تأثیرات پوزولانی متاهالوزیت و میکروسیلیس بر مقاومت مکانیکی و دوام بتن

نوع مقاله : پژوهشی

نویسندگان

1 دانشگاه تربیت دبیر شهید رجایی تهران

2 دانشگاه تربیت دبیر شهید رجایی، تهران

چکیده

به‌منظور تعیین اثرات پوزولانی متاهالوزیت و میکروسیلیس بر مقاومت و دوام بتن، 8 طرح اختلاط با دو نسبت آب به مواد سیمانی 40/0 و 45/0 ساخته شد. در این مخلوط‌ها متاهالوزیت به‌میزان 10 و 20 درصد و میکروسیلیس به‌میزان صفر و 7 درصد جایگزین سیمان پرتلند معمولی شدند. عمل‌آوری نمونه‌ها تا سنین 14، 28 و 90 روز انجام شد. نتایج نشان داد که توأم شدن این دو پوزولان در هر دو نسبت آب به مواد سیمانی به‌ویژه در نسبت کمتر (40/0) با مشارکت 10 درصد متاهالوزیت، به‌مقدار قابل‌توجهی (89/0) باعث افزایش مقاومت فشاری نمونه‌های بتنی گردید ( MPa7/47) گردید. بیشترین مقاومت خمشی ( MPa18/6) نیز در کمترین نسبت آب به مواد سیمانی به‌دست آمد. البته با افزایش نسبت آب به مواد سیمانی مقاومت خمشی همۀ نمونه‌ها به‌مقدار بسیار ناچیزی کاهش یافت. افزایش سرعت امواج اولتراسونیک نسبت به نمونه‌های شاهد مخصوصاً در جایگزینی 10 درصد متاهالوزیت، نشانۀ برتری عملکرد این پوزولان طبیعی در بهبود مقاومت و دوام بتن است.

کلیدواژه‌ها


عنوان مقاله [English]

Pozzolanic Effects of Meta-Halloysite and Micro-Silica on Mechanical Strength and Durability of Concrete

نویسندگان [English]

  • Abolfazl Soltani 1
  • Amir Tarighat 2
  • Mohammad Byezidi 1
1 Shahid Rajaee Teacher Training University
2 Shahid Rajaee Teacher Training University
چکیده [English]

To determine the effects of meta-halloysite and micro-silica pozzolans on mechanical strength and durability of concrete, 8 mix designs with two water/cementitious (W/C) ratios of 0.40 and 0.45 were performed. The ordinary Portland cement (OPC) was replaced by incorporations of 10 and 20% of meta-halloysite, and 7% of micro-silica. Samples were cured until the ages of 14, 28 and 90 days. Results imply that the combination of meta-halloysite and micro-silica for both W/C ratios particularly in the case of the lower ratio (0.40) when the sample contains 10% meta-halloysite, leads to a significant increase (89%) in the compressive strength of mixes (from 25.3 to 47.7 MPa). Also, the highest flextural strength (6.18 MPa) resulted in the lower W/C ratio (0.40). It is noteworthy that increases in W/C ratios for all mixes don’t lead to remarkable decreases in flextural strengths. Notably, the ultrasonic velocity (UV) for all mixes in the lower W/C ratio (0.40) shows a considerable increase particularly in 10% meta-halloysite compared with control samples. The findings above are all indications of better improvement of concrete strengths by natural pozzolan (meta-halloysite).
 

کلیدواژه‌ها [English]

  • concrete
  • Meta-halloysite
  • Silica-fume
  • Mechanical Strength
  • durability
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Standards:
ASTM: C311–05, Standard Test Methods for Sampling and Testing Fly Ash or Natural Pozzolans for Use in Portland-Cement Concrete.
ASTM: C78-02, Standard Test Method for Flexural Strength of Concrete (Using Simple - Beam with Third –Point Loading).
ASTM: C618–78, Standard Specification for Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Portland Cement Concrete.
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