بررسی رفتار مکانیکی بتن الیافی حاوی پومیس و متاکائولن و مقاومت شیمیایی آن در برابر حملات اسیدی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 استادیار- گروه سازه و زلزله - دانشکده مهندسی عمران، آب و محیط زیست - دانشگاه شهید بهشتی

2 دانشجوی دکترا- دانشکده مهندسی عمران، آب و محیط زیست

3 پژوهشگر، بخش پژوهش و توسعه، شرکت مهندسان مشاور ایمن راه، تهران

چکیده

اخیراً، در روسازی‌های بتنی فرودگاه‌ها و آزادراه‌ها، استفاده از الیاف در بتن برای کاهش ترک‌ها و افزایش فاصله درز اتصالات دال‌های بتنی رواج یافته است. اما، رفتار دوامی آن‌ها در برابر حملات باران‌های اسیدی کمتر مورد مطالعه قرار گرفته است. هدف این مقاله بررسی عملکرد مکانیکی و دوامی بتن تقویت شده با الیاف پلی الفین و پلی‌پروپیلن حاوی 15% مواد پوزولانی (پومیس یا متاکائولن) به‌ جای سیمان پرتلند تیپ دو می‌باشد. در این راستا مقاومت فشاری و خمشی جهت بررسی رفتار مکانیکی طرح مخلوط‌های مورد مطالعه در سنین مختلف اندازه‌گیری شدند. از سوی دیگر، مقاومت شیمیایی در برابر حملات باران‌های اسیدی شبیه‌سازی شده از طریق بررسی عینی، اندازه‌گیری افت وزنی و مطالعات ریزساختاری از طریق آنالیز سی‌تی‌اسکن و آزمایش SEM صورت گرفت. بر اساس نتایج به دست آمده، افزودن هر دو الیاف مذکور در بتن باعث کاهش مقاومت فشاری در مقایسه با مقدار متناظر در بتن شاهد شد. ولی برعکس افزایش مقاومت خمشی را در پی داشت، که این اثر با افزودن مواد پوزولانی به ‌مراتب چشمگیرتر گردید. با این وجود، بتن معمولی و الیافی حاوی مواد پوزولانی عملکرد منفی‌ای در برابر حملات باران اسیدی از خود نشان دادند. بر اساس نتایج سی‌تی‌اسکن و آنالیز SEM، بتن‌های حاوی مواد پوزولانی دارای ساختار متخلخلی هستند. همچنین به دلیل واکنش‌های آهک‌زدایی ناشی از حملات اسیدی نسبت کلسیم به سیلیسیم در آن‌ها به‌ مراتب کمتر از نمونه شاهد می‌باشد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Investigation of mechanical behavior of fibrous concrete containing pumice and metakaolin and chemical resistance to acid attack

نویسندگان [English]

  • kianoosh samimi 1
  • Mahyar pakan 2
  • amirhossein firoozbakht 3
1 Assistant professor - Faculty of Civil, Water and Environmental Engineering, Shahid Beheshti University, Tehran, Iran.
2 PhD student - Faculty of Civil, Water and Environmental Engineering, Shahid Beheshti University, Tehran, Iran.
3 Research and Development Service, Imen Rah Consulting Engineering Co., No7, 4th.St Khaled Eslamboli (Vozara) Ave. Tehran, Iran.
چکیده [English]

Using fibers to reduce cracks and increase the joint spacing of concrete slabs has become popular in the concrete pavements of airports and freeways recently. However, their durability behavior against acid rain has been less studied. The purpose of this paper is to investigate the mechanical performance and durability of concrete reinforced with polyolefin and polypropylene fibers containing 15% of pozzolanic materials (pumice or metakaolin) instead of Portland type II cement. In this regard, compressive and flexural strength were measured to investigate the mechanical behavior of the studied mixtures at different ages. On the other hand, chemical resistance against acid rain simulated was investigated through the visual examination and weight loss, and also microstructural analysis was performed by SEM analysis and CT scan testing. Based on these results, the addition of both of these fibers in concrete reduces the compressive strength of concretes compared to the similar content in the control concrete. On the contrary, fibers increased flexural strength, which became much more significant with the addition of pozzolanic materials. However, ordinary and fibrous concrete containing pozzolanic materials showed a weak performance against acid rain. Based on the results of CT scan and SEM analysis, concretes containing pozzolanic materials have a porous structure. Besides, the ratio of calcium to silicon in them is much lower than the control concrete due to decalcification reactions caused by acid attacks.

کلیدواژه‌ها [English]

  • Acid attack
  • CT scan analysis
  • Metakaolin
  • Microstructure
  • Pumice
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