اثر میدان مغناطیسی بر مقاومت پیوستگی میلگرد در بتن حاوی الیاف فولادی با استفاده از آزمون بیرون‌کشیدن میلگرد

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی دکتری سازه، دانشکده مهندسی عمران، دانشگاه سمنان، سمنان، ایران

2 استاد ممتاز گروه سازه، دانشکده مهندسی عمران، دانشگاه سمنان، سمنان، ایران

3 دانشیارگروه سازه، دانشکده مهندسی عمران، دانشگاه سمنان، سمنان، ایران

چکیده

در این پژوهش با بهره‌گیری از آزمون بیرون‌کشیدن میلگرد از داخل نمونه استوانه‌ای بتن حاوی 5/1 درصد حجمی الیاف فولادی، مقاومت پیوستگی بین میلگرد و بتن در شرایطی مورد ارزیابی قرار می‌گیرد که نمونه‌های بتن در حالت تازه به مدت 2 دقیقه در معرض مستقیم میدان مغناطیسی قرارگرفتند. در این پژوهش، نمونه استوانه‌ای استاندارد بتن با ابعاد300×150 میلی‌متر و میلگرد با دو قطر مختلف شامل 14 و20 میلی‌متر مورد بررسی قرار گرفت. به منظور بررسی اثر خواص مکانیکی و ریزساختاری بتن بر مقاومت پیوستگی، آزمایش‌های مقاومت‌های فشاری، کششی شکافت، خمشی و تصویربرداری میکروسکوپ الکترونی روی نمونه‌های مغناطیسی و غیرمغناطیسی انجام شد. نتایج آزمون بیرون‌کشیدگی میلگرد نشان داد که گسیختگی همه نمونه‌ها از نوع لغزش میلگرد بود. اعمال میدان مغناطیسی به بتن تازه موجب افزایش مقاومت پیوستگی تا بیش از 83 و 51 درصد متناظر با میلگردهای با قطر 14 و 20 میلی‌متر گردید. همچنین میزان طاقت نمونه‌های بتن تحت میدان مغناطیسی تا حدود 82 و 53 درصد متناظر با میلگردهای با قطر 14 و 20 میلی‌متر افزایش یافت. میدان مغناطیسی در بهبود خواص مکانیکی بتن نیز موثر است. بر این اساس مقاومت فشاری بتن تحت میدان مغناطیسی به بیش از 21 درصد افزایش یافت که این میزان در خصوص مقاومت‌های کششی و خمشی بتن به ترتیب تا حدود 9 درصد و 13 درصد تعیین گردید. همچنین تصاویر میکروسکوپ الکترونی مشخص کرد که اعمال میدان مغناطیسی به بتن تازه موجب متراکم‌تر شدن ریزساختار بتن از طریق اثرگذاری بر فرایند هیدراتاسیون سیمان می‌گردد.

کلیدواژه‌ها

عنوان مقاله [English]

The Effect of Magnetic Field on Bond Strength between Reinforcing Steel Bar and Steel Fiber Reinforced Concrete by means of Pull-out Test

نویسندگان [English]

  • Mohammad Hajforoush 1
  • Ali Kheyroddin 2
  • Omid Rezaifar 3
1 Ph.D. Student, Department of Civil Engineering, Semnan University, Semnan, Iran
2 Distinguished Prof., Department of Civil Engineering, Semnan University, Semnan, Iran
3 Assoc. Prof., Department of Civil Engineering, Semnan University, Semnan, Iran.
چکیده [English]

In this research, the effect of applying magnetic field directly to steel fiber reinforced concrete specimens containing 1.5% volume of steel fiber on bond strength between reinforcing steel bar and concrete was experimentally investigated using a direct pull-out test. For this purpose, magnetic field was applied externally to the fresh specimens by means of an electromagnetic instrument, capable of causing the flux density of 5000 Gauss. In this study, the pull-out specimens were tested with two different bar diameters: 14 and 20 mm. The study also investigated, mechanical properties of the specimens in the terms of compressive, splitting tensile and flexural strengths at an age of 28 days. In addition, the microstructure of the specimens was analyzed by the SEM images. The experimental results demonstrated that the pull-out failure occurred for all the specimens. Furthermore, the bond strength of the specimens increased by about 83 and 51% correspond to the #14 and #20 rebars, respectively. In addition, thoughness parameter of concrete exposed to magnetic field increased by 82 and 53% correspond to the #14 and #20 rebars, respectively. Applying magnetic field to fresh concrete caused an increase in its compressive strength more than 21%. Following this, splitting tensile and flexural strengths of concrete specimens were inhanced up to 9 and 13%, respectively. Magnetic field also has the ability to compact the microstructure of concrete.

کلیدواژه‌ها [English]

  • Bond strength
  • Pull-out test
  • Uniform magnetic field
  • Steel fiber reinforced concrete
  • Microstructure

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