“A lot of producers will say a performance-based project means I don't have to reveal what I put in the mix. That's wrong,” Lobo adds. “If we focus on that, it's a losing battle from the start because engineers are not going to accept it.”
Wolf gets more calls from customers who say they want concrete to have certain attributes. Will the concrete result in a crack-free floor, or someone asks about the material's solar reflective index. Those, to Wolf, are performance specifications, and the customer may not even know it.
When Shelby Materials manufactured concrete for parking garages in downtown Indianapolis, Walker Parking Consultants, the largest parking consulting and design firm in the U.S., had some requests of the producer. Walker asked the producer to prove that its admixtures would not destroy the material's air void structure, and wanted to know what the shrinkage and strength gain would be.
“They wanted to know that our concrete going into these structures would be at least at a certain level,” Wolf says. “When they tell me the concrete has to have shrinkage below .04 in 28 days, is that performance, or is that prescriptive? They didn't tell me how to do it. I have many options. I can use one type of cement or another type. They just told me to get there. So in my mind, that's performance.”
Performance specifications have meant changes for Shelby Materials. “I'm choosing better products,” Wolf says. “We have to look closer at our raw materials and how the materials we buy specifically perform. Some stone will not pass a shrinkage test very well, while other stone will. Some admixtures are effective but are very strong retarders. Some admixtures work with one brand of cement but not another.”
With better materials comes the need for better quality assurance. Now that the stone suppliers know how the stone must perform in the mix, Shelby Materials needs the suppliers to make the producer's entire inventory consistently better. “Now, he has a performance specification to meet,” Wolf says.
To Wolf, performance specifications go beyond the materials. For example, a customer may simply stress the importance of delivering the concrete on time because he is paying his crew $200 an hour in standaround time. Or, he may ask that the material set up so he can send his crew home in time to eat dinner with their families. “Those are all performance avenues,” he says.Moving forward
Despite many challenges, the industry has moved forward with P2P on many levels. ACI formed Innovative Task Group ITG-8, that wrote a report on performance specifications for concrete materials. ACI subsequently formed ACI Committee 329, Performance Criteria for Ready Mixed Concrete, on performance requirements for concrete materials.
The traditional MasterSpec used by most design firms to develop their official master specification for concrete has been revised. This is intended to provide suggestions to minimize prescriptive specifications and maximize a focus on performance. It states, in part, “Performance-based specifications will need a higher level of proficiency by concrete producers and testing agencies. Some qualification requirements are suggested.”
Along those lines, NRMCA is developing a certification program, whereby a producer will qualify to claim that it operates at a higher level, and therefore, can bid on performance-based projects.
“There has been some significant progress,” says Cemstone's MacDonald. “ACI Committee 318 (Structural Concrete Building Code) is getting much less prescriptive as we go forward. ACI is talking more about performance specifications.”
For more on the producers in this story, visit Shelby Materials at www.shelbymaterials.com and Cemstone at www.cemstone.com.