د. حكيمالسموعي

قسم الهندسة المدنية كلية الهندسة

الاسم الكامل

د. حكيم سالم عبدالقادر السموعي

المؤهل العلمي

دكتوراة

الدرجة العلمية

أستاذ

ملخص

يعمل الإستاذ الدكتور حكيم سالم عبد القادر بجامعة طرابلس – كلية الهندسة – قسم الهندسة المدنية. وقد حصل الأستاذ الدكتور حكيم عبد القادر على شهادة البكالوريوس من جامعـة طرابلس ، وشهادة الماجستير من جامعـة قدانسك ببولندا ،و شهادة الدكتوراه من جامعـة قدانسك ببولندا 1996م, وهو الآن أستـاذ بقسم الهندسة المدنية بكلية الهندسة جامعة طرابلس. ترأس الدكتور حكيم عبد القادر وشارك في العديد من البحوث من جامعة طرابلس - كلية الهندسة وجامعات أخرى من مختلف مناطق ليبيا وخارجها. وقد تميز د. حكيم ببحوثه التطبيقية في صب الخرسانة ذات المرحلتين وديمومة الخرسانة و صب الخرسانة في القوالب النسيجية و إعادة تدوير الخرسانة واستعمالات المواد البوزولونية و صب الخرسانة تحت الماء في المواد الإنشائية. كتب الدكتور حكيم أكثر من سبعون بحثاً منشوراً في مجلات ومؤتمرات محلية وعالمية مشهورة، ومن ضمنها بحوثاً باللغة العربية، وأشرفت على عدد من رسائل الماجستير في الجامعة وخارجها (بولندا ولبنان وإيران وايرلندا ) واخيرا قمت بمناقشة رسالة ماجستيرمن جامعة بيروت العربية. قمت كذلك بتقيم اطروحة دكتوراه من الهند. وتعتبر بحوث الدكتور حكيم عبد القادر المتعلقة صب الخرسانة ذات المرحلتين وديمومة الخرسانة و صب الخرسانة في القوالب النسيجية و إعادة تدوير الخرسانة و صب الخرسانة تحت الماء كثيرة الذكر كمراجع علمية في البحوث المحليّة والعالمية. في سنه 2019 قمت بزيارة الى جامعة ميونخ-المانيا بخصوص المشاركه في البرنامج العلمي التي قدمت شخصيا لي بصفتي عضو هيئه التدريس بجامعة طرابلس من جامعه ميونخ-المانيا تحت اشراف البرفسور Johann Plank. وقد تمت الموافقه على البرنامج العلمي المقدم من أ.د. حكيم عبدالقادر والبرفسور Johann Plank والممول من قبل خدمة التبادل الأكاديمي الألماني https://www.daad.de/en/ . في سنه 2020 تحصلت على شرف الزمالة من المعهد الأمريكي للخرسانة Fellow (ِACI) American Concrete Institute . https://www.concrete.org/aboutaci/honorsandawards/fellows.aspx

المنشورات

Palm Oil Fuel Ash-Based Eco-Efficient Concrete: A Critical Review of the Short-Term Properties

The huge demand for concrete is predicted to upsurge due to rapid construction devel- opments. Environmental worries regarding the large amounts of carbon dioxide emanations from cement production have resulted in new ideas to develop supplemental cementing materials, aiming to decrease the cement volume required for making concrete. Palm-oil-fuel-ash (POFA) is an indus- trial byproduct derived from palm oil waste’s incineration in power plants’ electricity generation. POFA has high pozzolanic characteristics. It is highly reactive and exhibits satisfactory micro-filling ability and unique properties. POFA is commonly used as a partially-alternated binder to Portland cement materials to make POFA-based eco-efficient concrete to build building using a green material. This paper presents a review of the material source, chemical composition, clean production and short-term properties of POFA. A review of related literature provides comprehensive insights into the potential application of POFA-based eco-efficient concrete in the construction industry today. arabic 16 English 78
Hakim S. Abdelgader , (1-2021)
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Repeated Projectile Impact Tests on Multi-Layered Fibrous Cementitious Composite

This research aims to experimentally evaluate the behaviour of multi-layered fibrous cementitious composites with intermediate Glass Fibre Meshes (GFM) under repeated projectile load. The impact load was subjected through a convex edge projectile needle at a low velocity on cylindrical specimens of three-layered fibrous cementitious composites, which have two different steel fibre distributions. In series A mixtures, a constant steel fibre dosage of 2.5% by volume was used. On the other hand, the fibre dosage of the outer layers was 3.0%; while it was 1.5% in the middle layer of series B mixtures. The number of intermediate GFM was the variable that distinguishes the mixtures of each series. The resistance to projectile impacts was evaluated on the basis of penetration depth, near surface distortion, weight loss, damage ratio and failure pattern. The test results showed that due to the combined effect of steel fibre and GFM, significantly lower weight losses were recorded for series A and B specimens compared with reference specimens. However, the different fibre distributions (series B) led to lower penetration depths and weight losses with less surface distortion compared with the fixed fibre distribution (series A). The reduction in the destroyed front surface area of series A specimens compared with reference specimens ranged from 27.8 to 38.1%; while that of series B specimens ranged from 34.8 to 53.4%. In addition, a simplified analytical model was introduced to predict the ejected composite mass. The model predictions were found to be in good agreement with the experimental masses. arabic 9 English 71
Hakim S. Abdelgader (1-2021)
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Evaluation of Mechanical Properties of Two-Stage Concrete and Conventional Concrete Using Nondestructive Tests

Different types of concrete mixtures are used as building materials. The manufacturing process of two-stage concrete (TSC) differs from that of conventional concrete. This study investigated conventional mechanical properties derive empirical relations for estimation of the mechanical parameters of TSC and conventional concrete mixtures. TSC was used to prepare 216 specimens and conventional concrete was used to prepare 108 specimens that then were aged for 28 days. Uniaxial compression, Brazilian tensile strength, and point load tests were carried out as destructive testing. Schmidt hammer and ultrasonic pulse velocity tests were carried out as nondestructive testing. The data from testing were categorized as regression or test data. Empirical relations were derived between the parameters for the two types of concrete, and these relations were validated. It was concluded that indirect, nondestructive testing of engineering materials, including concrete, considerably increases the speed and decreases the estimation cost of determining the mechanical parameters. This method can be recommended for estimation of these mechanical parameters. arabic 13 English 97
Hakim S. Abdelgader(7-2020)
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Toward the Future of Fabric Formwork

Since its invention by the Romans, concrete has been cast into all manner of formworks. Whether temporary or permanent, however, rigid formwork has been the traditional standard. Because concrete is the most widely used construction material, improvements in the economy of erecting concrete structures will have significant implications. One of the best opportunities for cost reduction is minimizing formwork costs—expenses that can represent about half the total cost of a concrete structure.1,2 Fabric formwork is a potential solution toward this goal. As a compounding benefit, fabric formwork can also enable the casting of structurally efficient, variable section building components.3 Taking advantage of fabric forms, however, is a joint task of concrete technology specialists, structural engineers, and architects. Fabric structures exhibit material and geometric nonlinearities when loaded, so forms must be designed based on experimentation or structural analysis using software capable of shape-finding.4,5 Education and research must focus on this barrier before the full potential of this formwork type can be realized. arabic 5 English 31
Hakim S. Abdelgader(7-2018)
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Mechanical properties of two-stage concrete modified by silica fume

Two-stage concretes, despite the fact that they have proven themselves in various types of construction, have not been studied to the same extent as traditional heavy concretes. Therefore, the article developed the composition of frame concrete with various additives in the composition of the cement-sand mortar. A comparison of the mechanical characteristics of the developed compositions with the addition of silica fume (SF) and superplasticizer (SP) in various combinations. In addition, test specimens were prepared with combinations of water/cement ratios of 0.45, 0.55, and 0.85, and cement/sand ratios of 0.5, 1, and 1.5. A total of 36 mixtures were prepared, silica fume was introduced as a partial replacement of cement in the amount of 6 wt.%. And a superplasticizer equal to 1.2 % of the cement content was added to the water. Compressive strength tests on two-stage concrete cylinders were carried out in accordance with ASTM-C873 and ASTM-C943. Tensile strength was also tested on 3 samples of each composition in accordance with the procedure described in ASTM-C496/C496M. As a result, the development of the strength of two-stage concrete for 7, 28 and 120 days was studied. It was found that the overall compressive strength of the two-stage concrete based on SF, SP and SF + SP was higher than in concrete without any additives. At the same time, the modified concrete has higher strength properties, because it provides better contact due to expansion, as well as by reducing the water-cement ratio in grout. The results obtained allow to design a cement-sand mortar capable of filling all the voids between the coarse aggregate, thereby creating a dense structure of two-stage concrete. arabic 9 English 58
Hakim S. Abdelgader(5-2019)
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Solving the Problem of the Coarse Aggregate Segregation

As we known the traditional concrete (TC) is primarily composed of a mixture of cement, fine and coarse aggregates, and water. TC is made by mixing together all the components before placing them. Using two-stage concrete to solve and to eliminate the problem of the aggregate segregation which appears in TC and in the self-compacting concrete. Two-stage concrete (TSC) is a type of concrete that is placed in two stages where the coarse aggregates are first placed inside the formworks and then the grout is pumped from underneath through a manual pump. The main difference between TC and TSC is the method of preparation and size of aggregates. The described above technology is unique as it allows us to prevent aggregate segregation in a ready mixture. The results presented in this paper indicate that this technology is promising for any kind of concrete applications. arabic 7 English 48
Hakim S. Abdelgader(1-2020)
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Impact response of two-layered grouted aggregate fibrous concrete composite under falling mass impact

Two-layered Grouted Aggregates Fibrous Concrete Composite (TGAFCC) is a new category concrete which became popular recently and attracted the attention of researchers globally. Recent studies indicated that TGAFCC has notable improvement in mechanical properties, which has been sufficiently documented. However, the impact behaviour of TGAFCC when combined with Glass Fibre Mesh (GFM) and Textile Fibre Mesh (TFM) is still unexplored. The research objective is to study the effect of GFM and TFM inser- tion in TGAFCC against the drop hammer impact. Twenty one TGAFCC mixtures were prepared and divided into two series; non-fibrous concrete and fibrous concrete. The combined action of GFM and TFM of various diameters were inserted between the two layers and tested experimentally against drop mass impact. Additionally, all fibrous specimens were reinforced with a constant 3% dosage of 5D hooked end fibre. All specimens were tested under repeated drop mass impact as per ACI Committee 544. The impacts number or number of blows till the first visible crack and failure, impact energy at the first vis- ible crack and failure, impact ductility index and cracking configuration were examined. Besides, Weibull distribution was used to examine the variations in the test results, where impact numbers were pre- sented using the reliability function. The research findings indicate that inserting GFM and TFM between the two layers combined with 5D hooked end steel fibres, provided high impact resistance, higher absorbed energy and prolonged failure duration. Increasing the diameters of the GFM and TFM insertions, in both non-fibrous and fibrous concrete resulted in increasing the impact numbers till the first visible crack and failure. The experimental findings confirm that the major contribution of impact resistance comes from the 5D hooked end steel fibres, while the share of the intermediate meshes was significantly lower. arabic 13 English 88
Hakim S. Abdelgader (12-2020)
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CONCRETE MIX DESIGN USING SIMPLE EQUATIONS

The behaviour of concrete, whether fresh or hardened, depends basically on the behaviour of its components and the relationship between them, therefore, obtaining a concrete with certain properties depends fundamentally on the concrete mix design. Concrete mix design generally includes two main steps: 1-Selection of the main components suitable for the concrete (cement, aggregate, water, and additives); 2-Determination of more economical mix ratios to fulfil the workability, strength and efficiency requirements. Currently, there are many international methods locally approved for mix designs. They are all related to each other, they give relatively the same quantities of the mix components and they are all capable of providing a good concrete mix. It is important to consider that these methods give approximate quantities which should be checked by experimental mixes in order to obtain results suitable for the requirements of the local environment and local materials. The ACI and BS methods are the most commonly used. Both of these methods depend on graphs and standard tables derived from previous research experience and actual concrete production as well as studies of the properties of the materials used. This paper illustrates a new approach for concrete mix design named as: “Double Coating Method”, which is currently used in some research centers in the republic of Poland and was recently applied in the laboratories of the Civil Engineering Departments in the Universities of Tripoli and Benghazi in Libya. This paper describes experiment in which 24 mixtures were used to assess the usefulness of this technique for problem of proportioning concrete mixtures in general. arabic 5 English 37
Hakim S. Abdelgader (12-2020)
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Impact performance of novel multi-layered prepacked aggregate fibrous composites under compression and bending

Multi-layered Prepacked aggregate fibrous composite (MLPAFC) is a new type of concrete, which is prepared in two subsequent stages of aggregate-fibre skeleton prepacking and cementitious grouting. In this study, ten MLPAFC mixtures were prepared in three subsequent layers incorporating different contents of four different types of steel fibres. Long and short hooked-end and crimped steel fibers were adopted with 3.0 and 1.5% dosages for the outer and interior layers, respectively. In-between the three MLPAFC layers, two layers of Glass Fiber Mesh (GFM) were inserted in five of the ten mixtures. The impact response of the MLPAFC mixtures was evaluated using two test methods. In the first, the ACI 544-2R repeated free-falling weight test was followed using disk specimens, while flexural free-falling weight on prism specimens was the second adopted impact test. Moreover, Weibull distribution was used to statistically analyse the discrepancies of the obtained experimental impact records. The impact tests results revealed that MLPAFC can absorb significantly high energy under falling weight impact due to its structure and the dual crack arresting activity of both steel fibers and GFM. The cracking number of impacts of MLPAFC cylindrical specimens without GFM was increased by approximately 530–870% compared reference specimens, while increment percentages reaching 1350% were recorded at failure stage. The impact resistance of MLPAFC prisms under flexural impact was noticeably improved, yet with lower percentages than cylindrical specimens. The insertion of intermediate GFMs let to additional developments in the impact strength of both cylindrical and prism specimens. arabic 14 English 97
Hakim S. Abdelgader (12-2020)
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Impact response of novel layered two stage fibrous composite slabs with different support type

The performance of novel Layered Two Stage Fibrous Composite slabs (LTSFC) was pioneered under falling mass collisions using a combined experimental and numerical study. Such LTSFC slabs consist of three layers with and without the insertion of glass fibre mesh between the layers. LTSFC techniques were used to fabricate the composite slabs with three layers including 3%, 1.5%, and 3% of fibre content for the top, middle, and bottom layers respectively. Sixteen MLPAFC square slabs were cast with only short hooked end fibres and tested under falling mass collisions by amending two parameters namely the type of support (fixed and hinge) and support layout. Two distinct support layouts on two types of support were considered and tested with and without the glass fibre mesh between layers of LTSFC. A glass fibre mesh was introduced between the three layers to block crack growth propagation and absorb additional collision energy. The glass fibre mesh insertion between the layers and the LTSFC production technique were considered as novel modifications. A numerical study using Auto desk Fusion 360 was conducted and compared with experimental results. The numerical results showed fair agreement with the experimental test results. Based on the validated numerical models, collision energy and cracking pattern evolution were studied. The findings indicated that the glass fibre mesh insertion between the layers combined with steel fibres disrupted crack proliferation, thus exhibiting superior engrossed collision energy and postponing crack growth. Additionally, the engrossed collision energy at crack initiation and ultimate crack for the slabs with four sides fixed and hinged support were greater with respect to two opposite sides fixed and hinged support. Numerical values were in reasonable agreement with the experimental values in terms of collision energy and cracking patterns. arabic 13 English 81
Hakim S. Abdelgader(2-2021)
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Structural Assessment of Reinforced Concrete Beams Incorporating Waste Plastic Straws

The behavior of reinforced concrete beams containing fibers made of waste plastic straws (WPSs) under the three point bending test is examined. The e ect of WPS fiber addition on the compressive and split tensile strength is reported. Four concrete mixes were prepared. The control mix PS-0 had a proportion of 1 cement: 1 sand: 2 coarse aggregate and a water cement ratio of 0.4. In the other three mixes PS-0.5, PS-1.5 and PS-3, 0%, 0.5%, 1.5% and 3% of WPS fiber (by volume) was added respectively. The results show that at 0.5% WPS, there is slight increase in compressive strength. However, beyond 0.5% addition, a decrease in compressive strength is observed. The split tensile strength shows a systematic increase with the addition of WPS fibers. The reinforced concrete beams containing WPS fibers show higher ductility as demonstrated by the larger ultimate tensile strain and ductility index (Du/Dy). There is a tendency to have more fine cracks with the presence of WPS fibers. arabic 9 English 76
Hakim S. Abdelgader(10-2020)
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BEHAVIOR OF REINFORCED CONCRETE BEAMS CONTAINING LIGHTWEIGHT AGGREGATE IN THE TENSILE ZONE

In reinforced concrete design, the concrete in the tensile zone is assumed to be ineffective and increase the dead load of the structural elements. In order to reduce the self-weight, this paper examines the structural behavior of reinforced concrete beams containing lightweight concrete in the tensile region and normal weight concrete in the rest of the beam. The lightweight concrete was made from waste polystyrene. Four reinforced concrete beams were prepared with different depth of lightweight concrete. The control beam B1 consists of normal concrete. In Beams B2, B3 and B4, the depth of lightweight concrete was 25%, 50% and 75% of the total depth of the beam measured from the bottom surface respectively. A four-point bending test was conducted on all beams. The beams were loaded in increments until failure. At each load increment, the central deflection was determined. Cracks initiation and the mode of failure were observed during the experiment. The failure load was found to decreases with the increase of depth of lightweight concrete. The presence of lightweight aggregate tends to cause brittle failure. In addition, the mode of failure for reinforced concrete beams containing lightweight concrete was a shear failure. arabic 11 English 79
Hakim S. Abdelgader(6-2020)
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Heavyweight Concrete: Measuring, Mixing, Transporting, and Placing

This document presents recommended methods and procedures for measuring, mixing, transporting, and placing heavyweight concretes that are used principally for radiation shielding in nuclear construction. Also covered are recommendations on cement, heavy- weight aggregates, water, and admixtures. Mixture proportioning of heavyweight concrete is discussed. Mixing equipment, form construction, placing procedures, and methods of consolidation are described. Quality control, inspection, and testing are empha- sized, and a list of references is included. Preplaced heavyweight concrete is not discussed in this version of 304.3R. It is covered in the 2004 version of the document.
Hakim S. Abdelgader (12-2020)
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Effect of coarse grain aggregate on strength parameters of two-stage concrete

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)
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Guide to Placing Concrete with Belt Conveyors

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)
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Assessing the physical, mechanical properties, and γ- ray attenuation of heavy density concrete for radiation shielding purposes

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)
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“Investigation on Mode I Fracture Behavior of Hybrid Fiber-Reinforced Geopolymer Composites

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)
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Production of self-compacting concrete using limestone powder

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)
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Fabric formwork – an alternative to traditional formwork

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)
Publisher's website


دراسة عامة حول استخدام القوالب النسیجیة في صب الخرسانة

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)
موقع المنشور


Standard and modified falling mass impact tests on preplaced aggregate fibrous concrete and slurry infiltrated fibrous concrete

Although several studies have been conducted to evaluate the impact response of concrete using the American Concrete Institute (ACI) 544-2R falling mass impact test, the variations in test results are the main drawback of this testing method. This study aims to reduce the variations in experimental impact test results by introducing two simple test setup modifications; (1) using coarse or fine aggregate bed- ding as an alternative to the steel base plate, (2) the use of line or cross-notched specimens with a line or cross-load distributing steel plate. One hundred thirty-five cylindrical discs were prepared with Preplaced Aggregate Fibrous Concrete (PAFC) and Slurry Infiltrated Fibrous Concrete (SIFCON), tested in nine groups to assess the proposed modified techniques. Steel hooked-end (2.5%) and macro polypropylene (8.0%) fibers were used to develop PAFC and SIFCON, respectively. The research findings revealed that using aggregate bedding increased the impact resistance by 38 to 429% for no-notch spec- imens and up to 283% for notched specimens. The presence of notches reduced the total energy absorbed by the bedding material. For instance, the specimens with a line notch and sand bedding exhibited 15 to 51% lower failure impact numbers than their corresponding no-notch specimens. Considering surface- notched specimens and aggregate bedding led to a lower scattering of the impact test results, while the line-notched specimens exhibited lower average scattering than the cross and no-notched specimens. In general, a percentage decrease in the coefficient of variation of 30 to 74% was attained for specimens with bedding and/or surface notch compared to reference specimens. arabic 16 English 111
Hakim Salem Abdelgader Abdelgader (9-2021)
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Fiber-reinforced alkali-activated concrete: A review

Alkali-activated materials (AAMs) received broad recognition from numerous researchers worldwide and may have potential applications in modern construction. The combined use of AAM and steel fibers are superior to typical binder systems because the matrix and fibers exhibit superior bond strength. The results obtained by various authors have shown that good dispersion of the fibers ensures good interaction between the fibers and the AAM matrix. The tensile strength of FR-AAC is superior to that of Ordinary Portland cement (OPC)-based materials, with the addition of silica fume (SF) being particularly remarkable. However, the tensile strength of fiber-reinforced alkali-activated concrete (FR-AAC) decreases with increasing fiber length. The bond strength increases with the increasing grade of concrete, the roughness of interface, and the solution's strength activated by alkalis. Regardless of fiber type, AAC's modulus of elasticity is linearly correlated with compressive strength. Fibers can affect the modulus of concrete due to the stiffness of the fiber and the porosity of the composite. Poisson's ratio for AAC corresponded to the ASTM C469-14 standard (about 0.22) and decreased to about 0.15–0.21 with silica fume addition. There are limited resources for the experimental Poisson's ratio and it is only estimated using the predictive equations available. Therefore, it is necessary to conduct additional experimental studies to estimate Poisson's ratios for FR-AAC composites. Retention of 59% and 44% in flexural strength during exposure at 800 °C and 1050 °C was observed in the FR-AAC stainless steel composite, and the chopped alumina fibers achieved higher yield strength at these temperatures. For FA-based AAC mortars with 1% SF with a hooked end, activated with a solution of NaOH and sodium silicate, an increase in the number of bends increased the bond strength, load pull-out and maximum pull-out strength. Autogenous shrinkage and drying shrinkage increase with higher silicate content, while shrinkage decreases with higher NaOH concentration. Relatively little research has been completed on FR-AAC in terms of durability or different environmental conditions. In addition, trends of development research toward the broad understanding regarding the application possibilities of FR-AAC as appropriate concrete materials for developing robust and green concrete composites for modern construction were extensively reviewed.
Hakim S. Abdelgader (11-2021)
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Cement kiln dust

Cement is still the most popular binder used in buildings construction. The volume of cement production in the world since 2013 has remained at the level of approximately 4.1 billion tons. The cement production process is energy intensive and is the world’s leading emitter of carbon dioxide. Therefore, the main activities cement plants are aimed at introducing technologies changes in production of clinkier (Edwards, 2019).The construction industry is responsible for the majority of CO2 emissions to the atmosphere: the industry emits 30% of total CO2, building emits 28%, transportation is responsible for 22% of CO2, the production of building materials causes 11% of CO2 emissions, including the cement industry is responsible for around 7% of emissions CO2. Other industries are responsible for around 9% of CO2 emissions to the atmosphere (Amran et al., 2020). The process of burning raw materials for the production of clinker is the most important stage of the entire cement production process (Mikulˇci´c et al., 2013; Andrew, 2019). Cement kiln dust (CKD) is waste generated during the production of clinker. The dust collected in the dust collectors is partly reused in the production process and some is stored. The storage method is not preferred due to its operations negative environmental impact. If the dust contains alkalis, chlorides, sulphates, or heavy metals, they cannot be recycled. Generally cement plants strive to reduce the formation of dust. About 1.5 tons of raw materials are used to produce 1 ton of clinker. After the extraction, grinding, and homogenization of rawmaterials, the process of calcination of calcium carbonate takes place.
Hakim S. Abdelgader(11-2021)
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3D-printable alkali-activated concretes for building applications: A critical review

The construction sector has embraced digitalization and industrialization to boost production, reduce material consumption, and improve workmanship. The 3D-printed concrete technology (3DPCT), more broadly recognized as the design of a 3D object via a computer-aided design (CAD) model or a digital 3D model, has accelerated considerable progress in these areas in other industries. Although 3DPCT has advanced remarkably in recent years, producing an appropriate 3D printing material that improves performance while reducing material consumption, which is really important for CO2 reduction, is urgently needed. The present 3DPCT faces many obstacles, one of which is the limited range of printable concretes. To tackle this limitation, extensive studies on developing creative approaches for formulating alkali-activated materials (AAMs) for 3DPCT for modern building applications have been conducted. AAMs are maintainable substitutive binders to ordinary Portland cement. Therefore, the need to undertake a comprehensive literature review on the current status of AAM performance on 3D-printable concretes for building applications is substantial. This article comprehensively reviews the quality requirements, advantages, disadvantages, common techniques, delivery, and placement of 3DCP. This literature also delivers indepth reviews on the behaviors and the properties of AAM-based concrete composites used in 3D-printed construction. Moreover, research trends are moving toward a wide-ranging understanding concerning the economic benefits and the environmental footprints of 3DCP for building applications with AAMs as suitable concrete materials for the emerging robust eco-friendly concrete composite for digital construction constructions nowadays. Given the merits of the study, several hotspot research topics for future investigations are also provided for facilitating the wide use of 3DPCT in real applications to address rapidly the gap between demand and supply for smart and cost-effective homes for upcoming generations.
Hakim S. Abdelgader(12-2021)
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Effect of slag coal ash and foamed glass on the mechanical properties of two-stage concrete

Two-stage concrete (TSC) is known by various names such as colcrete, Polcrete, preplaced aggregate concrete and prepacked concrete. It is different from traditional concrete in two fundamental ways, namely method of construction and mix proportion. Two-stage concrete (TSC) is defined as firstly, coarse aggregates are placed into the formwork and grout is applied to fill in the between coarse aggregate particles voids. Secondly, the percentage of coarse aggregates in the mix proportion of TSC is higher than that in normal concrete. The typical value is about 60% as compared with 40% in traditional concrete. As coarse aggregates are preplaced first, they can occupy up to 60–70% of the total volume. As coarse aggregates are not involved in the mixing process, TSC is environmentally friendly with lesser consumption of energy. With a higher content of aggregates, TSC reduces the use of cement by 20–30% and may minimize the temperature rise. Engineering properties of TSC, including its stress–strain relationship, is mainly governed by the properties of coarse aggregates as stress is transferred from the skeleton of aggregates to hardened grout. Main advantages of TSC include a higher volume of coarse aggregates and the ability to use larger size coarse aggregates. The latter also reduces the cost of crushing. TSC has beneficial properties such as low drying shrinkage, high bonding strength, high modulus of elasticity, and excellent durability. The method of TSC has proved particularly useful in a number of applications like underwater construction, and masonry repair, where placement by conventional methods is extremely difficult. The method is also applicable in case of massive concrete where low heat of hydration is required. It is studied the feasibility of casting two stage concrete with 100% steel slag as coarse aggregate. In term of formulation, to adopt two stage concreting method we could minimize the risk of concrete bleeding and segregation due to high water absorption and quite high density of slag aggregate. The effect of slag coal ash and foamed glass on the mechanical properties of two-stage concrete has rarely been reported. Thus, the development of an eco-efficient alkali-activated grout for two-stage concrete is a new research topic that has no robust results to draw solid conclusions and it should blaze the track towards a cleaner production of building materials with outstanding sustainability.
Hakim S. Abdelgader(1-2022)
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