scholarly journals Experiments on Fiber Concrete Foundation Slabs in Interaction with the Subsoil

2020 ◽  
Vol 12 (9) ◽  
pp. 3939 ◽  
Author(s):  
Radim Cajka ◽  
Zuzana Marcalikova ◽  
Marie Kozielova ◽  
Pavlina Mateckova ◽  
Oldrich Sucharda
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Laboratory Tests ◽  
Three Dimensional ◽  
Concrete Slabs ◽  
Two Dimensional ◽  
Load Step ◽  
Loading Test ◽  
Displacement Sensors ◽  
Fiber Concrete

This article focuses on researching the interactions of fiber concrete slabs with subsoil. The experimental series includes four slabs made of fiber concrete with different dosages of fibers, from 0 to 75 kg/m3. The slabs were exposed to a loading test on a specialized loading frame. The laboratory tests for detailed descriptions of the fiber concrete’s mechanical properties were also an integral part of the experiments, including tests of the compressive strength, the modulus of elasticity, and split and bending tensile strength. Each slab’s deformation in a particular load step was evaluated in two-dimensional (2D) sections based on data measured with displacement sensors and in three-dimensional (3D) charts with the use of interpolation.

scholarly journals Biological and Mechanical Properties of Platelet-Rich Fibrin Membranes after Thermal Manipulation and Preparation in a Single-Syringe Closed System

2018 ◽  
Vol 19 (11) ◽  
pp. 3433 ◽  
Author(s):  
Dorottya Kardos ◽  
István Hornyák ◽  
Melinda Simon ◽  
Adél Hinsenkamp ◽  
Bence Marschall ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Cell Adhesion ◽  
Closed System ◽  
Three Dimensional ◽  
Glass Tube ◽  
Biological Properties ◽  
Platelet Rich Fibrin ◽  
Handling Characteristics ◽  
Freeze Dried

Platelet-rich fibrin (PRF) membrane is a three-dimensional biodegradable biopolymer, which consists of platelet derived growth factors enhancing cell adhesion and proliferation. It is widely used in soft and hard tissue regeneration, however, there are unresolved problems with its clinical application. Its preparation needs open handling of the membranes, it degrades easily, and it has a low tensile strength which does not hold a suture blocking wider clinical applications of PRF. Our aim was to produce a sterile, suturable, reproducible PRF membrane suitable for surgical intervention. We compared the biological and mechanical properties of PRF membranes created by the classical glass-tube and those that were created in a single-syringe closed system (hypACT Inject), which allowed aseptic preparation. HypACT Inject device produces a PRF membrane with better handling characteristics without compromising biological properties. Freeze-thawing resulted in significantly higher tensile strength and higher cell adhesion at a lower degradation rate of the membranes. Mesenchymal stem cells seeded onto PRF membranes readily proliferated on the surface of fresh, but even better on freeze/thawed or freeze-dried membranes. These data show that PRF membranes can be made sterile, more uniform and significantly stronger which makes it possible to use them as suturable surgical membranes.

Mechanochemical Devulcanization of Vulcanized Gum Natural Rubber

2005 ◽  
Vol 21 (3) ◽  
pp. 183-199
Author(s):  
G.K. Jana ◽  
C.K. Das
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Natural Rubber ◽  
Three Dimensional ◽  
Elongation At Break ◽  
Tear Strength ◽  
Vulcanized Rubber ◽  
Dimensional Network ◽  
Polymeric Chains ◽  
Cure Time

De-vulcanization of vulcanized elastomers represents a great challenge because of their three-dimensional network structure. Sulfur-cured gum natural rubbers containing three different sulfur/accelerator ratios were de-vulcanized by thio-acids. The process was carried out at 90 °C for 10 minutes in an open two-roll cracker-cum-mixing mill. Two concentrations of de-vulcanizing agent were tried in order to study the cleavage of the sulfidic bonds. The mechanical properties of the re-vulcanized rubber (like tensile strength, modulus, tear strength and elongation at break) were improved with increasing concentrations of de-vulcanizing agent, because the crosslink density increased. A decrease in scorch time and in optimum cure time and an increase in the state of cure were observed when vulcanized rubber was treated with high amounts of de-vulcanizing agent. The temperature of onset of degradation was also increased with increasing concentration of thio-acid. DMA analysis revealed that the storage modulus increased on re-vulcanization. From IR spectroscopy it was observed that oxidation of the main polymeric chains did not occur at the time of high temperature milling. Over 80% retention of the original mechanical properties (like tensile strength, modulus, tear strength and elongation at break) of the vulcanized natural rubber was achieved by this mechanochemical process.

scholarly journals Autologous Platelet Gel (APG): A Preliminary Evaluation of the Mechanical Properties after Activation with Autologous Thrombin and Calcium Chloride

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3941
Author(s):  
Antonio Scarano ◽  
Calogero Bugea ◽  
Lucia Leo ◽  
Pablo Santos de Oliveira ◽  
Felice Lorusso
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Calcium Chloride ◽  
Preliminary Evaluation ◽  
Loading Test ◽  
Platelet Gel ◽  
Group I ◽  
Group Ii ◽  
Autologous Platelet

The tensional and mechanical behavior of regenerative components, grafts, and blood clots represent an essential condition for the success of bone regeneration protocols. Autologous platelet growth factors represent a useful protocol to enhance the soft and hard tissue healing in several fields of medicine and craniofacial surgery. Different protocols for blood concentrates with and without activation have been proposed in literature. The aim of the present study was to investigate in vitro the mechanical properties of autologous platelet gel (APG) with autologous thrombin and calcium chloride. Materials and Methods: A total of 20 APG samples were evaluated; 10 samples were activated by autologous thrombin and calcium chloride (Group I) and 10 samples were non-activated (Group II). The tensile strength and modulus of elasticity were calculated through a static loading test (Lloyd 30 K, Lloyd Instruments Ltd., Segensworth, UK). Results: Group I (activated) reported a tensile strength of 373.5 ± 14.3 MPa, while Group II showed a significantly lower value of of 360.5 ± 16.3 MPa (p < 0.05). The Young’s modulus was 145.3 ± 10.4 MPa for Group I and 140.3 ± 15.3 MPa for Group II (p < 0.05). Conclusions: The effectiveness of the present in vitro simulation showed that the APG activation protocol is able to increase the mechanical characteristics of the blood derivates and could be clinically useful to enhance regenerative procedures.

Research on the Basic Mechanical Properties of Fly Ash Fiber Reinforced Concrete

2011 ◽  
Vol 261-263 ◽  
pp. 8-12
Author(s):  
Shu Shan Li ◽  
Ming Xiao Jia ◽  
Dan Ying Gao
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Fly Ash ◽  
Compressive Modulus ◽  
Fiber Reinforced Concrete ◽  
Cement Ratio ◽  
Influence Mechanism ◽  
Fiber Concrete ◽  
Early Strength

The basic mechanical properties of fly ash fiber concrete were tested. The influences to the compressive strength, splitting tensile strength and compressive modulus of elasticity of fiber concrete by water-cement ratio, dosage of fly ash and other factors were analyzed. The influence mechanism of fly ash to concrete is discussed. The results indicate that with the increase of the dosage of fly ash, the early strength of double-doped concrete is reduced, while the later strength of concrete was obviously increased.

Measurement of Deflection in Concrete Beams During Fatigue Loading Test Using the Microsoft Kinect 2.0

2016 ◽  
Vol 10 (1) ◽  
Author(s):  
Herve Lahamy ◽  
Derek D. Lichti ◽  
Jeremy Steward ◽  
Mamdouh El-Badry ◽  
Mohammad Moravvej
Keyword(s):  
Three Dimensional ◽  
Fatigue Loading ◽  
Reinforced Concrete Beam ◽  
Microsoft Kinect ◽  
Beam Deflection ◽  
Load Testing ◽  
Loading Test ◽  
Peak Displacement ◽  
Displacement Sensors ◽  
Centre Line

AbstractThis study focuses on 3 Hz fatigue load testing of a reinforced concrete beam in laboratory conditions. Three-dimensional (3D) image time series of the beam’s top surface were captured with the Microsoft time-of-flight Kinect 2.0 sensor. To estimate the beam deflection, the imagery was first segmented to extract the top surface of the beam. The centre line was then modeled using third-order B-splines. The deflection of the beam as a function of time was estimated from the modeled centre line and, following past practice, also at several witness plates attached to the side of the beam. Subsequent correlation of the peak displacement with the applied loading cycles permitted estimation of fatigue in the beam. The accuracy of the deflections was evaluated by comparison with the measurements obtained using a Keyence LK-G407 laser displacement sensors. The results indicate that the deflections can be recovered with sub-millimetre accuracy using the centreline profile modelling method.

scholarly journals Experimental Study on Mechanical Properties of High Performance Hybrid Fiber Concrete for Shaft Lining

2021 ◽  
Vol 11 (17) ◽  
pp. 7926
Author(s):  
Qian Zhang ◽  
Wenqing Zhang ◽  
Yu Fang ◽  
Yongjie Xu ◽  
Xianwen Huang
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Reinforced Concrete ◽  
Reference Group ◽  
Splitting Tensile Strength ◽  
Fiber Reinforced Concrete ◽  
Fiber Reinforced ◽  
Hybrid Fiber ◽  
Fiber Concrete ◽  
Shaft Lining

In order to solve the problem of highly brittle shaft lining under dynamic loading, a combination of hybrid fiber concrete mixed with steel and polypropylene fiber is proposed to make shaft lining. C60, the concrete commonly used in shaft lining, was selected as the reference group. The static mechanical properties, dynamic mechanical properties, and crack failure characteristics of the hybrid fiber concrete were experimentally studied. The test results showed that compared to the reference group concrete, the compressive strength of the hybrid fiber-reinforced concrete did not significantly increase, but the splitting tensile strength increased by 60.4%. The split Hopkinson compression bar results showed that the optimal group peak stress and peak strain of the hybrid fiber concrete increased by 58.2% and 79.2%, respectively, and the dynamic toughness increased by 68.1%. The strain distribution before visible cracks was analyzed by the DIC technology. The results showed that the strain dispersion phenomenon of the fiber-reinforced concrete specimen was stronger than that of the reference group concrete. By comparing the crack failure forms of the specimens, it was found that compared to the reference group concrete, the fiber-reinforced concrete specimens showed the characteristics of continuous and slow ductile failure. The above results suggest that HFRC has significantly high dynamic splitting tensile strength and compressive deformation capacity, as well as a certain anti-disturbance effect. It is an excellent construction material for deep mines under complex working conditions.

scholarly journals Mechanical Properties of Glass Fiber Concrete with Different Dosages of Glass Fiber

2020 ◽  
Vol 8 (5) ◽  
pp. 3916-3919
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Flexural Strength ◽  
Glass Fiber ◽  
Glass Fibers ◽  
High Dispersion ◽  
Conventional Concrete ◽  
Micro Cracks ◽  
Deformation Properties ◽  
Fiber Concrete

Conventional concrete i.e. the concrete generally has low tensile strength with limited ductility and low resistance towards cracking. The micro cracks that are developed internally are inherent among concrete and can be explained with the help of propagation of that micro cracks due to its inferior tensile strength. Different fibers, added at a certain percentage of concrete known to improve the deformation properties of concrete along with the plasticity against crack resistance, such as flexural strength. Mainly concrete & ferroconcrete research has been moved to steel fibers, and glass fibers have recently become more available, with no corrosion problems associated with glass fibers. This article describes an experimental study of the usage of glass fibers in the structural concrete. High-dispersion CEM-FILL fiberglass of 14 μm diameter with an aspect ratio of 857 was used at a dosage of 0.33% to 1% by weight in concrete and its mechanical properties such as compressive strength, flexural strength and modulus of elasticity.

scholarly journals LABORATORY TESTS ON THE STRENGTHENING OF WET-MIX SHOTCRETE LINING WITH THE USE OF NANOMATERIALS

2021 ◽  
Vol 36 (1) ◽  
pp. 49-59
Author(s):  
Hamid Kalhori ◽  
Raheb Bagherpour ◽  
Mohammad Amir Akhlaghi ◽  
Sayed Mohsen Mirdamadi ◽  
Mehdi Nasiri Sarvi
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Laboratory Tests ◽  
Size Range ◽  
Maximum Increase ◽  
Nano Clay ◽  
Cement Based Materials ◽  
Cast Concrete ◽  
Shotcrete Lining ◽  
Micro Silica

Adding nanomaterials to concrete extends the size range of constituent particles well into nano-scale dimensions, which could help the compacting of particles in cement-based materials. Regarding the differences between shotcrete and cast concrete, in this study, the properties of shotcrete with nano and micro-silica and nano-clay were experimentally studied. The micro and nanomaterials have been added at different percentages (6%, 9%, and 12%) to a shotcrete paste. The comparison was based on the uniaxial compressive strength, flexural strength, tensile strength, and porosity tests of different specimens. The results indicated that the maximum increase in compressive, flexural, and tensile strengths of shotcrete was related to 12% nano-SiO2, while for 12% nano-clay, all of these strengths were decreased at 28 days. The optimum percentage for shotcrete substitution by nano-clay was established to be 6%. Also, the application of the nanomaterials led to a decrease in the water absorption and porosity of shotcrete. Eventually, the results revealed that the improvement of mechanical properties by the introduction of the nanomaterials in shotcrete could be satisfactory.

scholarly journals The effect of temperature on the mechanical properties and workability of rock salt

2019 ◽  
Vol 2 (1) ◽  
pp. 384-393
Author(s):  
Piotr Małkowski ◽  
Łukasz Bednarek ◽  
Krzysztof Kotwica ◽  
Grzegorz Stopka
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Shear Strength ◽  
Temperature Increase ◽  
Laboratory Tests ◽  
Effect Of Temperature ◽  
Transverse Strain ◽  
Salt Rock ◽  
The Road ◽  
Salt Mining

Abstract Underground salt mining accounts for about 16 percent of the total salt production worldwide. When excavating salt rock, the cutters of the road header come into contact with the rock. This produces friction and, consequently, a rise in temperature. Generally, as temperature increases, salt gradually loses its plasticity. The extent of these alterations depends on the presence of other minerals in the rock. This paper presents the results of laboratory tests on regularly shaped samples of salt. An analysis was performed of the results of compressive, tensile and induced-shear strength, and of Young's modulus, Poisson's ratio, cuttability index and side chipping angle. The testing was conducted on samples with a temperature of about 20°C and samples heated to 50°C and 80°C. The tests showed that as temperature increased, so did compressive and tensile strength, and longitudinal and transverse strain of salt. The temperature increase caused, however, a decrease in shear strength. The cuttability index and the side chipping angle also decreased when the heated samples were being cut. The percentage changes in the parameters within the 60-degree temperature range were as high as several dozen percent.

Mechanical Behavior of Ultrathin Whitetopping Structure Under Stationary and Moving Loads

2003 ◽  
Vol 1823 (1) ◽  
pp. 102-110 ◽  
Author(s):  
Tatsuo Nishizawa ◽  
Yoshiki Murata ◽  
Katsuro Kokubun
Keyword(s):  
Load Transfer ◽  
Concrete Slab ◽  
Three Dimensional ◽  
Element Model ◽  
Interface Condition ◽  
Interface Element ◽  
Concrete Slabs ◽  
Moving Loads ◽  
Mechanical Interaction ◽  
Loading Test

The structural design of ultrathin whitetopping (UTW) requires precise predictions of the loading stresses in the concrete slabs. A plate finite element model (FEM) is not used for structures with UTW because the model is not able to account for the asphalt subbase behaviors and the mechanical interaction between the concrete slab and asphalt subbase. A three-dimensional FEM (3DFEM) was used for the stress calculation of UTW. To take into account the mechanical interaction at the interface between the concrete slab and asphalt subbase as well as the load transfer across the joint, a general interface element was developed and incorporated into 3DFEM. Also, the viscosities of asphalt materials were considered by the viscoelastic formulation in the 3DFEM. A loading test was conducted on a test pavement. Stationary and moving loads were applied to the concrete slabs, and the strains in the slabs and the asphalt subbase were measured. By comparing the strains computed by 3DFEM with the measured strains, it was found that the viscosity of the asphalt subbase and the interface condition significantly affect the stresses in the concrete slab.

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