Circular Concrete Pours: Tips on Pouring a Circular Foundation for a Grain Bin

Farmers have a lot to manage when it comes to the upkeep of their farm, from sourcing seed to performing routine equipment maintenance. Having the knowledge and proper tools to easily pivot between tasks is what keeps their operation running smoothly. Even a unique task like pouring a grain bin foundation can be undertaken with ad-hoc tools commonly found around the farm. However, this may compromise the foundation’s quality and lead to expensive repairs down the road.

Investing in specialized tools, even just for occasional work, can provide a great return on investment with efficient, long-lasting results that benefit future generations. To achieve a lasting grain bin foundation, evaluate the options, recognize the drawbacks, and choose the equipment best fit for their scenario.

A pivot kit minimally consists of a metal stake fixed to a weighted base, which is affixed to the center of the work area. The kit can be used as a guide to frame out the circular pad and gives users the ability to attach one end of a concrete screed to the center stake and control the screed from the other end.Curb Roller Manufacturing

Where to Begin

Circular concrete pours most often start with a pivot kit, which minimally consists of a metal stake fixed to a weighted base. The stake is affixed to the center of the work area and can be used as a guide to frame out the circular pad. A pivot kit gives users the ability to attach one end of a concrete screed to the center stake and control the screed from the other end, screeding off concrete in a clockwise motion. Any number of concrete screed options can attach to a pivot kit. The most popular methods include hand screeding, using an A-frame screed or working with a roller screed, but each come with their own limitations.

Options & Limitations

Hand screeding utilizes a long aluminum or heavy wooden board which is extended to the center stake and pulled by hand around the circular form. This can be a strenuous, time-consuming task and may result in structural flaws due to a warped board and uneven concrete dispersion. With structural flaws rarely justifying savings, this option leads many to explore the methods implemented by professional contractors, like an A-frame or roller screed. These methods have varying levels of usability, with some more user-friendly than others.

Battery powered roller screeds are typically lighter and more easily maneuvered than alternative methods. The ability to change spin direction at the push of a button allows operators to effortlessly screed clockwise or counterclockwise.Curb Roller Manufacturing

A-frame screeds consist of multiple sections and can be more cumbersome than alternatives. Fins and vibratory attachments hang off the back of the main bar to provide a compacted and smooth finish as the screed pulls, vibrates, and spreads the concrete. However, this design limits screeding to one direction. A roller screed, on the other hand, consists of a drive head and pipe that spins in the opposite direction it is being pulled to level concrete. Roller screeds can be electric, hydraulic, or gas motor powered and are typically lighter and easier to maneuver than an A-frame. However, a gas motor can be a limiting factor as it restricts the direction of the spin, a shortcoming similar to the A-frame's.

But, what’s wrong with only screeding in one direction?

The Challenge With Unidirectional Screeding

Unidirectional screeding is often acceptable for conventional concrete flatwork but less favorable with circular pours. A circular concrete pad can take several hours to pour, and unidirectional screeds are committed to screeding one direction for the duration of the project. For efficiency and minimal wasted movement, the pad is usually poured in continuous sections with, for example, the first being from 12 to 2 o’clock. Screed that section and then the next is poured from 2 to 4 o’clock, and so on.

Roller screeds that can easily change spin direction allow operators to screed clockwise or counterclockwise during the pour, eliminating the risk of a cold joint.Curb Roller Manufacturing

This might seem effective, but once the pour is nearing completion and arriving back to the first section, the crew is now pouring and screeding wet concrete next to concrete that has been curing for several hours. This creates a cold joint which can cause a division in the uniformity of the concrete pad, preventing it from curing as one solid, smooth, level foundation. The visual irregularity from a cold joint may leave something to be desired for the concrete pad’s appearance, but it’s also a structural flaw that can result in future costly repairs or possible grain bin failure.

Now, Avoid That Cold Joint

The best method to avoid a cold joint is by pouring each section of concrete and alternating the left and right sides of the circle. For example, if a section is poured at the circle’s 12 to 2 o’clock position, the next section could be poured from 2 to 4 o’clock, but the third section should be poured from 10 to 12 o’clock. This alternating pattern ensures every section cures for the shortest amount of time before fresh concrete is poured next to it, leading to a more uniform cure.

This alternating pattern introduces the utility of screeds with a changeable spin direction. For all roller screeds to operate correctly, the screed pipe spins away from the operator. But, the ability of some screeds to change spin direction at the push of a button allows operators to effortlessly screed clockwise or counterclockwise, making these screeds capable of performing the alternating pattern efficiently. This means operators can alternate screeding sections rather than working in a full rotation and risking cold joints and wasted movement.

Roller screeds that utilize common 60-volt lithium-ion batteries like those found in standard battery-powered drills can screed up to 2,500 square feet of concrete on one charge, more than enough to screed-off any standard grain bin pad.Curb Roller Manufacturing

Multiple manufacturers offer directional changing features on their screeds, but many do not make the switch easy. Some screeds require the entire drive head of the screed to be removed from the attached pipe, rotated, and reattached to the other side to change the direction, whereas other models may feature design features like directional buttons to provide an efficiency that also carries over to maintenance and transport.

Location Challenges: Power

Grain bins are often located in areas that might make equipment access and transportation complicated. More importantly, remote locations may limit access to a power supply such as a portable generator or specialized hydraulic equipment. Battery-powered roller screeds address these issues having no cords or hoses and can be easily operated in remote environments.

Look for a screed that utilizes common 60-volt lithium-ion batteries like those found in standard battery-powered drills. Some screeds utilizing such batteries can screed up to 2,500 sq. ft. of concrete on one charge—more than enough to screed off any standard grain bin pad. The stress-free operation of battery-powered roller screeds combined with minimal assembly significantly lowers the learning curve and operational requirements. Paired with a manufacturer’s pivot kit, battery-powered roller screeds allow any skill level to take on jobs that could typically fall out of reach.

Both farmer and contractor are no strangers to recognizing efficient solutions. Where tackling a circular pour with ad-hoc equipment is possible, alternative methods can offer time savings and lasting quality that far outweigh the initial investment.

About the Author

Seth Ulmer is the sales manager at Curb Roller Manufacturing, a world leader in shaped concrete roller screeds. Ulmer joined Curb Roller Manufacturing after spending over a decade in the concrete and construction industries.