Shotcrete is defined as mixture of cement, sand, and small aggregate that is pneumatically sprayed and compacted under high velocity onto a surface (usually rock). In mining, it used mainly as a support liner, however it also has use in underground construction of bulkheads, seepage barriers, and other works. Shotcrete is also referred to as sprayed concrete. Another term, gunite refers to a sprayed mortar material, having a smaller top-size aggregate than typical shotcrete. Shotcrete is used in many construction applications, however by far the largest use of shotcrete is for rock support and reinforcement. Sprayed concrete was first carried out in 1907 by the Cement-Gun Company of Allentown, PA who protected the word "Gunite". The gunite mixture contained smaller aggregate and a higher percentage of cement than is typically found in typical shotcrete mixes today. There are two main methods of applying shotcrete namely the dry-mix method and the wet-mix method. The dry mix methods involves placing the dry ingredients into a hopper and then conveying them pneumatically through a hose to the nozzle. The nozzleman who holds the nozzle than controls the addition of water at the nozzle. The wet-mix method involves preparing the wet concrete normally in a mixer. The concrete is then pumped to the nozzle where compressed air is added to spray the shotcrete onto the rock surface. In the mining industry, dry-mix was used predominantly because of the smaller size and cost of dry-mix equipment. Since the 1990's however, this has changed as mines increase their use of shotcrete and as mobile equipment has developed for underground placement of wet-mix shotcrete. In civil tunneling applications, the wet-mix method is used almost exclusively. Dry-mix methods will continue to have a role in small shotcrete jobs and in areas where the conveying distance is great. In addition to cement and aggregate, shotcrete commonly contains the following ingredients:  Dry Mix Process
Wet Mix Process Shotcrete Reinforcement: Mesh vs. Fibre Use of Shotcrete Admixtures and Additives Shotcrete Rock Support Design Shotcrete Equipment | 
