X-ray Attenuation Method Research Articles

Tomography-based investigation on the early-time capillary imbibition in stained foam concrete

In this study, the vertical imbibition of water from foam concretes upward were studied with the assistance of staining, which illustrated the way contrast material spread in specimens during CT scans. The 20 × 20 mm2 bottom face of dried rectangular concrete was adopted, and the test was limited to the first 2.5 h. Using cesium (Cs) or iodine (I) as the staining agent, a new-developed X-ray attenuation method (XRAM) was used to obtain the spatial distribution of water. The result showed that Cs and I are equally trustable in tracing water during the early-time imbibition. Besides, two regions, namely “saturated verge” (near the imbibing face) and “unsaturated transport region” (from an inner area), could be recognized from the imbibition path regarding their variant evolving patterns. The saturated verge from the inlet was of constant width, while the scale of the unsaturated transport region kept increasing during imbibition, and the imbibing rate was similar for all specimens in this study. Moreover, even though the imbibition progress in this study was confirmed a diffusion-controlling progress, a broad imbibition front was revealed from the averaged 1D water content profile, which was mainly attributed to the irregular-shaped “saturated verge”.

Investigation on the microstructure of a 3D-printed mortar through a novel leaching-subsidiary tomography

The microstructure of a 3D-printed mortar was investigated in present study. To enhance the density contrast between sand and cementitious slurry, a novel leaching strategy was used as an auxiliary method, based on which the spatial dispersion of sands in 3D-printed mortar was rendered. Meanwhile, to alleviate the problem of CT’s limited resolution, X-ray attenuation method (XRAM) was introduced in this study to investigate the spatial distribution of local porosity in 3D-printed mortar. Besides, focusing on single filaments, the upper part of the filaments presented lower sand rate and higher porosity than the lower part, and the difference between the filaments located near the top of 3D-printed mortar was more significant. Finally, based on the sliding method, the interlayer width, average porosity and average sand ratio of 3D-printed mortar were estimated as 640 21.9% and 43.1%, respectively. The research results would deepen the understanding of 3D-printed concrete.

Investigation of the Neutralizing Behaviors of Cement-Based Materials Using a New pH Indicator Formulated from February Orchid Petals.

Investigation of the neutralizing behavior of concrete is essential, as it can help reveal the durability properties of concrete structures. In this paper, anthocyanin extracted from February orchid (F. orchid) petals was used to characterize the neutralized (carbonated, leached, and sulfate-attacked) regions of cement-based materials. The durability of F. orchid indicator was evaluated through comparison between discoloring behaviors of fresh and aged F. orchid indicators, and the capability of the new indicator in neutralization characterization was then verified by combining indicator (phenolphthalein, malachite green, indigo carmine, or thymolphthalein) spray, X-ray computed tomography (CT), and the X-ray attenuation method (XRAM). The result in the present study showed that, with a lower color intensity as compared to phenolphthalein/thymolphthalein, F. orchid indicator was less preferable in studying carbonation but a better choice in characterizing leaching and sulfate attack of cement-based materials. In addition, a sharp carbonation front was revealed in the present study, suggesting that the carbonation process in this study was controlled mainly by diffusion. For leaching and sulfate attack, the broader fronts revealed suggested that both processes were co-controlled by diffusion and reaction. The current work serves as a 'leap' toward the application of natural pigments in analyzing the durability of concrete structures.

Use of a novel pH indicator extracted from petals to investigate the carbonation behavior in cementitious materials

With increased realization on the deficiency to uncover the partial carbonated zone and potential toxicity to human body, the use of phenolphthalein indicator has been receiving increased controversy in recent years. In this study, a novel pH indicator, which was formulated from anthocyanin extracted via the petals of Orychophragmus violaceus (O. violaceus), is presented. Potential replacement of phenolphthalein by the new pH indicator was examined by spraying the newly developed indicator on the cross-sectional regions of accelerated carbonated mortar specimens. In comparison with the carbonation zones measured by phenolphthalein spray, computed tomography (CT) and X-ray attenuation method (XRAM), the experimental results confirmed that the O. violaceus indicator is reliable in detecting the carbonation fronts. Besides, due to a higher discoloration pH compared to phenolphthalein, the carbonation depths read from the newly developed indicator were larger due to the inclusion of the partial carbonated zone. Furthermore, the reliability of O. violaceus indicator in the characterization of natural carbonation was also verified in this study. The present work promotes the application of natural dye in the durability tests of civil engineering, and the experimental results based on the new indicator contribute to a deeper understanding on the carbonation mechanism of cementitious materials.

Effect of Carbonation on Microstructure Evolution of Alkali-Activated Slag Pastes

In order to reveal the carbonation mechanism of alkali-activated concrete, the accelerated carbonation tests based on alkali-activated slag pastes were carried out. The evolution of microstructure and chemical composition for alkali-activated slag pastes subjected to carbonation was analyzed combining thermogravimetric analysis (TGA), mercury intrusion porosimetry (MIP) and a recently developed extended X-ray attenuation method (XRAM). The results showed that, the microstructure of alkali-activated slag pastes deteriorated gradually. Based on MIP and XRAM, the porosity of S4 (sample with a water-binder ratio of 0.4) increased by 8.24% and 11% after carbonation, and that of S6 (sample with a water-binder ratio of 0.6) increased by 7.45% and 10%, respectively. Besides, thermal analysis showed that, after carbonation, 11.45 mol / L and 19.57 mol /L CaCO3 were produced separately by S4 and S6. The main carbonation product for S6 was calcite, but for S4 vaterite and disorderly stacked calcite were also presented.

Hygric properties of porous building materials (V): Comparison of different methods to determine moisture diffusivity

Moisture diffusivity is an important material property for performing the hygrothermal analysis of buildings and the built environment. Its experimental determination is still a challenge, albeit various destructive and non-destructive experimental methods are available. This paper compares the X-ray method, the ruler method, the multi-step method and the Kießl-Künzel method to non-destructively determine the moisture diffusivity of calcium silicate, ceramic brick and lime mortar. Results show that the ruler method can provide the closest results to the well-known X-ray attenuation method with a more straightforward process, but it's mainly suitable for materials with a sharp and visible water front. The multi-step method is easy to operate in experiments and suits most porous building materials, but it takes a long time to condition samples and needs complicated data processing, which seems too complex to get the moisture diffusivity as a step function. The Kießl-Künzel method is the simplest but not always accurate.

Investigation on porosity of partly carbonated paste specimens blended with fly ash through dual CT scans

Carbonation is one of the durability concerns for fly ash blended concrete. Unlike concrete made with ordinary Portland cement (OPC), the microstructure of fly ash blended concrete evolves in a different pattern during carbonation. In this research, paste samples blended with variant amounts of fly ash were taken for accelerated carbonation, and based on an extend X-ray attenuation method (XRAM), spatial distribution of porosity for partly-carbonated fly ash-blended pastes was investigated for the first time. Based on XRAM, the porosity before carbonation is 0.42, 0.35, 0.36 and 0.46 respectively for OPC, FA30, FA50 and FA70, and the porosity changed to 0.36, 0.42, 0.46 and 0.49 respectively after carbonation. The evolved microstructure subjected to carbonation was verified by mercury intrusion porosimetry (MIP). For quantitative porosity results, very sharp porosity gradients were observed on the carbonation front, which attests that all carbonations in this study were diffusion controlling processes. The results of current research can be used for the verification of carbonation models and for the understanding of carbonation mechanism.

Use of tomography to understand the influence of preconditioning on carbonation tests in cement-based materials

Recognition of the rising amount of atmospheric CO2 has brought renewed interest in understanding the effects of carbonation on reinforced concrete performance. In laboratory testing, the specimens must be preconditioned to effectively study carbonation. This paper studied the influence of several preconditioning schemes on the carbonation profiles of cement paste specimens subjected to accelerated carbonation tests. The evolution of microstructure and moisture during carbonation were investigated accordingly. Bulk of the work was based on an extended X-ray attenuation method (XRAM), which relied on X-ray computed tomography (CT). A novel method was introduced to evaluate the extent of damage due to drying. Based on extent of damage, the paper recommends standard-cured specimens for carbonation tests as compared to water-cured specimens. Also, when comparing between oven drying and mass balancing, the latter was shown to be more suitable, as the inner moisture distribution becomes more uniform after this drying protocol, and less fluctuation of humidity will occur during carbonation.

Measurements using X‐ray attenuation vertical distribution of the void fraction for different flow regimes in a horizontal pipe

Abstract METERO is an experimental facility built by the French Atomic Energy Commission (CEA) aimed at studying adiabatic air-water flows in horizontal pipes. The physical insight and the experimental data provided by METERO experiments support the validation of MCFD (NEPTUNE CFD) and System (CATHARE-3) codes as a part of the NEPTUNE project developed jointly by EDF, CEA, AREVA NP and IRSN. Bottin et al. (2014) have proposed a flow map of the different regimes encountered in the METERO experiments, i.e. stratified flows, slug flows, plug flows, stratified dispersed bubbly flows and dispersed bubbly flows. Following this work, we investigate the vertical distribution of the void fraction integrated horizontally using X-ray attenuation measurements. The use of the X-ray attenuation method presents the advantage of providing integrative measurements along the X-ray path. To obtain the vertical distribution of the void fraction integrated in the horizontal direction, the X-ray apparatus is rotated to ensure a spatial resolution of about 1 mm. For METERO’s pipe of 100 mm diameter, this provides a fine discretisation of the void fraction distribution with a reasonable amount of realisations, i.e. 7 angles. After a description of the experiments and the measurements’ method, different flow regimes and their transitions (e.g. slug, plug, and bubble flow regimes) are explored by varying the water and air superficial velocities within the ranges 0.71 m/s–5.31 m/s (Reynolds number of the liquid phase varying between 71,000 and 530000) and 0.023 m/s–0.68 m/s respectively. The evolution of the vertical distribution of the void fraction in horizontal pipes is discussed. Moreover, statistics such as the ratio of the air and water phase velocities are derived from the measurements. It is shown that due to the accumulation of bubbles in the upper part of the flow (where the flow is more going slowly than in the bottom part) the air phase velocity is generally smaller than the water phase velocity for bubble and plug flows. On the contrary, the air phase velocity is generally higher than the water phase velocity for slug flows with a ratio varying like five thirds of the supplied void fraction.

Determination of LIII subshell photoelectric parameters of iridium

The LIII subshell photoelectric cross section, jump ratio, jump factor, and Davisson–Kirchner ratio of iridium have been determined by mass attenuation coefficients. The measurements have been performed using the X-ray attenuation method in narrow beam geometry. The obtained results have been compared with the tabulated values of XCOM (Berger et al. XCOM: Photon cross section database (version 1.3). NIST. Available at http://physics.nist.gov/xcom . 2005) and FFAST (Chantler et al. X-ray form factor, attenuation and scattering tables (version 2.1). NIST. Available at http://physics.nist.gov/ffast . 2005).

Development of phantom for quantitative analyses of human dentin mineral density.

The purpose of the present study was to develop a novel-designed phantom that could be scanned with a sample in the same image, that specialize for quantitative analyses of human dentin mineral density using the X-ray attenuation method. A further attempt was made to demonstrate the intracoronal dentin mineral density using this phantom in mandibular incisors. The phantom prepared with a 15 mm hole in the center of an acrylic resin bar having an outside diameter of 25 mm and 8 small holes (diameter, 3 mm) were made at equal intervals around the center. Liquid dipotassium hydrogen phosphate (K2HPO4) solutions were established at 0.4, 0.6, 0.8 and 1.0 g/cm3, and were arranged to these holes. The mean value of the intracoronal dentin mineral density was 1.486 ± 0.016 g/cm3 in the present study. As the results of the present study corresponded to previous reports, this new phantom was considered to be useful. This phantom enables the analysis of samples that are not readily available by conventional mechanical tests and may facilitate biomechanical investigations using X-ray images. It was suggested that this system is a simple, accurate and novel mineralization measuring system.

Monitoring reinforcement corrosion and corrosion-induced cracking using non-destructive x-ray attenuation measurements

To test the applicability of the x-ray attenuation method to monitor corrosion products as well as the formation and propagation of cracks in cementitious materials, reinforced mortar samples were tested under accelerated corrosion conditions. Experimental results demonstrate x-ray attenuation measurements can track time-dependent development of corrosion products and the subsequent initiation and propagation of corrosion-induced cracks. Also, x-ray attenuation measurements allowed determination of the actual concentration of the corrosion products averaged through the specimen thickness. The total mass loss of steel, obtained by the x-ray attenuation method, was found to be in very good agreement with the mass loss obtained by gravimetric method as well as Faraday's law. Results of the presented experimental approach provide pertinent information for the further development and verification of numerical tools simulating corrosion-induced damage in reinforced concrete.

Thickness determination of SmCo films on silicon substrates utilizing X-ray diffraction

This paper presents a nondestructive measurement technique for the determination of the film thicknesses of Co and SmCo based magnetic films deposited by sputtering on single-crystal silicon (100) substrates. X-ray diffraction of Cu Kα radiation has been used to measure the intensity of the (400) reflection from bare silicon substrates and as attenuated by sputter coated Co and SmCo based films on Si substrates. A four-axis research diffractometer allowed the substrate orientation to be fine adjusted to maximize the (400) diffraction intensity. The thickness of SmCo based films was in a range from 0.05 to 5 μm. Co film thicknesses on Si could be measured to a few tens of nanometers. The accuracy of the thickness measurements depends on the effective mass attenuation coefficient of the film material. For the materials considered, the thicknesses determined by the X-ray attenuation method agree within at least several percent to values determined by other methods.

C-5 Absolute Thickness Determination of SMCO Films on Silicon Substrates Utilizing X-ray Diffraction and Their Composition Measurements By EXRF

This paper presents a nondestructive measurement technique for the accurate and absolute determination of film thicknesses of Co and SmCo based magnetic films deposited by sputtering on single crystal Silicon (100) substrates. X-Ray diffraction of Cu K radiation has been used to measure the intensity of the (400) reflection from bare silicon substrates and as attenuated by sputter coated Co and SmCo based films on Si substrates. A 4-axis research diffractometer allowed the substrate orientation to be fine adjusted to maximize the (400) diffraction intensity. The absolute thickness of SmCo based films was in a range from 0.05 to 5 Co film thicknesses on Si could be measured to a few tens of nanometers. The absolute accuracy of the thickness measurements depend on the effective mass attenuation coefficient of the film material. For the materials considered, thicknesses determined by the X-Ray attenuation method agree within at least several percent to values determined by other methods.

Density and atomic number measurements with spectral x-ray attenuation method

X-ray attenuation measurements are widely used in medical and industrial applications. The usual results are one- to three-dimensional representations of the attenuation coefficient μ(r). In this paper, we present the ρZ projection algorithm for obtaining the density ρ(r) and atomic number Z(r) with an energy-resolving x-ray method. As input data the algorithm uses at least two measurements μ1,μ2,… with different spectral weightings of the source spectrum S(E) and/or detector sensitivity D(E). Analytically, ρ is a function of μ1−cμ2, c=const, and Z is a function of μ1/μ2. The full numerical treatment yields ρ(μ1,μ2) and Z(μ1,μ2) with S(E) and D(E) as commutative parametric functions. We tested the method with dual-energy computed tomography measurements of an organic sample and a set of chemical solutions with predefined ρ and Z. The resulting images show ρ and Z as complementary information: The density ρ reflects the morphology of the objects, whereas the atomic number Z=number of electrons/atom describes the material distribution. For our experimental setup we obtain an absolute precision of 0.1 for Z and 20 mg/cm3 for ρ. The ρZ projection can potentially lead to these classes of quantitative information for various scientific, industrial, and medical applications.

EVALUATION OF PATH-LENGTH ESTIMATORS FOR CHARACTERIZING MULTIPHASE SYSTEMS USING POLYENERGETIC X-RAY ABSORPTIOMETRY

Polyenergetic, high-photon-flux X-ray absorption methods promise to make possible rapid, high-resolution measurements of phase fractions in multiphase systems. Improved statistical methods for data analysis, however, are needed. We develop a set of three new path-length estimators as alternatives to the traditional lumped-energy approach, and we compared this set of estimators for two classes of examples. The experimental comparisons were performed with clean systems to allow reliable measures of accuracy and precision of all material estimates; however, soil systems, for which X-ray attenuation methods have been routinely applied, have radiation attenuation properties similar to the systems used in this work, making these results directly applicable to soil systems. Results show that the new estimators provide more accurate and precise estimates of path length than the traditional lumped-energy approach, especially for challenging, multiple material estimation problems. The bias of estimated path lengths was reduced by at least 80% in all cases and was typically around 90% compared with the standard approach. Our sample results also demonstrate the reliable simultaneous measurement of three material path lengths, a new and desirable capability for multiphase flow experiments. Alternatively, the improved estimators developed in this work can be used to reduce measurement times compared with traditional methods for estimates of similar quality.

Effects of sodium hypochlorite solution on root dentine composition.

Sodium hypochlorite (NaOCl) solution,<or=5% w/v available chlorine (abbreviated subsequently to %), is widely used as an irrigant in root canal treatment of teeth, so its effects on dentine are of clinical importance. The effects of approximately 0.5%, 3% and 5% NaOCl solution on the composition of root dentine were studied at ambient temperature. For dentine powder treated for 30 min, depletion of the organic phase was confirmed by infrared spectroscopy. Apatite lattice parameters showed no significant change, but NaCl was also detected by X-ray powder diffraction. The low solubility of apatite mineral in the NaOCl solutions was demonstrated by the constant weight of bulk enamel specimens immersed for seven days. The stability of the mineral phase was confirmed by scanning microradiography (SMR), an X-ray attenuation method employing photon counting. Repeated SMR measurements of the local mineral content of bulk samples of root dentine and a synthetic hydroxyapatite aggregate during exposure to pumped NaOCl solutions for 100 h showed no mineral loss. As predicted from apatite chemistry, reaction of NaOCl with the mineral phase can be excluded as a primary factor in changes in mechanical properties of treated dentine. Effects of retention of NaCl on endodontic sealants requires further investigation.

Grazing incidence liquid metal mirrors (GILMM) for radiation hardened final optics for laser inertial fusion energy power plants

A thin film of liquid metal is suggested as a grazing incident mirror for robust final optics in a laser inertial fusion energy (IFE) power plant. The amount of laser light the grazing incidence liquid metal mirror (GILMM) can withstand, called the damage limit is limited by the surface disturbances initiated by rapid laser heating. For 0.35-μm light, the damage limit for a sodium film 85° from normal is calculated to be 57 J/cm 2 normal to the beam for a 20 ns pulse and 1.3 J/cm 2 for a 10-ps pulse (2 and 90 m 2 of mirror area per 100 kJ of laser energy at 20 ns and 10 ps, respectively). Feasibility relies on keeping the liquid surface flat to the required accuracy by a combination of polished substrate, adaptive (deformable) optics, surface tension and low Reynolds number, laminar flow in the film. The film's substrate must be polished to ±0.015 μm. Then surface tension keeps the surface smooth over short distances (<10 mm) and low Reynolds number laminar flow keeps the surface smooth (disturbances less than ±0.01 μm) over long distances (>10 mm). Adaptive optics techniques keep the substrate flat to within ±0.06 μm over 100-mm distance and ±0.6 μm over 1000 mm distances, even after 30 years of cumulative damage via neutron irradiation. The mirror can stand the X-ray pulse when located 30 m away from the microexplosions of nominal yield of 400 MJ (50 MJ of X-rays) when Li is used, but for higher atomic number liquids like Na there may be a significant rise in temperature, forcing the use of other X-ray attenuation methods such as attenuation by xenon gas. The GILMM should be applicable to both direct and indirect drive and pulse lengths appropriate to slow compression (∼20 ns) or fast ignition (∼10 ps). For direct-drive laser beams near the poles (70°, where 90° is vertical), stable thin films become more challenging. Proof of the concept experiments are needed to verify the predicted damage limit and required smoothness.

Real-time measurement of in vitro enamel demineralization in the vicinity of the restoration-tooth interface.

An X-ray attenuation method using photon counting (scanning microradiography) is presented for the real-time study of in vitro demineralization of dental tissues in the vicinity of the restoration-tooth interface. By repeated measurement of mineral content profiles during the course of demineralization, the pattern of lesion development and the rate of mineral loss can be studied. The method is illustrated by comparison of enamel demineralization near a polyacid-modified composite resin restoration, near a bis-GMA/TEGMA composite resin restoration, and in an unrestored control. The method has potential for study of the influence of restorative materials on susceptibility of tooth tissue to demineralization.

Multiple scattering correction in the measurement of particle size and number density by the diffraction method

A ray tracing (or angular flux) method is used to simulate multiple scattering of light by particles on the assumption that the angular distribution function of light scattered by a particle which is illuminated by a plane wave of light is applicable to the case in which a particle is illuminated by a light ray. Numerical results for 1-D slab geometry with azimuthal symmetry show that the measured width of the particle size distribution decreases more rapidly than the measured particle mean size with the number density of the particles, which is consistent with the measurements of particle size much larger than the wavelength of light. A correction increases the equivalent thickness (number density) of the particle phase to that by the x-ray attenuation method. Correction charts for the measurement of particle size distributions are given.