- Shotcrete is a sprayable, adhesive mixture that can be used to coat walls, walkways, rooftops and many other materials with a stone-like coating that dries into a permanent aggregate mixture. Shotcrete should not be confused with concrete, the two are very different in composition. It is not possible to pump through concrete through a hose or spray in any way, it is too heavy and must be constantly moved just to keep it from drying. Shotcrete is a much lighter mixture. While concrete can be used for foundations, supports, and walls themselves, shotcrete is used primarily for reinforcement and aesthetics.
- To make shotcrete, manufacturers combine a very fine mix of concrete with dust-like particles and water, then pump them through a thick hose where pressure shoots the mixture from a nozzle. There are two different ways to apply shotcrete. The first method combines the dry mixture and water and mixes them thoroughly in a tank before they are pumped through the hose. The second method combines only the cement and other necessary particles, then propels them through the hose with blasts of air, until they reach the nozzle and are combined with water from a separate compartment, a mixture referred to as gunite.
- While both methods result in similar spray-on forms of concrete, they do require different levels of skill. It takes a highly skilled applier to correctly spray shotcrete in normal circumstances, someone who can pay attention to the thickness and appearance of the shotcrete while carefully controlling the hose. For dry-mix application, where water is added at the moment of expulsion, even more skill is needed to properly direct the stream.
Once applied, however, shotcrete has many excellent qualities. It can be used to shore up minor faults in existing concrete, it can cover walkways, culverts and other areas where it would difficult or impossible to place normal concrete. It can be mixed with other materials to make it more fireproof or give it better insulating properties, as well.
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