We know shotcrete is projected pneumatically on backup surface. Then they built up required section gradually i.e. one side of formwork can be handled.
Thus economy of this process relative to concrete is achieved only when obstructions are less. Say a section having no or less ties.
We have discussed in previous posts that more skilled operator relative to concrete is required; equipment and form of placing are also more expansive than our conventional concrete. Besides cement consumption in this process is also high.
So application of shotcrete is carefully chosen to reach economy. The primary selection is based on less obstruction in projection like
-Light reinforcement in section
The examples of these types of sections are roofs/ slabs specially
In the repair work and stabilizing purposes and fire proofing also shotcrete plays important role. Some examples are
-Repair of concrete which is deteriorated due to different physical and chemical agents
-In stabilization of rock slopes
-Fireproofing steel members by encasing them with shotcrete; such thin overlay may be provided also over masonry and concrete.
For erosion resistance shotcrete can be applied to concrete exposed to surface runoff of rain /stormwater or any source of running water; but accelerator like washing soda should be used to provide flash set.
The accelerator reduces strength of shotcrete significantly, but to make possible repair work, we have to sacrifice strength.
We have forgotten important information that a thickness of up to 4 in. (10 mm) is generally provided.