Performance comparison test of new sprayed engineered cementitious composites and C25 sprayed concrete

Abstract

The Wulingtou tunnel in Xuancheng City is faced with complex geological conditions in the construction process, and the construction is difficult. The research team of Anhui University of Science and Technology applied the new sprayed engineered cementitious composites (NS-ECC) to the initial support structure of K43 + 546.3-K43 + 556.7 section of the tunnel. The mechanical properties of NS-ECC were significantly improved compared with that of single fiber (1% volume content), and the compressive strength is ‘positive hybrid effect’. In this paper, the ordinary C25 sprayed concrete (SC-C25) was compared with NS-ECC to precisely evaluate their performance. Slump and rebound rate tests and uniaxial compression tests under four water-containing states and five loading rates were carried out, and the differences in performance were studied in detail via scanning electron microscope and nuclear magnetic resonance tests and based on energy evolution and transformation characteristics. Results show that the real water absorption and rebound rate of SC-C25 were significantly higher than those of NS-ECC. Increasing the water content reduced the compressive strength, peak strain and energy storage density of both cements yet increased their elastic modulus. In the saturated water state, increasing the loading rate also increased the compressive strength, elastic modulus and energy storage density limit values of both cements yet decreased their peak strain. NS-ECC reported higher strength, peak strain, energy storage density and sensitivity to the ‘Strain rate effect’, under the saturated state, its peak stress is 32.92 MPa, peak strain is 0.65%, the energy storage density limit is 0.01MJ/m3, and the elastic energy conversion rate reaches 95.9%, which are better than SC-C25.