بررسی تاثیر الیاف پلی پروپیلن بر جمع شدگی، رفتار فشاری و مقاومت چسبندگی برشی و کششی ملات های تعمیری بر بستر بتنی

صابری ورزنه, علی; نادری, محمود

doi:10.22065/jsce.2020.246151.2224

بررسی تاثیر الیاف پلی پروپیلن بر جمع شدگی، رفتار فشاری و مقاومت چسبندگی برشی و کششی ملات های تعمیری بر بستر بتنی

نوع مقاله : علمی - پژوهشی

نویسندگان

¹ گروه عمران، دانشکده فنی و مهندسی، دانشگاه آزاد واحد قیام دشت، تهرن، ایران

² استاد، دانشگاه بین المللی امام خمینی (ره)، قزوین، ایران

10.22065/jsce.2020.246151.2224

چکیده

پدیده خشک شدن ملات و به دنبال آن به وجود آمدن جمع شدگی از دلایل اصلی در کاهش مقاومت چسبندگی بین ملات های تعمیری و بستر بتنی می باشد. یکی از راه کارهای کاهش جمع شدگی، استفاده از الیاف داخل ملات می باشد. لذا در این مقاله جهت بهبود چسبندگی بین ملات تعمیری و بستر بتنی از الیاف پلی پروپیلن در مخلوط ملات استفاده گردیده و بدین منظور مقدار جمع شدگی حاصل از خشک شدن ملات ها کنترل گردیده است. برای تعیین مقدار مقاومت چسبندگی بین ملات تعمیری و بستر بتنی از روش های "انتقال اصطکاک" و "کشیدن از سطح" استفاده شده است. همچنین علاوه بر تعیین مقدار جمع شدگی و مقاومت چسبندگی، مقدار مقاومت فشاری ملات های حاوی الیاف با به کارگیری روش های فوق و با مدل سازی اجزا محدود با نرم افزار ABAQUS مورد بررسی قرار گرفته و نحوه شروع و توزیع ترک ها و تنش ها نشان داده شده است. برای ارزیابی مقاومت فشاری درجای ملات های مسلح به الیاف پلی پروپیلن، با استفاده از تحلیل رگرسیون خطی و توانی، همبستگی بین قرائت های به دست آمده از روش های نیمه مخرب "انتقال اصطکاک" و "کشیدن از سطح" با آزمون های آزمایشگاهی تعیین گردید. سپس با استفاده از نمودارهای کالیبراسیون، معادلات مورد نیاز جهت تبدیل نتایج آزمون های درجا به مقاومت فشاری ملات های مسلح به الیاف پلی پروپیلن ارائه شدند. نتایج به دست آمده نشان دهنده تاثیر مثبت الیاف بر جمع شدگی، مقاومت چسبندگی برشی و کششی و مقاومت فشاری ملات ها می باشد. همچنین شدت همبستگی به دست آمده از روش های "انتقال اصطکاک" و "کشیدن از سطح" بیانگر رابطه قوی خطی بین این دو روش می باشد که در نتیجه می توان به جای استفاده از دستگاه گران قیمت Pull-off از دستگاه ساده و ارزان "انتقال اصطکاک" استفاده نمود.

کلیدواژه‌ها

موضوعات

مهندسی سازه و زلزله

عنوان مقاله [English]

Analyzing the Effect of Polypropylene Fibers on Compressive Behavior, Shrinkage and Bond Strength of Repair Mortars/Concrete Substrate

نویسندگان [English]

Ali Saberi Vaezaneh ¹
Mahmood Naderi ²

¹ Department of Civil Engineering, Faculty of Engineering, Azad University, Ghiamdasht, Tehran, Iran

² Professor, Department of Civil Engineering, Imam Khomeini International University, Qazvin, Iran

چکیده [English]

The dry shrinkage of mortars is one of the primary causes for the reduction of bond strength between repair mortars and concrete substrates. Utilizing fibers in the mortars is one of the methods used to reduce shrinkage. The current study used polypropylene fibers in mortars to improve the bond between repair mortar and concrete substrate, and also to control the dry shrinkage of mortars. The “friction-transfer” and "pull-off” methods were used to determine the bond strength between the repair mortar and concrete substrate. In addition to determining the amount of shrinkage and bond strength, the amount of compressive strength of fiber reinforced mortar by using the above methods and by modeling finite element with ABAQUS software has been investigated. In addition, the methods of initiation and distribution of cracks and stresses were shown. In order to assess the in-situ compressive strength of polypropylene fiber-reinforced mortars, the correlation of records obtained from semi-destructive methods of “friction-transfer” and “pull-off” with those of laboratory tests was determined, using the linear and exponential regression analyses. Then, using calibration curves, the equations required to convert the results of in situ methods to the compressive strength of polypropylene fiber-reinforced mortars were presented. The results demonstrate the positive effect of fibers on shrinkage, shear and tensile bond strength and compressive strength of mortars. The correlation coefficients of the “friction-transfer” and “pull-off” methods are indicative of a strong linear relationship between the two methods that instead of using an expensive “pull-off” device, a simple and inexpensive "friction-transfer" device can be used.

کلیدواژه‌ها [English]

Fiber
Bond Strength
.Shrinkage
In-situ Methods
Finite Element Method

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