بررسی تاثیر افزایش سیمان در دما و زمانهای مختلف بر خواص رئولوژی بتن خودتراکم

نوع مقاله : مقاله پژوهشی

نویسندگان

1 استادیار دانشکده مهندسی عمران، دانشگاه آزاد اسلامی واحد تهران‌جنوب

2 دانشجوی دکتری مهندسی و مدیریت ساخت دانشگاه آزاد اسلامی واحد تهران‌جنوب

10.22124/jcr.2021.17818.1459

چکیده

بتن خودتراکم در برابر تغییرات دما نسبت به بتن معمولی، دارای حساسیت بیشتری می‌باشند. افزایش دما، بر نرخ هیدراتاسیون سیمان تأثیر می‌گذارد که اشتباهات جزئی در مصرف سیمان سبب مشکلات قابل‌توجهی در خواص بتن تازه خودتراکم به‌ویژه از دست دادن کارایی می‌شود ازاین رو برای کنترل کارایی در بتن ‌خودتراکم، نیاز به آزمایش‌های متعدد در مقدار سیمان می‌باشد. در این تحقیق برای اندازه-گیری خواص رئولوژی، دمای مخلوط‌های بتن با توجه به شرایط محیطی فصل‌های مختلف انتخاب شده است. از‌این‌جهت، برای انجام آزمایش‌های کارایی و رئولوژی، ساخت نمونه ها در فصل‌های مختلف سال به انجام رسید. بر اساس نتایج به‌دست‌آمده از تنش جاری‌ شدن و لزجت خمیری حاصل از دستگاه رئومتر در طول زمان 60 دقیقه، افزایش سیمان تا 440 کیلوگرم بر مکعب، سبب بهبود رئولوژی می‌شود. با استناد به دیگر نتایج تحقیق، باید برای بهبود رئولوژی از بالا رفتن دمای بتن و زمان بتن‌ریزی کاست، زیرا در غیر این صورت، باعث سخت شدگی بتن و درنتیجه کاهش رئولوژی می‌شود.

کلیدواژه‌ها

عنوان مقاله [English]

Investigating the effect of cement at different temperatures and durations on the rheological properties of the self-compacting concrete

نویسندگان [English]

  • Seyyed Azim Hosseini 1
  • ali zal nezhad 2
1 Assistant Professor, School of Civil Engineering, Islamic Azad University, South Tehran Branch
2 PhD student in Construction and Management Engineering, Islamic Azad University, South Tehran Branch
چکیده [English]

The self-compacting concrete is more sensitive to changes in the temperature with respect to the ordinary concrete. Increase in the temperature affects the cement hydration rate and minor mistakes in the amount of used cement could bring about significant problems concerning the properties of self-compacting concrete, mostly affecting workability. Therefore in order to understand the cement mechanism in the self-compacting concrete, care should be exercised to regulate workability through right consumption of cement. In this research the temperature of the concrete mixtures was selected with respect to the ambient conditions in different seasons. Thus, after reaching the concrete temperature to the ambient temperature, the rheological properties of the self-compacting concrete with different amounts of cement as a function of mixing time, and temperature with water to cement ratio of 0.42 were investigated. According to the obtained results from the rheometer in terms of the yield stress and plastic viscosity during 60 minutes, it was found that addition of cement up to 440 kg/m3 improves the rheology. Furthermore referring to the results of this research it should be stated that for improving the rheology, one should prevent rise of temperature in the concrete and reduce the concrete placing time, otherwise it could result in concrete hardening and consequently reduced rheological properties.

کلیدواژه‌ها [English]

  • self-compacting concrete
  • rheology
  • cement
  • workability
  • temperature

مراجع

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