المستودع الرقمي لـكلية الهندسة

لعل استخدام القوالب والشدات المصنوعة من القماش أو النسيج لصب وتشكيل الخرسانة يصبح منافسا أساسياًّ في المستقبل للقوالب والشدات التقليديّة الشائعة المصنوعة غالباً من الخشب أو الفولاذ، وذلك لما يوفره إستخدام هذه القوالب كتقنية جديدة للإنشاء من مزايا متعددة، فهي تتكون من صفائح نسيجية (تكون مسامية غالبا) تصنع من مخلفات المنتجات النفطيّة مثل (النايلون، والبوليستر، والبولي بروبلين) الأمر الذي يجعلها غير مكلّفة مقارنة بمعظم مواد ومكونات القوالب التقليديّة التي يتم استيرادها من الخارج، بالإضافة إلى قدرتها على استيعاب الخلطات الخرسانيّة ذات التشغيليّة العالية والتي تحتوي على نسب عالية من الماء من دون الحاجة إلى استخدام الإضافات الكيميائيّة لتحسين التشغيليّة ومن دون أي تأثير سلبي على خواص ومقاومة الخرسانة، بل اثبتت الأبحاث والدراسات أن المقاومة تتحسن وذلك نظراً للمساميّة التي تتمتع بها الأغشية المكونة لهذه القوالب والتي تمنحها القدرة على التخلّص من كميّات كبيرة من ماء الخلط الزائد بالخرسانة أثناء الصب والدمك، كما تمتاز هذه القوالب و الشدّات أيضاً بمرونتها و قدرتها العالية على التشكّل وفق المتطلّبات المعمارية والإنشائية للعنصر الخرساني، إلى جانب العديد من المزايا الهامّة الأخرى التي تجعلها بديل فعّال ومجدي لأنظمة القوالب الشّائعة. وعليه، تم تحديـد الهـدف الرئيسـي لهذه الورقة فـي تقييم اسـتخدام القوالـب النسـيجية بشـكل عـام، كبــديل حــديث أفضــل وفعــال أكثــر مــن الناحيــة الاقتصــادية والإنشــائية مقارنــة بشــدّات وقوالــب صب الخرسانة التقليديّة الشائعة. arabic 100 English 0
حكيم سالم عبدالقادر السموعي (3-2021)

Fabric formwork can be used in both cast-in-place and precast applications. It offers several advantages over conventional formwork technology and provides opportunities for innovations in architectural and structural concrete members. arabic 10 English 48
Hakim Salem Abdelgader Abdelgader (3-2018)

Although there are visible signs of its gradual acceptance in North Africa through its limited use in construction, Libya has yet to explore the feasibility and applicability of self-compacting concrete (SCC) in new construction. The current study revolves around SCC made of locally available materials and the harsh environmental conditions. This paper deals with the investigation into the effect of the water to powder ratio and limestone powder (LSP) on the fresh and hardened properties of SCC. arabic 7 English 54
Hakim Salem Abdelgader Abdelgader (3-2019)

Download PDF Research Article - Civil EngineeringPublished: 31 July 2019Investigation on Mode I Fracture Behavior of Hybrid Fiber-Reinforced Geopolymer CompositesNeha P. Asrani, G. Murali, […]K. Karthikeyan  Arabian Journal for Science and Engineering volume 44, pages8545–8555(2019)Cite this article 225 Accesses 4 Citations Metricsdetails Abstract Recent reports in the literature have shown that fiber-reinforced geopolymer composites (FRGC) made with monofibers exhibit a significant enhancement in fracture energy. However, many aspects of the fracture performance of hybrid fiber-reinforced geopolymer composites (HFRGC) remain largely unexploited, and these are predominant for the structures. For the first time, the mode I fracture energy of HFRGC is investigated. The mode I behavior was assessed using pre-notched beams in accordance with the RILEM three-point bending test. Five different HFRGC mixtures were prepared using three fiber types: steel, polypropylene and glass (SF, PF and GF). The parameters of the pre-notched beam in flexure tested in this study were the first crack and peak load, crack mouth opening displacement at the first crack load and peak load, equivalent tensile strength, post-peak slope, reinforcing index, residual tensile strength and fracture energy. The results reveal that there is a positive interaction amidst the fibers in geopolymer composites that leads to an enhancement in the mode I fracture energy compared to the reference specimen. This study probes the influence of novel HFRGC while producing high-quality concrete, which can then be leveraged for sustainable infrastructure and various civil engineering works. arabic 15 English 79
Hakim Salem Abdelgader Abdelgader (7-2019)

The main purpose of this research is to improve the shielding of gamma rays by developing special concrete with high physico-mechanical properties using local aggregates. Various concrete mixtures are designed using heavy fine aggregate as a substitute for normal fine aggregate at rates of 20, 40, 60, 80, and 100%, by weight. Other concrete mixtures have been designed by replacing coarse aggregate with 50 and 60% of heavy fine aggregate. The properties such as density, compressive strength, and tensile strength of hardened mixtures were studied. Gamma ray attenuation has been studied on concrete mixtures after exposure to utilized radiation source comprised 137Cs radioactive element with photon energy of 0.662 MeV. From the results, we concluded that the density and compressive strength in addition to the linear attenuation coefficient of hardened mixtures increased with the ratio of replacing normal aggregate with heavy aggregate up to 60%. With an increase of the ratio more than 60%, compressive strength and tensile strength were reduced with the continued increase in density. On the other hand, density and the linear attenuation coefficient increased with the replacement of coarse aggregate by 50 and 60% of the heavy fine aggregate; while both compressive strength and tensile strength decreased. arabic 21 English 108
Hakim Salem Abdelgader Abdelgader (1-2019)

This report includes a short history on the early development of conveyor belts for transporting and placing concrete; the design of conveyor systems in relation to the properties of the plastic concrete, the delivery rate, and the job specifications; as well as belt widths, speeds, and angles of inclination as they apply to specific site requirements. Also discussed are the three types of concrete conveyors (portable, feeder, and spreader types) and their particular applications; field practices in the selection, use, and maintenance of conveyors; and the economics of belt conveyor placement. The quality of the in-place concrete and inspection procedures are also stressed. arabic 7 English 39
Hakim Salem Abdelgader Abdelgader (4-2020)

Two-stage concrete (TSC) is a special type of concrete that themethod of its construction and implementation is different fromconventional one. In TSC, coarse aggregate particles are first placed in the formwork and voids between themare subsequently injected with a special cementations mixture. TSC has been successfully used in many applications, such as underwater construction, casting concrete sections congested with reinforcement and concrete repair. Coarse aggregate forms about 60% of the total volume of TSC, while coarse aggregate forms about 40% of the total volume of conventional concrete. In TSC stresses are transferred through contact areas between coarse aggregate particles. In this paper coarse aggregate size influence on strength parameters of TSC and comparing it with conventional concrete is done (by uniaxial compressive strength test and Brazilian tensile strength test). According to results of tests in this paper, the TSC with finest grain of coarse aggregate has higher compressive and tensile strength, higher modulus of elasticity and less Poisson’s ratio from conventional concrete. arabic 11 English 66
Hakim Salem Abdelgader Abdelgader (3-2019)

There are three main aims that make this study particularly important and interesting to radiometric studies. Firstly, it will provides information on the concentration composition of natural and the associated man-made radioactivity of imported dental porcelain materials to be used by most dental laboratories in Great Jamahiriya. Since these materials do not pass radiation inspection tests before their entry or use and there is a large variety of supply source of these dental materials to be used for all dental works on Libyan patients, anomalies can be identified easily. Secondly, the analysis of selective elemental abundance (U, Th, and K ) and dose rate calculations may be used to calculate effective dose rates to dental laboratory technicians and also to the patient who will be using these specific materials. This research project will provide the first results of such measurements and the corresponding average annual effective dose rates equivalent to the patients using these materials and also to the dental technician and doctors work in the various dental laboratories that make use of these materials in their daily work. A total number of 30 dental powder samples were collected from a number of dental laboratories around Tripoli area will be analyzed. In this research project, the results from this preliminary survey regarding Th, U and K elemental concentrations in a wide variety of dental materials by means of high-resolution X-ray spectrometry will be presented. Further results from these investigations concerning activity concentrations and the associated dose rates, effective dose and the committed dose due to the use of these materials are going to be calculated and compared with other published data elsewhereandrecommendationoftheirusewillbederivedaccordingly. arabic 10 English 74
Karima Mohamed Ali Elmasri, Nouri A. Droughi(9-2010)