November 3, 2023
SCC Concrete, also known as self consolidating concrete and self compacting concrete is a highly flowable, non-segregating concrete that spreads into place, fills formwork, and surrounds even the most congested reinforcement, without the use of any mechanical vibration.
Self-consolidating concrete is defined as a concrete mix that can be placed solely by means of its own weight, with little or no vibration. As a high compressive strength concrete, SCC delivers these attractive benefits while preserving all of concrete's normal mechanical and durability qualities.
When normal mixes of concrete become to fluid, they segregate; large aggregates settle to the bottom of a placement and water and cement paste move to the top. SCC mix designs must maintain a tight balance; they must be fluid without segregating.
The two vital admixtures used for making SCC mixes are polycarboxylate (PCE) high-range water reducers (superplasticizers) and viscosity-modifying admixtures (VMA). Polycarboxylates extend both the high-slump placing time and the maximum spread over previous admixtures. Viscosity-modifying admixtures keep the concrete mix from segregating without restricting flow properties of SCC.
By adding these plasticizer admixtures to traditional concrete mix designs, a highly flowable concrete is created that meets tough performance requirements.
The use of SCC concrete mixes has grown tremendously since its inception in the 1980s. The development of high performance polycarboxylate polymers and viscosity modifiers have made it possible to create flowing concrete without compromising durability, cohesiveness, or compressive strength.
The flowability of self consolidating concrete is measured in terms of spread when using a modified version of the slump test (ASTM C 143). Testing personnel lift a slump cone full of concrete, let it spread out, and measure the diameter of the spread. SCC concrete is usually defined as having a spread of 18 to 30 inches wide, making it possible to place concrete under difficult conditions.
The viscosity, as visually observed by the rate at which concrete spreads, is an important characteristic of plastic SCC and can be controlled when designing the mix to suit the type of application being constructed.
SCC's unique characteristics give it significant economic, constructability, aesthetic and engineering advantages. SCC is an increasingly attractive choice for optimizing site manpower (through reduction of labor and possibly skill level), lowering noise levels, and allowing for a safer working environment.
Self-consolidating concrete allows for easier pumping (even from bottom up), flows into complex shapes, transitions through inaccessible spots, and minimizes voids around embedded items to produce a high degree of homogeneity and uniformity.
That's why SCC mixes allow for denser reinforcement, optimized concrete sections and shapes, and greater freedom of design while producing superior surface finishes and textures.
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