المستودع الرقمي لـقسم الهندسة المدنية

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)

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)

Estimating the service life of Reinforced Concrete (RC) bridge structures located in corrosive marine environments of a great importance to their owners/engineers. Traditionally, bridge owners/engineers relied more on subjective engineering judgment, e.g. visual inspection, in their estimation approach. However, because financial resources are often limited, rational calculation methods of estimation are needed to aid in making reliable and more accurate predictions of the service life of RC structures. This is in order to direct funds to bridges found to be the most critical. Criticality of the structure can be considered either from the Structural Capacity (i.e. Ultimate Limit State) or from Serviceability viewpoint whichever is adopted. This paper considers the service life of the structure only from the Structural Capacity viewpoint. Considering the great variability associated with the parameters involved in the estimation process, the probabilistic approach is most suited. The probabilistic modelling adopted here used Monte Carlo simulation technique to estimate the Reliability (i.e. Probability of Failure) of the structure under consideration. In this paper the authors used their own experimental data for the Correlation Length (CL) for the most important deterioration parameters. The CL is a parameter of the Correlation Function (CF) by which the spatial fluctuation of a certain deterioration parameter is described. The CL data used here were produced by analyzing 45 chloride profiles obtained from a 30 years old RC bridge located in a marine environment. The service life of the structure was predicted in terms of the load carrying capacity of an RC bridge beam girder. The analysis showed that the influence of SV is only evident if the reliability of the structure is governed by the Flexure failure rather than by the Shear failure. arabic 14 English 80
Omran Mohamed Saleh Kenshel(2-2021)

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)