Gunite is an industry term that describes the process of concrete being pneumatically pumped through a hose and sprayed onto metal framework. It was originally developed in the early 1900’s by Carl Akely for the art of taxidermy. In 1910 a double chamber cement gun was developed to patch deteriorated concrete. Instead of Akely’s use of plaster, this method utilized sand and cement mortar. As time passed the many uses of gunite became apparent. It was ideal for creating thin but strong linings and coatings. It was easy to create curves and unusual shapes in concrete. It was ideal for the pool industry and revolutionized the process in which pools are built.
There are two primary methods of applying gunite. One is the “wet method” commonly called “SHOTCRETE”. Cement is batch mixed at a plant and driven by trucks to the site. Water is introduced to the mix at the plant as well. Once water is introduced into cement a chemical reaction begins to take place as the concrete hardens. There is a definitive time limit in which the concrete needs to be put into place. The only way to keep the concrete workable as it gets harder is to introduce more water, which makes the concrete weaker.
The second method commonly called “GUNITE” in the industry refers to the “dry method”. In this method, the sand and cement arrive on site unmixed in a special hopper truck. They are mixed on site and pumped through the hose dry at high pressure. The water is introduced to the mix at the nozzle by the nozzle man who has full control over how much or how little water he wants. The end result is a far superior product in terms of limiting cold joints, water retention abilities and strength. Gunite routinely achieves 5,000 psi in strength. Batch mixed concrete can vary greatly in strength depending of how much water was added and how it was placed.
Many of our competetitors use “SHOTCRETE” because it is less expensive and there is less waste during the application process. We at Surfside Pools have used the dry method or “GUNITE” because of its superior strength. Our pool shells are guaranteed for life. We are still servicing pools we built over 35 years ago, and the pool shells are in perfect condition.