SOME MECHANICAL PROPERTIES OF SHOTCRETE AT HIGH TEMPERATURES

Despite the importance of tunnel fire protection, relatively few studies are related to the behavior of shotcrete at high temperatures. The paper presents the results of uniaxial compressive strength tests conducted on shotcrete samples after exposure to temperatures ranging from 100 to 800 degrees Celsius and cooling (residual tests). A total of 59 cylindrical samples of shotcrete were cut with a rotary machine from panels with dimensions of 60x60x12cm. The panels were obtained from the construction site of the Vežeščnik tunnel on the Bar-Boljare highway, Montenegro, where the shotcrete was sprayed onto molds using the wet process technology. The results indicate a drop in uniaxial strength of up to 70%, a loss of mass of up to 13% and a drop in the speed of ultrasonic waves through the sample up to 50% in the tested temperature range.