Concrete Floors with Minimal Joints

Design-Build system

The Ductilcrete system has been expanding nationally for the past two years and through its design-build process provides a minimally jointed concrete slab system that has been shown to be virtually curl-free. “Ductilcrete reduces slab cracking, crack and joint spalling, joint filler and sealant failure, slab rocking, and floor covering material distress, while increasing loadbearing capacity, and vehicle ride stability,” says Greg Scurto, president, Ductilcrete, Gilberts, Ill. It overcomes the core problem of “differential shrinkage (curl) at equal to or less than cost competitive figures when compared to ACI standard designs.”

Ductilcrete systems have been developed for interior slabs, exterior pavements, industrial and retail toppings, whitetopping, and elevated slabs on metal deck or precast. It is cost-effective for applications such as refrigerated/cold storage facilities, industrial/manufacturing facilities, warehouses, big box stores, logistics centers, white topping, and exterior pavements.

“In addition to long-term flatness and levelness, it has an approximately 70% reduction of joints,” says Scurto. “It’s also low maintenance and the warranty covers flatness and levelness. The warranty may be customized to meet an owner’s lease requirement. This is a great marketing advantage for owners and developers.”

The Ductilcrete system is currently in use in 16 states and Washington, D.C.,, including well-known big box retail stores, manufacturing, distribution, worldwide logistic providers, office, and freezer/cooler facilities.

Case studies

Ductilcrete has performed as intended on many projects. Here are two that demonstrate the success of the system.

Easton-Bell Sports, Rantoul, Ill.: Easton-Bell Sports is an 80-year-old designer and developer of sports equipment and accessories. With 34 locations, the Rantoul facility is one of the newest.

Robert Guarnaccio, president of Stout Development Services Inc., Libertyville, Ill., a real estate developer and construction consultant, was in charge of construction and was interested in a system that could potentially minimize future slab maintenance by reducing curling and joints. He had heard about Ductilcrete from an engineer on another project, prompting him to research the system.

Easton-Bell Sports had the typical questions about product integrity and durability. The Ductilcrete team of professionals with many years in the construction industry was able to answer those questions. Ductilcrete was chosen for its ability to reduce slab cracking, crack and joint spalling, joint filler and sealant failure, and slab rocking, while improving load-carrying capacity.

The project included 780,000 square feet of Ductilcrete slab on grade in the warehouse and office, and 5,184 square feet in the paint shop. The Ductilcrete design reduced contraction/construction joints from the original estimate of 109,800 linear feet to about 28,000 linear feet. An additional 688,000 square feet of Ductilcrete pavement was used for the parking lot with 13,000 linear feet of integral curb.

“Ductilcrete actually reduced the time frame, because they could pour more at a quicker pace,” says Guarnaccio.

Floor flatness and levelness was tested to compare the Ductilcrete slab behavior long term with initial placement. The initial overall FF (OAFF) was 81 and overall FL (OAFL) was 45. The test performed three months later showed that the floors were unchanged, within the 90% confidence interval, indicating that no curling is occurring in the floor. The inspection showed no evidence of curling and overall inspection of the joints showed no visible deterioration or joint edge spalling. The surface showed no signs of excessive or unusual wear, delamination, or deterioration.

“Ductilcrete exceeded everyone’s expectations, including minimizing wear and tear and retaining a high gloss sheen just by cleaning the floor,” says Guarnaccio. “Ductilcrete not only convinced the project team, but now they endorse the product for other projects.”

Central Grocers, Joliet, Ill.: This retail cooperative supplies approximately 400 independent supermarket stores in the Chicago area, making it the second-largest in the area and the seventh largest grocery cooperative in the U.S.

A 900,000-square-foot warehouse (including 327,000 square feet of Ductilcrete) in Joliet, Ill., enables Central Grocers to move and process a large number of goods every day, and the facility’s operations include an extensive amount of equipment traffic. It was a requirement, therefore, that the building be outfitted with a floor system that could offer a long service life.

As part of Ductilcrete’s warranty agreement, periodic inspections are performed. An inspection conducted five years after slab placement in the Joliet warehouse demonstrated that the floor was still providing outstanding performance.

Flatness and levelness tests were conducted on the floor slabs of a refrigerated area of the warehouse. The cold storage warehouse is an 8-inch Ductilcrete system with panels ranging from 36×29 feet to 36×50 feet. The initial specification called for FF50/FL35. The five-year inspection indicated that the refrigerated warehouse using the Ductilcrete Slab System had an OAFF of 59 and an OAFL of 43. These findings show that even after the passage of years, the Ductilcrete system exceeds initial specifications and that curling is virtually nonexistent.

Joint openings for the Ductilcrete system in the refrigerated warehouse performed as expected. Steel plated (armored) construction joints had openings that were between 3/8 inch and 5/8 inch and continued to perform well. Contraction joint openings were between 1/8 inch and 5/16 inch, indicating that the openings are behaving normally regardless of temperature conditions.

The floor contained no mid-panel cracks, no delamination, and no joint cusps or steps. Neither was there deterioration or excessive wear. After five years, even under demanding conditions, there are no problems with the slab.

Conclusion

Each project team must evaluate the needs for its facility and decide on the best choice. The newest player in the market, Ductilcrete, by offering a design-build solution, can carefully guide the process from the beginning and throughout the entire process to ensure success and a long-term solution.

“The Ductilcrete solution is seeing an upsurge in popularity due to the complete solution: flat, high-quality floors, an increase in volume, and the protection the system offers against liability through working with Ductilcrete’s Engineers of Record,” says Scurto. Ductilcrete is delivered through an alliance of carefully chosen contractors who create a design-build relationship. Alliance members are effectively the engineers of record and the slabs they produce are no longer just commodities.

Kari Moosmann is a freelance writer with Constructive Communication Inc.

F-numbers

The F-number system was developed by Allen Face and is the American Concrete Institute (ACI 117) and Canadian Standards Association (CSA A23.1) standard for the specification and measurement of concrete floor flatness and levelness. The F-number system only applies to random-traffic floors.

• FF is the flatness number and expresses the floor’s characteristic curvature over 24 inches. Floor flatness indicates the local bumpiness of the floor surface and is primarily determined by the quality of the initial strike off and finishing process. Essentially, FF numbers evaluate the elevation differences along a sample line at 1-foot intervals.
• FL is the levelness number and expresses the floor’s characteristic elevation difference over 10 feet. Floor levelness indicates the departure of the floor surface from the specified slope or plane of the surface. The higher the FL number, the more level the floor. Levelness of the edge forms and the accuracy of the concrete screeding operation determine the overall levelness of the floor.
• Both F-numbers are computed from successive point elevation measurements on 12 inch centers. The greater the number, the more “flat” or “level” the floor.
• The scale is linear so an FF60/FL40 floor is twice as flat and level as an FF30/FL20 floor.
• FF/FL numbers have the following floor flatness classifications:
• FF25/FL20 – moderately flat
• FF35/FL25 – flat
• FF45/FL35 – very flat
• FF60/FL40 – super flat