بررسی اثر زمان و سرعت مخلوط کردن بر خواص رئولوژی بتن خودتراکم

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشگاه علم و صنعت ایران

2 استادیار دانشکده مهندسی عمران، دانشگاه علم و صنعت ایران

چکیده

ترکیبات و ساختار مخلوط‌های بتن خودتراکم سبب می‌شود که تولید آن ها نسبت به مخلوط های بتن معمولی به انرژی بیشتری نیاز داشته باشد. این میزان انرژی بیشتر که صرف ایجاد یکنواختی و همگنی ترکیبات تشکیل دهنده این نوع مخلوط ها می‌گردد، سبب می‌شود که میزان تولید آن‌ها نسبت به مخلوط های معمولی با محدودیت روبرو باشد که به لحاظ زمانی و اقتصادی، فاکتور مهم و تأثیرگذاری است. هدف این پژوهش مطالعه و بررسی زمان و سرعت مخلوط کردن (انرژی مخلوط کردن) در مخلوط‌های بتن خودتراکم و تأثیر این دو شاخصه مهم بر خواص رئولوژی آن ها می‌باشد. به همین منظور چند نسبت مخلوط از بتن خودتراکم شامل نوع اول بتن خودتراکم پودری و نوع دوم بتن خودتراکم حاوی ماده اصلاح کننده روانگروی VMA ) ) ساخته شد. هر کدام از نسبت ها در سه زمان مخلوط کردن 3 ،8 و 11 دقیقه و هرکدام در دو سرعت مخلوط کردن 20 و 40 دور بر دقیقه مخلوط شدند. نتایج نشان داد که در هر دسته از مخلوط‌ها، با افزایش زمان مخلوط کردن تا حد مشخصی که زمان تثبیت نامیده می‌شود )کوتاه‌ترین زمان مخلوط کردن که در این تحقیق 8 دقیقه است)، کارایی بتن افزایش یافته و با افزایش زمان مخلوط کردن تا 11 دقیقه 6 درصد کاهش می‌یابد. آزمایش های رئولوژی نیز این نتیجه را تأیید می‌کنند به طوری که کمترین مقدار تنش جاری استاتیک نیز در زمان مخلوط کردن 8 دقیقه به دست آمد و با افزایش زمان مخلوط کردن تا 11 دقیقه، مقدار این پارامتر تا 42 درصد افزایش یافت.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Evaluation of mixing time and mixing speed on the Rheological Properties of SelfConsolidating Concre

نویسندگان [English]

  • parviz ghoddousi 1
  • ali akbar shirzadi javid 2
  • sadaf aghajani 1
1 Iran University of Science and Technology
2 assistant professor, school of civil engineering, iran university of science and technology
چکیده [English]

Due to the composition, the production of self-consolidating concrete (SCC) requires more mixing energy to uniform and homogenize the concrete components. This limits the rate of concrete production in comparison with the conventional concrete and therefore it is an important financial factor. So, mixing energy (mixing time and power) is one of the main factors in concrete production and before large production, the appropriate mixing time and speed should be determined for each mixture. In this study, according to objectives and considering that mixing time and mixing speed are two main factors in content of mixing energy and according to guidelines and regulations, two SCC mix designs (powder type and VMA type) were mixed in three mixing times (3, 8 and 11 minutes) and each of them in two mixing speeds (20 and 40 rpm) and their effect on rheological properties was evaluated. The results showed that in each series of mixtures by increasing the mixing time up to a certain level that is called stabilization time (the shortest mixing time) and in this study is 8 minutes, the workability of concrete increased and after that, by mixing up to 11 minutes it decreased by 6 percent. Static yield stress in the 8 minutes mixing also had a minimum amount and by mixing up to 11 minutes it increased by 42 percent. This increment reached 62 percent for dynamic yield stress, so the rheology tests also confirmed these results.

کلیدواژه‌ها [English]

  • Mixing time
  • mixing speed
  • mixing energy
  • self-consolidating concrete
  • stabilization time
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