Ultrasound Propagation Velocity Research Articles

Evaluation of cortical bone strength using a quantitative ultrasound measurement device in dogs.

This study was performed to evaluate cortical bone strength in dogs using a quantitative ultrasound measurement device. In this study, 16 clinically healthy dogs with no lameness underwent measurement of the ultrasound propagation velocity of cortical bone (namely, speed of sound [SOS]) at the radius and tibia. Additionally, computed tomography examination with a calibration phantom was performed in 10 dogs. We calculated the bone mineral density (BMD) and Young's modulus from the computed tomography data using bone strength evaluation software. SOS, BMD, and Young's modulus were statistically compared between the radius and tibia. In addition, we examined the correlation between SOS and BMD and between SOS and Young's modulus. We also examined the correlation between SOS and age in the 13 dogs whose age was known. BMD and Young's modulus were not significantly different between the radius and tibia, but SOS was significantly different (P<0.05). Moreover, SOS and BMD showed a positive correlation in both radius and tibia. Similarly, SOS and Young's modulus showed a positive correlation. In addition, SOS and age showed a strong positive correlation (radius: r=0.77, P<0.05, tibia: r=0.83, P<0.05). Our finding that SOS of the radius and tibia cortical bone was correlated with BMD and Young's modulus indicates that quantitative ultrasound can be useful for evaluating cortical bone strength in dogs.

Mechanical properties of ignimbrites of Tenerife Island employed as building stone and their correlation with some physical properties

The aim of this research work was to determine and analyse the mechanical properties of a group of four varieties of ignimbrites, which are differentiated according to their colour: brown, violet, grey and green. These ignimbrites are mined in the southern part of Tenerife (Canary Islands) and are widely used as building stone. Mechanical characterisation was carried out by determining: ultrasound propagation velocity, uniaxial compressive strength, flexural strength under concentrated load, point load strength, Schmidt hammer rebound number and rupture energy. To evaluate the influence of the anisotropy planes and the degree of correlation between the different directions, all tests were done in more than one direction, except for the rupture energy. A simple regression analysis incorporating the physical properties available in the literature is included, with special emphasis on those with the highest correlation coefficient. Finally, a multiple regression analysis is performed to find the best fitting equations to predict the compressive strength. Of the four varieties studied, the green ignimbrite proved to be the one with the highest mechanical strength, with some properties three times higher than those obtained for the brown ignimbrite and almost twice as high as those obtained for the violet ignimbrite and the grey ignimbrite, the latter varieties having a similar behaviour to each other. In most cases, the behaviour of the ignimbrites studied is consistent with their lithology, but some properties of the green ignimbrite exceed the range reported in the literature, thus providing a new reference for this lithotype. Simple regression analysis revealed strong correlations between uniaxial compressive strength and water absorption (r = −0.89) and point load strength (r = 0.85). Flexural strength showed very strong correlation with ultrasonic velocity (r = 0.91) and point load strength (r = 0.95). Applying the multiple regression method, the best estimators of compressive strength found were a model with four independent variables; apparent density, open porosity, water absorption and Schmidt hammer rebound index (R2 = 0.91) and a model with five variables, adding point load resistance (R2 = 0.93).

Effect of Salt Mist Ageing on the Physical and Mechanical Properties of Two Ignimbrites from the Canary Islands (Spain).

The aim of this research work is to study the effect of salt mist ageing on the physico-mechanical properties of two ignimbrites from the Canary Islands (Spain). Due to their insular nature and extensive coastlines, these regions are highly susceptible to atmospheric salt aerosols, which is a significant weathering agent for building materials. The ignimbrites analysed are marketed under the names "Azul Lomo Tomás de León" and "Marrón de Abades" and are widely used as building stones. Petrographic, mineralogical and chemical properties were obtained via polarisation microscopy, X-ray diffraction and X-ray fluorescence. The samples were subjected to 60 cycles of a salt mist environment, following relevant European standards. Scanning electron microscopy images of the specimens were analysed along with physical properties, including apparent density, open porosity, water absorption, colourimetry and ultrasound propagation velocity, initially and after every 20 cycles, allowing us to assess their evolution during the ageing test. Mechanical properties were evaluated using uniaxial compressive strength and flexural strength under concentrated load tests on two groups of specimens: one unaged and the other subjected to 60 ageing cycles. With the exception of apparent density, the other properties show a decrease between 5% and 30%. However, open porosity increases and is one of the properties most affected by the ageing test.

Dynamics of changes in the velocity of ultrasound propagation in the bone tissue of premature children according to the data of ultrasound densitometry

All premature babies lack the intrauterine phase of active mineralization of the bones, osteogenesis changes, speed of ultrasound propagation in bone tissue changes. Aim. The purpose of the article was to determine osteopenia in premature babies (PB) based on ultrasound densitometry at birth and during the period of intensive care. Materials and methods. 70 premature babies and 20 full-term newborns were studied. The authors determined the bone ultrasound speed (SOS, m/s) and its comparative evaluation (Z-score) with the representative base of the ultrasound sonometer “Sunlight Omnisense 9000” (Israel). SOS was defined as average at Z ≥-1.0 SD, as low – at Z from -1.1 to -2.0 SD, and as significantly low – Z ≤- 2.0 SD. Results. 54.3 % of PB had osteopenia at birth: low indicators in 28.6 %, significantly low in 25.7 %. Postnatally, an increase in bone tissue deficiency of PB was observed – osteopenia with a low Z was diagnosed in 41.1 %, with a significantly low – in 37.5 % of PB. Conclusions. The number of PB with osteopenia increased 1.4 times, during the first 4 weeks of life. An increase in bone tissue deficiency was most often (p &lt; 0.05) observed among children (52.0 %) with normal / average Z-score SOS indicators. Z-score SOS indicators in children with osteopenia were stable during the first month of life. The odds ratio of having osteopenia were 3.37 times higher for those born in GA of 33 weeks or less (OR = 3.37; CI 95 % [1.25, 9.09], p &lt; 0.05), and 7.50 times higher odds of having significantly low Z-scores (OR = 7.50; CI 95 % [1.60, 34.59], p &lt; 0.05), ), and 8.15 times higher odds of having significantly low Z-scores after 1 month of life (OR = 8.15; CI 95 % [2.23; 29.70], р &lt; 0.05), than in children with greater GA. Indicators of physical development of premature newborns do not allow assessing the state of bone mineral velocity and require dynamic ultrasonic densitometry, despite the presence of correlations of SOS with indicators of the mass or length of infants depending on the gestational timing of birth.

A characterisation study of ignimbrites of Tenerife Island employed as building stone

The objective of this study is to evaluate the petrophysical properties of four ignimbrites employed as dimension stones. The natural stone under study is produced in Tenerife Island (Spain) under the commercial brand name of Piedra Chasnera and are differentiated according to their chromatic variety into: brown, violet, grey and green. To assess the suitability for feasible applications, it is essential to have a comprehensive knowledge of its properties. In this respect, mineralogical, petrographic and chemical properties were obtained by X-ray diffraction (XRD), polarisation microscopy (POM) and X-ray fluorescence (XRF). According to the procedure described in the standardised methods, apparent density, open porosity, water absorption at atmospheric pressure, water absorption coefficient by capillary and ultrasound propagation velocity were measured. The four variants of ignimbrites were analysed and classified according to the results obtained. It was found that the properties vary depending on the depth of the stratigraphic volcanic level from which the stone is extracted. From the review of the published data, it can be seen that the test results are within the expected values for this lithotype. A comparison was also made with other types of dimensional stones. The correlation analysis shows that there is a high degree of correlation between the physical properties studied.

Analysis of the Stressed State of Sand-Soil Using Ultrasound

The maintenance of the ballast substructure is an important cost-driver for railway systems. The problem is that today’s condition monitoring methods are insufficient to collect detailed data on the compaction and stress allocation inside the ballast bed. That makes it challenging to improve the maintenance technology and organization. This study aimed to investigate the applicability of the ultrasound method for analyzing the state of stress of sand-soil and the relation between the residual stress and wave propagation velocity. The experiments on the sand in a box with different allocations of the ultrasonic receivers and pressure measurement cells were produced under different external loading. In addition, the vertical and horizontal stress distributions were measured. The results showed a correlation between the test load, the state of stress, and the ultrasound propagation velocity. Moreover, the residual stresses after the loading cycles were analyzed.

СОСТОЯНИЕ КОСТНОЙ ТКАНИ У ДЕТЕЙ С БРОНХИАЛЬНОЙ АСТМОЙ

To date, the question of the effect of the nature of the course of bronchial asthma on the state of bone tissue in patients is being studied. 465 children with bronchial asthma aged 7 to 16 years were monitored. The examined performed ultrasound osteodensitometry. We found that 72.3% of patients with bronchial asthma had a low body mass index, and in 22.1% of the examined body mass index exceeded the average values. Only in 5.6% of patients its value was within the normal range. The average level of physical development was revealed in 64.3% of patients, above the average - in 16.5%, below the average - in 12.9%, and high and low physical development in 4.1% and 2.2% of patients, respectively. According to ultrasonic osteodensitometry in the presence of asthma in patients, a significant decrease in the mean values of the bone density index, broadband ultrasound attenuation and ultrasound propagation velocity relative to the comparison group values was registered. In patients receiving long-term inhaled glucocorticosteroids, all densitometry indicators were lower than in patients who did not take them or who were on short courses of this therapy. When analyzing the gender characteristics of ultrasound osteodensitometry, we identified the fact of a greater risk of developing bone fractures in female patients.

Study of the Course of Cement Hydration in the Presence of Waste Metal Particles and Pozzolanic Additives.

As the construction of hydrotechnical and energy facilities grows worldwide, so does the need for special heavyweight concrete. This study presents the analysis of the influence of waste-metal particle filler (WMP) on Portland cement (PC) paste and mortars with pozzolanic (microsilica and metakaolin) additives in terms of the hydration process, structure development, and physical–mechanical properties during 28 days of hardening. Results have shown that waste-metal particle fillers prolong the course of PC hydration. The addition of pozzolanic additives by 37% increased the total heat value and the ultrasound propagation velocity (UPV) in WMP-containing paste by 16%; however, in the paste with only WMP, the UPV is 4% lower than in the WMP-free paste. The density of waste-metal particle fillers in the free mortar was about two times lower than waste-metal particle fillers containing mortar. Due to the lower water absorption, the compressive strength of WMP-free mortar after 28 days of hardening achieved 42.1 MPa, which is about 14% higher than in mortar with waste-metal particle filler. The addition of pozzolanic additives decreased water absorption and increased the compressive strength of waste-metal particle filler containing mortar by 22%, compared to pozzolanic additive-free waste-metal particle fillers containing mortar. The pozzolanic additives facilitated a less porous matrix and improved the contact zone between the cement matrix and waste-metal particle fillers. The results of the study showed that pozzolanic additives can solve difficulties in local waste-metal particle fillers application in heavyweight concrete. The successful development of heavyweight concrete with waste-metal particle fillers and pozzolanic additives can significantly expand the possibility of creating special concrete using different local waste. The heavyweight concrete developed by using waste-metal particle fillers is suitable for being used in load balancing and in hydrotechnical foundations.

Особенности оценки сплошности свай методом сейсмоакустической дефектоскопии

Introduction. The authors present the results of pile continuity studies conducted using seismoacoustic defectoscopy. Tests were conducted in the Rostov region and Moscow. Reflectograms of tested piles, as well as the subsequent interpretation and confirmation of the design length and continuity of the pile shaft are provided. Materials and methods. The research results were obtained using Spektr 4.3, whose operating principle is based on the theory of elastic wave propagation. This device is used for the recording of the pile response to external impacts with the preset pulse parameters. The signal is recorded by means of an accelerometer sensor, connected to a special computer with the software for the digitization and interpretation of incoming information. Data processing results are presented in the form of computer graphic images (reflectograms), which show the pile length, continuity, damages (if any) and their location. Results. The dependence between soil homogeneity and signal purity has been identified. At the interface between two types of soils that are different in density, the sound wave was reflected and partially passed further, creating characteristic peaks of false defects. To eliminate false defects, studies of layered soils are necessary. Conclusions. The results confirm the effect of the soil homogeneity on signal purity. The higher the heterogeneity of the soil structure, the bigger the number of false peaks that the reflectogram demonstrates. A prerequisite for the correct interpretation of the results of pile continuity testing is the study of the geological section and preliminary instrumental identification of the ultrasound propagation velocity for each individual pile.

Application of paper sludge and clay in manufacture of composite materials: Properties and biological susceptibility

With the aim of developing composite materials to be used on indoor wall systems, different composite materials (paper sludge (100 wt%) and paper sludge (60 wt% and 80 wt%) + clay (20 wt% and 40 wt%) were produced. Composite materials were tested for biological susceptibility, physic-mechanical characteristics (shrinkage, density, water erosion resistance, compressive stress at 10% relative deformation and Young's modulus, ultra sound propagation velocity, thermal conductivity) and microstructure. The granulometric composition of paper sludge and clay content of the samples are essential factors that affect the physic-mechanical characteristics of the composite materials. This study considered 2 types (S type and S* type) paper sludge granulometric compositions. S type composite materials (paper sludge particles were smaller than 8 mm) have the better thermal conductivity, S* type composite materials (paper sludge particles were smaller than 4 mm) show the better performances in terms of compressive stress at 10% relative deformation. Increasing clay content (20% and 40%, S* type composite materials) increases density, shrinkage, compressive stress at 10% relative deformation, also, decreases biological susceptibility (Rhizopus oryzae mould). The results showed that, all composite materials had bulk density around 0.65–1.12 g/cm3, shrinkage 1.7–6.0%, compressive stress at 10% relative deformation 0.95–7.0 MPa, thermal conductivity 0.072–0.154 W/(mK). Also, all composite materials have good resistance to water erosion.

Sodium Alginate Ultrasound Phantom for Medical Education.

The ultrasound phantoms used to educate medical students should not only closely mimic the ultrasound characteristics of human soft tissues but also be inexpensive and easy to manufacture. I have been studying handmade ultrasound phantoms and proposed an ultrasound phantom comprising calcium alginate hydrogel that met these requirements but caused a speckle pattern similar to that observed in ultrasound images of liver. In this study, I show that adding ethanol to the precursors used to fabricate the phantom reduces the speckle pattern. The ultrasound propagation velocity and attenuation coefficient of the phantom were 1561 ± 8 m/s and 0.54 ± 0.18 dB/cm/MHz, respectively (mean ± standard deviation), which are within the ranges of those in human soft tissues (1530-1600 m/s and 0.3-1.0 dB/cm/MHz, respectively). This phantom is easy to fabricate without special equipment, is inexpensive, and is suitable for elementary training on ultrasound diagnosis, operation of ultrasound-guided needles, and blind catheter insertion.

Application of the ultrasound control to evaluation of the crack-resistance of low-carbon martensite steel 07Kh3GNMYuA

The goal of the study is to reveal the impact of change in the structural state of steel 07Kh3GNMYuA after heat treatment on the values of the critical stress intensity coefficient (K1c) obtained at a temperature of 50°C and on the velocity of ultrasound wave propagation, as well as to determine a correlation between them for rapid assessment of the crack resistance using acoustic characteristics. The mechanical characteristics of the material and the critical stress intensity coefficient K1c were obtained on the test machine «Inspekt 100 Table». The tangent method is used for determination of K1c. Three samples per K1c value were used in the experiment for a three-point bending scheme at the operating temperature T = –50°C. Acoustic parameters were measured using the echo-pulse method. The results of ultrasonic scanning of heat-strengthened samples made of steel 07Kh3GNMYuA demonstrated the possibility of non-destructive quantitative evaluation of the critical stress intensity coefficient. New data on the mechanical properties of steel 07Kh3GNMYuA and on the correlation between the velocity of longitudinal elastic waves and the values of the critical stress intensity coefficient of structures were obtained. Deviation of the calculated values of K1c obtained using acoustic measurements from the experimental values does not exceed 10%. The proposed model, which explains change in the acoustic characteristics of steel 07Kh3GNMYuA on the basis of phase changes occurring in the steel structure upon tempering, provides conducting of similar studies for other modes of heat treatment and other steel grades. The method is a low labor- and time-consuming procedure for determination of the mechanical characteristics of the products made of steel 07Kh3GNMYuA, since it does not require the manufacturing of samples and their testing. The developed procedure can be proposed for manufacturing application, as the main or additional method for evaluation of the mechanical parameters of materials after various modes of heat treatment.

Contribuição Para O Desenvolvimento De Uma Metodologia De Dosagem Para Concreto Permeável Baseada No Desempenho

Na atualidade não existe uma metodologia consolidada que permita determinar os consumos de materiais para obter as propriedades mecânicas e hidráulicas do concreto permeável, isso limita a aplicação deste concreto em obras civis. Além disso, as metodologias mais utilizadas para a dosagem de concreto permeável são fundamentas no teste e repetição de experimentos. O objetivo deste artigo é contribuir no desenvolvimento de uma metodologia de dosagem simples, versátil e baseada no desempenho (propriedades finais) do concreto permeável. Para isso foi realizado um programa experimental focado em estudar a influência do volume da pasta nas propriedades finais (porosidade, densidade, velocidade de pulso ultrassônico, permeabilidade e resistência à compressão) do concreto permeável. Os resultados apresentaram diferenças estatisticamente significativas em todas as propriedades finais, exceto a velocidade de pulso ultrassônico, entre as composições com diferentes volumes de pasta. O estudo confirma a possibilidade de uso de uma metodologia experimental simples para dosar concretos permeáveis.

Flexural behavior of HPFRCC: Enhancing post-crack strength and toughness by magnetic alignment of the reinforcement

This paper presents an investigation on the effect of magnetic orientation of steel fibers on the physical–mechanical and electrical properties of a High Performance Fiber Reinforced Cement Composite. A simplified magnetic circuit was proposed to align the reinforcement within the cementitious matrix. X-ray Computer Tomography was employed to qualitatively access the fiber distribution in hardened specimens. Physical and electrical properties were characterized by ultrasound propagation velocity and electrical resistivity, while mechanical performance was evaluated by flexural and compressive tests. Scanning electron microscopy was used to study the damage processes in the fiber–matrix interfaces. Results showed that the magnetic circuit designed in this study was able to generate a preferential orientation of the steel fibers, increasing the ultrasound propagation velocity and causing anisotropy in the electrical properties. Furthermore, the modulus of rupture and toughness of the composite were significantly enhanced, leading to a feasible reduction in the critical fiber volume for bending when fibers are aligned.

Effects of aberration on super-resolution ultrasound imaging using microbubbles

Visualizating vasculature beyond the diffraction limit can be achieved using ultrasound super-resolution (USR). Typically, ultrasound (US) scanners model the target medium as homogeneous, assuming a constant speed-of-sound for time-of-flight based calculations. However, variations in US propagation velocity caused by varying tissue layers affect beamforming operations. This aberration is likely to have considerable effect on USR accuracy when imaging at depth. Here we investigate the effect of aberration on USR localization accuracy. Wave propagation through different tissue media was modelled from a linear transducer using k-Wave, and the resulting pulse-echo data from a point scatterer located at 45mm depth was beamformed. Media included a control homogeneous propagation medium, and aberrating media typical of liver imaging. Aberration effects were estimated using RMS arrival-time fluctuations (ATF) and energy-level fluctuations (ELF) at the scatterer location. Signals were extracted and localized with existing localization techniques. Results indicated USR localisation accuracy decreased with increasing aberration. Axial localisation errors reached 836.6 mm for an ATF 30.9 ns. Furthermore, errors increased with decreasing frequency from 4 to 3 MHz. The scale of these errors relative to micro-vascular structures of interest suggests that aberration will have considerable impact on USR performance and requires attention to ensure its success.

Impact of ultrasound speed choice on the quality of the second-trimester fetal ultrasound examination in obese women

PurposeThe purpose of this study was to assess the impact of the free choice of ultrasound propagation velocity on ultrasound image construction to improve the completion rate and anatomical quality of fetal second-trimester ultrasound examination in obese women. Materials and methodsThis repeated cross-sectional single-center study retrospectively collected second-trimester ultrasound images of 88 obese women. During the first period, ultrasound examinations were performed in 44 women (mean age, 31.4±5.9 [SD] years; range: 21.1 - 45.3 years) applying only the standard 1540m/s tissue ultrasound velocity (group 1). During the second period, ultrasound examinations were performed in other 44 women (mean age, 31.4±5.1 [SD] years; range: 20.6 - 41.6 years) with the operator free to choose among three available velocity settings (1420m/s, 1480m/s or 1540m/s) for the scanning planes for the morphological images (group 2). All women underwent mid-trimester ultrasound examination at 20 to 24 gestational weeks. Two observers assessed the examinations in both groups for completeness, quality, and duration of fetal ultrasound examinations. ResultsNo differences in age (P>0.99), body mass index (P=0.67), prevalence of previous cesarean delivery (P=0.30) or gestational age at the second-trimester scan (P=0.20) were found between the two groups. The mean cumulative duration of these ultrasound examinations was longer in group 1 than in group 2 (for both the complete (P=0.04) and incomplete (P=0.03) examinations). The quality of the anatomic images according to Salomon's criteria was less often acceptable in group 1 (5/44, 11.4%) than in group 2 (15/44, 34.1%) (P=0.02). ConclusionFree choice of ultrasound velocity improves the overall performance of fetal second-trimester ultrasound examinations in obese women.

Influence of Crimped Steel Fibre on Properties of Concrete Based on an Aggregate Mix of Waste and Natural Aggregates.

This research was inspired by the growing global shortage of natural aggregates. Different types of waste ceramics (apart from recycled concrete) are the most popular materials for the production of waste aggregates as possible substitutes for natural ones. The aim of this research was to analyse the efficiency of different aggregate mixes composed of waste and natural materials focusing on two waste ceramic aggregates, which were prepared concrete mixes based on specifically composed aggregates (blend of natural aggregate, porous and iron oxide-rich (red) waste ceramic aggregate, and dense, kaolin-based (white) waste ceramic aggregate). All aggregates were thoroughly tested before utilisation for concrete mix creation. Altogether, four blends of aggregates were prepared in order to prepare concrete mixes using a simplex experiment design. The mixes were then modified by adding various amounts of crimped steel fibre. Such properties of hardened steel fibre-reinforced concrete (SFRC) such as density, compressive strength, shear strength, ultrasound propagation velocity, dynamic modulus of elasticity, and limit of proportionality during flexural testing were of special interest. Tests were conducted according to European and Japanese standards. The achieved fibre-reinforced concretes were characterised by satisfactory strength characteristics, thereby enabling the substitution of traditional reinforcement. Strength classes according to the fib Model Code 2010 were assigned.

An experimental approach to design self-consolidating concrete

This paper presents the analysis of an experimental mixture design approach for self-consolidating concrete (SCC) based on two design parameters to optimize mechanical properties and durability. The first approach is based on an empirical determination of the self-consolidation ability of mixtures with a fixed mortar content, while the second approach is based on enhancing the aggregate packing. The proposed procedures enable the establishment of a mixture design nomogram that can correlate the materials’ composition and properties. The effect of mixture design parameters on hardened properties of investigated mixtures developed using each of the proposed approaches was compared in terms of compressive strength to secure a given modulus of elasticity, ultrasound wave propagation velocity and rapid chloride ion penetration. The modulus of elasticity and ultrasound wave propagation velocity of the designed SCC mixtures are found to be, respectively, almost 50% and 8% higher than those of conventional concrete, even at SCC mixtures with lower compressive strength values. Lower modulus of elasticity and ultrasound wave propagation velocity were obtained for SCC mixtures than conventional concrete with compressive strength between 50 and 60 MPa.

The efficiency of nanolime and dibasic ammonium phosphate in the consolidation of beige limestone from the Pasargadae World Heritage Site

The limestone used at the Pasargadae World Heritage Site in Iran, an outstanding open-air architectural heritage site dating from the Achaemenid period (sixth century BC), has suffered weathering due to interaction with the environment. It was built out of beige limestone that today shows scaling and pitting decay patterns. Two inorganic consolidating products that are very promising: nanolime and dibasic ammonium phosphate (DAP) were considered for the consolidation of the limestone. Consolidation treatments were conducted on samples from a quarry and applied using a paintbrush with 50% nanolime dispersion in isopropyl alcohol and 1.0 M DAP water solution. Superficial consolidation was evaluated by means of a micro-drilling resistance test, and color changes were assessed by spectrophotometry. The microstructure of the treated samples was observed using FE-SEM. The efficacy of the two consolidation treatments was also assessed by testing their hydric properties and durability (hydric tests, freeze-thaw, and salt crystallization cycles). The compactness in the altered samples was monitored by measuring the ultrasound propagation velocity. We found that the superficial resistance increased in a similar way with both treatments. However, spectrophotometry revealed a yellowish color in the samples treated with DAP. During FE-SEM observations, some diffused microcracks were detected on the surface of DAP treatment. When subjected to accelerated aging tests, both treatments managed to postpone the formation of the first microcrack during the freeze-thaw test and both showed outstanding stability during salt crystallization cycles. In conclusion, the nanolime product seems to be more compatible with beige limestone because it does not affect its aesthetic qualities (color, lightness, and a homogeneous layer formed on the surface of the stone). Moreover, previous research found that lime has a low propensity for biological growth. This supports its use as a consolidating product for the stone used in open-air archeological sites that are prone to microbial growth, such as the beige stone used in the Pasargadae WHS.

Change in the physical­mechanical and decorative properties of labradorite under thermal exposure

We have experimentally investigated samples from the four fields of coarse-grained labradorite, which is extracted in Ukraine. The samples of labradorite were tested at high temperatures of 200, 300, 400, 500, 600, 700, 800, 900 °С. Red spots at the surface of samples is the result of oxidation of the metal Fe 2+ : at different fields of labradorite they cover a different area of the sample's surface of natural stone: it ranges from 39 to 60 %. An analysis of the polished labradorite surface after heating revealed that red inclusions are evenly distributed over the surface of labradorite samples. Oxidation of minerals, which is visually observed on all the samples of labradorite, starts at a temperature of 300 °С. One of the features in the research described in this paper is the application of digital image processing in order to quantitatively assess the Fe oxidation area (red spots) at the polished surface of labradorite samples. To a temperature of 500‒600 °С, there is a gradual increase in the oxidized area of the samples' surface. At temperatures above 700 °С, there is a sharp increase in the oxidized area at the samples' surface. In general, the oxidized spots of metals cover between 40 to 60 % of the surface of labradorite samples. When heated, the labradorite samples become 50 % brighter than the original value for indicator L in the color system Lab. A decrease in the velocity of ultrasonic wave propagation in labradorite samples occurs evenly, without surges. The reason for a decrease in the ultrasonic wave velocity is the formation of defects and cracks in labradorite samples due to an uneven thermal expansion of minerals. At a temperature of 700 °С ° or higher, there is a decrease in the velocity of ultrasound wave propagation in the samples of natural stone. At heating, there is a decrease in the indicators for gloss in all labradorite samples. In general, when labradorite was heated up to 900 °С, the samples from the Ocheretyansky deposit lost 11.21 % of their gloss, from the Neviryvsky deposit ‒ 4.03 %, from the Osnikivske deposit ‒ 33.57 %, from the Katerinovsky deposit ‒ 15.3 %.