بررسي اثر زمان اختلاط بر مقاومت فشاري بتن نانوسيليس حاوي پوزولان پوسته برنج

The examination of mixing time on the compressive strength of Nano-silica concrete with rice husk pozzolan

باتوجه به كاربرد روزافزون بتن وگسترش استفاده ازافزودني‌هادرآن،انجام تحقيقات دراين راستا از اهميت خاصي برخورداراست.مقاومت يكي از كميت هاي مؤثردرطرح وكنترل كيفيت بتن مي باشدكه عوامل متعددي برآن تأثير گذار است. افزايش زمان اختلاط بتن شايد يكي ازپارامترهايي باشد كه كمترمورد توجه و بررسي قرار گرفته كه دراين تحقيق تاثيرزمان اختلاط بر مقاومت فشاري بتن نانو سيليس همراه با پوزولان پوسته برنج بررسي وبا بتن بدون نانو سيليس وپوزولان پوسته برنج مقايسه گرديد. همچنين تاثيرمحيط سولفاته بركاهش مقاومت اين نوع بتن موردبررسي قرار گرفته وبا هم مقايسه شد. بدين منظور تعدادي آزمونه بتني مكعبي به اضلاع15سانتيمتر حاوي1%نانو سيليس و20%پوزولان پوسته برنج بازمانهاي اختلاط متفاوت بين10تا40 دقيقه ساخته شدندكه هر5 دقيقه،3 نمونه ازبتن گرفته شدودر روزهاي3،7و28 تحت تست فشاري قرارگرفته ودر نهايت نتايج مقاومت فشاري برحسب زمان اختلاط ودرسنين مختلف ترسيم وگزارش گرديد. همچنين پوسته برنج تحت آزمايش XRD قرارگرفته و ازنمونه ها نيز عكس SEM گرفته شد تا از نظر تراكم ذرات باهم مقايسه شد ود رآخر توسط نرم افزار تاگوچي طرح آزمايش از بتن نوشته شد. نتايج تحقيق نشان مي دهد كه براي دستيابي به بيشترين مقاومت فشاري دربتن نانوسيليس همراه با پوزولان پوسته برنج، زمان مناسب(بهينه) 25دقيقه است كه بانتايج آزمايش تاگوچي حدود 9درصد اختلاف دارد كه پايين تر از ميزان خطاي مجاز مي باشد.اين بتن داراي ساختار آمورف تر وهمگن تري بوده و باكاهش تخلخل مقاومت خوبي در برابر حمله سولفاتها از خود نشان داده است.

Due to the increasing use of concrete and the use of additives in it , research in this direction is very important . Resistance is one of the effective values in the design and control of concrete quality that numerous factors and parameters affect it . Perhaps increasing in concrete mixing time is one of the parameters that are considered less attention and in this research ; the effect of mixing time on compressive strength of Nano - silica concrete with pozzolan rice husk was studied and were compared with concrete without Nano - silica and pozzolan rice husk .Therefore the effect of sulfate to reduce the resistance of this type of concrete was studied and compared . So , a number of pieces of concrete cube with sides of 15 cm contains %1 Nano - silica and 20% pozzolan husk Rice with a time of mixing varies between 10 to 40 minutes , that every 5 minutes , 3 samples of concrete were taken and made in the days 3 , 7 and 28 under the stress test and ultimately the results of mixing different compressive strength by the time was drawn and reported . Rice husk also tested and its components determined and compared with the standard . Nano - silica concrete and concrete pozzolan rice husk and without Nano – silica and pozzolan was also photographed to compare the density of particles , and at the end testing plan was written by Taguchi testing of concrete . The results show that for the most compressive strength of concrete pozzolan Nano comes with rice husk , the right time (optimal) 25 minutes with a Taguchi test results differ by about 9 percent lower than the margin of error is permitted , that at this time the concrete maximum compressive strength shows the maximum compressive strength at 28 days after the concrete 415 kg/cm2 and then does not show significant strength concrete . Pozzolan concrete without silica and rice husk increasing mixing time increases the compressive strength of concrete 375 kg/cm2 in 28 days from the time the concrete mixing process increase the resistance of shows . Ash consumption in the non - crystalline silica , which is 88% of the project , has shown its high pozzolanic activity . Physical and chemical (XRF) examination showed that rice husk ash used in this project within the requirements of ASTM C-618 for pozzolan is located . XRD results show that the consumer is fully amorphous silica from rice husk ash . As the electro - microscopic pictures (sem) is observed in samples without Nano - silica and pozzolan rice husk , the concrete has uneven texture and large crystals are clearly visible which are connected with needle - shaped crystals and large pores are clear in concrete . However , the concrete samples with Nano - silica and rice husk pozzolan , concrete has a more amorphous structure which are homogeneous and integrated together . an‎d the porosity of the concrete is significantly reduced , which increases the resistance of concrete.