پديد آورندگان :
اماني، سعيد دانشگاه تربيت مدرس - دانشكده عمران و محيط زيست , كاووسي، امير دانشگاه تربيت مدرس - دانشكده عمران و محيط زيست , محمد كريمي، محمد دانشگاه تربيت مدرس - دانشكده عمران و محيط زيست
كليدواژه :
گرمايش و ترميم القايي , پيرشدگي و كربن فعال , آزمايش خمش نيم دايره اي , امواج الكترومغناطيس
چكيده فارسي :
روسازي هاي آسفالتي به مرور زمان دچار پيرشدگي مي شوند كه اين امر موجب كاهش سطح خدمت دهي و انعطاف پذيري اين روسازي ها مي گردد. ترك خوردگي در اثر پيرشدگي يكي از شايع ترين علل خرابي در روسازي هاي آسفالتي است. عدم ترميم به موقع روسازي هاي ترك خورده مي تواند باعث گسترش ترك و ايجاد ساير خرابي ها در روسازي گردد. برخي از ترك ها مي توانند با استفاده از اعمال گرمايش به روش تابش امواج الكترومغناطيس ترميم شوند. استفاده از روش گرمايش به روش تابش امواج الكترومغناطيس يكي از روش هاي نوين در ترميم ترك ها در روسازي ها است. القاي گرمايش از طريق امواج الكترومغناطيس موجب افزايش دماي قير درون مخلوط هاي آسفالتي شده و موجب حركت كردن قير و پر كردن ترك ها مي شود. در اين تحقيق، تاثير سطوح مختلف پيرشدگي مخلوط هاي آسفالتي روي گرمايش و ترميم القايي روسازي مورد ارزيابي قرار گرفته است. به منظور اعمال شرايط پيرشدگي، مخلوط هاي آسفالتي به مدت هاي 3، 5، 7 و 9 روز در گرمخانه در دماي °C85 نگهداري شدند. در اين تحقيق، قير خالص با استفاده از كربن فعال اصلاح شد. علاوه براين، تاثير كربن فعال در خصوصيات مكانيكي و نرخ گرمايش آن به روش تابش امواج الكترومغناطيس در مخلوط هاي آسفالتي مورد بررسي قرار گرفت. براي بررسي تاثير سطوح مختلف پيرشدگي در نرخ ترميم القايي، آزمايش خمش نيم دايره اي در دماهاي مياني و پايين انجام شد. نتايج آزمايش ها نشان داد كه افزودن كربن فعال به قير نه تنها موجب كاهش مقاومت آن نمي شود، بلكه مي تواند موجب افزايش مقاومت نمونه ها در برابر ترك خوردگي نيز شود. نتايج بدست آمده نشان داد كه افزايش سطح پيرشدگي موجب كاهش نرخ گرمايش نمونه هاي آسفالتي به روش تابش امواج الكترومغناطيس مي شود. علاوه براين نتيجه گرديد كه، افزايش سطح پيرشدگي در مخلوط آسفالتي و افزايش طول شيار در نمونه هاي خمش نيم دايره اي موجب كاهش نرخ ترميم القايي مي گردد. علاوه براين، نتايج نشان داد كه ميزان ترميم القايي در مخلوط هاي آسفالتي ترك خورده در دماهاي پايين بيشتر از مخلوط هاي آسفالتي مي باشد كه در دماهاي مياني ترك خورده اند.
چكيده لاتين :
Aging in asphalt pavements results in reduced serviceability and flexibility of pavements. Aging is not commonly considered as distress, but it substantially effects the rate of evolution of various distresses. One of the common distress observed in aged asphalt pavements is cracking. If cracks/micro-cracks are healed during their initial formation, the service life of the pavement will be increased. Otherwise, there will be the risk of crack propagation that results in more cracking and loss of pavement strength. It is well known that asphalt mixes have capability of self-healing their cracks/micro-cracks when they are exposed to high temperatures. Cracks/micro-cracks in asphalt mixes can be healed through an induced healing process. Induced healing of asphalt mixes by applying external electromagnetic radiation is an innovative technique to repair cracks/micro-cracks. Applying external energy through electromagnetic radiation increases the temperature of the asphalt binder in mixes, allowing it to move and fill the cracks/micro-cracks. Flowing and crack filling of asphalt binder play a significant role in induced healing characteristics of mixes. As temperature of the asphalt binder is increased, its viscosity will be decreased drastically. When asphalt binder gets to Newtonian fluid temperature or higher, the melted binder moves inside the cracks and micro-cracks and subsequently, the cracks will be healed. The aim of this research was to evaluate the effects of different aging levels on induced heating-healing of asphalt mixes. In order to impose different aging levels, asphalt mixes were aged in oven for 3, 5, 7 and 9 days at 85 ºC. Activated carbon was added to mixes so that to enhance electromagnetic sensitivity of mixes. In addition, effects of activated carbon on mechanical properties and microwave heating rate of mixes were determined. Results indicated that activated carbon, as a powder-based additive, improves electrical conductivity, induced heating-healing rate of asphalt mixes. In addition, it was shown that aging phenomenon in asphalt mixes decreases their heating rate, which was more pronounced in higher aging level. Lower heating rate of asphalt mixes resulting in lower efficiency of induced healing of mixes. For evaluating healing capability of mixes that were subjected to different aging levels, Semicircular Bending tests (SCB) was conducted at intermediate and low temperatures. It presented that induced healing efficiency of mixes decreased as the aging level and the notch length in SCB testing were increased. The adverse effects of aging on induced healing process can be attributed to increased viscosity of the asphalt binder in mixes, which limits moving capability of melted asphalt binders to move through damages and properly heal the cracks. Moreover, it resulted that, lower heating rate of aged mixes can be considered as another reason of reduction in induced healing efficiency. The results indicated that increased notch lengths not only affects load at fracture and fracture energy of mixes, but also it plays a significant role in induced healing efficiency of mixes. For further evaluation of the healing ability of asphalt mixes, combination effects of aging, notch lengths and testing temperature parameters were also investigated. Notch length and testing temperature was found to have significant effects on induced healing efficiency of mixes. In addition, the results indicated that induced healing efficiency of low temperature cracked asphalt mixes were more than that of asphalt mixes that were cracked at intermediate temperatures. The results suggest that the necessity of considering aging level in analyzing induced heating-healing process of asphalt mixes.
