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Raw kaolinitic–illitic clays as high‑mechanical‑performance hydraulically pressed refractories
Get PDFThe usage possibility of 19 composites of raw refractory clays from Serbia containing approximately 53.29% of SiO2 and 26.73% of Al2O3 is presented. The sum of fluxing oxides was 57.74%, while these materials contained 32% of quartz, 29% of kaolinite and 26% of illite–mica. Dilatometry tests revealed a sudden shrinkage with the peak at approximately 1115 °C, owing to the formation of mullite. The refractoriness was in the range of 1581–1718 °C, which classifies the composites from low- to high-duty refractories. Based on correlation analysis, the refractoriness mostly depended on the content of alumina. The lightness of the fired test pieces was lower after firing when compared to the dry samples, and it decreased with the firing temperature from reddish to grayish. The study presents a novel attempt to define all the necessary properties of raw refractory clays and products fired at the 1100–1300 °C range on a laboratory level. Most of these clays can be used as natural refractory materials for ceramic and glass furnace lining. The organic matter in some of the samples influences negatively the fast-firing process
Identifying the capabilities of ground penetrating radar in structural condition assessment
No full textThe condition assessment of structures using the non-destructive ground penetrating radar
(GPR) method is based on the analysis of the strength, sign and shape of the signal reflected
from the objects under the examined surface. Therefore, it is used for locating reinforcement in
reinforced concrete structures, determining the type and structure of structural elements,
evaluating the corrosion of reinforcement, etc. This paper presents the applicability of the GPR
method for locating reinforcement and determining the geometry of structural elements, as well
as the study of the sensitivity of the GPR signal to chloride-induced corrosion parameters
Process for making multicomponent perovskites
No full textInternational Publication Number: WO2023/170304 A
Biomimetics Design of Tooth Root Zone at Cylindrical Gears Profile
No full textDuring the last few decades, the requirements for modern machine elements in terms of size
reduction, increasing the energy efficiency, and a higher load capacity of standard and non-standard
gears have been very prevalent issues. Within these demands, the main goals are the optimization
of the gears’ tooth profiles, as well as the investigation of new tooth profile designs. The presented
design idea is based on the optimal solutions inspired by nature. Special attention is paid to the new
design of the tooth root zones of spur gears in order to decrease the stress concentration values and
increase the tooth root fatigue resistance. The finite element method is used for stress and strain
state calculations, and the particular gear pair is modeled and optimized for these purposes. For
tooth root strength analysis, the estimations are based on the theory of critical distances and the
stress gradients obtained through finite element analysis. The obtained stress gradients have shown
important improvements in the stress distribution in the transition zone optimized by biomimetics.
An analysis of the material variation influence is also performed. Based on the investigations of a
particular gear pair, a significant stress reduction of about 7% for steel gears and about 10.3% for cast iron gears is obtained for tooth roots optimized by bio-inspired design
Gamma and X radiation attenuation characteristics for ultrahigh properties of concrete, concrete with barite and concrete with magnetite and steel
No full textDuring the implementation of construction barrier design procedures for protection against gamma and X radiation, the inevitable question arises of choosing building materials with suitable mechanical and radiation characteristics for protective barriers. Based on engineering practice, it is necessary to compare different types of concrete used for the construction of buildings in which there are sources of gamma and X radiation, as in cases where radiation sources appear in medical institutions with linear accelerators, cyclotron installations for the acceleration of nuclear particles, in the environment of nuclear reactors, in radioactive waste warehouses or in radiation sterilization units. In the analysis of costs and benefits, several criteria are used to evaluate the characteristics of concrete, so that, in addition to the mechanical ones, the radiation characteristics of the building material are also taken into account. One of the most important characteristics of radiation shielding concrete is its overall mass attenuation coefficient. In this paper, the XCOM computer code was used to calculate the total mass attenuation coefficients in the energy range from 0.01 MeV to 100 MeV for three types of concrete: ultrahight properties concrete (UHPC), concrete with barite and concrete with magnetite and steel. Based on the comparison of the calculation results, it was concluded that concrete with magnetite and steel has a greater protective power than the other two types of concrete for gamma and X radiation energy lower than 30 keV. Another important conclusion is that concrete with barite has a higher protective power than the other two types of concrete in the photon energy range from 30 keV to 300 keV, and for photon energy greater than 6 MeV. A detailed analysis of the calculation results revealed that in the energy range from 400 keV to 6 MeV the values for the total mass attenuation coefficients are approximately the same for three different types of concrete
Raw Kaolinitic Clays from Serbia and their Potential in the Production of Extruded Ceramic Tiles
Get PDFThe present study analyses the usage possibility of the 7
raw kaolinitic clays from Serbia. The characterization of
raw materials is done by using instrumental techniques to
determine chemical and mineralogical compositions, particle
size distribution and behavior during firing (changes in
mass, temperature of the system and dimensions). Additionally,
refractoriness is determined for each of the materials.
The samples are shaped by the extrusion process and fired
in a 1000-1250 °C range. The ceramic and technological
characteristics of the fired samples are determined, and
micromorphology is recorded. It is concluded that most of
the tested clays can be used to produce cream-colored
extruded ceramic tiles with water absorption between 0.20
and 5.28 % by firing at 1250 °C. The majority of the samples
can be used as ceramic tiles for flooring purposes after
firing at 1200 °C. Additionally, all samples are found suitable
for special purpose roofing tiles production after firing
at 1100 °C
Heavyweight Ultra-High-Performance Concrete with Micro-Reinforcement
No full textThe impacts of nano-silica addition, steel micro-reinforcement, and aggregate type on the mechanical properties and durability of ultra-high-performance concrete (UHPC) were studied. As aggregates, quartz and barite were used. The amounts of steel fibers and nano-silica were alternated. Six concrete mixes were produced with quartz sand, and the remaining six concrete mixes were designed with barite sand. Fibers made about 3-5% of the concrete composition’s mass. In a 2-5% concentration, nano-silica was used as a cement replacement. The inclusion of nano-silica significantly boosted the compressive strength of UHPC. The compressive and flexural strengths were also positively impacted by fiber supplementation ranging from 3% to 5%. The amount of fiber utilized proved to be more influential than the aggregate used. The UHPC concrete's durability was increased as all samples were highly resistant to freezing and thawing cycles. UHPC designed with barite aggregate demonstrated good X and gamma ray absorption at energies below 300 keV
Numerical Determination of the Life of Steel Exposed To Low Cycle Fatigue
Get PDFIn the paper, based on the results of the experimental research of high-strength low-alloy steel
(HSLA), Nionicral 70 (NN-70), under conditions of low-cycle fatigue (LCF), a numerical analysis of
stress and determination of the life of steel samples was performed. Experimental testing of the
behavior of the samples were performed with controlled and fully reversible strain (/2 = const,
R = min/max = -1), according to the standard ISO 12106:2003 (E). For computational analyses, the
following were used: the method of least squares and the method of finite elements (FEM). On the
basis of the analysis of the results of the stress-deformation state and the determination of the life
span through the isolines of the life span and comparison with the results of experimental tests, a
graphic representation is given. The analysis justified the effort to numerically solve the estimation
of the lifespan of steel under low cycle fatigue (LCF)
Assessment of concrete structures using ground penetrating radar (GPR): Main findings of the ASAP project
No full textNovel and rapid drying characterization test suitable for the brick and tile industry
No full textThe industrial raw material compositions in brick
or tile production are normally adapting from time to time
with novel clays. The proper raw material change must be
based on the reliable raw material characterization tests.
Regardless to the fact that commonly used (Bigot, Muller-
Biehl, Ratzenberger, Piltz, Hermansons, etc.) drying
sensitivity criterions allow the comparison of different raw
materials they are not related with the mineral composition
and mechanical nature of clays. Besides these are timedemanding
tests. The X-ray characterization of raw
material is reliable only when orientated samples are
prepared. In other cases, it is necessary to have additional
characterization test such as thermo-differential (DTA) and
thermo-gravimetric (TG) analysis in order to confirm the
presence or absence of individual clay minerals. The
quantity of the interlayer water content present in clays is
in direct correlation with the mineralogical composition
and the clay type. This effect can be easily qualified on the
DTA/TG curves. This was a trigger for establishing the
novel rapid drying sensitivity criteria. The analysis of
different raw materials has confirmed that the moisture
loss registered on TG curves at 2000C can be used as novel
drying sensitivity criterion. This value is respectively for
insensitive raw materials less than 2.0 while for highly
sensitive one is larger than 2.80. The proposed method is
very simple, rapid and reliable for the application in brick
and tile industry. The second objective of this paper was to
compare the results of the proposed method with the
widely used Bigoth, Ratzenberg and Piltz tests. A good
correlation was found