Glass Reinforced Concrete - Premix · 2 Glass Reinforced Concrete - Premix GRC (Glass Reinforced...
Transcript of Glass Reinforced Concrete - Premix · 2 Glass Reinforced Concrete - Premix GRC (Glass Reinforced...
Glass Reinforced Concrete - Premix
Cement Research & Application Center
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Glass Reinforced Concrete - Premix
GRC (Glass Reinforced Concrete) is a type of concrete which is formed by
using a certain amount of fiber glass in the cement paste. The flexural strength
of this type of concrete becomes much higher than regular concrete
In the last 30 years, the usage of premix GRC applications becomes popular.
High performance glass reinforced applications are generally done by the
usage of spraying stations.
Spraying Station
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Glass Reinforced Concrete - Premix
GRC is a combination of;
Concrete
Water
Aggregate
Alkali Resistant Fiber Glass
Chemical or/and Mineral Additives
.
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Glass Reinforced Concrete - Premix
GRC is produced in severous ways;
Spraying GRC – 25 mm fiber glass or fabric
Hand Spraying
Automatic Spraying
Premix GRC – 12 mm fiber glass
Other Production Techniques
Pressing, Band Plate Production
.
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Glass Reinforced Concrete - Premix
GRC is used in different areas like;
Facing Panels
Thermally Isolated Facing
Stud Frame Facing
Textured Facing
Building Design Components
Industrual Products
.
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If we have a look at the fiber glass consumption amount for different
binder systems, the premix glass reinforced concrete takes the second
line in terms of fiber ratio
Glass Reinforced Concrete - Premix
Graph 1. Fiber Content of Different Systems
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GRC – Premix flow properties are affected by;
Fiber Glass Size Type
Fiber String Arrangement
Fiber String Diameter
Fiber Ratio
Fiber Length
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The Effect of Fiber Amount and Length
As the fiber glass amount and length increases, the flexural strength values are
improved on the other hand processability becomes harder. The optimum working
conditions must be determined considering these issues.
Premix Application
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Effect of Fiber Ratio
Very Difficult: Pumping and the
mixing of the premix is very hard.
Blockages occur repeatedly..
Difficult: The mixture has
acceptable density. Blockages
can be seen time to time while
pumping.
Good: No serious problems is
seen while mixing or pumping.
Easy: Mixing and pumping is
easy as cement with no fiber
content.
The premixes are investigated under 4 groups with 3 different lengths according to workability.
Glass Reinforced Concrete - Premix
Graph 2. Fiber Content vs. Processability
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Effect of Polymer Type
Polymer selection is another important issue for the premix concrete.
In general, acrylic thermoplastic polymer mixtures are used for GRC. Dry
curing is another application that helps to keep polymer effect and not to
damage the elastic structure of the material.
Glass Reinforced Concrete - Premix
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Fiber Type Length
mm
Max Fiber Ratio
%
Optimum Fiber
Ratio
%
ACS**PH901X
13 5 2,5-4
25 3 2,5
38 2,5 2
The Effect of Fiber Ratio and Amount
As the length of the fiber increase, the amount of fiber in the mix should be
decreased in order to keep the workability in an acceptable limit.
Glass Reinforced Concrete - Premix
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Material Selection for the Premix;
In the previous applications of GRC, it can clearly be seen that if the
workability and placeablity is easy, the concretes become more stable and
long term durability properties become better.
As it can be seen from the Graph 2.; with 13mm fiber glass, the dosage can
be increased to 6% till the workability becomes very hard. On the other hand,
with 38 mm fiber glass usage maximum dosage can be 2,5% before the
workability becomes very hard.
Glass Reinforced Concrete - Premix
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Premix Design and Raw Materials
This method can be used for all of the portland cement systems.
By including calcium aluminate cement into the binder system, qualifications
like; high abrasion resistance, thermal stability, acid resistance, sulphate
resistance can be gained to the concrete.
Low water/cement ratio is recommended. (About 0,3-0,35).
As chemical additive 3 different materials can be used;
Polycarboxylate Polymers
Rheology Modifiers
Acrylic Polymers
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Premix Design and Raw Materials
In order to avoid segregation, mix design should be well composed. If not,
the aggregate and the fiber glass stays under the mixture and only the water
and cement will be pumped out of the spraying station.
When confronting pumping problems, the common mistake is adding water
to the mixture. This action generally causes more segregation and strength
loss, instead of solving the problem.
Rheology modifiers or special pumping equipment is suggested to solve the
segregation problems.
Glass Reinforced Concrete - Premix
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Premix Design and Raw Materials
The most significant factor for the GRC applications is raw material control.
The sand should be dried or the moisture content should be analyzed before
using.
The other raw materials should be fed to the system carefully and the amounts
should be weighted sensitively. For the mixing process; using a multiple speed
control mixer is suggested.
Till 5% fiber glass usage is appropriate. For fiber’s mixing homogenously, a
peristaltic pomp usage is recommended.
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Sample Premix Designs with Additives
Material 1 2 3 4 5
Cement 100 100 100 100 100
Silica Sand 100 100 100 100 100
Water 30 28-31 30 30 30
Silica Fume 5
AEHR – Air Retrainer 1,5 1,4 1,0 0,7
SRHR – Su kesici 1,0
PAP - Powder Acrylic
Polymer 1,0
MC – Methylcellulose 0,02
HPHT – Thickener 0,3
AFA – Foam Retrainer 0,05 0,05 0,05
Fiber Glass (NEG
ACS13PH901X) %3 %3 %3 %3 %3
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The graphs demonstrates flow value, self compactivity, bending strength values,
respectively..
Glass Reinforced Concrete - Premix
Sample Premix Designs with Additives
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Advantages of Premix GRC Manufacture:
1- GRC has high flexural strength.
2- Mechanical properties are stable.
3- Thermal isolation properties are efficient.
4- GRC has low thermal expansion.
5- Application of GRC is practical and fast.
6- Durability properties are satisfactory.
7- Labor cost is low.
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Disadvantages:
1- Arranging optimum workability level is troublesome.
2- The strength is slightly low with respect to fiber spraying glass
reinforced concrete.
3- The equipments are expensive than the conventional concrete
equipment.
4- Defining premix ratio requires sensitivity.
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1) British Standards Institution. Precast concrete products. Test method for
glass-fibre reiforced concrete. Part 5:Measuring bending strength, ‘complete
bending test’ method. BSI, London, 1998, EN 1170-5.
2) Peter, I. D. (2003) ‘Advances in Premix GRC’, 13th Biennial congress of
the GRCA, 16-18 October, Barcelona, Spain.
3) Peter, I. D. (2005) ‘Sprayed Premix, the New GRC’, 14th Biennial
congress of the GRCA, 14-16 December, Hong Kong.
4) PETER I.D. and JONES J. Improvements to the strength and ductility of
PremixGRC. GRCA Congress Proceedings, Cambridge 1998.
5) Y. Takeuchi el al. High-fluidity and lightweight premix GRC. Proceedings
of International GRC Congress 2001, Dublin, GRCA, 2001
References
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