Matakuliah
Tahun
: S0793 – Teknologi Bahan Konstruksi
: 2009
PERKEMBANGAN TEKNOLOGI BETON
Pertemuan 13
Learning outcomes
• Mahasiswa dapat menyebutkan perkembangan
teknologi beton di dunia dan di Indonesia
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Outline Materi
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Perkembangan Teknologi Beton
Beton Pracetak
Beton Fiber
Self Compacting Concrete
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Perkembangan Teknologi Beton
• Seiring dengan berkembangnya teknologi bahan dan
komputer. Penemuan material baru yang lebih ekonomis
dan tahan lama.
• Penggunaan bahan lain misalnya fiber, semen komposit,
polimer dan sebagainya.
• Perkembangan teknologi komputer yang dapat membuat
pengujian secara virtual sehingga lebih cepat dan akurat
dilakukan oleh National Institute of Standard and Testing
(NIST).
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Jenis Beton Lain
• Beton Berat (berat isi lebih besar, menahan radiasi,
benturan)
• Beton Massa (bendungan besar, kanal, pondasi
jembatan, agregat yang digunakan lebih besar, slump
rendah)
• Ferro-Cement (beton dengan kawat anyam, kuat tarik
tinggi, waterproofing, struktur tipis dan ringan,
memungkinkan untuk di fabrikasi, kemudahan
pengerjaan, penghematan bahan cetakan
• Beton Siklop (agregat besar hingga 20 cm, digunakan
untuk beton massa)
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Beton Pra Cetak (Precast Concrete)
• Precast concrete is a form of construction, where
concrete is cast in a reusable mould or "form" which is
then cured in a controlled environment, transported to
the construction site and lifted into place.
• In contrast, standard concrete is poured into site specific
forms and cured on site. Precast stone is distinguished
from precast concrete by using a fine aggregate in the
mixture so the final product approaches the appearance
of naturally occurring rock or stone.
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Precast Concrete
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Fiber Concrete
• Fiber reinforced concrete (FRC) is concrete containing
fibrous material which increases its structural integrity. It
contains short discrete fibers that are uniformly
distributed and randomly oriented. Fibers include steel
fibers, glass fibers, synthetic fibers and natural fibers.
Within these different fibers that character of fiber
reinforced concrete changes with varying concretes,
fiber materials, geometries, distribution, orientation and
densities. (wikipedia)
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Effect Fiber in Concrete
• Fibers are usually used in concrete to control plastic shrinkage
cracking and drying shrinkage cracking.
• They also lower the permeability of concrete and thus reduce
bleeding of water.
• Some types of fibers produce greater impact, abrasion and shatter
resistance in concrete.
• Generally fibers do not increase the flexural strength of concrete, so
it can not replace moment resisting or structural steel reinforcement.
• Some fibers reduce the strength of concrete.
• The amount of fibres added to a concrete mix is measured as a
percentage of the total volume of the composite (concrete and
fibres) termed volume fraction (Vf).
• Vf typically ranges from 0.1 to 3%. Aspect ratio (l/d) is calculated by
dividing fibre length (l) by its diameter (d).
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Effect Fiber in Concrete
• Fibres with a non-circular cross section use an equivalent diameter
for the calculation of aspect ratio.
• Some recent research indicated that using fibers in concrete has
limited effect on the impact resistance of concrete materials
• This finding is very important since traditionally people think the
ductility increases when concrete reinforced with fibers. The results
also pointed out that the micro fibers is better in impact resistance
compared with the longer fibers
• The High Speed 1 tunnel linings incorporated concrete containing
1 kg/m³ of polypropylene fibres, of diameter 18 & 32 μm, giving the
benefits noted below. Polypropylene fibres can:
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Improve mix cohesion, improving pumpability over long distances
Improve freeze-thaw resistance
Improve resistance to explosive spalling in case of a severe fire
Improve impact resistance
Increase resistance to plastic
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Fiber Reinforced Concrete
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Self-Compacting Concrete
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The Important Properties
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Self-compactability
Avoidance of bleeding and segregation
Low shrinkage
Low permeability
Strength as needed
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The Benefits
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Less dependent on skill on site
Safer, quieter sites (no vibration)
Better appearance
Better durability
Strength as needed
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What’s Different?
• Segregation resistance from mortar viscosity, not
aggregate grading
• Workability through admixtures, not water content
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What’s The Snag?
• Higher cost – especially if high strength not needed
• Plant control has to be better
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Will it happen?
• My guess is that 50% of concrete will be self-compacting
within 10 years
• In USA a very large proportion of precast concrete is
already SCC
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What is the secret?
Paste Viscosity! Attained by one of three means:
• High cement content
• High content of Fly Ash, Silica Fume etc
• Use of Viscosity Modifying Admixture
Plus low water content using HRWR
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How to Check Suitability?
• There are many new tests: V-funnel, L-box, U-box,
Fill-box, Orimet, GTM Screen + Slump Flow and Jring
• While several of these may be used in mix
development, only the latter will find site use
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What is Slump Flow Test?
Measuring spread rather than height plus:
• Speed of flow outwards
• Ability to pass through J-ring
• Observation of edge during flow
• Interesting to note that it works better with the cone
upside down!
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Why Does It Look Better?
• Perfect compaction
• No bleeding
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Conclusion
• We are going to expect concrete that is a little more
expensive per cubic metre to buy
• BUT
• It will require less skill and effort to place
• It will look better with no appearance defects
• It will be more durable
• It will require more skill at the batching plant
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