تأثیر ناحیه انتقال بر خواص و ریزساختار بتن

نوع مقاله : مقاله پژوهشی

نویسندگان

گروه عمران، واحد اهواز، دانشگاه آزاد اسلامی، اهواز، ایران

چکیده

در این پژوهش سنگدانه‌های طبیعی با سیلیس بالا و نسبت آب به مواد سیمانی به میزان 0/45 استفاده شدند. به‌منظور بررسی تأثیر ناحیه انتقال بر خواص بتن‌ با بررسی رئولوژی بتن تازه، 30 نمونه در قالب 10 طرح اختلاط در محدوة سنی7 تا 180 روزه بررسی گردید و از روش تاگوچی طرح اختلاط منتخب مشخص شد. آزمایش‌های تعیین خواص مکانیکی و دوام بتن انجام شدند و درنهایت ریزساختار مخلوط‌ها بررسی گردید. نتایج نشان داد که با افزایش سن نمونه‌ها، خواص مکانیکی بهبود یافته و به تبع آن کاهش در جذب آب حجمی، نفوذ آب تحت فشار و نفوذ تسریع‌شده یون کلراید و افزایش قابل توجه در مقاومت الکتریکی نمونه‌ها رخ داده ‌است. هم‌چنین در میزان فاز بلوری اکسید کلسیم و تعداد منافذ بزرگ کاهش و در فاز سیلیکات کلسیم هیدراته ناحیه انتقال افزایش حاصل شد که این منجر به بهبود کیفیت ریزساختار گردید. با افزایش سن، سیلیکات‌ کلسیم هیدراته و کربنات‌کلسیم به‌ترتیب %24 و %21/5 زیاد شدند و به تبع آن مقاومت‌های فشاری و ویژه الکتریکی نیز به‌ترتیب %10/3 و %48/6 افزایش یافتند و نفوذ تسریع‌شده یون کلراید %5/2 کاهش یافت. در محدودة 30 میکرومتری، به‌دلیل اغتشاش موجود در منطقه مرزی، روابط همبستگی قابل قبولی بین نسبت عناصر سازنده و خواص بتن به‌دست نیامد. در محدودة 30 تا 50 میکرومتری روابط خطی با ضرائب تعیین 0/85 بین نسبت وزنی کلسیم به سیلیسیم با مقاومت فشاری و نفوذ تسریع‌شده یون کلراید برقرار شد، به‌طوری که با کاهش %82 نسبت وزنی مذکور، مقاومت فشاری %10/3 افزایش و  نفوذ %5/2 کاهش یافت.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Effect of Interfacial Transition Zone on Properties and Microstructure of Concrete

نویسندگان [English]

  • Seyed Fathollah Sajedi
  • Seyed Qasem Mirahmadi
Professor, Department of Civil Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran
چکیده [English]

The interfacial transition zone (ITZ) is a relatively heterogeneous region with a thickness of 50 micrometers, whose physical and mechanical properties are determined descriptively due to the fine length scale and heterogeneous characteristics. In this research, by focusing on the ratio of different elements forming the ITZ and simultaneous examination of microscopic images, it was possible to numerically investigate the effect of changes in the ratio of elements on the properties and microstructure of concrete. In order to investigate the effect of the ITZ on concrete properties by examining the rheology of fresh concrete, 30 standard cubic samples were examined in the form of 10 mixing plans, and then the selected mixing plan was determined by trial and error. Then, 54 cubic and cylindrical samples of aggregates with high silica and w/c as 0.45 were made, and tests were conducted to determine the mechanical properties and durability of concrete in the age range of 7 to 180 days; finally, the microstructure of the mixtures was investigated. With increasing age, hydrated calcium silicate and calcium carbonate increased by 24% and 21.5%, respectively, and accordingly, the compressive strength (CS) and specific electrical resistances also increased by 10.3% and 48.6%, respectively, and the accelerated penetration of chloride ions decreased by 5.2%. In the limit of 30 micrometers from the aggregate boundary, due to the disturbance in the boundary region, no acceptable correlation relations between the ratio of different constituent elements and concrete properties were obtained. From the limit of 30 to 50 micrometers, linear relationships with coefficients of determination of 0.85 were established between the weight ratio of calcium to silicon with CS and the accelerated penetration of chloride ions, so that by reducing the said weight ratio by 82%, the CS increased by 10.3% and penetration decreased by 5.2%.

کلیدواژه‌ها [English]

  • Interfacial Transition Zone (ITZ)
  • Microstructure
  • X-ray Spectroscopy
  • Atomic Tatio of Elements
  • Scanning Electron Micrograph (SEM)

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نشریه مهندسی عمران امیرکبیر
دوره 57، شماره 2
1404
صفحه 291-316

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