scholarly journals Effect of Metallic Inclusions on the Compressive Strength of Cement-Based Materials

2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Tomáš Ficker
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Mechanical Stability ◽  
Transition Zones ◽  
Metallic Inclusions ◽  
Cement Based Materials ◽  
Concrete Materials ◽  
Materials Used ◽  
The Stability ◽  
Critical Limits

In the concrete foundations, materials come into contact with bedrocks. The surfaces of bedrocks are often covered by sharp protrusions called asperities. Although geotechnical engineers have developed a reliable theory for assessing the mechanical stability of rocky terrains, the stability of transition zones between concrete and sharp asperities remains unsolved. Due to the large pressures that exist in these transition zones, the invasive influence of sharp asperities on the integrity of the concrete raises a question about possible changes of the mechanical properties of concrete materials used in foundations. These circumstances have inspired experiments in which metallic needles of various lengths have been embedded into cement-based materials to assess the influence of the needles on the compressive strength. This influence has been quantified, and the critical limits identifying the changes of material integrity have been determined. It has been conjectured that sharp rock asperities or needle-like rods of steel reinforcement in concrete may cause similar changes of material integrity as the metallic needles used in the experiments performed.

An analysis of the transport properties and mechanical stability of rapidly solidified Al-Sb alloy

2015 ◽  
Vol 10 (2) ◽  
pp. 2663-2681
Author(s):  
Rizk El- Sayed ◽  
Mustafa Kamal ◽  
Abu-Bakr El-Bediwi ◽  
Qutaiba Rasheed Solaiman
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Melt Spinning ◽  
Elastic Moduli ◽  
Mechanical Stability ◽  
Microstructural Analysis ◽  
Alloy System ◽  
Antimony Content ◽  
The Stability ◽  
Rapidly Solidified

The structure of a series of AlSb alloys prepared by melt spinning have been studied in the as melt–spun ribbons  as a function of antimony content .The stability  of these structures has  been  related to that of the transport and mechanical properties of the alloy ribbons. Microstructural analysis was performed and it was found that only Al and AlSb phases formed for different composition.  The electrical, thermal and the stability of the mechanical properties are related indirectly through the influence of the antimony content. The results are interpreted in terms of the phase change occurring to alloy system. Electrical resistivity, thermal conductivity, elastic moduli and the values of microhardness are found to be more sensitive than the internal friction to the phase changes. 

scholarly journals Study of the Electrical Properties of Aluminate Cement Adhesives for Porcelain Insulators

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2232
Author(s):  
Huiwen Wan ◽  
Zhangyin Hu ◽  
Gang Liu ◽  
Jiadong Xiao
Keyword(s):  
Compressive Strength ◽  
Electrical Properties ◽  
Silica Fume ◽  
Drying Time ◽  
Pore Connectivity ◽  
Cement Based Materials ◽  
Porcelain Insulators ◽  
Materials Used ◽  
The Cost ◽  
Aluminate Cement

Electrical properties are one of the essential parameters of cement-based materials used in suspension porcelain insulators. This paper studied the electrical properties of aluminate cement adhesives (ACA) containing silica fume (SF), as well as their compressive strength and porosity. The results indicated that the addition of silica fume improved the resistivity of ACA under a saturated state (relative humidity is 50%). This was mainly attributed to the decrease of the ACA’s pore connectivity due to the SF’s filling effect. However, the early compressive strength of ACA was slightly reduced by the addition of SF. Under an unsaturated state, the ACA’s resistivity without the SF gradually exceeded that with the SF at the extension of drying time. The nuclear magnetic resonance (NMR) results indicated that the addition of SF content increased the ACA’s porosity; for the tiny pores especially, (the size less than 25 nm), this increased by 3.4%. Meanwhile, the addition of SF increased the tortuosity of the ACA’s conductive channels, which could improve its resistivity. Therefore, SF is recommended to be used in cement-based adhesives on insulators to lower the cost and improve the resistivity.

scholarly journals Longitudinal Tension and Mechanical Stability of a Pressurized Straw Tube

Instruments ◽  
2018 ◽  
Vol 2 (4) ◽  
pp. 27
Author(s):  
Levan Glonti ◽  
Temur Enik ◽  
Vladimir Kekelidze ◽  
Alexander Kolesnikov ◽  
Dmitry Madigozhin ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Charged Particle ◽  
Measurement Technique ◽  
Mechanical Stability ◽  
Stability Conditions ◽  
Particle Detectors ◽  
Straw Tube ◽  
Special Measurement ◽  
The Stability ◽  
Tube Study

For the development of charged particle detectors based on straw tubes operating in vacuum, a special measurement technique is required for the evaluation of their mechanical properties. A summary of the known equations that govern straw behavior under internal pressure is provided, and a new experimental method of a strained pressurized straw tube study is presented in this paper. The Poisson’s ratio of the straw wall, which defines the stability conditions of a built-in tube, was measured for the NA62 spectrometer straw, and its minimum pre-tension was estimated.

scholarly journals New crosslinkers for electrospun chitosan fibre mats. I. Chemical analysis

2012 ◽  
Vol 9 (75) ◽  
pp. 2551-2562 ◽  
Author(s):  
Marjorie S. Austero ◽  
Amalie E. Donius ◽  
Ulrike G. K. Wegst ◽  
Caroline L. Schauer
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Scanning Electron Microscopy ◽  
Mechanical Stability ◽  
Dissolution Tests ◽  
Natural Polysaccharide ◽  
Biomedical Field ◽  
The Stability ◽  
Scanning Electron

Chitosan (CS), the deacetylated form of chitin, the second most abundant, natural polysaccharide, is attractive for applications in the biomedical field because of its biocompatibility and resorption rates, which are higher than chitin. Crosslinking improves chemical and mechanical stability of CS. Here, we report the successful utilization of a new set of crosslinkers for electrospun CS. Genipin, hexamethylene-1,6-diaminocarboxysulphonate (HDACS) and epichlorohydrin (ECH) have not been previously explored for crosslinking of electrospun CS. In this first part of a two-part publication, we report the morphology, determined by field emission scanning electron microscopy (FESEM), and chemical interactions, determined by Fourier transform infrared microscopy, respectively. FESEM revealed that CS could successfully be electrospun from trifluoroacetic acid with genipin, HDACS and ECH added to the solution. Diameters were 267 ± 199 nm, 644 ± 359 nm and 896 ± 435 nm for CS–genipin, CS–HDACS and CS–ECH, respectively. Short- (15 min) and long-term (72 h) dissolution tests (T 600 ) were performed in acidic, neutral and basic pHs (3, 7 and 12). Post-spinning activation by heat and base to enhance crosslinking of CS–HDACS and CS–ECH decreased the fibre diameters and improved the stability. In the second part of this publication, we report the mechanical properties of the fibres.

Effect of Sintering Temperature on Porous Structures and Mechanical Properties of Ti-39Nb-6Zr Alloys

2016 ◽  
Vol 848 ◽  
pp. 532-537 ◽  
Author(s):  
Ye Shao ◽  
Xiao Yun Song ◽  
Wen Jun Ye ◽  
Song Xiao Hui ◽  
Yang Yu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Sintering Temperature ◽  
Porous Structures ◽  
Powder Metallurgy Technique ◽  
Porous Ti ◽  
The Stability ◽  
Surrounding Bone ◽  
Compressive Tests

Titanium and its alloys have been widely used as implants replacing hard human tissues in biomedical fields. To improve the stability of implants in the surrounding bone tissues, the materials with porous structures were fabricated. In this paper powder metallurgy technique was employed to fabricate porous Ti-39Zr-6Nb (wt.%) alloys. The porous structures and mechanical properties of the porous alloys were examined by scanning electron microscopy (SEM) and compressive tests. The results showed that with increasing the sintering temperature the porosity of the alloys decreased and the compressive strength and the elastic modulus increased. The porosity of the alloys was in the range from 20.8% to 23.2%, and the pore sizes mostly centered in 10~30μm. The compressive strength and the elastic modulus were in the range from 110.4 to 292.4MPa and 4.7 to 12.4GPa respectively, which was close to human bone.

Review on Different Types of Geopolymer Concrete Fibres

2016 ◽  
Vol 857 ◽  
pp. 388-394 ◽  
Author(s):  
Meor Ahmad Faris ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
Khairul Nizar Ismail ◽  
Ratnasamy Muniandy ◽  
Aeslina Abdul Kadir ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Flexural Strength ◽  
Ordinary Portland Cement ◽  
Geopolymer Concrete ◽  
Base Materials ◽  
Different Types ◽  
History Of ◽  
Binder Material ◽  
Materials Used

Ordinary Portland Cement (OPC) has been used over the than hundred years for material construction especially as a binder in production of concrete. However, there are a few disadvantages with the using of OPC that have been found especially in terms of properties and green house effect. This paper reviews the potential of an alternative binder material with no cement usage (cementless) called as “geopolymer”. The history of the development geopolymer will be described. Different types of base materials used in the formation of geopolymer will be explained in details. The influence of different types of fibres to the mechanical properties especially compressive strength and flexural strength were explained well.

scholarly journals Effect of Additives on the Rheological and Mechanical Properties of Microfine-Cement-Based Grout

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Shuai Zhang ◽  
Weiguo Qiao ◽  
Yanzhi Li ◽  
Kai Xi ◽  
Pengcheng Chen
Keyword(s):  
Mechanical Properties ◽  
Particle Size ◽  
Compressive Strength ◽  
Fly Ash ◽  
Mechanical Performance ◽  
Setting Time ◽  
Effect Of Additives ◽  
Microfine Cement ◽  
The Stability ◽  
Grouting Materials

Enhancement of the fluidity and mechanical performance of grouting materials has proven to be an effective method of seepage prevention in geotechnical engineering. In this research, a microfine-cement-based grout mixed with microfine fly ash (MFA), nano-CaCO3 (NC), and superplasticizer (SP) was designed to improve the rheological and mechanical properties of grouting materials, and the particle size distribution, fluidity, spreading ability, bleed capacity, setting time, and mechanical properties were studied. A water/solid (W/S) ratio of 1.2 was selected, and the contents of MFA, NC, and SP by mass of microfine cement (MC) were 0–40%, 0–2.0%, and 1.5%, respectively. The results showed that MFA and 1.5% SP improved the fluidity and spreading ability of fresh grouts, while prolonging the setting time. The addition of NC can increase the yield stress and plastic viscosity and decrease the fluidity and spreading ability; nevertheless, it obviously enhances the stability and shortens the setting time of grouts. The addition of MFA and 1.5% SP reduced the compressive strength of hardened grouts; however, the addition of NC improved the mechanical properties.

Relationship between Compressive Strength and Young's Modulus of Cement Paste with Recycled Concrete Powder

2016 ◽  
Vol 722 ◽  
pp. 254-259 ◽  
Author(s):  
Jaroslav Topič ◽  
Jan Trejbal ◽  
Tomáš Plachý ◽  
Zdeněk Prošek
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
High Speed ◽  
Reference Sample ◽  
Milled Powder ◽  
Recycled Concrete ◽  
Cement Pastes ◽  
Cement Replacement ◽  
Cement Based Materials

This article deals with utilization of recycled concrete in form of high-speed milled powder into cement based materials. Recycled concrete powder in that form is used as microfiller and cement replacement. This article contains results of mechanical properties of the cement pastes with different amount of recycled concrete powder. The mechanical properties as the compressive strength, flexural strength, dynamic Young's and share moduli are observed during 409 days. According to results can be assumed that recycled concrete powder can be used as microfiller and cement replacement under 30 wt. % of total amount. Especially the results of compressive strength are comparable with reference sample. But there are some abnormalities in long term development of the strength that need to be explained.

scholarly journals Peculiarities of hydration of Portland cement with synthetic nano-silica

2017 ◽  
Vol 12 (2) ◽  
pp. 101-106 ◽  
Author(s):  
Galyna Kotsay
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Portland Cement ◽  
Cement Hydration ◽  
Physical And Mechanical Properties ◽  
The Other ◽  
Nano Materials ◽  
Nano Silica ◽  
Other Hand ◽  
Materials Used

Abstract Application of nano-materials in cement products significantly, improves their properties. Of course, the effectiveness of the materials depends on their quantity and the way they are introduced into the system. So far, amongst nano-materials used in construction, the most preferred was nano-silica. This research investigated the effect of synthetic precipitated nano-silica on the cement hydration as well as, on the physical and mechanical properties of pastes and mortars. Obtained results showed that admixture of nano-silica enhanced flexural and compressive strength of cement after 2 and 28 days, however, only when admixture made up 0.5% and 1.0%. On the other hand, the use of nano-silica in the amount 2% had some limitations, due to its ability to agglomerate, which resulted in deterioration of the rheological and mechanical properties.

scholarly journals Evolution of the Mechanical Properties and Cracking Pattern of Cementitious Composites Reinforced with Hooked Steel Fibers

2020 ◽  
Vol 16 (1) ◽  
pp. 119-130
Author(s):  
Hamid Ranjbar ◽  
Ali Jadidi ◽  
Hosein Amerei
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Bending Strength ◽  
Tensile Specimen ◽  
Steel Fibers ◽  
Micro Cracks ◽  
The Matrix ◽  
Materials Used ◽  
Cracking Pattern

AbstractDegradation and disintegration of concrete depend on the formation of cracks and micro cracks intensively. With increase loading, micro cracks are linked together and form cracks. To solve the problem and to provide the homogenous condition, a series of thin fibers having been spread through the volume of concrete are used in the several last decades and they are called as fibers. In the study, the steel fibers integrated in the different percentages of weight have been investigated. The performance of fibers has been studied how to increase compressive strength, tensile strength, and bending strength. To survey compressive strength, tensile strength, and bending strength in the produced concrete, three plans of mixtures including the different percentages of the steel fibers have been examined. The results show that compressive strength in the concrete reinforced with steel fibers relies mainly on the quality of mortar. The added steel fibers cause the inconsiderable changes in the compressive strength of concrete. The results demonstrate that the concrete reinforced with steel fibers increase tensile strength considerably. The more the volume of steel fibers is, the more tensile strength is. Pozzolanic materials used in the specimens reinforced in steel fibers improve tensile strength. To investigate bending strength of the specimens reinforced with steel fibers, the study has used 4-point loading system. Generally, steel fibers used in the concrete increase bending strength of the concrete. The results indicate the increased steel fibers enhance bending strength in three plans of mixtures. Among the specimen reinforced with steel fibres, the most mechanical properties are related to the plans including 1, 1.5, and 2 percentages of dramix hooked steel fibers in the study. To examine crack pattern of the matrix tensile specimen reinforced with the different percentages of fibers, parameters such as the number of cracks, width of cracks, and distance between them are investigated.

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