Self-compacting concrete (SCC), sometimes known as self-consolidating concrete, is
one of the most popular forms of concrete. SCC has outstanding flow ability in
its fresh state, performing self-compaction and material consolidation without
segregation concerns.
Self-compacting concrete is a type of non-segregating
concrete that can settle into formwork and envelop heavily reinforced, narrow,
and deep portions with its weight.
Self-compacting concrete is new concrete that flows under
its weight and does not require external vibration to compact. It is utilized
in construction where vibrators cannot be used for concrete consolidation.
To decrease bleeding and segregation, certain
self-compacting concrete mixtures use admixtures such as superplasticizers and
viscosity modifiers. Concrete loses strength when it segregates, resulting in
honeycombed regions on the surface. However, due to its plasticity and
stability, well-designed self-compacting concrete will not segregate.
1. Cement
Self-compacting concrete can be made with ordinary/regular
Portland cement in grades 43 or 53.
2. Aggregates
The aggregate size utilized in SCC design is limited to
20mm. If the structure’s reinforcement is crowded, the aggregate size can be 10
to 12mm. The optimum choice is well-graded aggregates in round or cubical
shapes.
Fine aggregates used in SCC can be either natural aggregates
or uniformly graded manufactured aggregates (M- Sand). Fine aggregates with
particle sizes less than 0.125mm are commonly used.
3. Water
The water quality is the same as in reinforced concrete and
prestressed concrete construction.
4. Mineral Compounds
The mineral admixtures utilized can vary depending on the
mix design and needed qualities. Many mineral admixtures can be used, and the
properties they provide are listed below.
• GGBS (Ground Granulated Blast Furnace Slag): The addition
of GGBS improves the flowing properties of self-compacting concrete.
• Fly ash: The fine fly ash particles aid in filling the
interior concrete matrix, resulting in fewer pores. This increases the quality
and durability of structures made from self-compacting concrete.
• Silica Fumes: The addition of silica fumes to the
self-compacting concrete structure improves its mechanical qualities.
• Stone Powder: Stone powder is used in SCC to increase the
powder content of the mix.
5. Chemical Compounds
New-generation superplasticizers are often employed in the
design of self-compacting concrete mixes. Air-entraining agents are used to
strengthen the freezing and thawing resistance of the concrete construction.
Retarders are used to control the timing of the setting.
Properties of Self-compacting
Concrete:
Self-compacting concrete and traditional vibrated concrete
with comparable compressive strengths have comparable qualities. Hence SCC can
be utilized in most applications where traditional vibrated concrete is
employed.
However, the composition of SCC differs from that of
conventional concrete, and the difference exists in the performance during the
fresh state; not much in terms of hardened state attributes.
Self-compacting concrete with the same water cement or
cement binder ratio has a little higher strength than typical vibrated
concrete, owing to an improved interface between the aggregate and solidified
paste due to the absence of vibrations.
SCC varies from normal concrete in that its fresh qualities
are critical in determining whether or not it can be successfully laid. To
guarantee that its ability to be placed stays satisfactory, the aspects of
workability that affect its filling ability, passing ability, and Segregation
resistance must all be properly regulated.
Advantages of Self-compacting
Concrete:
• The permeability of the concrete structure is reduced, as
self-compacting concrete has a high filling ability.
• SCC allows for greater flexibility when developing
concrete structures due to its high flowability.
• The SCC construction is more rapid as compared to
traditional concrete.
• The vibration-related issues have been resolved.
Vibrational noise is decreased.
• SCC is easily laid, which results in significant cost
savings.
• The construction’s quality is improving.
• It can create creative architectural concrete
constructions.
• SCC produces smoother and more aesthetically attractive
surface finishes.
• The cost of manpower is reduced as there is no requirement
for laborers to vibrate the concrete.
• Using SCC reduces cavities in heavily reinforced sections
of the structure.
• It allows for easier pumping and a wide range of
positioning methods. SCC necessitates lower pumping pressures. As a result,
compared to standard concrete, SCC can be pumped more efficiently across
greater distances and heights.
Disadvantages of Self
Compacting Concrete:
• Self-compacting concrete, like any other building material, has the following limitations.
• The materials used for making SCC have to be selected very
carefully. Hence the material selection process becomes more stringent.
• Using a planned blend necessitates multiple trial batches
and laboratory tests.
• The greater flow velocity of SCC, in contrast to ordinary
concrete, may result in a dynamic pressure in addition to the hydrostatic
pressure of poured concrete for formwork design.
• There is no internationally recognized test standard for
self-compacting concrete mix. Hence maintaining quality standards can be
challenging while using SCC.
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