Whether you specialize in concrete work, or self-perform this aspect of your projects, careful matching of power trowels to the job size and specs can make the difference between profitability and loss.
"Most of the time, if something happens to the floor, the owner and the general contractor are going to blame the concrete contractor," says Jay Allen, president, Allen Engineering. "He's the guy that's probably bearing the most risk in the process. So he needs to be sure that he has the tools and the equipment to do his job."
Both walk-behind and ride-on trowels can be used for floating and finishing large slabs. However, a number of factors can determine which trowel will be most effective in a given application.
Walking the floor
Most walk-behind trowels come with a single four-bladed rotor. Sizes run as small as 2 ft. (24-in. rotor diameter) with as little as 5 hp, and up to 4 ft. and roughly 13 hp. The majority are powered by gasoline engines, although some manufacturers offer specialized electric-powered models. These trowels are commonly found on residential or light commercial pours involving less than 10,000 sq. ft. a day and/or numerous obstacles or tight spaces.
Baker Equipment & Materials, Monroe, Ohio, has walk-behind units from Multiquip/Whiteman and Husqvarna's Superior Power Trowel Division, as well as Whiteman and Allen ride-on trowels in its fleet. These units are rented out to its sister company, Baker Concrete, as well as other area contractors.
According to Jammy Anglin, purchasing manager, walk-behinds are generally specified for the smaller jobs, but there are some larger projects that may call for a more compact unit. For example, certain projects performed by Baker Concrete already have walls in place prior to pouring the floors. "Some schools they're doing right now require a 2-ft. walk-behind machine to get through the doorways," he notes.
Tight spaces and obstacles in the slab certainly influence the type of trowel Ahal Contracting, Bridgeton, Mo., uses on a project. Ahal Contracting does a variety of concrete flatwork and concrete tilt-up projects, as well as foundation work. It has roughly 25 walk-behind and 25 ride-on trowels consisting of both Allen and Multiquip/Whiteman units in various sizes.
"The equipment we're able to use really depends upon the type of work - how much we're pouring, access to the area (in other words, if we are pouring multi-story buildings), any obstructions in the floor," Keith Ahal, president of Ahal Contracting, explains. "If we're pouring 10,000 sq. ft. and it's wide open with no pipes or anything sticking up, that would be one thing. If there are numerous electrical conduits, plumbing drains, etc. in the slab, it would also influence the size of the equipment."
In cases where obstacles are numerous, Ahal will typically bring in the walk-behind units.
Bigger slabs call for ride-ons
Ride-on trowels feature dual rotors with four to six blades each. The smallest production models typically have dual 36-in. rotors, and may be referred to as a 3-ft., double 3-ft. or 6-ft. trowel, depending on the manufacturer. The largest ride-on models typically feature two 60-in. rotors, and are known as 5-ft., double 5-ft. or 10-ft. machines. Allen Engineering also offers a 12-ft. "stretch frame" model incorporating 2 ft. of space between two 5-ft.-diameter rotors.
Ride-ons can be powered by gasoline or diesel engines and offer power ratings from 20 hp or less to nearly 100 hp.
When it comes to finishing large slabs, ride-on trowels are really the only option. "You need a machine that can cover as much ground as possible as quickly as possible because you do have a finishing window with concrete," says Allen. "Most contractors that are doing large pours are probably going to err to the conservative and get bigger, more productive machines, because the incremental cost of the machine is much lower than tearing out concrete."