Glass Reinforced Concrete - Premix · 2 Glass Reinforced Concrete - Premix GRC (Glass Reinforced Concrete) is a type of concrete which is formed by using a certain amount of fiber

Glass Reinforced Concrete - Premix

Cement Research & Application Center

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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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GRC is a combination of;

Concrete

Water

Aggregate

Alkali Resistant Fiber Glass

Chemical or/and Mineral Additives

.

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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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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


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.


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.


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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.


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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.


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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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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.


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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..


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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Çimsa Research and Application Center

For Further Information :

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33013 Yenitaşkent - Mersin TÜRKİYE

T : +90 324 241 23 37

C : +90 505 939 64 98

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Glass Reinforced Concrete - Premix · 2 Glass Reinforced Concrete - Premix GRC (Glass Reinforced Concrete) is a type of concrete which is formed by using a certain amount of fiber