بررسی مرز سنگدانه- خمیر سیمان در بتن های حاوی دوده سیلیسی و خاکستربادی

نوع مقاله: علمی - پژوهشی

نویسندگان

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

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

چکیده

پیوستگی بین سنگدانه و خمیر سیمان موسوم به ناحیه انتقال میان سطحی (ITZ) از پارامترهای مهمی است که بر خواص مکانیکی و دوام بتن تاثیر می­گذارد. ریزساختار ناحیه انتقال و تخلخل (حفرات) خمیر سیمان و بتن متاثر از نوع و خواص مصالح مصرفی است که  بررسی آن از اهداف این تحقیق می باشد. از طرفی استفاده از روش­های کارآمد، کم هزینه و قابل اتکا برای ارزیابی عملکرد بتن در برابر نفوذ یون کلراید و رابطه آن با ناحیه انتقال، به عنوان معیار مناسب برای ارزیابی دوام، اهمیت ویژه­ای دارد. تاکنون روش­های مختلفی با رویکرد شاخص­های الکتریکی ارائه شده است. در این پژوهش، تاثیر مواد پوزولانی خاکستربادی (10%، 20% و 30%) و  دوده سیلیسی (5% و 10%) به عنوان جایگزین با وزن سیمان به صورت مخلوط­های دوجزیی و سه­جزیی، بر خواص بتن تازه و سخت شده مورد بررسی قرار گرفته است. از آزمایش های مقاومت فشاری، مقاومت کششی غیر مستقیم و مدول الاستیسیته برای ارزیابی خواص مکانیکی استفاده شد. همچنین برای ارزیابی دوام بتن، آزمایش­های عمق نفوذ آب، تخلخل، جذب آب موئینه، مقاومت الکتریکی ویژه، نفوذ تسریع شده یون کلراید (RCPT)، انتقال تسریع شده یون کلراید (RCMT) بکار برده شد. جهت بررسی ریخت شناسی مرز مشترک سنگدانه و خمیر سیمان از تصاویر ریزنگار الکترون پویشی (SEM) استفاده شد. نتایج آزمایش بر روی بتن تازه نشان داد که حضور دوده سیلیسی در مخلوط های دوجزیی و سه­جزیی موجب کاهش کارایی و هوای محبوس و حضور خاکستر بادی موجب افزایش این دو می­شود. افزودن دوده سیلیسی به مخلوط­های حاوی خاکستربادی ضمن  افزایش مقاومت مکانیکی، موجب کاهش تخلخل و حفرات تا 18% می­شود. همچنین حضور مواد پوزولانی علاوه­بر افزایش کیفیت پیوند و یکنواختی مرز سنگدانه با خمیر سیمان، به طور چشمگیری بر خواص انتقال بتن تاثیر مثبت می­گذارد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Assessment of aggregates- cement paste border in concretes containing silica fume and fly ash

نویسندگان [English]

  • Ali Sademomtazi 1
  • Behzad Tahmouresi 2
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
چکیده [English]

The bond between aggregate and cement paste, called the interfacial transition zone (ITZ) is an important parameter that effect on the mechanical properties and durability of concrete. Transition zone microstructure and porosity (pores) of cement paste or concrete are affected by the type and properties of materials used which evaluated in this research. On the other hand, the use of efficient, low-cost and reliable method is particularly important for evaluating of concrete performance against the chloride ion penetration and its relationships with transition zone as a suitable index to assess the durability. So far, various methods to approach the electrical Indices are presented. In this research, the effect of pozzolanic materials fly ash (10%, 20% and 30%) and silica fume (5% and 10%) as substitute of cement by weight in binary and ternary mixtures on the fresh and hardened concrete properties were investigated. To determine mechanical properties, the compressive strength, splitting tensile strength and modulus of elasticity tests were performed. Also, water penetration depth, porosity, water sorptivity, specific electrical resistivity, rapid chloride penetration test (RCPT) and rapid chloride migration test (RCMT) tests were applied to evaluate concrete durability. To examine the border of aggregate and cement paste morphology of concrete specimens, scanning electron microscope images (SEM) was used. The fresh concrete results showed that the presence of silica fume in binary and ternary mixtures reduced workability and air content but fly ash increased them. Adding silica fume to mixtures of containing flay ash while increasing mechanical strength reduced the porosity and pores to 18%. The presence of pozzolanic materials in addition to increasing bond quality and uniformity of aggregate-cement matrix border a considerably positive effect on the transport properties of concrete.

کلیدواژه‌ها [English]

  • Fly ash
  • Silica fume
  • transition zone
  • porosity
  • Durability

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