Shotcrete has often been described not as a material but as a process. Both wet and dry processes produce a material that exhibits superior hardened properties to high quality conventional concrete, such as high strength, low permeability and high durability. these properties allow shotcrete to be used in most cases as a structural material.
Although the hardened properties of shotcrete are similar to conventional cast-in-place concrete, the nature of the shotcrete placement process provides additional benefits, such as excellent bond with most substrates and instant or rapid capabilities, particularly on complex forms or shapes.
The properties of both wet and dry process shotcrete can be further enhanced through the addition of many different additives or admixtures such as:
• Silica Fume – Provides reduced permeability, increased compressive and flexural strength, increased resistance to alkali and chemical attack, improved resistance to water washout, reduced rebound levels, and allows for thicker single pass applications;
• Air-Entrancing Admixtures – Improves pumpability and adhesion in wet-process shotcrete and freeze-thaw durability in both wet and dry processes;
• Fibers – Control cracking, increase toughness values, improve impact resistance and energy absorption; and
• Accelerators – Improve placement characteristics in adverse conditions, allow for thicker single pass applications, increase production capabilities and reduce the occurrence of fallouts on structures subjected to vibration.
Source: American Shotcrete Association