Self-consolidating concrete (SCC) has been accepted as a unique type of concrete for more than 25 years. Its advantages are well recognized (better finishes, faster placement, easy consolidation in tight or segregated areas) and its challenges are accepted (higher material cost, the need for tighter forms, better control of mix ingredients, unique testing techniques).
Specifiers and contractors usually feel the advantages outweigh the challenges and will request SCC. So why isn’t it used more often on projects that would clearly benefit? In 2011, Bill Phelan and the Industry Critical Technology Committee on Self-Consolidating Concrete (part of the Strategic Development Council, SDC) declared a goal of 15 by 15; that is, to have 15% of all ready-mixed concrete be SCC by 2015. It’s three years later and we’re nowhere close to 15%--not even 5%.
At the SDC meeting last week, Anton Schindler, a professor at Auburn University and long-time proponent of SCC, reviewed its current use and noted that there has been some progress, such as development of an ACI certification program for SCC testing technicians. The potential of SCC remains great, he noted, with one challenge being the lack of a quantitative test method to assess the SCC’s resistance to segregation on the job site.
During a follow-up discussion session, audience members noted that the challenges remain and the greatest challenge identified by specifiers and contractors is the reluctance in many markets of ready-mixed concrete producers to supply SCC. They often don’t have the well-graded aggregate that SCC demands, they don’t have the personnel to do the proper QC, and the SCC spills out the back of the truck during delivery. Sure contractors save time and money by eliminating vibration and get great finishes but producers feel that they get blamed if anything goes wrong and that the risk isn’t worth the reward.
But is blaming producers the whole truth? Don’t some specifiers still see SCC as experimental? Aren’t contractors concerned about formwork blowouts and load-to-load consistency that could interrupt a placement? What do you feel is holding SCC hostage?