Concrete producers have to retrain their "eyes" when it comes to determining the proper viscosity of self compacting concrete. It is, by its very nature, much more fluid than regular concrete mixes and for this very reason requires little to no vibration yet can seep into and around the most tangled reinforcement. Additionally, it requires no compaction, settling under its own weight, yet it meets the most stringent performance requirements.
Self compacting concrete is both a time saver as well as a money saver. On a large building job, even a five minute delay can cost the project thousands in penalties because processes are interconnected and the more variables that can go wrong the higher the likelihood that they will. The use of self compacting concrete eliminates the need for additional machinery as well as manpower, both saving time and money.
However, one important aspect of self compacting concrete is the mix design because the strength and viscosity of the concrete needs to be adjusted according to the type of application. For example, the floor in a commercial center has one requirement in terms of durability and robustness, while a tunnel lining will require completely different characteristics.
As building becomes more complex, from underground tunnels to massive bridges, self compacting concrete is becoming the preferred solution due to the ease with which it can be poured into precast structures, from tunnel linings to self-leveling floors in residences. In both residential and commercial applications, self compacting concrete has helped increase the bottom line for builders and developers substantially as it requires little handling other than being pumped, compared to traditional concrete.
The advantage of self compacting concrete is that not only is it self-leveling but it can also be mixed to dry with a shiny finish that requires little else in terms of finishing. This saves time on a number of procedures including vibration, leveling, compaction and finishing with power floats. Finishing alone can be quite time intensive as it requires a number of passes and if you wait too long or start too early you can wave good-bye to having any type of decent finish.
Advancements in the development of a variety of polymers and viscosity modifiers have led to a concrete that is easy to work with yet maintains its strength, cohesiveness and robustness. In fact, due to these admixtures self compacting concrete mixes have been designed that are much stronger than traditional concrete making it ideal for complex applications where access is limited, as with tunnel linings.
A project consisting of three tunnels in Spain used self compacting concrete with a variety of admixtures, including one to prevent shrinkage and deformation in time, to line the tunnel walls. It was decided to use self compacting concrete for the simple reason that access was virtually impossible and costs were already extremely high due to the nature of the project.
Source: Today's Concrete Technology
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