امكان‌سنجي بازيافت مصالح در بازسازي پس از سانحه (مورد پژوهش بازيافت بتن)

Feasibility Study of Concrete Recycling in Post-Disaster Reconstruction

بازيافت مواد و مصالح ساختماني از جمله موضوعات مهم در صنعت ساختمان سازي است. بازيافت به معني استفاده مجدد از مصالح يا توليد مصالح جديد از مواد استفاده شده و دور ريختني از جمله ضايعات بتني است. استفاده از بتن هاي بازيافتي از طريق تخريب و استفاده مجدد بتن هاي فرسوده منافع بسياري به دنبال دارد كه صرفه جويي اقتصادي يكي از آن هاست. به طور تقريبي هر ساله 25 ميليارد تن بتن در جهان توليد مي شود به طوري كه به ازاي هر نفر 3.8 تن بتن در سال توليد مي شود. در ايران نيز رشد روز افزون ساخت و ساز ساختمان از يك طرف و الزام به بازسازي سازه هاي فرسوده يا تخريب شده ، باعث كاهش ذخاير معادن سنگدانه هاي طبيعي و افزايش نخاله هاي ساختماني در آينده خواهد شد. به همين دليل بررسي امكان بازيافت بتن از دو جنبه حجم زياد بتن دور ريز و غير قابل مصرف ناشي از توليد كارخانه هاي بتن سازي و حجم قابل توجه آوار و نخاله هاي بتني و ماسه سيماني ناشي از نوسازي ساختمان ها و بازسازي پس از سانحه مي تواند مورد توجه قرار گيرد. كاهش مصرف سنگدانه هاي جديد كه از معدن استخراج شده اند ، كاهش مساحت زمين هاي مختص به دفع بتن ، كاهش توليد CO2 در مقايسه با بتن هاي معمولي نيز از ديگر مزاياي بازيافت نخاله هاي بتني ساختماني است. اين مقاله با بررسي و ارزيابي تحقيقات و اقدامات انجام شده در زمينه بازيافت بتن و يافته هاي گوناگون در اين زمينه در پي روشن نمودن ضرورت توجه به بازيافت بتن و شيوه هايي است كه به كمك آن مي توان از منافع بازيافت در جهت توسعه صنعت ساختمان و حفظ محيط زيست و صرفه جويي هاي ناشي از آن استفاده نمود.

Reusing concrete that is obtained through recycling provides significant environmental and economic benefits. Approximately, 25 billion tons of concrete is produced annually that is 3.8 tons per capita worldwide. In Iran, the booming construction as well as decayed urban fabric renovation and reconstruction have caused pure aggregate mines to diminish and increasing amount of wasted construction materials. As a result, the significance of recycling wasted materials is further emphasized especially since there are huge amount of fresh and used wasted during production process as well as great amount of remained concrete after disasters. Reduction in usage of pure aggregates, landfill disposal for the wasted concrete and CO2 emission in comparison to processing and transporting new aggregates are among the advantages of recycling wasted concrete. This study attempts to present a new perspective of using recycled aggregates for a better sustainable planning by gathering and processing past data producing new results to pave the way for recycled concrete applicability in Iran. Earthquake stricken city of Bam PostDisaster management is a good case in order to determine how recycling waste materials could significantly reduce costs. According to a report from ldquo BonyadeMaskanrdquo housing foundation, A thousand trucks were needed to transport and dispose twelve million tons of wasted material, which costed 3.375 million dollar for the government. However, this could have been greatly reduced by using recycling plant sites in different places of city. The other case for transportation in cycle time reduction is the renovation project of Eden Highway in 1950 in USA. The study showed that in case of using recycled aggregates for repairing the surface of the road, the constructors could have saved 85% of their trips to infill sites. Many methods are available for recycling wasted materials especially for concrete recycling among which, is rubbing and crushing wasted material to obtain aggregates is very common. Studies show that the water absorption of these aggregates made of different sizes is more than pure ones, which leads to heighten the W/C ratio. In addition, the resistance of concrete made by recycled aggregates could be stabilized by replacing 10% of recycled aggregates. The Germans engineers measured the percentage of 45 for allowable replacement needs to maintain the resistance. Other recycling methods include electrical shocks, Heating methods and using microwave radiation. HRM (Heating and Rubbing Method) is also one of the optimized ways of recycling. In conclusion, there are numerous advantages in recycling waste materials. Aggregates from recycling process used in subbase layer of road pavements could be used for recycled concrete in case of disaster by using HRM powder (product of HRM process).