Constitutive relation and microstructure on shotcrete after freeze and thaw damage
Wang Jiabin , Niu Ditao , Yuan Bin
DOI:
Received November 03, 2015,Revised , Accepted , Available online May 10, 2016
Volume ,2016,Pages 30-39
- Abstract
Using prismatic specimens of concrete, we examined the uniaxial compression stress-strain curve of ordinary concrete (mixture C43F10), ordinary shotcrete (mixture S43F10) and steel fiber reinforced shotcrete (mixture S43F10SF50) with the same mixture by using the accelerating freeze-thaw method. By fitting the relationship between parameters and the number of freeze-thaw cycles, the stress-strain curve of specimens under damaging was calculated. The test results show that with the increase of freezing and thawing cycles, the peak stress is low and has a liner relation with the freezing and thawing cycles. However, the peak strain is bigger and demonstrates an exponential relationship. The peak stress of shotcrete decreases more slowly than that of ordinary concrete, and that of shotcrete with steel fiber reduces much more slowly. We also observed and analyzed the microstructure and pores of specimens after damage by using scanning electron microscope and the mercury intrusion method. The result shows that with an increase number of freeze-thaw cycles, the amount of micro-creaks and pores and the diameter of pores increase by the effect of osmotic pressure and frost heave pressure while the specimens’ density decreases. In the same situation, there are only several connected capillary pores in steel fiber reinforced shotcrete, which is consistent with macro-mechanical properties.