A cement gun is a machine that uses compressed air to project a stream of cement or concrete onto construction surfaces at high velocity. Pressure gun applications of cement are represented by two different basic processes: dry and wet mix applications. Cement gun techniques allow for the rapid application of large amounts of structural or non-structural cement on both vertical as well as horizontal surfaces. Many decorative mortar applications are also possible with a cement gun due to its ability to project the mix at high speed onto vertical surfaces. A cement gun machine typically consists of a large hopper into which the cement mixture is added, a cement hose and, depending on the type of process, a separate water hose.
Also known as gunite or shotcrete, the cement gun process was originally developed as a method of applying plaster slurry to taxidermy models by Carl Akeley in the early 1900s. The process is fairly flexible and well suited to applying simple cement and sand mixtures or structural concrete aggregates. The cement gun process is used extensively in construction projects ranging in size from large commercial high rise buildings to residential swimming pools and redecorating projects. The high speed projection involved in the process allows for mortar mixes to be sprayed onto external surfaces at all angles including overhead applications. This makes decorative procedures such as the construction of rock features and the application of textured wall coatings a quick and easy affair.
Cement gunning applications fall into two basic categories and each with distinct benefits. The first is a dry mix method where a dry mixture of cement and sand is projected down the cement hose and mixed with water as it exits the nozzle. The mixing process of dry components and water then takes place upon impact with the coated surface. Dry mix cement gun processes allow for fine control of the consistency of the mix because the nozzleman can constantly adjust the water flow during application. This process is particularly useful for repair work and decorative coatings.
Wet mix cement gunning work involves the pressurized application of a premixed concrete aggregate. The machinery and techniques used are similar to dry mix although wet mix applications are better suited to structural work such as floors, joists, and swimming pool liners. Both wet and dry cement gun machines generally consist of a large hopper used to hold the cement mix, cement, and air pumps and hoses and nozzles which project the mixtures.