مطالعه ی تجربی میزان دوام بتن الیافی حاوی فراک تحت حرارت بالا

The use of pozzolans is very necessary and inseparable for the sustainable development and better performance of the concrete industry. In the production of concrete, the combination of iron powder, fly ash, metakaolin and limestone powder under the name of fracking is used as materials and substitutes for cement in different percentages. The compressive strength of this concrete is higher than normal concrete. This type of concrete is a very new concrete that few tests have been done on it in the world, so there is not lot of information available about it. According to the studies, the most important features of this concrete are the use of iron waste, reduction of air and environmental pollution, cost savings and higher compressive strength than ordinary concrete. In this research, in order to protect the environment and reduce environmental pollution, fracking has been used as a relative substitute for cement. After obtaining the appropriate proportions, the frac mixture with percentages of 0, 3, 6, and 9 was considered as a substitute for cement. There were 8 tests in this research, 4 tests of the first category were carried out with the mentioned percentages of frac and 0% of steel fibers, but in the 4 tests of the second category, the volume of 1% of steel fibers was considered in the mixture. In this research, a total of 16 concrete samples were made, of which 8 of the first batch were used for pre-heating tests and 8 of the second batch were used to collect the results and performance of the concrete after heating. took After making the concrete samples and performing the necessary processes, the concrete samples were molded and placed on the vibrating table in order to make them denser and prevent voids in the concrete. After vibrating for a sufficient time, the samples were placed in the open space for 24 hours and then placed in the water basin for the processing process. A group of samples was taken out of the pond after 7 days to perform compressive and tensile strength tests (at the age of 7 days, due to the freshness of the concrete, exposure to high heat was not done) . After 28 days, the second batch was removed from the water and prepared for testing. The tests performed on these samples include compressive strength before and after heating, bending strength before and after heating, ultrasonic before and after heating, and water absorption before and after high heat. To test the performance of the samples after heating, the samples were placed in the furnace at a temperature of 450 degrees Celsius for 60 minutes (one hour) and after one hour, the samples were removed from the furnace and The samples were cooled at a temperature of 24 degrees Celsius. After the cooling of the samples, the tests were conducted on the samples, and the results indicated that the increase in the amount of frac leads to a 16% increase in the compressive strength before heating and improving its mechanical properties compared to ordinary concrete.