ارزیابی تأثیر سیمان پرتلند آهکی بر ویژگیهای مکانیکی و عملکردی بستر رسی تثبیت شده

نوع مقاله : پژوهشی اصیل (کامل)

نویسندگان
سید فرزین فائزی
سیدرضا شریفی
مهرداد میرشکاریان بابکی
گروه عمران، دانشگاه پیام نور تهران
چکیده
بسترهای رسی در حالت خشک از استحکام و سختی مناسبی برخوردار هستند ولی در حضور رطوبت مقاومت آنها به شدت افت کرده و بستر مستعد تغییر شکل‌های پلاستیک شده و ظرفیت باربری آن کاهش محسوسی می‌کند. پس هدف از این پژوهش ارزیابی فنی تأثیر سیمان آهکی بر ویژگی‌های مکانیکی و عملکردی بر بستر رسی است. بدین منظور 400 کیلوگرم نمونه خاک از بستر راه روستایی راز به پسین دره تهیه شد. در مرحله اول آزمایش‌های دانه‌بندی، حدود اتربرگ و... روی 20 نمونه از خاک انجام شد. مرحله دوم وزن مخصوص خشک بیشترین و میزان رطوبت بهینه مخلوط خاک-سیمان تعیین شد. در این پژوهش برای بررسی تاثیر آهک بر عملکرد بستر رسی، از دو نمونه سیمان پرتلند آهکی با نام‌های PKZ1 (دارای 80 درصد کلینکر +17 درصد آهک+3درصد گچ) و PKZ2(دارای 85 درصد کلینکر +12 درصد آهک+3درصد گچ) استفاده شد. مرحله سوم برای تعیین درصد سیمان آهکی مناسب برای اختلاط، آزمایش تراکم مخلوط خاک-سیمان با درصدهای مختلف (6% ، 8% ، 10% ، 12% و 14%) با سیمان آهکی نوع 1 و نوع 2 انجام شد. در مرحله چهارم 24 نمونه استوانه‏ای با افزودن (6% ، 8% ، 10% ، 12% و 14%) سیمان آهکی نوع 1 و نوع 2 به نمونه خاک ساخته شده و تحت آزمایش مقاومت فشاری قرار گرفتند. در مرحله پنجم مقاومت کششی غیرمستقیم و آزمایش مدول تنش-کرنش مخلوط خاک-سیمان تعیین شد. نتایج نشان داد دانسیته خشک حداکثر مخلوط خاک-سیمان با افزودن 10 درصد سیمان آهکی نوع 1 و نوع 2 به دست می‏آید. همچنین نتایج حاکی از افزایش مقاومت فشاری، مقامت کشش غیر مستقیم مخلوط ساخته شده با سیمان پرتلند آهکی نوع 1 نسبت به سیمان پرتلند آهکی نوع 2 داشته و کلیه اینکه کلیه نمونه‌ها با عمل آوری 28 روزه مقاومت بیشتری نسبت به نمونه‌های 7 روزه داشتند.

کلیدواژه‌ها

موضوعات

عنوان مقاله English

The Effect of freezing and Thawing cycles on the Durability Parameters of Lime- Cement Stabilized Clay Subgrade based on compressive strength results

نویسندگان English

seyed farzin faezi
seyed reza sharifi
civil engineering, payame noor university
چکیده English

Clay soils often cause problems in construction projects. In cold regions, freezing and thawing of clay soils can cause significant changes in the geotechnical characteristics of the soil. Frozen and thawed soils have shown changes in volume, strength, compressibility, frozen moisture content, bearing capacity and microstructural changes. In road construction projects in cold regions, freezing and melting is one of the factors affecting the unstability of soil engineering behavior, including the durability and performance of pavement and pavement layers. Therefore, the purpose of this research is to evaluate the effect of freezing and melting cycles on the parameters of the durability of calcareous stabilized clay bed based on compressive strength test results. 400 kg of soil samples were collected from the subgrade of the RAZ-PASIN rural road. In the first stage, granulation experiments, Atterberg and ... on 20 soil samples were performed. The second stage was the dry maximum dry matter and optimum moisture content of the soil-cement mixture. The third step was to determine the percentage of suitable cement for mixing, soil-cement mixed density with different percentages (6%, 8%, 10%, 12% and 14%) with limestone cement type 1 and type 2. In the fourth stage, 24 cylindrical specimens were added to the soil sample by adding (8%, 10%, 12%) of type 1 and type 2 calcareous cement and tested for compressive strength. In the fifth step, the indirect tensile strength and the stress-strain modulus of the mixed soil-cement were determined. The results indicated that the maximum dry matter density of the soil-cement mixture was obtained by adding 10% of type 1 and type 2 calcareous cement. The results also showed an increase in the compressive strength of the composite made with type 1 lime Portland cement compared to Type 2 lime Portland cement, and all specimens containing 8% calcareous cement additive exhibit more than 35 kg / cm2 after 7 days of resistance treatment. This means that samples made with Portland cement have a sufficient durability against atmospheric agents. If the use of calcareous Portland cement is used only for bed consolidation as a layer of pavement layers and the appropriate weight percentage of Portland Type II cement is selected to be 8% for the consolidation of the studied soil, the cost of the Rural Road Project will be compared. The Late Valley showed a 13% reduction in the cost of supplying calcareous Portland cement compared to Type II Portland cement (Table 10). This is due to a 15% reduction in energy costs (gas and electricity consumed) in the manufacture of calcareous Portland cement compared to Type II Portland cement. By comparing the results of compressive strength of soil-mixture of type 1 calcareous Portland cement and type 2 cement, it can be concluded that the effect of type 1 calcareous Portland cement in obtaining compressive strength is better than type 2 calcareous Portland cement due to increasing Lime is made of cement composition. This increased resistance is due to the ion exchange reaction and the agglomeration-compaction reaction between lime and soil and is achieved by lime contact with most fine-grained soils. Thus, the calcium ions in the lime are replaced by the lower-capacity positive ions in the soil. This results in the accumulation of calcium ions around the clay particles.

کلیدواژه‌ها English

Freezing
THAWING
durability
Stabilization
LIME CEMENT
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مهندسی عمران مدرس
دوره 20، شماره 2
خرداد و تیر 1399
صفحه 123-133