Development of morphological properties of road surfacing aggregates during the polishing process

This study investigated the morphological properties of different road surfacing aggregates. Eleven types of aggregates with great variances in their mineralogical properties were chosen for the study. For each type, 500-gram test samples were prepared and subjected to polishing using the Micro-Deval (MD) apparatus. Before and after polishing, 48 particles from each type of aggregate were selected and run through the aggregate imaging system and X-ray computed tomography equipment to capture the change of morphological characteristics, including sphericity, angularity and texture. The results showed that log-normal functions are ideally suited to describe distributions of the analysed morphological characteristics before and after MD. The mass loss of each aggregate can be well described with a function using the expected value of morphological parameters with the aid of a multiple regression analysis. The change of angularity is the main cause for the mass loss whilst the changes of both the sphericity and texture only have an ancillary influence.     

Study of adsorption characteristics of long chain alkyl amine and petroleum sulfonate on silicates by electrokinetic potential,microflotation, FTIR,and AFM analyses

The long-chain alkyl amines and petroleum sulfonates are mostly used to remove unwanted minerals from feldspar ores in acidic pHs. In this study, their adsorption characteristics on pure albite and quartz were investigated by electrokinetic potential measurements, microflotation tests, Fourier transform infrared spectroscopy, and atomic force microscopy studies. According to the results, amine had strong influence on zeta potentials of both albite and quartz turning them positive and resulting over 90% flotation recovery at certain pH values. Petroleum sulfonate, on the other hand, was less effective in terms of both zeta potential values and flotation recovery responses of albite. Although albite and quartz had different zeta potentials and flotation recovery responses with each collector, they displayed similar adsorption bands of CH₂ group over fingerprint region and adsorption layers with different intensities after being treated with the collectors. However, the adsorption of each collector on the minerals was altered by rinsing with acetone indicating that the interaction of the collectors with albite and quartz surfaces were mostly by Coulombic forces and hydrogen bonding.     

Sorption-barrier properties of granitoids and andesite-basaltic metavolcanites with respect to Am(III) and Pu(IV): 2. Absorption of Am and Pu from groundwater on crushed samples of granitoids and andesite-basaltic metavolcanites and also on their rock-forming minerals

A model study is made of the sorption-barrier properties of crushed samples of granitoids and andesite-basaltic metavolcanites with respect to Am(III) and Pu(IV). In sorption from simulated groundwater (pH 8.3), the volume distribution coefficient K _d of Am was determined to be (0.8–1.6) × 10³ and (3.4–7.0) × 10³ cm³ g^?1, and that of Pu, (0.5–1.7) × 10³ and (1.0–10.0) × 10² cm³ g^?1 for metavolcanites and granitoids, respectively, suggesting good sorption-barrier properties of these rocks. The sorption power of the basic rock-forming minerals of granitoids decreases in the order biotite > feldspar > quartz. The results obtained in this study can be used as input data in predicting the rates of Am and Pu migration with groundwater.     

Effect of crystal orientation on lapping and polishing processes of natural quartz

Lapping and polishing processes of natural quartz are investigated in relation to crystallographic orientation and applied normal stress. Weight loss measurements and surface profilometry were carried out in X-, Y-, Z-, and AT-cut samples. The relationship found between material removal rate and stress depends on specimen orientation. Based on indentation fracture mechanics, this behavior is discussed in relation to fracture toughness and scratch hardness anisotropy of quartz crystals. Scanning electron microscopy (SEM) shows that brittle microcracking is the primary mechanism involved with material removal in the lapping process. Plastic deformation mechanisms begin to operate on lapped and polished surfaces above a certain value of stress. Surface profiles and SEM micrographs show that the roughness of lapped surfaces decreases with increasing normal stress, but an opposite behavior is observed in polished surfaces     

Effect of granite flour proportion on the strength properties of geopolymer mortar based on fly ash

Given global trends and challenges, the development of binders for the production of geopolymer concretes has become a topical area of building science. The purpose of this study is to determine whether granite can replace traditional construction aggregate, such as river sand, during geopolymer production, as well as to demonstrate the effect of the proportion of granite flour on the strength properties of fly ash-based geopolymer mortar. A combination of granite flour, quartz sand, and fly ash in various proportions was used as an aluminosilicate precursor. The scope of the study includes density measurements, compressive and flexural strength tests, abrasion by the Boehme method, and microstructural observations. Based on the obtained results, it can be concluded that granite can be successfully used as a replacement for quartz sand during the production of fly ash-based geopolymers. Moreover, the addition of granite makes it possible to improve the strength properties of geopolymers, compared to a geopolymer composite containing quartz sand.     

Fabrication of quartz diaphragms for helium leak detection

The feasibility of 50 μm thick diaphragms with a metallic film heater integrated on a quartz disc and working up to 500 °C has been demonstrated. The diaphragms have been realized with the coupling of abrasive jet machining and mechanical polishing techniques. The metallic film has been obtained by means of a sequence of e-gun evaporation and electrochemical growth steps. No degradation of the adhesion characteristics was registered. Electrical properties were retained without electro-migration even for working conditions of 50 h at 500 °C. Aim of the device is the application in quartz molecular sieves thermally/electrically modulated, basically for helium leak detection.     

Bio-beneficiation of kaolin and feldspar and its effect on fired characteristics of triaxial porcelain

Presence of iron compounds as impurities in kaolin and feldspar, impart reddish colour to ceramic products manufactured using these minerals. The quality of kaolin and feldspar was enriched mainly through iron removal by biological methods. Bacteria isolated from kaolin of Indian origin were used for bioleaching. Biotreatment of kaolin and feldspar using indigenous bacteria not only lowered the iron content of the minerals but also improved their whiteness. The porcelain prepared with these biobeneficiated minerals was compared to that prepared with non-beneficiated one. Physico-mechanical properties of porcelain were distinctly improved by using biobeneficiated kaolin and feldspar, without affecting the individual mineralogical compositions of kaolin and feldspar.     

Deformation band and texture of a cast Mg-RE alloy under uniaxial hot compression

Microstructural evolution and texture of a cast Mg-9Gd-4Y-0.6Zr ingot under hot compression were studied in this paper. Post-deforming microstructures were characterized by optical microscopy, scanning electron microscopy and transmission electron microscopy, while crystallographic orientation information was obtained from X-Ray macro-texture measurement and EBSD micro-texture analysis. Dynamic recrystallization (DRX) initiated from the deformation bands (DB) forming on original grain boundaries; the DB became widen with continuously conversion of low-angle-boundary grains into high-angle-boundary grains. The tendency of strain localization increased with Z parameter. The macro-texture analysis indicates that uniaxial compression yielded out the randomized basal texture component. This texture component was found to be strengthened with increasing Z parameter. The micro-texture analysis shows that the deviation from the ideal basal texture arose from orientated growth within DBs. Moreover, the localization deformation promoted dynamic precipitation within DBs, which inhibited the development of DRX.     

开级配沥青磨耗层宏观构造特征及其降雨条件下抗滑性能研究

使用三维扫描仪获取3种级配OGFC沥青混合料试件表面三维数据,计算了试件表面的平均轮廓深度(MPD)、峰顶数目和算术平均峰顶曲率,用摆式仪对不同降雨量条件下OGFC试件的抗滑性能进行了测试,并分析了表面特征与抗滑性能的关系。结果表明,OGFC的MPD随着级配变粗呈增大趋势;OGFC试件表面的总峰顶数目随级配变细而增多,且峰顶数目在深度方向呈偏态分布,而算术平均峰顶曲率与级配无明显关系;随着降雨量增加,OGFC的摩擦系数先迅速减小,略有增大后,趋于稳定;降雨条件下,OGFC摩擦系数与MPD有一定关系,但受浅层表面峰顶数量的影响更大。     

Acoustoelastic response of polycrystalline aggregates exhibiting transverse isotropy

Acoustoelasticity is an ultrasonic technique which has been used for the determination of active and residual stresses in common structural materials. This paper examines the effect of texture on the acoustoelastic response in polycrystalline bodies. In particular materials which are transversely isotropic aggregates of cubic crystals are studied. The second- and third-order elastic constants of the polycrystal are derived from the elastic properties of the constituent crystals, and the crystalline orientation relative to the body's symmetry axis. The acoustoelastic relations between velocity and deformation are then presented for the aggregate. Finally, evaluation of the acoustoelastic response for several ideal textures using data for aluminum single crystals shows that the response is highly dependent on the texture.     

Forensic investigation of the cause(s) of slippery ultra-thin bonded wearing course of an asphalt pavement: influence of binder content

This paper documents the second part of a forensic investigation performed to determine the causes of loss of skid resistance and bleeding in two pavement sections rehabilitated with an ultra-thin bonded wearing course. The first part of the study explored the influence of the aggregate fraction on the loss of skid resistance. This second part focuses on binder-related issues to understand the cause of the bleeding. A detailed investigation was performed on cores removed from both sections to quantify the binder content profile with depth. The chemical characteristics of all the recovered binders were determined using Fourier transform infrared spectroscopy and X-ray fluorescence spectroscopy. The results suggested that bleeding due to excess binder in the tack coat contributed to this deleterious performance. Chemical analysis identified an upward migration of a part of the binder from the interface and confirmed this hypothesis.     

Forensic investigation of the cause(s) of slippery ultra-thin bonded wearing course of an asphalt pavement: influence of aggregate mineralogical compositions

The cause(s) of slippery ultra-thin bonded wearing course (UTBWC) of an asphalt pavement was investigated. Petrographic analysis showed that the aggregate used in the UTBWC is mainly limestone with an average acid-insoluble residue of 5.1%. Coefficient of friction tests were performed both on a comparative UTBWC from Virginia with a different aggregate mineralogy VA-UTBWC and on slabs extracted from the slippery UTBWC pavement overlay. The tests clearly showed that the slippery UTBWC overlay sharply declined throughout the polishing process, consistent with the aggregate mineralogical composition and its low amount of acid-insoluble residue. In contrast, the comparative VA-UTBWC mix showed a gradual increase and then decrease in friction with continued polishing. This investigation clearly showed that the cause of the slippery asphalt pavement problem of the road mainly attributed to limestone aggregate polishing.     

Rheological studies of nickel oxide and quartz/hematite mixture systems

This study aimed to investigate the rheology of two-mineral mixture systems as a function of pH and solid concentration. Single minerals (nickel oxide, quartz and hematite) and two-mineral systems (nickel oxide–quartz and nickel oxide–hematite) were studied. Rheology tests were conducted to investigate the effect of pH and solid concentration on shear yield stress of suspensions while zeta potential measurements of suspensions were used to explain the rheology results. Rheology results indicated that single mineral experiments showed that 5 and 10 vol.% of quartz and hematite had no shear yield stress whereas the one of nickel oxide was positive value. Shear yield stress of nickel oxide–quartz mixture and nickel oxide–hematite mixtures increased as increasing pH and solid concentration, and the value was higher than the one obtained with only nickel oxide. These results obtained with two-mineral mixture systems were explained by electrokinetic properties of the minerals, i.e. zeta potential of the minerals.     

Electron-trapping probability in natural dosemeters as a function of irradiation temperature

The electron-trapping probability in OSL traps as a function of irradiation temperature is investigated for sedimentary quartz and feldspar. A dependency was found for both minerals; this phenomenon could give rise to errors in dose estimation when the irradiation temperature used in laboratory procedures is different from that in the natural environment. No evidence was found for the existence of shallow trap saturation effects that could give rise to a dose-rate dependency of electron trapping.     

Surface state improvement of ground AT and SC quartz cuts by controlled dissolution in NaOH,KOH, LiOH

After the studies which allowed us to perfect the chemical thinning down, or controlled dissolution, of both AT and SC quartz plates in NaOH and KOH media, respectively, we have investigated mixtures of these with another basic compound (LiOH) in order to discover a common solvent for both AT and SC cuts. The results show that crystallographic orientation and solvent nature have a great influence on controlled dissolution especially on the surface texture. It appears that the basic compound which has the smallest cation imposes its properties and consequently, the chemical polishing of both AT and SC cuts cannot be made in good conditions with the same solvent.     

Micro-Texture Evolution in Aggressive Machining of Al Alloy 7075

The effects of process parameters on micro-texture evolution of Al alloy 7075 in machining under extreme conditions were investigated. For the first time, the process parameters in machining are related to the micro-texture evolution below the machined surface, through a computational modeling framework verified by robust experimentation. Finite element analyses (FEA) were performed to obtain the mechanical loads that the material experiences due to chip removal. The viscoplastic self-consistent (VPSC) approach was used to follow the evolution in texture due to the applied loads. The most outstanding texture component, which was seen in the case of increased feed rate, is closely followed by the texture evolution model. The observed discrepancy in experimental and computational results of texture evolution in a few studied cases is believed to be due to the activation of other microstructural evolution phenomena rather than dislocation slip, as a result of the ultra-high levels of exerted strain and strain rates to the machined surface.     

Characterisation of unbound aggregate materials considering physical and morphological properties

The objective of this paper is to evaluate the factors affecting resilient and permanent deformation behaviour of unbound granular materials, with a focus on the aggregate physical and morphological characteristics. To evaluate the behaviour of base course, repeated load triaxial testing is commonly used to establish the stress-dependent resilient modulus properties of unbound aggregate base and subbase materials. Although resilient modulus of aggregates is a critical input into mechanistic-empirical pavement design methods, the resilient modulus of unbound base material is often estimated from empirical correlations with index properties in the AASHTOWare Pavement ME design procedure for its simplicity. Since actual field stress conditions and resilient modulus stress states are generally quite different from those generated in the empirical test methods, use of an empirical correlation could lead to an unreliable prediction of resilient modulus and permanent deformation. In order to properly assess the stability of an unbound aggregate layer, it is necessary to establish a proper process to understand the factors affecting fundamental and performance-related properties of unbound granular materials. In this study, aggregate samples from four different sources were tested for resilient modulus and Poisson’s ratio measurements using the Precision Unbound Material Analyzer equipment. Morphological or shape properties of aggregate samples were also measured using an image analysis device. The results demonstrate that aggregate physical and morphological properties affect aggregate resilient and permanent deformation. Further, it is suggested that the resilient modulus of the aggregate should not be used as the sole indicator of rutting performance of aggregate base.     

Alkali-aggregate reaction—identifying reactive silicates in complex aggregates by ESEM observation of dissolution features

A petrographic examination can only be used to qualify a concrete aggregate in regard to its potential for AAR when the reactivity of the corresponding lithologies and minerals are known. In this study, two complex Swiss aggregates with polished surfaces were immersed in an alkaline solution in order to identify reactive minerals. Afterwards, dissolution and precipitation phenomena were investigated by environmental scanning electron microscopy.In general, quartz is the most reactive mineral in both aggregates. Feldspar, biotite and chlorite exhibit dissolution phenomena, and liberate alkalis and calcium. Various morphological types of gels are formed as precipitates on the polished surface: thin calcium silicate hydrate structures exhibiting card house morphology; small agglomerates (2–20 μm) with a smooth surface; and large agglomerates (20–500 μm) characteristic of common ASR reaction products. These gels mainly consist of Si and Ca with variable amounts of Na, Mg, Fe and Al.     

Experimental investigation on skid resistance of asphalt pavement under various slippery conditions

The skid resistant performance of slippery pavement is one of the most important pavement surface characteristics, as it is associated with both pavement serviceability and traffic safety. Through simulating different pavement conditions in the freezing laboratory, skid resistance of asphalt pavement under various slippery conditions is measured with pendulum friction coefficient tester. Then, the effects of pavement temperature on skid resistance of dry, wet, icing and snowy pavements are quantitatively analysed. Furthermore, factors exerting effects on test results are taken into account, such as thicknesses of ice and water film on pavement. Through quantitative analysis, empirical evaluation model of pavement friction coefficient (PFC) under different conditions is established. To facilitate practical engineering application, reference standard values of PFC are recommended. Finally, the PFC is classified into seven levels, which illustrates the corresponding relationships of friction rank, skid resistance assessment, PFC range and pavement conditions.