STUDY ON THE ESTIMATION METHOD OF COMPRESSIVE STRENGTH OF STRUCTURAL CONCRETES BY A COMBINATION OF THE IMPACT ELASTIC WAVE METHOD AND THE SMALL DIAMETER CORES METHOD

The majority of the water distribution pipes which take the greater part of Japanese drinking water utilities' assets are made of iron such as gray/ductile cast iron or steel. It will be necessary to replace most of these pipes due to corrosion in the near future. In general, pipeline assessment which is done before replacement is carried out through digging to take visual observation; however, digging costs and environmental burden due to digging will become a problem. This study therefore undertakes a research into methods of pipeline assessment which reduce the digging necessity. In the study of the Impact Elastic-Wave Method, elastic-waves were applied to cast iron pipes whose external surfaces were in various states of corrosion (pitting, partial, uniform, etc.); the frequency component of the received waves showed that there was a tendency for the frequency component of the waves for corroded iron pipes to be distributed in a lower range than sound pipes. In addition, it also showed that it is possible to discriminate the thickness reduction of approximately one mm. These results demonstrate the possibility of applying this method to pipeline assessment without or with minimum digging.

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Effect of combined drink cans and steel fibers on the impact resistance and mechanical properties of concrete

JOURNAL OF MECHANICAL ENGINEERING AND SCIENCES ◽

10.15282/jmes.14.2.2020.15.0527 ◽

2020 ◽

Vol 14 (2) ◽

pp. 6734-6742

Author(s):

A. Syamsir ◽

S. M. Mubin ◽

N. M. Nor ◽

V. Anggraini ◽

S. Nagappan ◽

...

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Compressive Strength ◽

Reinforced Concrete ◽

Impact Resistance ◽

Fiber Reinforced Concrete ◽

Steel Fibers ◽

Fiber Reinforced ◽

Indirect Tensile ◽

The Impact

This study investigated the combine effect of 0.2 % drink cans and steel fibers with volume fractions of 0%, 0.5%, 1%, 1.5%, 2%, 2.5% and 3% to the mechanical properties and impact resistance of concrete. Hooked-end steel fiber with 30 mm and 0.75 mm length and diameter, respectively was selected for this study. The drinks cans fiber were twisted manually in order to increase friction between fiber and concrete. The results of the experiment showed that the combination of steel fibers and drink cans fibers improved the strength performance of concrete, especially the compressive strength, flexural strength and indirect tensile strength. The results of the experiment showed that the combination of steel fibers and drink cans fibers improved the compressive strength, flexural strength and indirect tensile strength by 2.3, 7, and 2 times as compare to batch 1, respectively. Moreover, the impact resistance of fiber reinforced concrete has increase by 7 times as compared to non-fiber concretes. Moreover, the impact resistance of fiber reinforced concrete consistently gave better results as compared to non-fiber concretes. The fiber reinforced concrete turned more ductile as the dosage of fibers was increased and ductility started to decrease slightly after optimum fiber dosage was reached. It was found that concrete with combination of 2% steel and 0.2% drink cans fibers showed the highest compressive, split tensile, flexural as well as impact strength.

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Mechanical Behavior of Hydroxyapatite-Chitosan Composite: Effect of Processing Parameters

Minerals ◽

10.3390/min11020213 ◽

2021 ◽

Vol 11 (2) ◽

pp. 213

Author(s):

Hamid Ait Said ◽

Hassan Noukrati ◽

Hicham Ben Youcef ◽

Ayoub Bayoussef ◽

Hassane Oudadesse ◽

...

Keyword(s):

Molecular Weight ◽

Compressive Strength ◽

Mechanical Strength ◽

Bone Repair ◽

Mechanical Stability ◽

Three Dimensional ◽

Processing Parameters ◽

Composite Effect ◽

Solid Liquid ◽

The Impact

Three-dimensional hydroxyapatite-chitosan (HA-CS) composites were formulated via solid-liquid technic and freeze-drying. The prepared composites had an apatitic nature, which was demonstrated by X-ray diffraction and Infrared spectroscopy analyses. The impact of the solid/liquid (S/L) ratio and the content and the molecular weight of the polymer on the composite mechanical strength was investigated. An increase in the S/L ratio from 0.5 to 1 resulted in an increase in the compressive strength for HA-CSL (CS low molecular weight: CSL) from 0.08 ± 0.02 to 1.95 ± 0.39 MPa and from 0.3 ± 0.06 to 2.40 ± 0.51 MPa for the HA-CSM (CS medium molecular weight: CSM). Moreover, the increase in the amount (1 to 5 wt%) and the molecular weight of the polymer increased the mechanical strength of the composite. The highest compressive strength value (up to 2.40 ± 0.51 MPa) was obtained for HA-CSM (5 wt% of CS) formulated at an S/L of 1. The dissolution tests of the HA-CS composites confirmed their cohesion and mechanical stability in an aqueous solution. Both polymer and apatite are assumed to work together, giving the synergism needed to make effective cylindrical composites, and could serve as a promising candidate for bone repair in the orthopedic field.

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Towards Sustainable Concrete Composites through Waste Valorisation of Plastic Food Trays as Low-Cost Fibrous Materials

Sustainability ◽

10.3390/su13042073 ◽

2021 ◽

Vol 13 (4) ◽

pp. 2073 ◽

Cited By ~ 1

Author(s):

Hossein Mohammadhosseini ◽

Rayed Alyousef ◽

Mahmood Md. Tahir

Keyword(s):

Compressive Strength ◽

Low Cost ◽

Impact Resistance ◽

Food Tray ◽

World Population ◽

Fibrous Materials ◽

Palm Oil Fuel Ash ◽

Waste Plastic ◽

Compressive Strength Of Concrete ◽

The Impact

Recycling of waste plastics is an essential phase towards cleaner production and circular economy. Plastics in different forms, which are non-biodegradable polymers, have become an indispensable ingredient of human life. The rapid growth of the world population has led to increased demand for commodity plastics such as food packaging. Therefore, to avert environment pollution with plastic wastes, sufficient management to recycle this waste is vital. In this study, experimental investigations and statistical analysis were conducted to assess the feasibility of polypropylene type of waste plastic food tray (WPFT) as fibrous materials on the mechanical and impact resistance of concrete composites. The WPFT fibres with a length of 20 mm were used at dosages of 0–1% in two groups of concrete with 100% ordinary Portland cement (OPC) and 30% palm oil fuel ash (POFA) as partial cement replacement. The results revealed that WPFT fibres had an adverse effect on the workability and compressive strength of concrete mixes. Despite a slight reduction in compressive strength of concrete mixtures, tensile and flexural strengths significantly enhanced up to 25% with the addition of WPFT fibres. The impact resistance and energy absorption values of concrete specimens reinforced with 1% WPFT fibres were found to be about 7.5 times higher than those of plain concrete mix. The utilisation of waste plastic food trays in the production of concrete makes it low-cost and aids in decreasing waste discarding harms. The development of new construction materials using WPFT is significant to the environment and construction industry.

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Institutional Quality and Trade Flow: Empirical Evidence from Malaysia and Other OIC Member Countries in Africa

Insight on Africa ◽

10.1177/0975087820987174 ◽

2021 ◽

pp. 097508782098717

Author(s):

Hammed Agboola Yusuf ◽

Luqman Olanrewaju Afolabi ◽

Waliu Olawale Shittu ◽

Kafilah Lola Gold ◽

Murtala Muhammad

Keyword(s):

Economic Growth ◽

Bilateral Trade ◽

Trade Flow ◽

Estimation Method ◽

Institutional Quality ◽

Likelihood Estimation ◽

Political Stability ◽

Bilateral Trade Flow ◽

World Governance Indicators ◽

The Impact

This article examines the impact of institutional quality on bilateral trade flow between Malaysia and selected 25 African Organisation of Islamic Cooperation (OIC) member countries. Four institutional qualities were selected from World Governance Indicators with other trade predictors from the period from 1985 to 2016. Using gravity model of trade and Poisson pseudo-maximum likelihood estimation method (PPML) technique, the results confirm that government effectiveness, regulatory quality and political stability have an adverse effect on bilateral trade flow among the OIC countries in Africa. On the other hand, these institutional quality variables were considered as a strength for Malaysian economic growth. Therefore, better institutional quality reforms are needed among OIC member countries in Africa in order to accelerate trade, economic growth and development in their region.

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Reliability Assessment of a Multi-State HVDC System by Combining Markov and Matrix-Based Methods

Energies ◽

10.3390/en14113097 ◽

2021 ◽

Vol 14 (11) ◽

pp. 3097

Author(s):

Roberto Benato ◽

Antonio Chiarelli ◽

Sebastian Dambone Sessa

Keyword(s):

Current System ◽

Estimation Method ◽

Reliability Estimation ◽

Voltage Source ◽

Voltage Source Converter ◽

Hvdc System ◽

Critical Elements ◽

The Matrix ◽

The Impact

The purpose of this paper is to highlight that, in order to assess the availability of different HVDC cable transmission systems, a more detailed characterization of the cable management significantly affects the availability estimation since the cable represents one of the most critical elements of such systems. The analyzed case study consists of a multi-terminal direct current system based on both line commutated converter and voltage source converter technologies in different configurations, whose availability is computed for different transmitted power capacities. For these analyses, the matrix-based reliability estimation method is exploited together with the Monte Carlo approach and the Markov state space one. This paper shows how reliability analysis requires a deep knowledge of the real installation conditions. The impact of these conditions on the reliability evaluation and the involved benefits are also presented.

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