بررسی خاصیت پوزولانی مواد مختلف و تاثیر آنها بر خصوصیات بتن فوق توانمند

نوع مقاله : مقاله پژوهشی

نویسندگان

دانشکده مهندسی عمران، دانشگاه تحصیلات تکمیلی صنعتی و فناوری پیشرفته، کرمان، ایران

چکیده

جایگزینی بخشی از سیمان با مواد زائد صنعتی به خصوص در بتن‌های با حجم بالای مواد سیمانی همچون بتن‌های فوق توانمند می‌تواند اثرات مثبتی از لحاظ زیست محیطی و بهبود خواص به ارمغان آورد. لیکن تاثیر برخی از این مواد همچون پسماند باطله زغال سنگ و سرباره مس بر خواص بتن‌های فوق توانمند مورد بررسی جدی قرار نگرفته است. مطالعه حاضر به بررسی تاثیر چندین ماده جایگزین سیمان با عملکرد پوزولانی کاملا متفاوت از رده بسیار فعال )همچون دوده سیلیسی( تا تقریبا غیرفعال )همچون پودر سنگ سیلیس( بر خواص بتن‌های فوق توانمند پرداخته است. دمای عمل آوری 70 - 100 درجه سانتیگراد احتمال تشکیل دیرهنگام اترینگایت را تشدید می‌کند، لذا دماهای عمل آوری ℃ 60 و ℃ 90 درجه سانتیگراد به عنوان دماهای عمل آوری با احتمال خطر پایین و بالا از لحاظ احتمال تشکیل دیرهنگام اترینگایت در مقایسه با دمای استاندارد 25 درجه سانتیگراد انتخاب شده­اند. برای مقایسه نرخ واکنش پوزولانی مواد از روش رسانایی الکتریکی استفاده شده است. نتایج این مطالعه در خواص مکانیکی شامل مقاومت فشاری و مدول گسیختگی، مشخصات دوام شامل انتشار تسریع شده یون کلرید و بررسی ریزساختاری با عکس‌های میکروسکوپ الکترونی روبشی انجام پذیرفته است. نتایج نشان می‌دهند که استفاده از حرارت برای تمام مواد جایگزین سیمانی مذکور به جز دوده سیلیسی میتواند سبب کاهش مقاومت و افزایش نفوذ یون کلرید بتن‌های فوق توانمند شود. مقاومت‌های بدست آمده از عمل آوری تسریع شده ℃ 60 و ℃ 90 تغییرات چندانی نسبت به یکدیگر نداشته است در حالی که استفاده از عمل آوری تسریع شده ℃ 90 ، انرژی بیشتری نسبت به عمل آوری تسریع شده ℃ 60 احتیاج دارد و خطر دیرهنگام اترینگایت را تشدید می‌کند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

An Investigation on the Pozzolanic Reactivity of Different Materials and Their Effects on the Properties of Ultra-high Performance Concrete (UHPC)

نویسندگان [English]

  • H. Madani
  • A. Pourjhanshahi
Civil engineering faculty, Graduate University of Advanced Technology, Kerman, Iran
چکیده [English]

The partial replacement of cement with industrial wastes, especially in the concretes with high volume of cement-based materials such as ultra-high performance concretes (UHPC) may have positive effects on the environment and could lead to improvements in concrete properties. However, the effects of some types of these materials, such as coal waste and copper slag, have not been investigated seriously. In this study, the effects of several cement-based materials with different pozzolanic reactivity from very active (like silica fume) to approximately inactive (like silica powder) have been studied on the UHPC properties. Since the treatment temperature of 70-100 0C intensifies the possibility of delayed ettringite formation, thermal curing at 60 0C and 90 0C have been selected as the treatment temperatures of low and high risk of delayed ettringite formation, furthermore the results have been compared with the standard thermal curing at 20 0C. An electrical conductivity method has been used to compare the pozzolanic reaction rate of materials. In this study, compressive strengths, modulus of rupture and rapid chloride migration coefficients have been determined and the investigation of microstructure has been carried out using scanning electron microscopy. The obtained results show that use of heat treatment for the mixtures incorporating materials with low pozzolanic reactivity may reduce the strength and durability of ultra-high performance mixtures. The differences between the results obtained from the thermal curing conditions of 60 0C and 90 0C were not significant, however use of thermal curing at 90 0C requires higher energy demand compared with the thermal curing at 60 0C, moreover higher risk of delayed ettringite formation is expected.

کلیدواژه‌ها [English]

  • pozzolanic activity
  • Mechanical Properties
  • Durability
  • cement replacement materials
  • thermal curing
  • ultra-high performance concrete
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