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Article
BEHAVIOR OF REINFORCED SELF-COMPACTING CONCRETE BEAMS CONTAINING STEEL FIBERS AND RECYCLED COARSE AGGREGATES
سلوك العتبات المسلحة الذاتية الرص المحتوية على الياف الحديد والركام الخشن المعاد

Author: Lubna Mohammed Abd
Journal: Journal of Engineering and Sustainable Development مجلة الهندسة والتنمية المستدامة ISSN: 25200917 Year: 2018 Volume: 22 Issue: 5 Pages: 170-187
Publisher: Al-Mustansyriah University الجامعة المستنصرية

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Abstract

Concrete wastes are generally delivered to the landfill sites for disposal. Due to increase charges of landfill and shortage of natural coarse aggregate (NCA), recycled coarse aggregate (RCA) (resulting from concrete wastes) is growing interest in building engineering. It is sustainable to use recycled construction materials to preserve the natural resources and maintain the environmental of cities. In the present study, RCA was used as a full replacement of NCA in some specimens of beams to produce self-compacting concrete (SCC). The experimental work consists of casting and testing eight rectangular simply supported reinforced concrete beams of (1200*180*250) mm for length, width, and height respectively with concentric point load as well as tests for control specimens to determine the mechanical properties of SCC. Four of these eight beams were tested for flexural and the other four beams for shear behavior. The present research includes the following main variables: transverse reinforcement (stirrups spacing, 50 mm and 100 mm), coarse aggregate (RCA and NCA) and steel fibers of (Vf = 0.5%). All beams have constant longitudinal steel reinforcement ratio=0.008. Experimental results have generally showed that ultimate loads (Pu) of beams made with RCA were approximately close to the results of beams made with NCA by percentages (1.08% and 1.11%) for flexural and shear behavior respectively. RCA can be used as a full replacement in the future construction industry. The presence of steel fibers increases the maximum deflection of beams by 1.55% for flexural and 1.02% for shear behavior.


Article
Effecting of Steel Fibers and Fly Ash on the Properties of Concrete
تأثير األلياف الحديدية والرماد المتطاير على خصائص الخرسانة

Authors: Mazin B. Abdul-Rahman --- Alya’a A. Ali --- Amenah M. Younus
Journal: Tikrit Journal of Engineering Sciences مجلة تكريت للعلوم الهندسية ISSN: 1813162X 23127589 Year: 2018 Volume: 25 Issue: 4 Pages: 30-36
Publisher: Tikrit University جامعة تكريت

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Abstract

In this research, the effect of the addition of fly ash particles with different weight ratios of 15%, 20%, and 25% as well as the addition steel fibers with different volume fractions of 0.25%, 0.75%, and 1.25% on the mechanical properties of concrete (compressive strength and modulus of rupture) was studied. To carry out this research, ten concrete mixes were prepared, one of which is the reference normal concrete (without any additives), the others contain steel fibers and fly ash as additives with the mentioned volumetric and weight proportions. For each type of concrete mix, three standard 150×300 mm cylinders and three standard prisms100×100×500 mm were casted, water to cementing material ratio was fixed for all concrete mixes (W/cm = 0.435) and the superplasticizer was used with ratio of 0.98%-1.22% by weight of the cementitious material in mixtures that contain steel fibers and fly ash particles as a partial replacement of cement weight. The results showed that the addition of fly ash particles had little effect on the mechanical properties of normal concrete, while the steel fibers had the greatest effect. The highest increase in compressive strength and flexural strength compared with reference concrete was 61.60% and 78.84%, respectively in the volume fractions 1.25% of steel fiber.

في هذا البحث تم دراسة تأثير إضافة جزيئات الرماد المتطاير بنسب وزنية مختلفة (15، %20، %25%) وكذك إضافة األلياف الحديدية بنسب حجمية مختلفة (25.0% ،75.0%، 25.1%)على الخصائص الميكانيكية للخرسانة اإلعتيادية في االنضغاط واالنثناء . وإلجراء هذه الدراسة تم تحضير عشر خلطات خرسانية، واحدة منها للخرسانة االعتيادية المرجعية )الخالية من المضافات(، واالخرى تحتوي على مضافات األلياف الحديدية والرماد المتطاير وبالنسب الحجمية والوزنية المذكورة أعاله. لكل نوع من ( ملم، وثالثـة مواشير قياسـية أيضا 100×100×500 )ملم، وكانت نـسـبـة الـماء الى الســمنت ثابتة ً انواع الخلطات الخرسانية تم صب ثالثة اسطوانات قياسية )150×300( في الخلطات الخرسانية كافة ومساوية الى (435.0 الملدن الفائق بنسبة ستخدم (، وأ 98.0-1.22 )%من وزن المواد السمنتية للخلطات المعززة باأللياف الحديدية والتي تحتوي على جزيئات الرماد المتطاير كاستبدال جزئي من وزن السمنت. وقد أظهرت النتائج بان اضافة جزيئات الرماد المتطاير لها تأثير قليل على الخواص الميكانيكية للخرسانة االعتيادية ، في حين كان لاللياف الحديدية التأثير األكبر، إذ كانت أعلى نسبة زيادة في مقاومة االنضغاط ، ومقاومة االنثناء بالمقارنة مع الخرسانة المرجعية هي )60.61 )% و )84.78 )%على التوالي عند النسبة الحجمية )25.1 )%لاللياف الحديدية.


Article
Workability of Hybrid Fiber Reinforced Self-Compacting Concrete

Authors: Anmar S. Dhaher --- Samer F. Daoud --- Tareq S. Al-Attar
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2018 Volume: 36 Issue: 2 Part (A) Engineering Pages: 111-116
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

The aim of this work is to evaluate the effect of adding different types of fibers on the fresh properties of the self-compacting concrete, SCC. The used types of fibers were steel (with volume ratios of 0.75, 1.0 and 1.25 %) and polypropylene fibers (0.10 and 0.15 %) and a hybrid system of these fibers (0.65 % steel and 0.10 % polypropylene). The conducted tests in the fresh state were slump flow, T500, V-funnel, and L-box. It was noticed that increasing the volume fraction of fibers would lead to decrease in the workability of SCC. According to EFNARC requirements for SCC, many test results were nonconforming. It was also concluded that polypropylene fibers have higher detrimental effect on fresh properties of SCC than steel fibers and that was attributed to the ability of polypropylene to absorb part of mixing water.

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