Structural engineers for the project, specified Grace’s STRUX 90/40 synthetic macrofibers
Wal-Mart’s new Salt Lake City Supercenter offers shoppers everything from groceries and general merchandise to a McDonald’s, vision center, hair salon, and portrait studio all under one roof. Encompassing more than 200,000 square feet of retail space, the store attracts thousands of Salt Lake County shoppers each year.
The store’s location in a crowded urban area limited the available room for open-air parking. The solution to accommodate the heavy traffic was construction of a one-level supported parking terrace that would more than double the capacity.
Carl Walker, Inc., structural engineers for the project, specified Grace’s STRUX 90/40 synthetic macrofibers to reinforce the slab on ground concrete of the parking terrace, as well as other high traffic areas at the new store, such as the pedestrian ramp connecting the terrace and the store, and the delivery area in the busy loading docks. Carl Walker, Inc., involved in the completion of approximately 500 parking studies and the design of more than 1000 new multilevel parking facilities, had successfully used STRUX in a number of previous jobs.
“When STRUX was first introduced, we jumped on the bandwagon for slab on ground applications. One of the reasons we like STRUX so much is that it reduces the possibility of corrosion that would result from use of welded wire mesh or other secondary steel reinforcement in the concrete. Additionally, we have gotten feedback that STRUX is easier to work with from the contractor’s perspective since it eliminates the issues surrounding proper placement of welded wire mesh,” said Robert McConnell, P.E., vice president, regional manager of Carl Walker’s Denver office.
Made from a polymer blend, STRUX 90/40 synthetic macrofibers are patented, high tenacity synthetic monofilaments, designed to replace steel fibers, welded wire mesh, light rebar, and other secondary reinforcement used to control thermal and drying shrinkage cracking in concrete slab on ground applications.
When Jack B. Parson Companies, part of the nationwide network of Oldcastle manufacturing facilities, was selected to supply the concrete for the parking structure and loading docks, Rod Higley, quality control and technical sales representative, turned to Grace to develop a concrete mix incorporating STRUX. “We were familiar with other types of fibers, but this was our first time using STRUX 90/40 macro fiber reinforcement. We didn’t know what to expect,” he said.
Higley worked on the mix design with a Grace team. The team created a 611-pound mix, consisting of 490 pounds of cement and 120 pounds of fly ash. STRUX 90/40 was added at a rate of 4.5 pounds per cubic yard to provide the residual strength required for the project. The mix also incorporated Grace’s ADVA 100 super-plasticizer.
This high-range water-reducing admixture produces a low water-cement ratio and promotes high slump, extremely flowable concrete that achieves high strengths while providing superior workability.
Before proceeding with the project, the team did a 13-yard test pour near the entrance. “It worked beautifully,” said Higley. “We ended up pouring 3400 yards of concrete. The concrete was 6 inches thick in the parking terrace and 8 inches to 10 inches thick in the loading docks to accommodate the heavy trucks. We found that STRUX 90/40 worked very well. STRUX 90/40 prevented cracking and really enhanced the performance of the concrete.”
Higley also commented on other benefits of using STRUX macrofibers. “STRUX comes in a concrete-ready bag, so it is easy to handle, and it disperses evenly throughout the concrete matrix. By using STRUX, we saved on time and labor because we could drive our trucks directly on the grade to pour the concrete. In all, STRUX 90/40 passed the test with flying colors.”
Concrete Supplier: Jack B. Parson Companies, Inc.
Engineer: Carl Walker, Inc.
Admixture/Fiber supplier: Grace Construction Products