مهندسی سازه و ساخت

مهندسی سازه و ساخت

تاثیر تغییرات نسبت آب به سیمان و مصرف ریزدانه یا درشت دانه غیر واکنش‌زا در کنترل اثرات منفی واکنش سیلیسی- قلیایی بر مقاومت پیوستگی بتن

نوع مقاله : علمی - پژوهشی

نویسندگان
1 دانشجوی دکتری سازه، گروه مهندسی عمران، دانشکده مهندسی، دانشگاه بوعلی سینا، همدان، ایران
2 دانشیار گروه مهندسی عمران، دانشکده مهندسی، دانشگاه بوعلی سینا، همدان، ایران
3 استادیار گروه مهندسی عمران، دانشکده مهندسی، دانشگاه بوعلی سینا، همدان، ایران
چکیده
واکنش سیلیسی- قلیایی موجب تضعیف مشخصات مکانیکی از جمله مقاومت پیوستگی بتن می‌شود. این پژوهش به بررسی کمی تأثیر ریزدانه یا درشت‌دانه بودن سنگدانه واکنش‌زا و تغییرات نسبت آب به سیمان بر مقاومت پیوستگی بتن تحت این واکنش می‌پردازد. بدین منظور تعدادی نمونه مکعبی مسلح با میلگردهای به قطر 12 و 16 میلی‌متر و شش مخلوط بتنی از ترکیب‌های مختلف درشت‌دانه و ریزدانه واکنش‌زا و غیرواکنش‌زا و با نسبت‌های آب به سیمان 45/0، 5/0 و 55/0 ساخته و در محلول NaOH غوطه‌ور شد. نتایج آزمایش بیرون‌کشیدگی نشان داد، مصرف صرفا درشت‌دانه غیرواکنش‌زا در نمونه‌های مسلح با میلگرد به قطر 12 و 16 میلی‌متر مقاومت پیوستگی را به ترتیب 2/2 و 3/8 درصد و مصرف صرفا ریزدانه غیرواکنش‌زا به ترتیب 3/8 و 18 درصد در مقایسه با نمونه R-0.5 افزایش داد. بنابراین مصرف ریزدانه غیرواکنش‌زا در مقایسه با مصرف درشت‌دانه غیرواکنش‌زا برای کنترل افت مقاومت پیوستگی و بهبود مهار میلگرد مؤثرتر می‌باشد. همچنین در نمونه‌های مسلح با میلگرد 12 میلی‌متر، افت مقاومت پیوستگی با افزایش نسبت آب به سیمان شدت یافت، اما در نمونه‌های مسلح با میلگرد 16 میلی‌متر، افت مقاومت پیوستگی و تغییرات نسبت آب به سیمان روند ثابتی نداشت. هر دو گزینه کاهش نسبت آب به سیمان و یا تعویض سنگدانه واکنش‌زا، راهکار مناسبی برای بهبود رفتار پیوستگی بتن آسیب‌دیده ناشی از واکنش سیلیسی- قلیایی می‌باشد. اما با پیشرفت واکنش در بلند مدت، تأثیر گزینه اول کم‌رنگتر می‌شود. علاوه بر این به نظر می‌رسد، گزینه دوم راهکار مناسب‌تری برای کنترل تأثیرات منفی این واکنش بر رفتار پیوستگی میلگردهای قطورتر در بلند مدت می‌باشد.
کلیدواژه‌ها

موضوعات


عنوان مقاله English

Effect of variations in W/C ratio and using non-reactive fine or coarse aggregate in controlling the negative effects of ASR on the concrete bond strength

نویسندگان English

Maryam Abbasiyan Taeb 1
Freydoon Rezaie 2
Ebrahim Ghiasvand 3
1 Ph.D. Student, Department of Civil Engineering,, Faculty of Engineering, Bu-Ali Sina University, Hamedan, Iran
2 Associate Professor, Department of Civil Engineering, Faculty of Engineering, Bu-Ali Sina University, Hamedan, Iran
3 Assistance Professor, Department of Civil Engineering, Faculty of Engineering, Bu-Ali Sina University, Hamedan, Iran
چکیده English

Alkali-silica reaction (ASR) is accompanied by expansion and cracking in the concrete, which weakens the mechanical properties, including bond strength of the concrete. This paper intends to quantitatively investigate the effect of fine and coarse reactive aggregate and variations in the water-cement (W/C) ratio on bonding strength of the ASR-damaged concrete. To this aim, a number of cubic specimens reinforced with 12 and 16 mm rebars and six concrete mixtures of different combinations of reactive/non-reactive fine and coarse aggregate and different W/C (0.45, 0.5, 0.55) were produced and immersed in NaOH solution. Then, pull-out tests (POTs) are conducted to evaluate the bond strength of the specimens. The results showed that the use of only non-reactive coarse aggregate in specimens with 12 and 16 mm diameter rebars increased the bond strength by 2.2 and 8.3 percent, respectively, and the use of only non-reactive fine aggregate increased by 8.3 and 18 percent, respectively, compared to R-0.5 sample. Therefore, the use of non-reactive fine aggregate is more effective than non-reactive coarse aggregate to improve the rebar anchorage in the ASR-damaged concrete. Also, in the specimens with 12 mm rebar, the loss in bond strength tended to intensify with the increase in W/C ratio. In contrast, in the specimens with 16 mm rebar, the amount of bond strength loss did not follow a constant trend according to the changes in W/C ratio. Finally, both solutions namely W/C reduction and reactive aggregate replacement were recommended as suitable strategies to control the negative effects of ASR on bonding behavior. However, with the furthering of the reaction and in the long term, the effect of the former alternative tends to diminish. In addition, it seems that the second option is a more suitable solution to improve bonding strength of thicker rebars in the long term.

کلیدواژه‌ها English

Alkali-silica reaction
concrete bond strength
pull-out test
fine and coarse aggregate
water-cement ratio
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  • تاریخ دریافت 15 فروردین 1403
  • تاریخ بازنگری 18 تیر 1403
  • تاریخ پذیرش 14 مرداد 1403