تاثیر میکروسیلیس و نانوسیلیس بر روانی و مشخصات مکانیکی بتن خودتراکم حاوی الیاف پلی‌پروپیلن

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشکده عمران، دانشگاه تربیت دبیر شهید رجایی

2 تهران - لویزان - دانشگاه شهید رجایی - دانشکده عمران

چکیده

با توجه به گسترش بتن خودتراکم و لزوم کاهش عیار سیمان و افزایش مقاومت بتن، در این مطالعه اثر میکروسیلیس، نانوسیلیس و الیاف پلی‌پروپیلن بر بتن خودتراکم بررسی شد. در واقع میکروسیلیس، نانوسیلیس و الیاف پلی‌پروپیلن به صورت تکی، دوتایی و ترکیب سه تایی در طرح مخلوط بتن خودتراکم مورد بررسی قرار گرفتند. به این منظور 23 طرح مخلوط ساخته ‌شد. در راستای بررسی خواص خودتراکمی بتن آزمایش‌های حلقه J، قیف V، جریان اسلامپ و T50 انجام شد. همچنین آزمایش‌های مقاومت فشاری، کششی و خمشی بر روی بتن سخت ‌شده در سن 28 روزه بررسی گردید. نتیجه آزمایش­ها نشان داد که میکروسیلیس و نانوسیلیس علاوه بر کاهش کارایی بتن خودتراکم، مقاومت فشاری، کششی و خمشی آن را افزایش می‌دهند. الیاف پلی‌پروپیلن مشخصات مکانیکی بتن، به خصوص مقاومت کششی و خمشی آن، را افزایش داد. همچنین با افزودن همزمان میکروسیلیس، نانوسیلیس و الیاف مشخصات مکانیکی بتن خودتراکم بهبود مضاعف یافت. بهترین طرح با بیشترین مقاومت فشاری، نمونه دارای 5 درصد میکروسیلیس،0/75 درصد نانوسیلیس و 1/5 درصد الیاف بود. مقاومت فشاری این طرح نسبت به نمونه شاهد 40 درصد افزایش یافت. همچنین طرح بهینه در مقاومت کششی و خمشی دارای 5 درصد میکروسیلیس، 0/75 درصد نانوسیلیس و 1 درصد الیاف بود. مقاومت کششی و خمشی این طرح نسبت به نمونه شاهد به ترتیب 26 و 28 درصد افزایش داشت. به دلیل روان­تر بودن این طرح مخلوط نسبت به طرح دارای 1/5 درصد الیاف، کار کردن با آن آسان­تر بود. کاهش مقاومت فشاری آن هم نسبت به طرح دارای 1/5 درصد الیاف کمتر از 3 درصد بود. بنابراین بهترین طرح مخلوط این تحقیق شامل 5 درصد میکروسیلیس، 0/75 درصد نانوسیلیس و 1 درصد الیاف پلی‌پروپیلن بود.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

The effects of silica fume and nano-silica on the workability and mechanical properties of self-compacting concrete containing polypropylene fibers

نویسندگان [English]

  • Amirhosein Abna 1
  • Moosa Mazloom 2
1 Civil Engineering Department, Shahid Rajaee Teacher Training University
2 Shahid Rajaee Teacher Training University
چکیده [English]

         Due to the widespread usage of self-compacting concrete and the need to reduce the level of cement and increase the strength of concrete, this study investigates the effects of silica fume, nano-silica and polypropylene fibers on self-compacting concrete. For this purpose, 23 mixes were made. In order to study the self-compacting properties of concrete, J-ring, V-funnel, slump flow and T50 tests were casted. Compressive, tensile and flexural strength tests also were performed on hardened concrete at the age of 28 days. The experimental results showed that silica fume and nano-silica, in addition to reducing the workability of self-compacting concrete, increased its compressive, tensile and flexural strengths. Polypropylene fibers increased mechanical properties, especially tensile and flexural strengths. In addition, with the simultaneous addition of microsilica, nanosilica and fibers, the mechanical properties of self-compacting concrete were further improved. The best mix, with the highest compression characteristics, had 5% silica fume, 0.75% nano-silica and 1.5% fibers. The compressive strength of this mix design increased by 40% compared to the control mix. The best mix in tensile and flexural strength had 5% silica fume, 0.75% nano-silica and 1% fibers. Tensile and flexural strengths of this mix design increased by 26% and 28% compared to the control mix, respectively.

کلیدواژه‌ها [English]

  • Silica fume
  • Polypropylene fibers
  • Nano-silica
  • Compressive strength
  • Self-compacting concrete
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