What Is The Purpose?used to enhance the fluidity of the concrete without adding water.
Imagine a concrete mix design that would have
—no voids, no honeycombing, perfect encapsulation of rebar—without using any type of vibration.
It already exists.
“Self-consolidating concrete, also known as self-compacting concrete and SCC, is a highly flowable, non-segregating concrete that spreads into place, fills formwork, and encapsulates even the most congested reinforcement, all without any mechanical vibration,” explains the website of the National Ready Mix Concrete Association (NRMCA).
How it Works
In the past, “soupy” high-slump concrete meant adding lots of extra water. But excess water allows aggregate to separate, greatly increases form pressures, and compromises strength and durability.
SCC has none of these drawbacks. In fact, it contains the same percentage of water as a typical four to six-inch-slump mix.
The “secret ingredient” is a super-plasticizer called Polycarboxylate (pronounced poly-carbo-ZYE-late). More precisely a “polycarboxylate-based high-range water-reducing (HRWR) admixture,” it makes the concrete flow freely. This HRWR works by “magnetizing” the aggregate and cement. Polycarboxylate molecules have an electrical charge, and when they coat the cement particles, the particles repel each other, increasing flowability and keeping the aggregate suspended. Aggregate suspension is also helped by increasing the percentage of sand and mineral fines.
Additional information on SCC is readily available from all of the major concrete organizations, including the Portland Cement Association (PCA) and NRMCA, as well as major admixture manufacturers, such as BASF and Fritz-Pak.
NRMCA has published an informative, four-page
brochure, titled Self-Consolidating Concrete, that explains the benefits of the product. They also created a new website, www.selfconsolidatingconcrete.org that addresses most of the common questions. The research paper cited above dealing with form pressures is also on this site, and can be downloaded free
Self-Consolidating Concrete can be placed at a faster rate with no mechanical vibration.
Ease of filling restricted sections and hard-to-reach areas. Opportunities to create structural and architectural shapes and surface finishes not achievable with conventional concrete.
Improved consolidation around reinforcement and bond with reinforcement.