Shotcrete has been an important part of the construction industry for more than 90 years. As a specialty concrete technique, it is basically another means for the placement of concrete with its own peculiarities and characteristics. In the early years after its introduction by the Cement Gun Company of Allentown, Pa., in 1910, relatively little testing was done, prima-rily because the technique had limited use. What testing was performed was done to pro-mote the technique”to show its efficacy for specific applica-tions or to exhibit its superior-ity over other existing concrete technologies. The tests in-cluded were for material and design criteria and properties such as compressive, tensile, and flexural strengths, bond, permeability, shrinkage, and soundness. These tests were based on American Society for Testing and Materials (ASTM) concrete tests adapted for the shotcrete process. When inter-est in concrete durability began to heighten after World War II, freeze-thaw tests were also in-troduced. As in conventional concrete, compressive strength has been the defining property of shotcrete testing. However, if other properties are required for a particular application, they can be arranged at the time of specification. The main dif-ference in the tests is in the preparation of samples, which is usually different because of the unique nature of the shotcrete process.
While interest in shotcrete was limited prior to the 1940s, an upsurge developed, espe-cially in the wet-mix process, in the 1950s. In 1990, ASTM decided that the technology had grown sufficiently enough that a new ASTM subcommittee on shotcrete, ASTM C09.46, should be organized. This would complement the existing American Concrete Institute Committee 506 on Shotcreting. ASTM Subcommittee C09.46, Shotcreting, would absorb the