مطالعه اثر دوده‌ سیلیسی بر روی چقرمگی و انرژی شکست بتن خود تراکم سبک

نوع مقاله : مقاله کامل پژوهشی

نویسندگان

1 دانشکده مهندسی مکانیک، دانشگاه پدافند هوایی خاتم‌الانبیاء(ص)، تهران

2 دانشکده مهندسی عمران، دانشگاه تربیت دبیر شهید رجایی، تهران

چکیده

این مطالعه به بررسی چقرمگی و انرژی شکست بتن خود تراکم سبک می‌پردازد. بدین منظور چهار طرح مخلوط با نسبت آب به سیمان‌های 37/0 تا 52/0 ساخته شد. همچنین برای بررسی تأثیر استفاده از دوده‌ سیلیسی بر خواص شکست بتن خود تراکم سبک، نسبت جایگزینی سیمان با دوده‌ سیلیسی برابر صفر، 5 و 10 درصد در نظر گرفته شد. برای تعیین پارامترهای شکست بتن از روش اثر اندازه استفاده شد. در این روش برای هر طرح مخلوط، آزمایش خمش سه‌نقطه‌ای بر روی 12 نمونه تیر شکاف­دار انجام شد. نتایج آزمایش‌ها نشان داد که در بتن خود تراکم سبک، با کاهش نسبت آب به سیمان از 52/0 به 37/0، انرژی شکست (Gf) حدود 7/2 برابر شد و چقرمگی شکست (KIC) حدود 88% افزایش یافت. همچنین در این حالت مقاومت‌های فشاری، کششی و مدول الاستیسیته (Modulus of Elasticity) بتن به ­ترتیب حدود 68%، 57% و 28% بهبود یافتند. از سوی دیگر، افزودن دوده‌ سیلیسی به بتن خودتراکم سبک سبب کاهش کارایی آن شد؛ برای حفظ این کارایی، نیاز به استفاده از فوق روان­ کننده افزایش یافت. زمانی‌که نسبت جایگزینی وزن سیمان با دوده ‌سیلیسی از صفر به 5 و 10 درصد افزایش داده شد، انرژی شکست به ­ترتیب 4/19% و 2/24% و چقرمگی آن 14% و 3/18% بهبود یافت. در این حالت، بهبود کیفیت مشابهی برای کلیه خواص مکانیکی بتن خود تراکم سبک رخ داد. از طرفی با افزایش نسبت جایگزینی دوده‌ سیلیسی در ساخت بتن، مشاهده شد که پیوند میان سنگ‌دانه‌ها و خمیر بتن بهبود یافته و در تیرها سطح شکسته شده بتن بسیار نرم‌تر‌ و صاف‌تر گردید.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Studying the Effect of Silica Fume on the Fracture Toughness and Fracture Energy of Self-Compacting Lightweight Concrete

نویسندگان [English]

  • Hasan Salehi 1
  • Moosa Mazloom 2
1 Department of Mechanical Engineering, Khatam Ol Anbia University, Tehran, Iran
2 Department of Civil Engineering, Shahid Rajaee Teacher Training University, Lavizan, Tehran, Iran
چکیده [English]

Self-compacting lightweight concrete (SCLC) is one type of concrete that its usage has widely increased. The use of some additives in the production of SCLC can both reduce its costs and improve its properties. The effects of different cement replacement materials have been studied by several researchers. Jalal et al. (2012) claimed that the use of silica fume could improve the electrical resistance and mechanical properties of self-compacting concrete, and reduce its water absorption. Moreover, the use of silica fume in normal concrete improves the bond between aggregate and paste surfaces, and it has positive effects on fracture toughness, compressive strength and tensile strength (Lam et al., 1998).
To simulate the fracture behavior of concrete in numerical models of concrete, depending on the model, some parameters such as fracture energy, fracture toughness and critical effective crack-tip opening displacement ( or δc), which generally are known as fracture parameters, must be determined. In this regard, Peterson (1980) showed that the fracture parameters are significantly affected by water to cement ratio (w/c) and the quality of aggregate. In other words, by reducing w/c or using stronger aggregate, the fracture energy of concrete increases.
In this study, the effect of w/c and silica fume on the fracture toughness and fracture energy of SCLC has been investigated. Therefore, by making six mix designs and 126 concrete specimens, fracture parameters, mechanical properties and the workability of fresh concrete were carefully studied. Initially, four mix designs with the w/c of 0.37, 0.42, 0.47 and 0.52 were made. Afterwards, by replacing 0, 5% and 10% of the weight of cement with silica fume, the effects of changing this parameter on the fracture parameters of SCLC were studied.

کلیدواژه‌ها [English]

  • Self-compacting lightweight concrete
  • Silica fume
  • Mechanical properties
  • Fracture energy
  • Fracture toughness
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