In response to environmental regulations and engineering specifications, a market that traditionally steered overwhelmingly toward gunite now is incorporating shotcrete more than before.
Though both forms of pneumatically applied concrete are technically called shotcrete, pool industry vernacular labels the dry form as gunite and the wet form as shotcrete. As part of the gunite process, water is added to the dry materials in the nozzle, whereas shotcrete is mixed at a batch plant and trucked wet to the site to be shot. Gunite has been much more popular in the West, particularly California, but over the past couple of years shotcrete has made large inroads.
Each has its strengths and weaknesses. Shotcrete requires fewer workers to apply, and some in the industry feel more secure knowing that the concrete’s strength is certified by the batch plant. On the down side, however, the material begins setting as soon as that truck hits the road, shortening the window to work.
Others say that because of its thicker consistency, gunite stacks up more easily to form a pool wall. Some also prefer the on-site control over the mix, though an inexperienced or harried worker can use too much water.
But now certain statewide environmental regulations and engineering requirements are skewing things in favor of shotcrete. Where gunite applicators typically transport cement and sand to the site, some localities, such as the city of Laguna Niguel, no longer permit the dry materials on the street or driveways.
“They’ve basically required that you haul the sand in a separate truck and feed it directly into the dry-mix truck,” said Cecil Fraser, owner of Swan Pools in Lake Forest, Calif. “So you have a string of equipment along the street that is like a full train: You have a compressor, then the dry-mix rigs all strung along the street. ... You essentially have two 18-foot-long trucks, one backed up to the other, to make this work. Then each load of sand is going to come with another truck so you can get one standing by.”
Other regulations mandate that trucks and equipment be altered or replaced to reduce emissions. For Arco Gunite Inc. in Orange, Calif., it would have cost more than $1 million to make those changes on the gunite equipment the firm previously used, said the company’s CEO, Tammy Counoupas. Conversely, altering the company’s shotcrete trucks and equipment cost closer to $150,000.
“There’s not enough working in the construction field to facilitate having an expenditure that high,” she said.
For this reason, after about 35 years of solely using the dry process, Arco Gunite offered both for three years, then became a shotcrete-only applicator last February.
Empire Shotcrete in Rancho Cucamonga, Calif., evolved in a similar manner. “Gunite is still a very good application,” said Matt Gorman, company CEO. “It’s been around since the 1950s, it’s a strong pool and there are no real problems with it. But shotcrete just became an easier way to manage ...”
Contractors are finding that shotcrete costs about the same as gunite. While the pre-mixed concrete from the batch plants is more expensive than the materials to create gunite, the prices began to dip with the recession. Additionally, the wet-mix procedure requires fewer workers and trucks than its dry counterpart.
“A lot of the big rigs that we have, they get 4 to 5 gallons [of gas] per minute,” Gorman said. “The fact is you have less trucks on the road, less insurance, less gas. It just seems like a natural transition.” Gorman’s company also transitioned from gunite-only to both materials and has offered shotcrete exclusively for two years.
The process itself also can work as a selling point for builders, Gorman said. “[Builders are] able to sell it to their customers as a cleaner application,” he said. “It’s less of a mess in the streets … and there’s really no cleanup.”
The change has required a learning curve for gunite workers. Gorman brought in certified shotcrete nozzlemen to teach his crews and guide the transition, so even his gunite foremen had to take a back seat for a while. It took about six months for them to become proficient, Gorman said, but once they mastered the process, the crews found the wet process to be easier on them because they don’t have to shovel and move rebound out of the pools and spas and into trucks to transport away.