بررسی آزمایشگاهی تأثیر سیمان و گرانول‌های HDPE بازیافتی بر مقاومت، دوام و ریزساختار خاک ماسه‌ای

نوع مقاله : مقاله پژوهشی

نویسندگان

گروه مهندسی عمران-مکانیک خاک و پی، دانشکده فنی و مهندسی، دانشگاه بین المللی امام خمینی (ره)، قزوین، ایران

چکیده

با توجه به نگرانی‌های فزاینده‌ی زیست‌محیطی ناشی از تولید سیمان و دفع ضایعات پلاستیکی و پلیمری، استفاده از مواد جایگزین پایدار در تثبیت خاک مورد توجه قرار گرفته است. در این تحقیق، تأثیر سیمان و گرانول پلی‌اتیلن بازیافتی با دانسیته‌ی بالا (HDPE) بر مقاومت و ریزساختار خاک ماسه‌ای بررسی شده است. مخلوط‌هایی با مقادیر مختلف سیمان (5، 8 و 11 درصد وزنی) و گرانول‌HDPE بازیافتی (2، 4، 6 و 8 درصد وزنی) تهیه شده و تحت آزمایش‌های مقاومت فشاری محصورنشده ‌(UCS) و مقاومت کششی غیرمستقیم (ITS) قرار گرفته‌اند. همچنین، تحلیل ریزساختاری با استفاده از میکروسکوپ الکترونی روبشی (SEM) انجام شده است. نتایج نشان دادند که افزایش مقدار سیمان از 5 به 11 درصد، موجب افزایش مقاومت فشاری تا 340 درصد و افزایش مقاومت کششی تا 261 درصد، نسبت به نمونه‌ی شاهد می‌شود، اما رفتار مکانیکی تردتری ایجاد می‌کند. افزودن گرانول HDPE بازیافتی در مقادیر بهینه (6-4 درصد)، سبب بهبود شکل‌پذیری و افزایش مقاومت مکانیکی شد. همچنین، نتایج نشان دادند که افزودن گرانول HDPE در محدوده‌ی 4 تا 6 درصد، در کنار مقادیر بهینه‌ی سیمان، می‌تواند به‌طور مؤثری دوام و نگهداشت مقاومت خاک تثبیت‌شده را در برابر چرخه‌های تر و خشک شدن بهبود بخشد، در حالی‌که مقادیر بالاتر منجر به افت عملکرد می‌شوند. نتایج ریزساختار نیز مؤید سازگاری گرانول HDPE با ماتریس سیمانی در مقادیر بهینه بود. این نتایج نشان می‌دهند که می‌توان از گرانول‌های‌HDPE بازیافتی در یک مقدار بهینه برای بهبود مقاومت مکانیکی خاک‌های تثبیت‌شده با سیمان استفاده نمود. این امر، به مدیریت پایدار پسماندهای پلیمری با کاربرد آنها در مهندسی ژئوتکنیک نیز کمک می‌کند. برخلاف اکثر مطالعات قبلی که از پلی‌اتیلن‌های دست‌نخورده یا غیربازیافتی استفاده کرده و عمدتاً بر خاک‌های رسی متمرکز بوده‌اند، ویژگی منحصربه‌فرد این تحقیق، در بکارگیری گرانول‌های HDPE بازیافتی برای بهسازی خاک‌های ماسه‌ای و بررسی رفتار مقاومتی آنها است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Experimental Investigation of the Effect of Cement and Recycled HDPE Granules on the Strength, Durability and Microstructure of Sandy Soil

نویسندگان [English]

  • Ashkan Gholipoor Noroozi
  • , Alireza Ardakani
Department of Civil Engineering, Imam Khomeini International University, Qazvin, Iran
چکیده [English]

ABSTRACT

Increasing environmental threats from cement manufacturing and disposal of plastic and polymer waste necessitated the implementation of sustainable alternatives in soil stabilization. This study focuses on the effects of application of cement and recycled high-density polyethylene (HDPE) granules on the strength, and microstructure of sandy soil. The mixtures were prepared with different amounts of cement (5%, 8%, and 11% of dry weight) and recycled HDPE granules (2%, 4%, 6%, and 8% of dry weight) and were subjected to UCS and ITS testing. The microstructural study was also done using scanning electron microscopy (SEM). Tests showed that increasing cement content from 5 to 11% produced compressive strength increases of 340% and a 261% increase in tensile strength over the control sample, which made it more brittle in terms of mechanical response; however, incorporating recycled HDPE granules at the optimal amounts (4-6%) made the mixture more ductile and better overall mechanically. Moreover, the results indicated that incorporating HDPE granules within the range of 4–6%, in conjunction with the optimum cement content, can effectively enhance the durability and strength retention of the stabilized soil under wetting–drying cycles, whereas higher contents lead to a reduction in performance. SEM observations showed that HDPE granules were compatible with the cementitious matrix at these optimum levels. The findings suggest that recycled HDPE granules are able to be used in optimal amounts to improve the mechanical performance of cement-stabilized soils, whereas the sustainable management of polymer waste in geotechnical engineering is served better. Unlike earlier studies that mostly employed virgin or non-recycled polyethylene on clayey soils, This study for the first time employs recycled HDPE granules to enhance the mechanical behavior of sandy soils and thus brings novel insights into the mechanisms by which their strength is improved.

کلیدواژه‌ها [English]

  • Cement stabilized soil
  • Recycled HDPE granules
  • strength
  • Durability under wetting –drying cycles
  • Scanning electron microscopy (SEM)
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