تاثیرالیاف مختلف بر ترک های انقباضی سنین اولیه و مقاومت مکانیکی بتن پر مقاومت

نوع مقاله: علمی - پژوهشی

نویسندگان

1 دانشیار، دانشکده فنی، دانشگاه گیلان، رشت، ایران

2 کارشناسی ارشد مهندسی سازه، دانشگاه گیلان، رشت، ایران

3 کارشناسی ارشد مهندسی سازه، پردیس دانشگاهی، دانشگاه گیلان، رشت، ایران

چکیده

زمانی که بتن رطوبت خود را از دست می دهد، دچار جمع شدگی (آبرفتگی) و کاهش حجم شده و در نهایت باعث ایجاد ترک و افزایش تغییر شکل بتن می شود. در این پژوهش اثر الیاف های پلی پروپیلن، فولادی، شیشه، بازالت و پلیمری بر مقاومت فشاری، مقاومت خمشی و ترک‌های انقباضی (سنین اولیه) مخلوط های بتنی پر مقاومت ارزیابی می شود. آزمایش انقباض از نوع مهار شده (مقید داخلی)، بر روی نمونه های بتنی به شکل حلقه با ارتفاع 150 میلی متر، قطر داخلی 30 میلی متر و قطر خارجی 40 میلی متر مطابق استاندارد ASTM C 1581 انجام شد. پارامترهای اصلی مورد مطالعه در این پژوهش عرض و نوع ترک و نیز سن ترک خوردگی ناشی از انقباض مهار شده است. نتایج نشان داد که افزودن الیاف موجب افزایش مقاومت فشاری در سن 3، 7 و 28 روز به ترتیب تا 16%، 20% و 3% و نیز موجب افزایش شاخص چقرمگی خمشی تا 7/7 برابر می شود. الیاف فولادی و شیشه عملکرد خوبی در تامین مقاومت خمشی داشتند اما در کاهش سرعت و زمان ترک خوردگی انقباضی، عملکرد نسبتا ضعیفی داشتند. همچنین ترک در تمام حلقه های بتنی به جز مخلوط حاوی پلی پروپیلن به ترک عمقی (full depth crack) توسعه پیدا کرد. مخلوط های حاوی الیاف پلی‌پروپیلن تا 84% کاهش عرض ترک و 62% افزایش سن ترک خوردگی را از خود نشان دادند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Effect of various fiber on early- age shrinkage cracks and mechanical strength of high strength concrete

نویسندگان [English]

  • Ali Sademomtazi 1
  • Behzad Tahmouresi 2
  • Ashkan Saradar 3
1 Associate professor, Civil Engineering Department, University of Guilan, Rasht, Iran
2 MSc in Structural Engineering, Department of Civil Engineering, University of Guilan, Rasht, Iran
3 M.Sc in Structural Engineering, Civil Engineering Dept, Campus University, University of Guilan., Rasht, Iran.
چکیده [English]

When the concrete loses its moisture, shrinkage and volume reduction is happening and eventually cracks create and deformations in the concrete are increased. In this study, the effect of polypropylene, steel, glass, basalt and polymer fiber on compressive strength, flexural strength and shrinkage cracks (early ages) of high strength concrete mixtures were evaluated. The restrained shrinkage test was performed on concrete ring specimens with height of 150 mm, inner diameter of 30 mm and outer diameter of 40 mm according to ASTM C 1581 standard. The crack width and age of restrained shrinkage cracking were main parameters studied in this research. The results showed that, adding fiber, caused increases the compressive strength 16%, 20% and 3% at the age of 3, 7 and 28 days respectively, and also, increased flexural toughness index up to 7.7 times. steel and glass fiber provided good performance in flexural strength, but had relatively poor action in the velocity reduction and cracking time of restrained shrinkage. Also, crack in all of concrete ring specimens except polypropylene containing mixture, was developed to full depth crack. The mixture of polypropylene fiber containing showed reduction in crack width up to 62% and increasing age cracking up to 84%.

کلیدواژه‌ها [English]

  • Fiber
  • high strength concrete
  • Crack
  • Early-age Shrinkage
  • Mechanical Strength

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