Self-consolidating concrete flows easily under its own weight.
Self-consolidating concrete flows easily under its own weight.

Self-consolidating concrete (SCC) was developed in Japan during the late 1980s. As its name implies, it does not require any external compaction for consolidation. In its fresh state, SCC readily can flow through restricted spaces under its own weight without segregation. These properties are achieved through adequate mix proportioning and addition of superplasticizers. A viscosity-modifying agent or increasing the fines content provides the segregation resistance.

One major advantage of SCC is the ease of casting complicated shapes or densely reinforced structures. Generally, SCC has a better surface finish and requires less cosmetic retouching. Reductions in workforce, casting time, energy requirements, and equipment result in placement cost savings. In addition, the environment benefits from lower noise levels due to the elimination of mechanical vibration.

In North America, SCC usage has been spearheaded by the precast industry, while progress in the ready-mix industry has been slow due to concerns about quality control and formwork pressure. While SCC is well suited for both vertical and horizontal components, extra precautions should be taken to ensure adequate formwork support when casting vertical components. Progress has occurred in standardizing test procedures, but much work is still needed to develop a generalized mix design approach.

—Surendra Shah

Read more highlights from 50 Years of Concrete Construction Progress.