پديد آورندگان :
اميري، محمد دانشگاه هرمزگان - گروه مهندسي عمران , آريانپور، مرضيه دانشگاه آزاد اسلامي بندرعباس - گروه فني مهندسي , احمدي، نبي الله دانشگاه تربيت دبير شهيد رجايي - دانشكده مهندسي عمران
كليدواژه :
حرارت زياد , بتن و مقاومت فشاري , نانوساختار C-A-S-H , نانوساختار C-S-H
چكيده فارسي :
اﻣﺮوزه ﻣﺤﺎﻓﻈﺖ از ﺳﺎزهﻫﺎي ﻣﺨﺘﻠﻒ ازﺟﻤﻠﻪ زﯾﺮﺳﺎﺧﺖﻫﺎي ﺗﺠﺎري، درﻣﺎﻧﯽ، ﺻﻨﻌﺘﯽ و ﻣﺴﮑﻮﻧﯽ در ﺑﺮاﺑﺮ آﺗﺶ اﻣﺮي ﺑﺴﯿﺎر ﭘﯿﭽﯿﺪه اﺳﺖ. ﺣﺮارت زﯾﺎد ﻣﻮﺟﺐ ﺗﻐﯿﯿﺮات رﯾﺰﺳﺎﺧﺘﺎري و ﮐﺎﻫﺶ ﻣﻘﺎوﻣﺖ ﻓﺸﺎري ﺑﺘﻦ ﺑﺎ ﺳﯿﻤﺎن ﭘﺮﺗﻠﻨﺪ ﻣﻌﻤﻮﻟﯽ ﻣﯽﺷﻮد؛ اﻣﺎ ژﺋﻮﭘﻠﯿﻤﺮﻫﺎ ﺑﻪﻋﻨﻮان ﻧﺴﻞ ﺳﻮم ﺳﯿﻤﺎن ﺑﺎ ﺗﻮﺟﻪ ﺑﻪ ﺳﺎﺧﺘﺎر آﻣﻮرف و ﺷﺒﮑﻪﻫﺎي ﺳﻪﺑﻌﺪي آﻟﻮﻣﯿﻨﻮﺳﯿﻠﯿﮑﺎﺗﯽ، رﻓﺘﺎر ﭘﺎﯾﺪارﺗﺮي را در ﻣﻘﺎﯾﺴﻪ ﺑﺎ ﺑﺘﻦ ﻣﻌﻤﻮﻟﯽ ﺗﺤﺖ ﺣﺮارت زﯾﺎد از ﺧﻮد ﻧﺸﺎن ﻣﯽدﻫﺪ. ﻧﺎﻧﻮﺳﺎﺧﺘﺎرﻫﺎي ﻫﯿﺪرات ﺳﯿﻠﯿﮑﺎت ﮐﻠﺴﯿﻢ )C-S-H( و ﻫﯿﺪرات آﻟﻮﻣﯿﻨﻮﺳﯿﻠﯿﮑﺎت ﮐﻠﺴﯿﻢ )C-A-S-H( ﻣﺤﺼﻮل واﮐﻨﺶﻫﺎي ﻫﯿﺪراﺗﺎﺳﯿﻮن و ژﺋﻮﭘﻠﯿﻤﺮﯾﺰاﺳﯿﻮن اﺳﺖ ﮐﻪ ﻧﻘﺶ ﻣﻬﻤﯽ در اﻓﺰاﯾﺶ ﻣﻘﺎوﻣﺖ ﺑﺘﻦ ژﺋﻮﭘﻠﯿﻤﺮي و ﻣﻌﻤﻮﻟﯽ دارد؛ اﻣﺎ ﺣﺮارت ﭼﻪ در ﺣﺎﻟﺖ ﮔﺬرا ﭼﻪ در ﺣﺎﻟﺖ ﭘﺎﯾﺪار ﻣﻮﺟﺐ ﺗﻐﯿﯿﺮ در ﻣﺸﺨﺼﺎت ﻣﮑﺎﻧﯿﮑﯽ و رﯾﺰﺳﺎﺧﺘﺎر ﺑﺘﻦ ﻣﯽﺷﻮد. ﺑﺮ اﯾﻦ اﺳﺎس ﺑﻪﻣﻨﻈﻮر درك ﻋﻤﯿﻖﺗﺮ از ﺗﻐﯿﯿﺮ رﻓﺘﺎر ﻧﺎﻧﻮﺳﺎﺧﺘﺎرﻫﺎي C-S-H و C-A-S-H ﺑﺘﻦ ﺑﺮاﺛﺮ اﻋﻤﺎل ﺣﺮارتﻫﺎي زﯾﺎد، ﺑﺘﻦ ژﺋﻮﭘﻠﯿﻤﺮي ﺑﺎ ﺑﺘﻦ ﻣﻌﻤﻮﻟﯽ ﻣﻮرد ﻣﻘﺎﯾﺴﻪ ﻗﺮارﮔﺮﻓﺘﻪ اﺳﺖ. در اﯾﻦ راﺳﺘﺎ ﺣﺪود 300 ﻧﻤﻮﻧﻪ ﺑﻪ ﻣﺪت 14 ،3 و 28 روزه در ﺣﻤﺎم رﻃﻮﺑﺖ ﻋﻤﻞآوري ﺷﺪه اﺳﺖ. ﺳﭙﺲ ﻫﻤﻪ آزﻣﻮﻧﻪﻫﺎ ﺑﻪ ﻣﺪت 2 ﺳﺎﻋﺖ در دﻣﺎﻫﺎي 700 ،500 ،300 ،100 ،25 و 900 درﺟﻪ ﺳﻠﺴﯿﻮس ﻗﺮارﮔﺮﻓﺘﻪ اﺳﺖ. ﻣﻘﺎوﻣﺖ ﻓﺸﺎري، ﻣﯿﺰان ﺟﺬب آب و درﺻﺪ ﺗﻐﯿﯿﺮات وزﻧﯽ در ﺗﻤﺎم آزﻣﻮﻧﻪﻫﺎ ﻣﻮرد ﺑﺮرﺳﯽ ﻗﺮارﮔﺮﻓﺘﻪ اﺳﺖ. ﻫﻤﭽﻨﯿﻦ ﺑﺮاي ﺗﺠﺰﯾﻪ ﺗﺤﻠﯿﻞ رﻓﺘﺎر رﯾﺰﺳﺎﺧﺘﺎري آزﻣﻮﻧﻪﻫﺎ در دﻣﺎﻫﺎي ﻣﺨﺘﻠﻒ از ﺗﺼﺎوﯾﺮ ﻣﯿﮑﺮوﺳﮑﻮپ اﻟﮑﺘﺮوﻧﯿﮑﯽ روﺑﺸﯽ )SEM( و ﻃﯿﻒﺳﻨﺠﯽ ﭘﺮاش اﻧﺮژي ﭘﺮﺗﻮاﯾﮑﺲ )EDX( اﺳﺘﻔﺎده ﺷﺪ. ﺑﺮ اﺳﺎس ﻧﺘﺎﯾﺞ اﯾﻦ ﭘﮋوﻫﺶ ﺑﺎ اﻓﺰاﯾﺶ در درﺟﻪ ﺣﺮارتﻫﺎي زﯾﺎد ﻣﻘﺎوﻣﺖ ﻫﺮ دو ﻧﻮع ﺑﺘﻦ ﮐﺎﻫﺶ ﻣﯽﯾﺎﺑﺪ. ﺑﺎ اﻓﺰاﯾﺶ دﻣﺎ ﺑﻪ ﺑﯿﺶ از 700 درﺟﻪ ﺳﻠﺴﯿﻮس ﺳﺎﺧﺘﺎر ﺑﺘﻦ ژﺋﻮﭘﻠﯿﻤﺮي ﺗﺒﺪﯾﻞ ﺑﻪ ﺳﺎﺧﺘﺎر ﺳﺮاﻣﯿﮑﯽ ﻣﺘﺨﻠﺨﻞ و ﻧﯿﻤﻪ ﭘﺎﯾﺪار ﺷﺪه اﺳﺖ. اﯾﻦ ﺗﻐﯿﯿﺮ در ﺳﺎﺧﺘﺎر ﺳﺮاﻣﯿﮑﯽ ﺑﺎﻋﺚ اﯾﺠﺎد ﺗﻤﺎﯾﺰ در ﻣﻘﺎوﻣﺖ ﻓﺸﺎري ﺑﺘﻦ ژﺋﻮﭘﻠﯿﻤﺮي ﻧﺴﺒﺖ ﺑﻪ ﺑﺘﻦ ﻣﻌﻤﻮﻟﯽ ﺗﺤﺖ ﺣﺮارت زﯾﺎد ﺷﺪه اﺳﺖ. ﻣﻘﺎوﻣﺖ ﻓﺸﺎري ﻧﻤﻮﻧﻪ 28 روزه ﺑﺘﻦ ژﺋﻮﭘﻠﯿﻤﺮي و ﻣﻌﻤﻮﻟﯽ ﺗﺤﺖ دﻣﺎي 900 درﺟﻪ ﺳﻠﺴﯿﻮس ﺑﻪ ﺗﺮﺗﯿﺐ 7/35 و 4/31 ﻣﮕﺎﭘﺎﺳﮑﺎل اﺳﺖ.
چكيده لاتين :
Nowadays, protecting various structures including commercial, medical, industrial, and residential infrastructures against fire is a very complex issue. High heat causes microstructural changes and decreases compressive strength of the concrete containing conventional portland cement, but geopolymers as the third generation of cement due to amorphous structure and aluminosilicate 3D networks lead to more stable behavior under high heat conditions considering the conventional concrete. Calcium silicate hydrate (C-S-H) and calcium aluminosilicate hydrate (C-A-S-H) nanostructures are products of the hydration and geopolymerization processes that play an important role in increasing the strength of conventional and geopolymeric concrete, But heat, either in transient or steady state, changes the mechanical properties and microstructure of the concrete. Hence for a deeper understanding of the behavior of C-S-H and C-A-S-H nanostructures affected by high temperatures, geopolymer concrete has been compared with conventional concrete. In this regard, about 300 samples were cured in the humidity bath for 1, 3, 7, 14, and 28 days. All samples were then put in of 25, 50, 100, 200, 300, 500, 700, and 900°C temperatures for 2 hours. Length and weight change percentages, compressive strength, and ultrasonic and cracking behavior tests were performed on all samples. Images from the scanning electron microscope (SEM) and the energy-dispersive X-ray (EDX) analysis were also used to evaluate the microstructural behavior of samples in various temperatures. According to the results, the strength of both types of concrete decreases with increasing temperature. By increasing the temperature to more than 700 °C, the geopolymer concrete structure has transformed to a porous and semi-stable ceramic structure. This change in the ceramic structure has made a difference in the high heat compressive strength of geopolymer concrete vs. conventional concrete. The compressive strength of 28-day aged geopolymer concrete and conventional concrete samples at 900 °C was 7.35 and 4.31 MPa, respectively.
