Construction Solutions LLC
PO Box 1334
Cedar Park, TX 78630
Shotcrete/ Gunite is a process and method of pneumatically applying cementious material to a structure. It is commonly used to build pools, as well as bridges, homes, tunnels, water tanks, retaining walls, movie sets, and repair all above mentioned as well. Gunite has been in use since the early 1900's with excellent success.
Shotcrete comes in two basic forms: dry process or dry gun method and wet process
The dry gun method or dry process shotcrete (also known throughout the industry as gunite) uses a volumetric mixer truck in which concrete sand and type 1 Portland cement are hydraulically mixed on site and compressed by an auger conveyor system. This mixture is then moved into a gunning machine where it is mixed with air from the air compressor and is blown through a hose by extreme pressure to the nozzle where water is added and mixed at the tip of the hose and then blown pneumatically into the rebar enforced walls and floor. Only the necessary amount of water is added for hydration resulting in superior strength over conventional concrete.
FYI: the term Gunite which is a process rather than a material is a former trademark and now a generic term that has been recognized by the GCA (Gunite Contractor's Association), ASA (American Shotcrete Association) and the ACI (American Concrete Institute) since 1967.
The wet process also referred to in the pool industry as "shotcrete" uses pre-mixed concrete from a batch plant and is a hot and live load and is transported via a conventional barrel mixer. This mixture is poured into a concrete pump and is pumped to a nozzle and pneumatically placed or shot onto the walls and floor of the structure via an air powered nozzle. Computers are used to control the concrete mixture by using a predefined design that can not usually be adjusted at the site (other than adding water) and must be at a consistency to be able to flow through the hose.
We shoot a standard 12-inch continuous bond beam and regress to a minimum of 12-inch-11inch walls and a minimum of a 10-inch floor (or a minimum of 3-inch coverage over the rebar depending on how the rebar is set) or to the specifications of the pool contractor. Anything less than what is written here can and will be shoot but it is not covered under our warranty.
Dry method pneumatically applied cementitious material (or concrete) also known as Gunite is superior in strength to poured or ready-mix concrete for several reasons. Only the amount of water necessary for hydration is added to the concrete sand and Portland Type 1 cement mixture to make Gunite. There is no excess water as found in conventional poured concrete. The excess water found in poured concrete occupies space, and when it finally leaves the curing or hydration process, small voids are left behind.
So it can be said that the dry method Gunite is denser than that of poured concrete. In fact, 14 yards of gunite are equal to about 10 yards of ready-mix concrete or shotcrete mix. Denseness is an important factor in the superior strength of gunite and its high resistance to the passage of water.