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Chloride Resistance of Concrete under Complex Stress and Environment

Open Journal of Civil Engineering 2023年第1期13卷 171-180页

作者： mohammed saed yusuf Xue Wen Department of Civil Engineering Hormuud University Mogadishu Somalia

The presence of stress is shown to have a significant impact on chloride ions in concrete. Reinforced concrete is usually durable and cost-effective which has resulted in its widespread use for construction, however, the concrete subjected to environment and load has become increasingly apparently that attacked by aggressive agents such as chloride ion. In this study, the coupling influences are stress effects and environmental problems on the coastline concrete durability have been investigated. A series of cyclic of a wet-dry cycle and submersion tests were performed onto the stressed concrete to obtain an understanding of the physical mechanisms causing the accumulation of chlorides in the interior pores of concrete under different stress types and exposure environments, based on the same duration. Specimens were prepared and subjected to NaCl solution in a wet-dry cycle and submersion, the chloride in the tension zone is gradual with increasing the stress level, as well as the chloride ion in the wet-dry cycle, is increasing the number of cycles. The apparent diffusion coefficient of each specimen was calculated respectively, the profile of concentration at a different section of tension and compression zones were presented in influence factors of the number of cycles, the length of drying phase, and periodic wetting cycles with sodium solution was discussed. After employed Fick’s second law, the results suggested Da in a wet-dry cycle is much higher than the Da in submersion zones.

关键词： Concrete Durability Chlorideion Penetration Wet Dry Cycle’s Zone Submerges Zone Compressive Stress Tensile Stress Life Prediction Micro-Structure

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Effect of Steel Fiber on Concrete’s Compressive Strength

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Open Journal of Civil Engineering 2023年第1期13卷 192-197页

作者： mohammed saed yusuf Abdirisak Bashir Isak Guled Ali Mohamud Abdullahi Hashi Warsame Yahye Ibrahim Osman Abdullahi Husein Ibrahim Liban Abdi Aziz Elmi Department of Civil Engineering Hormuud University Mogadishu Somalia

The general goal of this research is to investigate whether steel fiber has a significant “positive” or “negative” influence on concrete compressive strength, as well as the optimal steel fiber ratio that delivers best result. Manually, cement, fine aggregates, coarse aggregates, steel fibers, and water were mixed together properly. A slump test was carried on the mixed concrete. After determining the workability, the mixed concrete was poured into cubes dimension 150 mm × 150 mm × 150 mm and left for 24 hours. After 24 hours, the samples were removed from the mold and placed in a water tank to cure for 7 to 28 days. The cube was tested for compressive and flexural strength in a universal testing machine after the samples had cured for the required 7 - 28 days. This study focuses on how to obtain high strength concrete using with steel fiber in the Conventional mix ratio to enhance concrete strength. Concrete reinforcement using steel fibers alters the characteristics of the concrete, allowing it to withstand fracture and hence improve its mechanical qualities. This study reports on an experimental study that reveals the effect of steel fiber on concrete compressive strength and the optimal steel fiber ratio that produces the best results. Steel fiber reinforcing improved the compressive strength of concrete. The average compressive strength of normal M25 concrete with 0% steel fibers and curing ages of 7 and 28 days was determined to be 22.97 N/mm2 and 25.78 N/mm2, respectively. The steel fibers are then added in various concentrations, such as 1%, 2%, and 3%, with aspect ratios of 70. The compressive strength of concrete with 1%, 2%, and 3% steel fiber with an aspect ratio of 70 was examined at 7 days and found to be 23.96, 24.80, and 26.14 N/mm2 correspondingly.

关键词： Steel Fiber Reinforced Concrete Fiber Reinforcement Compression Strength of Concrete Improvement Compression Strength

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The Effect of Longitudinal Stretching of Muscles and Nerve versus Deep Transverse Friction Massage in the Management of Patients with Carpal Tunnel Syndrome

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Open Journal of Therapy and Rehabilitation 2014年第4期2卷 199-206页

作者： Ashraf Ramadan Hafez Aqeel mohammed Alenazi Shaji John Kachanathu Abdulmohsen Meshari Alroumi Elham saed Mohamed Cairo University Hospital Cairo University Cairo Egypt Physical Therapy and Rehabilitation Department College of Applied Medical Sciences Salman Bin Abdulaziz University Alkharj Saudi Arabia Collage of Applied Medical Sciences King Saud University Riyadh Saudi Arabia Physical Therapy Department College of Applied Medical Sciences Shaqra University Shaqra Saudi Arabia

Background and Purpose: Carpal tunnel syndrome (CTS) is a common source of hand numbness and pain. The goal of this study was to compare longitudinal stretching of muscles and nerve to deep transverse friction massage for decreasing pain and improving hand function in patients with chronic CTS. Subjects and Methods: Thirty patients, 25 to 40 years old, were included in this study and randomized into two groups: the first group (36.8 ± 0.262) followed a physical therapy program group receiving stretching of wrist and hand flexors in combination with ultrasound, strengthening exercises of wrist and hand flexors, and wrist splint, three sessions per week for 12 weeks;and the second group (35.9 ± 0.225) followed the physical therapy program of deep transverse friction massage on the carpal tunnel site at the wrist joint, with using ultrasonic therapy, strengthening exercises of wrist and hand flexors and wrist splint, three sessions per week for 12 weeks. Outcome measures were range of motion (ROM), pain using visual analog scale (VAS), and hand grip strength measured with a sphygmomanometer. Results: There was a significant difference in both groups in all outcome measures compared to baseline. Over stretching group showed significant difference at the end of study in terms of range of motion of wrist flexion, extension and strength of handgrip when compared to deep friction massage group P < 0.05. However, there is no significant difference between groups in pain. Discussion and Conclusion: This study showed that the effect of stretching exercises is more beneficial than deep transverse friction massage in the treatment of patients with CTS in decreasing the compression of the median nerve in the tunnel.

关键词： Carpal Tunnel Syndrome Median Nerve Stretching Exercises Ultrasonic Therapy Deep Transversefriction Massage Hand Weakness and Numbness

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Enhanced dielectric and electrocaloric properties in lead-free rod-like BCZT ceramics

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Journal of Advanced Ceramics 2020年第2期9卷 210-219页

作者： Zouhair HANANI Soukaina MERSELMIZ Abdelaadim DANINE Nicolas STEIN Daoud MEZZANE M’barek AMJOUD mohammed LAHCINI Yaovi GAGOU Matjaz SPREITZER Damjan VENGUST Zdravko KUTNJAK Mimoun El MARSSI Igor ALUK'YANCHUK Mohamed GOUNE IMED-Lab Cadi Ayyad UniversityMarrakesh 40000Morocco ICMCB University of 1.BordeauxPessac 33600France IJL University of LorraineNancy 54000France UM6P Ben Guerir 43150Morocco LPMC University of Picardy Jules VerneAmiens 80039France Jozef Stefan Institute Ljubljana 1000Slovenia Physics Faculty Southern Federal UniversityRostov-on-Don 344090Russia

Ba0.85Ca0.15Zr0.10Ti0.90O3(BCZT)lead-free ceramics demonstrated excellent dielectric,ferroelectric,and piezoelectric properties at the morphotropic phase boundary(MPB).So far,to study the effect of morphological changes on dielectric and ferroelectric properties in lead-free BCZT ceramics,researchers have mostly focused on the influence of spherical grain shape *** this study,BCZT ceramics with rod-like grains and aspect ratio of about 10 were synthesized by surfactant-assisted solvothermal route.X-ray diffraction(XRD)and selected area electron diffraction(saed)performed at room temperature confirm the crystallization of pure perovskite with tetragonal *** electron microscopy(SEM)image showed that BCZT ceramics have kept the 1D rod-like grains with an average aspect ratio of about ***-like BCZT ceramics exhibit enhanced dielectric ferroelectric(εr=11,906,tanδ=0.014,Pr=6.01μC/cm^2,and Ec=2.46 kV/cm),and electrocaloric properties(ΔT=0.492 K andz=0.289(K×mm)/kV at 17 kV/cm)with respect to spherical BCZT ***,rod-like BCZT lead-free ceramics have good potential to be used in solid-state refrigeration technology.

关键词： lead-free Ba0.85Ca0.15Zr0.10Ti0.90O3(BCZT) rod-like Ba0.85Ca0.15Zr0.10Ti0.90O3(BCZT) dielectric ferroelectric electrocaloric effect

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