into starch solution. Chemically modified starch microparticles (CMSs) by reaction with malic acid were obtained and incorporated within glycerol plasticized-corn starch (GCS) matrix, composites being further prepared by the casting process. Three natural fillers (NFs) – keratin, lignin, and spruce cellulose – were incorporated within the CMS–GCS matrix. The surface properties and water sorption, as well as mechanical and thermal properties of chemically modified starch/plasticized starch/natural filler (CMS/S/NF) films were investigated. The water resistance and thermal stability were improved through addition of NF. Higher tensile strength and lower elongation capacity were also observed.     

重质碳酸钙/硅灰石复合填料的填充性能与填充增强原理研究

研究了简单混合、研磨复合以及表面改性后的重质碳酸钙 /硅灰石复合活性填料填充PVC材料的力学性能与填充增强原理。结果表明 ,与单一填料及简单混合后的重质碳酸钙 /硅灰石填料相比 ,研磨复合及表面改性后的重质碳酸钙 /硅灰石复合活性填料可以显著增强PVC材料的力学性能。这种复合活性填料的主要填充增强原理是复合活化增强以及颗粒粒度和形状配合增强 ,即两种不同无机非金属矿物粉体混合后的化学组成和结构复杂化、复合加工后的表面活性化、表面改性后与高聚物基料的相容化以及在填充材料中的取向和堆砌效应的优化     

基于关联性的玄武岩纤维沥青胶浆及其混合料性能研究

为全面提升玄武岩纤维沥青混合料性能,研究了纤维类型及玄武岩纤维长度、掺量等因素对沥青胶浆抗裂性能、抗剪性能及流变特性的影响规律;基于纤维胶浆与纤维沥青混合料性能的关联性分析,揭示了玄武岩纤维对沥青混合料性能的细观增强机制。结果表明:玄武岩纤维对沥青胶浆的抗裂性能及流变特性影响显著,其极限拉力和车辙因子分别达到原沥青胶浆的4.5倍及1.08倍;纤维沥青胶浆高温流变特性与其沥青混合料高温稳定性变化规律存在差异,而前者抗裂性能与后者低温抗裂性能关联性较强;玄武岩纤维与沥青胶结料、集料之间形成三维网状结构,有利于抑制裂缝扩展。     

Influence of hydrated lime on linear viscoelastic properties of bituminous mastics

Mechanics of Time-Dependent Materials - The influence of hydrated lime (HL) on linear viscoelastic (LVE) behavior of mastic is investigated. One bitumen and five mastics with different HL content...     

Chemical treatments of coir pith: Morphology,chemical composition,thermal and water retention behavior

Coir pith is one of the most abundant agro waste found in the southern coastal regions of India, where the economy and livehood of people are largely dependent on the coconut industry. Many technologies have been developed successfully for the alternate use of coir pith. However the application of coir pith as fillers in polymer composite is limited. The major drawback of coir pith as filler in polymer is its low adhesion with the matrix and high water sorption and retention behavior. The present work is a part of research work carried out in our laboratory to modify the morphology and chemical properties of pith to make it better filler in the processing of polymer composites. Coir pith was subjected to mercerization followed by different types of chemical treatment. The products were analyzed in detail using FTIR, XRD, optical microscope, AFM and SEM. The chemical treatment resulted in increased density, thermal stability and reduced water retention behavior.     

Characterisation of high-performance cold bitumen emulsion mixtures for surface courses

Cold bitumen emulsion mixture (CBEM) is not yet widely used as a surface course around the world. In this study, 0/14-mm-size dense-graded surface course CBEMs have been investigated. The mechanical performance was evaluated in terms of stiffness modulus over 3 months and resistance to permanent deformation under three different stress levels (100, 200, 300 kPa), whilst durability evaluation was carried out in terms of resistance to moisture and frost damage. The study has also investigated the incorporation of low cement content (1%) with relatively sustainable by-product fillers, namely ground-granulated blast furnace slag (GGBS) and fly ash (FA) type 450-S on both mechanical and durability performance. A comparison has been carried out between the low and high cement content CBEM, as well as with respect to corresponding hot mix asphalt (HMA). The results revealed that the incorporation of GGBS and FA in CBEMs leads to superior performance, similar to CBEMs treated with high cement content and comparable to an equivalent HMA. Furthermore, GGBS replacement exhibited better performance than that of FA replacement. The findings suggest that the new sustainable types of CBEM can be developed for using as a surface layer for medium- to heavy-trafficked roads.     

Effect of Reactivity of Quick Lime on the Properties of Hydrated Lime Sorbent for SO_2 Removal

The hydration of quick lime and the sulfation of hydrated lime were carried out for verification of relationship between the reactivity of quick lime and the properties of hydrated lime as a sorbent. The effect of reactivity of quick lime was investigated with the change of calcination temperature and time. Results obtained showed that the temperature rise during the hydration of quick limes varied from 31 to 69℃ with the variation of calcination temperature and time. The specific surface area and the sulfa...     

Modelling dilation in an idealised asphalt mixture using discrete element modelling

This paper investigates the use of discrete element modelling (DEM) to simulate the behaviour of a highly idealised bituminous mixture under uniaxial and triaxial compressive creep tests. The idealised mixture comprises single-sized spherical (sand-sized) particles mixed with bitumen and was chosen so that the packing characteristics are known (dense random packing) and the behaviour of the mixture will be dominated by the bitumen and complex aggregate interlock effects will be minimised. In this type of approach the effect of the bitumen is represented as shear and normal contact stiffnesses. A numerical sample preparation procedure has been developed to ensure that the final specimen is isotropic and has the correct volumetrics. Elastic contact properties have been used to investigate the effect of the shear and normal contact stiffnesses on bulk material properties. The bulk modulus was found to be linearly dependent on the normal contact stiffness and independent of the shear contact stiffness. Poisson’s ratio was found to be dependent on only the ratio of the shear contact stiffness to the normal contact stiffness. An elastic contact has been assumed for the compressive normal contact stiffness and a viscoelastic contact for shear and tensile normal contact stiffness to represent the contact behaviour in idealised mixture. The idealised mixture is found to dilate when the ratio of compressive to tensile contact stiffness increases as a function of loading time. Uniaxial and triaxial viscoelastic simulations have been performed to investigate the effect of stress ratio on the rate of dilation with shear strain for the sand asphalt. The numerical results have been validated with experimental data.     

牙科复合树脂中无机填料的研究进展

牙科复合树脂是一类由有机树脂基质和经过表面处理的无机填料及引发系统组合而成的牙科修复材料。无机填料作为复合树脂的分散相,在牙科复合树脂中具有重要作用,对复合树脂的力学性能、物理性能、化学性能都有着重要的影响。介绍了无机填料的种类、形态、含量、粒径大小及其表面处理,并结合许多学者对复合树脂中无机填料的研究,探讨无机填料对复合树脂性能的影响,最后展望了复合树脂应提高的性能和无机填料努力的方向。     

Influence of de-icing agents on the viscoelastic properties of asphalt mastics

A study using dynamic mechanical analysis (DMA) and stress rheometry was done on the viscoelastic properties of different bitumen-filler blends disposed to de-icing agents. The blends were mixtures of the same bitumen, B200 (B), and four different filler grades, limestone (L) filler, Oulu (O) stone (mica-gneiss with high biotite amount), Rovaniemi (R) stone (diabase) and Hietavaara (H) stone (diabase). The de-icing agents tested were water, formic acid, potassium acetate (KAc) and potassium formate (KFo). From the DMA measurements, the elastic modulus (stiffness) at −25 °C, the glass transition temperature (T _g) of the bitumen phase, and the softening temperature were measured. The stiffness data at −25 °C proposed that all agents seem to decrease the stiffness levels of the B-O blend with biotite to a larger extent. Formic acid and 50% potassium formates significantly decreased the stiffness level of the B-L blend. The stiffness of B-H blends was not affected by the chemical treatment. A plasticizing effect of water, formic acid, and 5% potassium acetate, was found for the B-L blend. From the changes in the softening temperatures in the temperature range 15–28 °C, it was concluded that chemical treatment may have an increasing effect on the softening temperatures of all blends, although the effect of hardening could not be omitted. Oscillatory flow measurements with a shear stress rheometer demonstrated that the viscosities of the blends increased significantly after the immersion in de-icing agents.     

Effect of Reactivity of Quick Lime on the Properties of Hydrated Lime Sorbent for SO2 Removal

The hydration of quick lime and the sulfation of hydrated lime were carried out for verification of relationship between the reactivity of quick lime and the properties of hydrated lime as a sorbent. The effect of reactivity of quick lime was investigated with the change of calcination temperature and time. Results obtained showed that the temperature rise during the hydration of quick limes varied from 31 to 69°C with the variation of calcination temperature and time. The specific surface area and the sulfation ability of hydrated lime prepared by hydration of quick lime showed a proportional relationship with the reactivity of quick lime. The hydrated lime which was prepared by hydration of quick lime calcined at 1100°C had the highest reactivity and showed 41.53 m²/g of the speci¯c surface area, 0.16 cm³/g of the pore volume and 87% of the removal effciency for SO₂ removal.     

Time dependent viscoelastic rheological response of pure,modified and synthetic bituminous binders

Bitumen is a viscoelastic material that exhibits both elastic and viscous components of response and displays both a temperature and time dependent relationship between applied stresses and resultant strains. In addition, as bitumen is responsible for the viscoelastic behaviour of all bituminous materials, it plays a dominant role in defining many of the aspects of asphalt road performance, such as strength and stiffness, permanent deformation and cracking. Although conventional bituminous materials perform satisfactorily in most highway pavement applications, there are situations that require the modification of the binder to enhance the properties of existing asphalt material. The best known form of modification is by means of polymer modification, traditionally used to improve the temperature and time susceptibility of bitumen. Tyre rubber modification is another form using recycled crumb tyre rubber to alter the properties of conventional bitumen. In addition, alternative binders (synthetic polymeric binders as well as renewable, environmental-friendly bio-binders) have entered the bitumen market over the last few years due to concerns over the continued availability of bitumen from current crudes and refinery processes. This paper provides a detailed rheological assessment, under both temperature and time regimes, of a range of conventional, modified and alternative binders in terms of the materials dynamic (oscillatory) viscoelastic response. The rheological results show the improved viscoelastic properties of polymer- and rubber-modified binders in terms of increased complex shear modulus and elastic response, particularly at high temperatures and low frequencies. The synthetic binders were found to demonstrate complex rheological behaviour relative to that seen for conventional bituminous binders.     

Shear creep response of an airport asphalt mastic

Two runways were resurfaced with 50–60 mm of typical airport asphalt at the same airport. One runway surface performed well while the other exhibited a lack of resistance to cyclic shear stress under heavy aircraft braking. Both runways had the same hydrated lime filler and coarse aggregate source. The fine aggregate (dust) used to manufacture the two runway surfaces was obtained from two different basalt quarries. The dust associated with the poorly performing asphalt contained a potentially detrimental clay mineral (Hisingerite). It was subsequently determined that the crude oil used to manufacture the feedstock for the acid-modified binder also changed at the transition from one runway to the other. The changes in dust and binder were confounded. A combination of viscosity testing and performance-based multiple stress creep recovery (MSCR) testing determined that the two runway binders responded significantly differently to shear stress and aged differently with sample storage time. The differences were magnified at higher temperatures. Further, mastic samples were manufactured from binder associated with both feedstocks, in combination with dust from both quarries. MSCR testing of mastic indicated that the dust containing significant Hisingerite had no adverse impact on the mastic response to shear stress. The change in binder feedstock was concluded to be the root cause of the lack of resistance to cyclic shear stress observed in one runway surface. This occurred despite all batches of binder meeting the viscosity-based Australian specification for paving grade bitumen. The specification has no mechanism to prevent similar changes in bitumen feedstock affecting airport bitumen performance in the future. Incorporating performance-based testing in the Australian bitumen specification is recommended.     

Sorption of aqueous phosphorus onto bituminous and lignitous coal ashes

Aiming at the development of a phosphorus removal technology for waste water, phosphate (PO(4)(3-)) retention behavior of bituminous and lignitous coal ashes was investigated using a batch reactor. Ash samples, including fresh and weathered fly and bottom ashes, were studied for their sorption isotherms and reversibility. Fly ashes had a much higher phosphate retention capacity (4000-30,000mgP/kg) than bottom ashes (15-600mgP/kg). Lignitous coal ashes were more capable of retaining phosphate than bituminous coal ashes. The retention process was largely irreversible, and the irreversibility increased with the increase in the retention capacity. Weathering enlarged the retention capacity of the bituminous bottom ash, but substantially lowered that of the fly ash, likely due to the difference in the weather-induced changes between the fly and bottom ashes. Sorption isotherms of fly ashes were found to be adequately represented by the Langmuir model while those of bottom ashes fitted better to the Freundlich model. Concentrations of Ca(2+) and PO(4)(3-) in the aqueous phase were measured at the end of sorption and desorption experiments, and were compared with solubilities of three calcium phosphate minerals. The aqueous solutions were saturated or super-saturated with respect to tricalcium phosphate (Ca(3)(PO(4))(2)) and hydroxyapatite (Ca(5)(PO(4))(3)OH), and slightly under-saturated with respect to amorphous calcium phosphate. It is concluded that precipitation of calcium phosphate is the predominant mechanism for phosphate retention by coal ash under the conditions studied. There is a strong and positive correlation between alkalinity and phosphate sorption capacity. Consequently, acid neutralization capacity (ANC) can be used as an indicator of phosphate sorption capacity of coal ashes.     

From virgin to recycled bitumen: A microstructural view

In the present work, soft and hard bitumens recovered from unaged, aged and recycled asphalt concrete (AC) mixtures, which in laboratory tests performed mechanically as well as an AC mixture produced with virgin materials, were investigated regarding rheological, thermal and surface microstructural aspects. For comparison purposes, bitumen containing 50 wt% of virgin bitumen and 50 wt% of bitumen recovered from reclaimed asphalt pavement (RAP) was studied. Some properties of the bitumens remained unchanged throughout the preparation of the AC mixture, aging and recycling: Soft and hard bitumens retained their general rheological properties significantly, and their thermal and surface microstructural properties partially. Soft bitumens presented larger “bee” structures and, therefore, higher surface roughness, while hard bitumens presented smaller “bee” structures and, thus, lower surface roughness. Furthermore, soft bitumens seemed to contain higher crystalline-like content than hard bitumens. For the soft cases, the unaged recovered bitumen did not show the same characteristics (rheological and surface microstructure) as the virgin bitumen. Similarly the recovered recycled bitumen did not show the same characteristics (surface microstructure) as the bitumen prepared from the mixture of virgin bitumen and RAP bitumen. Aging of the AC mixture changed the rheological properties of the soft bitumen by increasing the complex modulus and decreasing the phase angle. Similarly, recycling changed the rheological properties by increasing the complex modulus and decreasing the phase angle. Compositional changes occurred during AC mixture preparation (possibly also aging and recycling) for both soft and hard bitumens. Consequently, more “phases” were observed on the surface microstructure for the recovered bitumens as compared with the virgin bitumens. However, no significant trend was found for the surface microstructure characteristics between the unaged, aged and recycled recovered bitumens. Moreover, the nature of the virgin bitumen influenced the properties of the recycled recovered bitumen, e.g. the glass transition temperature.     

The mechanical properties of rubber compounds containing soft fillers

A detailed examination of failure of properties of polybutadiene containing soft elastomeric fillers has previously been described [1]. Here the effect of filler modulus and filler-matrix adhesion on tear strength is measured. Tear behaviour depends upon the level of interfacial adhesion; when high, tear strength increases with increasing filler hardness, but if interfacial adhesion is low, incorporation of fillers may result in low tear strengths. An estimate of the edge flaw size is made from the tear strength and strain energy densities at break. It was found that compounds with low interfacial adhesion generally had edge flaw sizes of the same order as the maximum filler particle size. A correlation between tear strength and tear surface morphology is made.     

Diffusion with micro-sorption in bentonite: evaluation by molecular dynamics and homogenization analysis

We here give a numerical analysis method of a diffusion problem including sorption chemistry for bentonite clay. Bentonite predominantly consists of the microscopic smectitic clay minerals (mainly montmorillonite and beidellite). Physico-chemical properties of smectite clays such as diffusivity of chemical species and adsorptivity on surface of clay mineral are characterized by crystalline structure of hydrated smectite minerals. To obtain the microscopic properties of the hydrated smectite, the molecular behavior is analyzed by a molecular dynamic (MD) simulation. We understand at least two types of adsorption are formed on the smectite surface; outer sphere complex and inner sphere complex. The inner sphere complex occurs on the edge sites of clay minerals. The amount of mono-layer of cations on the edge surface is considered as the adsorptivity of smectite in the microscopic level. A multiscale homogenization analysis (HA) is applied to extend the microscopic characteristics of the hydrated smectite to the macroscopic behavior. The diffusion and adsorption of a radioactive specie, cesium (Cs), is introduced by this analysis. The calculated results appear to be acceptable.