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)

Reclaimed asphalt pavement is used as an aggregate in the cold recycling of asphalt paving mixtures. The more common method involves a process in which the asphalt pavement is recycled in-place (cold in-place recycling), CIPR. Where the reclaimed asphalt pavement is combined without heat with foamed bitumen and cement and mixed at the pavement site, at full- depth to produce a new cold mix end product. There are no universally accepted structural coefficient values for cold in-place recycled mixes (CIPR). Even though, the structural capacity of CIPR mixes considered equal to that of conventional cold mix paving material, it is not the structural is equivalent to hot mix asphalt (HMA), but is superior to gravel or crushed stone base course. The structural layer coefficient is used to calculate the structure number (SN) needed for the design of layer thicknesses. In this study, the maximum vertical compressive strain on the top of the subgrade layer was used to calculate the equivalency factor and the structural coefficient. By using the KENLAYER; the elastic layered program, the subgrade compressive strains were calculated for the typical pavement system commonly used for the major highways in Libya to get the thickness of FDR layer that would give the same compressive strain as six inches (150 mm) HMA. The thickness equivalency was taken as the ratio of the thickness of the FDR layer to that of the HMA layer of six-inch (150 mm). This was done for different FDR modulus values and different mean annual air temperatures (MAATs) which imply different resilient modulus values of HMA. As a result a relationship was developed between FDR modulus and FDR structural coefficient for various MAATs which are considered as the upper bound structural coefficient values. The conservative equation: MR= 30,000(ai/0.14)3 is considered as the lower bound values of structural coefficient. A reasonable single structural coefficient value could be specified within the specified range based on the levels of experience and quality control. A case study is used to verify the developed procedure for the design of pavement structural systems with FDR layers. arabic 7 English 51
Haifa Ali Ragab Abuhaliga(9-2014)

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)