Self-consolidating Concrete (SCC)

Guest Post by K. Phillips

Concrete is a compound material, which has been used in construction for over 2000 years. It is made from a mixture of sand, cement and gravel. It is thought that the Romans, in their roads and aqua ducts, first used it. The Romans mixed horsehair and animal blood into their concrete. The horsehair helped to reduce shrinkage and the blood created small air bubbles in the mix, which made it more durable.

In 1824 Joseph Aspdin invented Portland cement. He created this material by burning ground limestone and clay together in a kiln. By adding iron rods to concrete Joseph Monier invented reinforced concrete in 1849.

Self-consolidating Concrete (SCC)

Self-consolidating concrete is a material that has all the benefits of conventional concrete with some added improvements. High-range water-reducing admixtures and increased fines content allow this concrete to become very fluid without losing compressive strength or compromising durability.

Also known as self-compacting and self-levelling concrete, SCC has allowed architects to be more creative with the forms used in their designs. It has also allowed for the materiality of the building surface to be exposed as SCC has very few or no surface defects.

Advantages of using SCC

• It can be poured much faster than normal concrete
• No mechanical vibration is needed
• Near perfect surface finish so no need for surface touch ups:
• Easily fills confined spaces
• Bonds to reinforcement much better than conventional concrete
• Allows the creation of shapes and finishes not achievable with normal concrete
• Savings can be made on labour
• Mixing trucks do not have to move around the site as much
• Improves site safety
• Project time is decreased
• Elimination of vibrator noise means sites can work longer hours
• Reduces the wear on equipment

Self-consolidating concrete can be tested using the slump flow test. This is the most common field test used for this material. It involves filling the slump cone to the top without consolidation and then lifting the cone allowing the concrete mix to flow out onto a flat area. The concrete then levels out and the spread is measured. Spreads range from diameters of 18 inches to 32 inches.

The viscosity of the concrete can also be estimated using the slump test. It is estimated by timing how long it takes for the concrete to spread to 20 inches from the time the cone is lifted. Self-consolidating concrete with a high viscosity value is appropriate for use in structures with congested reinforcement or deep sections. A low viscosity value in concrete will make the mix good for use in long horizontal distances.

Resistance to segregation can be measured using the Visual Stability Index (VSI). As the concrete spreads out the person carrying out the evaluation should be observing whether there is bleed water at the leading edge. They also need to check if aggregate collects in the centre of the spread. The VSI value ranges from zero meaning highly stable to three which means unacceptable stability.



Fiona is an Architect and has written and published numerous articles. She is engaged and lives with her partner Ryan. http://www.articlewritingtoday.info
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