Experimental Study On The Frost Resistance Of Sprayed Concrete

In cold regions, the sprayed concrete structures subjected to freeze-thaw damage,seriously affecting the life of bridges, tunnels and other projects. However, the currentresearch on frost resistance and durability of sprayed concrete is relatively rare.Therefore, it has important significance to research the frost resistance of sprayedconcrete.The accelerated freezing and thawing test had been carried out to analyze changingrules of concrete exterior appearance, mass, the relative dynamic elastic modulus,compressive strength and splitting tensile strength of sprayed concrete under the actionof freeze-thaw cycles in this paper. Scanning electron microscopy(SEM) analysis wascarried out to observe the microstructure characteristics of sprayed concrete before andafter freeze-thaw. According to the test results, the attenuation model of mass, therelative dynamic elastic modulus and the strength of sprayed concrete were established.The influence of the incorporation of steel fiber on the frost resistance of sprayedconcrete was also discussed. Compared the antifreeze indicators of sprayed concreteand normal concrete, discussed the impact of the construction process on concrete frostdurability. The results show that: under the effect of freeze-thaw cycles, the mass,relative dynamic elastic modulus, compressive strength and splitting tensile strengthdecrease. The state of microstructure deteriorates significantly, micro-cracks expand andthe structural state of hydration products gradually shape. Due to the differentconstruction methods, the frost resistance of sprayed concrete is better than normalconcrete. Steel fiber reinforced shotcrete has the role of crack resistance, the incorporation of steel fiber can improve the frost resistance of sprayed concrete.To study the complete uniaxial compressive stress-strain curve of sprayed concretesubjected to freeze-thaw cycles. After injection of the freezing and thawing, allspecimens were tested under uniaxial compressive loading. The test results show that:with the increase of freeze-thaw cycles, elastic modulus and peak stress are graduallydeclining, while the peak strain and ultimate compressive strain are increasing. Thecomplete uniaxial compressive stress-strain curves tend to be flatter. Compared withnormal concrete, the frost resistance of sprayed concrete is better. Steel fiber caneffectively inhibit the production and development of micro-cracks inside sprayedconcrete during freeze-thaw cycles, and improve the frost resistance of sprayedconcrete.