Durability of cellulose fiber reinforced concrete under bending load in tunnel engineering

According to the bending load conditions of tunnel lining concrete in service, the durabilities of cellulose fiber reinforced concrete(CFRC)unloaded and loaded to 40% four-point bending strength were studied: resistances of chloride ion permeability, carbonation, freezing-thawing and sulfate attack. These results were also compared with the durability of unloaded plain concrete without fibers. The micro-mechanisms of the effect of cellulose fiber on the durability of CFRC were investigated as well. The results show that compared with the unloaded plain concrete, the durability of the unloaded CFRC is increased dramatically due to the effects of the special hollow microstructure and hydrophilicity of cellulose fiber on the optimized pore structures and homogeneous dispersion of cellulous fibers in hardened CFRC matrix, and the electric flux of CFRC only decreases by 25%; the carbonization depth of unloaded CFRC with different ages reduces by 0.9 to 2.5 mm. The external bending load slightly weakens the durability of CFRC compared to unloaded CFRC, e.g. the electric flux increases by 17%, and the carbonization depth increases by 0.2 to 1.3 mm. However, the durability of loaded CFRC is still better than that of the unloaded plain concrete, e.g. the electric flux only reduces by 12%, and the carbonization depth reduces by 0.4 to 1.2 mm. The relative dynamic elastic modulus increases by 3% after 200 times of sulfate dry-wet cycles. © 2016, Editorial Department of Journal of Southeast University. All right reserved.