بررسی آزمایشگاهی پارامترهای شکست، خواص مکانیکی و جمع شدگی بتن سبکدانه

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی کارشناسی ارشد، گروه مهندسی عمران، دانشکده مهندسی، دانشگاه فردوسی مشهد، مشهد، ایران

2 گروه مهندسی عمران ،دانشکده مهندسی، دانشگاه فردوسی مشهد ،مشهد

10.22124/jcr.2021.18261.1471

چکیده

استفاده از سبکدانه‌ها بدلیل کاهش وزن بتن روز به روز افزایش یافته است. از طرفی سبکدانه‌ها منجر به تغییر در رفتار شکست بتن در مقایسه با سنگدانه معمولی می‌شوند. با توجه به ضعف روش‌های مقاومتی در طراحی اعضای بتنی، پژوهشگران و آیین‌نامه‌های طراحی، تحلیل سازه‌های بتنی و تعیین خواص و مشخصه‌های بتن به روش مکانیک شکست را ضروری می‌دانند. در این پژوهش آزمایشگاهی و تحلیلی، رفتار شکست اعضای بتنی ساخته شده از بتن سبک با استفاده از روش کار شکست و روش اثر اندازه بر روی تیرهای شکاف‌دار بررسی می شوند. همچنین، خواص مکانیکی و جمعشدگی بتن سبک مورد مطالعه قرار می‌گیرند. در مجموع 30 عدد نمونه منشوری خمشی و 42 عدد نمونه جهت تعیین پارامترهای شکست، خواص مکانیکی و جمع شدگی از بتن سبک ساخته و آزمایش شدند. نتایج آزمایش‌ها و تحلیل‌ها نشان می‌دهند که نظریه اثر اندازه بازانت رفتار شکست اعضای بتنی سبک را بخوبی ارزیابی می‌کند. در نمونه‌های آزمایش شده، انرژی شکست کل G_F در بتن سبک نسبت به بتن معمولی بدلیل کمتر بودن ظرفیت نهایی آن، به میزان 1/68% کمتر شده است. این در حالی است که انرژی شکست اولیه G_f حاصل از روش اثر اندازه در بتن سبک در مقایسه با بتن معمولی قدری بیشتر است. مطابق نمودارهای روش اثر اندازه، بتن سبک در مقایسه با بتن معمولی شکل‌پذیری بیشتری داشته است. همچنین، روش اثر اندازه دارای دقت مناسب‌تری نسبت به روش کار شکست جهت مطالعه رفتار شکست بتن سبک است. استفاده از سبکدانه بجای سنگدانه معمولی در بتن باعث کاهش جمع‌شدگی بتن میشود.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

An Experimental Study on Fracture Parameters, Mechanical Properties and Shrinkage of Lightweight Aggregate Concrete

نویسندگان [English]

  • Alireza Hosseini Mehrab 1
  • Mohammad Reza Esfahani 2
1 M.Sc., Department of Civil Engineering, Faculty of Engineering, Ferdowsi University of Mashhad (FUM), Mashhad, Iran
2 Department of Civil Engineering, Faculty of Engineering, Ferdowsi University Of Mashhad (FUM)
چکیده [English]

The use of lightweight aggregates in concrete has been widely increased to reduce the weight of concrete members. On the other hand, the fracture behavior of lightweight concrete is different with that in normal concrete. Due to the limitations of conventional designing methods for concrete members, researchers and design codes have led to consider the analysis of fracture mechanics in predicting the behavior of concrete structures. In this experimental and analytical study, the fracture behavior of lightweight aggregate concrete (LWAC) is investigated on notched beams using the work of fracture method (WFM) and size effect method (SEM). Also, the mechanical properties and shrinkage of LWAC are studied. A total of 30 bending prismatic specimens and 42 compressive samples were constructed and tested to determine the fracture parameters, mechanical properties and shrinkage of LWAC. The results of experiments and analyses show that the Bazant’s size effect theory can evaluate the fracture behavior of lightweight concrete members, appropriately. The total fracture energy G_F of LWAC is by 68.1% less than that of normal concrete due to its lower load-bearing capacity. However, the initial fracture energy G_f obtained from the SEM in LWAC is approximately higher than that in normal concrete. According to the diagrams obtained from the SEM, the LWAC has more ductility and less brittleness than normal concrete. Additionally, the SEM is more accurate than the WFM to study the fracture behavior of LWAC. The use of lightweight aggregates instead of normal aggregates reduced the concrete shrinkage.

کلیدواژه‌ها [English]

  • Lightweight aggregate concrete
  • Fracture energy
  • Size-Effect
  • Shrinkage
  • Toughness

مراجع

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