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Fibre reinforced cement-based (FRC) composites after over 40 years of

development in building and civil engineering

Andrzej M. Brandt

Institute of Fundamental Technological Research, Polish Academy of Sciences, Warsaw, Poland

a r t i c l e i n f o

Available online 12 March 2008

Keywords:

Fibres

Cement-based matrix

Fibre reinforced concretes (FRC)

High performance concretes (HPC)

a b s t r a c t

Fibres have been used since Biblical times to strengthen brittle matrices; for example straw and horse-hair was mixed with clay to form bricks and floors. In modern technology, steel fibres were for the first

time proposed as dispersed reinforcement for concrete by Romualdi in his two papers in 1963 and 1964.

Since that time, the concept of dispersed fibres in cement-based materials has developed considerably:

hundreds of books and papers, many dissertations, and also applications in building and civil engineering

structures all over the world.

After over forty years, it is interesting to review the present state of knowledge and technology of FRC.

The balance of achievements and shortcomings is certainly positive. Our knowledge, based on theoretical

solutions and experimental findings, is rich and quite large. Test methods that are transferred from the so

called high-strength composites are very effective. However, practical applications are not so numerous

as it was initially expected with developments not exactly in the foreseen directions.

In this paper the main fields of application of FRC composites are examined and future perspectives dis-

cussed. After a brief review of various kinds of fibres and applied techniques, some attention is paid to

computation methods and composite materials’ design approaches. Large practical application of FRC

in construction is mostly hampered by insufficient development of relevant standards, based on perfor-

mance concepts. It should also be admitted that the cost of fibre reinforcement and related technological

operations is certainly an obstacle for use of FRC in ordinary structures. On the other hand, in successfulapplications in demanding structures very special requirements are satisfied; probably future develop-

ments will go in this direction.

Ó 2008 Elsevier Ltd. All rights reserved.

1. Introduction

Concrete is by far the most important building material and its

consumption is increasing in all countries and regions in our globe.

The reasons are multiple: its components are available everywhere

and relatively inexpensive, its production may be relatively simple,

its application covers large variety of building and civil infrastruc-

ture works. Moreover, since around 30 years, its development has

gone in new directions: high performance concretes (HPC). This

new kind of building materials is defined as ‘a concrete in which

certain characteristics are developed for a particular application

and environment’; these characteristics are not only strength, but

improved durability, increased resistance to various external

agents, high rate of hardening, better aspect, etc.

The only disadvantage of concrete is its brittleness, i.e. rela-

tively low tensile strength and poor resistance to crack opening

and propagation. In the development of concrete-like materials

the reinforcement with dispersed fibres plays an important role.

Since Biblical times, approximately 3500 years ago, brittle

building materials, e.g. clay sun baked bricks, were reinforced with

horse-hair, straw and other vegetable fibres.

The concept of fibre reinforcement was developed in modern

times and brittle cement-based paste was reinforced with asbestos

fibres when in about 1900 the so called Hatschek technology was

invented for production of plates for roofing, pipes, etc. Later, glass-

fibres were proposed for reinforcement of cement paste and mor-

tar by Biryukovichs [1]. The ordinary E-glassfibres are not resistant

and durable in highly alkaline Portland cement paste and the alka-

li-resistant (AR) glassfibres with addition of zircon oxide ZrO2 were

invented by Majumdar and Ryder [2]. Important influences of the

development of steel fibre reinforced cements (SFRC) are papers

published by Romualdi and his co-authors [3,4] for the first times

on this subject.

It is not surprising that in such an excellent material as con-

crete, after many recent improvements of additions and admix-

tures, with considerable development of technology in precast

factories and in situ, and with exploitation of highly sophisticated

test methods, the application of dispersed fibre reinforcement re-

sults after three decades in a large variety of excellent building

0263-8223/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.doi:10.1016/j.compstruct.2008.03.006

E-mail address: [email protected]

Composite Structures 86 (2008) 3–9

Contents lists available at ScienceDirect

Composite Structures

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http://www.sciencedirect.com/science/journal/02638223

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materials for different purposes – fibre reinforced cements and

concretes (FRC).

The aim of the paper is to describe the present state of knowl-

edge and technology of FRC and to discuss main directions of their

application. The attention is concentrated on structural concretes

for high-rise buildings, long-span bridges, highway and airfield

pavements, and many other kinds of outstanding structures. For

obvious reasons, ordinary concretes without fibres but of improvedquality are used for low performance structures and non-structural

elements.

2. Matrices and fibres

Cement-based matrices have developed considerably during

last 40 years. The main components are still Portland cement and

coarse and fine aggregate of different origin, and there are several

other components: superplasticizers, admixtures and microfillers.

Also proportions between these components have changed.

There are many kinds of Portland cements that may be selected

for particular purposes. The national and international companies

mayfurnishcements that arecharacterizedby high or lowstrength,

high-early strength or low heat of hydration, high sulfate resistance,

low content of C3A, and large variety of blended cements, i.e. with

additionup to 70% byweight of flyash andground blastfurnaceslag.

The next groups of concrete components are additions and

admixtures that create special properties of fresh mix and hard-

ened concrete; these are superplasticizers, air-entraining agents,

microfillers and secondary cementing materials: fly ash, natural

pozzolans, rice husk ash, metakaolin, etc. In fact, often binary, ter-

nary or quarternary concretes are distinguished, i.e. based on com-

positions of different binders.

As aggregate, not only crushed stone and natural gravel with

sand are used, but also various artificial materials, carefully se-

lected and inserted into fresh mix in well determined proportions.

In concrete, many kinds of waste materials are used, including

recycled aggregate, in order to decrease cost and to satisfy increas-ing demands of sustainability and ecology.

As a result, concretes and particularly concretes that have to

satisfy special requirements, became rather complicated materials

and are ‘tailor-made’ to provide the precise properties necessary

for a particular project. The design of such a concrete is based on

deep knowledge and substantial experience; with the same con-

cerns regarding the selected applications of technology. At all

stages high competence of the personnel is needed.

In general, modern concretes are more brittle than those in the

first half of 20th century, with higher rates of strength and higher

heat of hydration, and often less durable, i.e. less resistant against

intensive corrosive attacks from environment if not specially de-

signed. As remedies, there are special kinds of concretes called high

performance concretes, described hereafter, frequently with appli-cation of dispersed reinforcement in different forms. The main role

of short dispersed fibres is to control the crack opening and prop-

agation. Basic groups of fibres applied for structural concretes and

classified according to their material are Brandt [5]:

– steel fibres of different shapes and dimensions, also microfibres;

– glassfibres, in cement matrices used only as alkali-resistant (AR)

fibres;

– synthetic fibres made with different materials: polypropylene,

polyethylene and polyolefin, polyvinyl alcohol (PVA), etc.;

– carbon, pitch and polyacrylonitrile (PAN) fibres.

Natural vegetable fibres are not suitable for high performance

structural concrete, but are applied in ordinary concretes. Asbestosfibres are completely abandoned in construction because of their

detrimental influence on human health and are replaced by other

kinds of fibres, e.g. polymeric.

Certainly the most important for structural concrete are steel fi-

bres; a few examples are shown in Fig. 1; hooks at the ends and

various modifications of shape improve fibre-matrix bond and in-

crease efficiency of the fibres.

The influence of the fibres on cracking of cement-based matrixis

explained in Fig. 2: thanks to the fibres, large single cracks are re-placed with dense systems of microcracks, which may be accept-

able from both safety and durability viewpoints. The role of fibres

is clear from the data presented in Table 1. Numbers of fibres dis-

tributed in one cube centimetre are shown for a few examples of fi-

bres and their volume fractions. Only fibre volume up to 3% is

considered, because higher volumes require special techniques that

are described below. Fine fibres control opening and propagation of

microcracks as they are densely dispersed in cementmatrix. Longer

fibres up to 50 or 80 mm control larger cracks and contribute to in-

crease the final strength of FRC, as it is shown in Figs. 3 and 4.

With the increase of fibre volume and efficiency, their influence

on behaviour of a SFRC element modifies completely its behaviour

under load, as it is described in Fig. 5 with strain–stress diagrams.

The conventional SFRC element is characterized by initial linear in-

crease of stress and after the 1st crack opening there is a slow de-

crease, the so called softening branch. In contrast, where the

reinforcement is sufficient, after the 1st crack there is a strain hard-

ening stage, which accompanies multiple cracking and consider-

able amount of energy is absorbed that is proportional to the

area under the curve. The softening branch follows that stage. In

Fig. 5 the main difference between conventional FRC and high per-

formance fibre reinforced cement composites (HPFRCC) is defined.

The effects of fibre reinforcement on the behaviour of an element

under bending are discussed in Fig. 6, and it is shown how such

beam may be designed for a particular purpose.

Beside steel fibres, also high tenacity PVA fibres, either monofil-

ament or fibrillated polypropylene, with lengths varying from 10 to

Fig. 1. Examples of deformed steel fibres, after Sujivorakul and Naaman [6].

Fig. 2. Crack pattern in reinforced concrete (RC) and fibre reinforced concrete (FRC)elements subjected to tension.

4 A.M. Brandt/ Composite Structures 86 (2008) 3–9

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Fig. 4. Structure of short and long fibres controlling microcracks and its influence on the stress – crack opening curve, after Rossi [9].

Fig. 5. Comparison of typical stress–strain response in tension of HPFRCC with conventional FRCC, after Naaman [10].


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micro-aggregate and special additives like fly ash and silica

fume. The high fluidity (low viscosity) of the slurry is necessary

for adequate penetration of the dense fibre systems in a mould.

Very high-strength and resistance against local impacts and pen-

etration of projectiles characterize the elements made with SIFCON.

When instead of single fibres the woven or plaited mats are

used, then the name SIMCON (slurry infiltrated mat concrete)is used. The main applications of both materials are heavy-duty

pavements, anti-terrorist shields, walls in bank treasuries, etc.,

where additional cost of materials and special technology are

acceptable.

4. Design and composition of FRC

For various applications of FRC where strength is not necessar-

ily verified, the composite material is designed using test results

and experience. The effect of reinforcement is proportional to the

volume and efficiency of the fibres. Because fibres are an important

part of the cost, the fibre volume in ordinary applications (indus-

trial floors, pavements, etc.) is usually limited to 0.5% or even low-

er. The difficulties in a correct distribution of fibres also increasewith their volume and this aspect should be always considered.

Flexural toughness of FRC is traditionally estimated according to

ASTMC1018 [14]. Forthat aim, standardteston a beam underbend-

ing is necessary, and after the load-deflection curve (Fig. 8), the so

called flexural toughness indices I 5, I 10, I30, . . . may be calculated.

The results allow estimating quantitatively the load-deflection

curve – how do the fibres influence the descending branch of the

curve. There are several objections as to the precision of theindices,

but this approach is universally applied; it serves also to compare

different fibres or mixture compositions as to their efficiency.

In structural elements, where it is essential to verify the tensilestress, a fewprocedures areappliedto determine theso called equiv-

alent strength f eq, in which input from the fibres is included. For

example, according to Japanese Standard [15], the equivalent

strengthis calculated from the bending test of a beam andit is equal:

f eq ¼ T bL

dL=150bh

where T b – work of bending calculated after the area under the

load-deflection curve up to the deflection dL/150 = L/150, b and h

are width and depth of the beam, L is its span.

Similar formulae are proposed in RILEM Recommendation [16]

as a result of a few year work of the Technical Committee TC

162-TDF led by L. Vandewalle.

The lack of a universally accepted approach to the calculationand strength verification of SFRC and respective standards is one

of the major obstacles in large development of this material in

structural design. For steel fibres, as well as for other fibres (glass-

fibres, carbon fibres, etc.), there are several experimental methods

proposed and used by different contractors and fibre producers.

5. Application of FRC in building and civil engineering

structures

Steel fibres are largely used as dispersed reinforcement of

industrial floors and pavements in many countries and this is prob-

ably the most important field of application. There are also several

kinds of structural elements where steel fibres are used togetherwith steel bars, e.g. structures exposed to impact and fatigue,

Fig. 6. Typical load-deflection response curves of fibre reinforced cement composites, after Naaman [10].

Fig. 7. Comparison of the stress–displacement curves of beams made with ordinary

concrete and DuctalÒ, after Behloul [12].

A.M. Brandt / Composite Structures 86 (2008) 3–9 7

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columns in building in seismic zones, refractory structure, etc.

Glassfibres are used mostly for external claddings, facade plates

and other elements where their strengthening effects are required

particular during construction.

Natural vegetal fibres (cellulose pulp, sizal, bamboo, hemp, flax,

jute, ramie fibres, etc.) are used in the countries where these fibres

are easily available, Coutts [17]. Structural elements with vegetal

fibres are important for construction of inexpensive buildings in

developing regions of the world.

In last few years, the dispersed steel fibres are successfullyused in prestressed concrete bridge beams where they replace

mild steel reinforcement. In Fig. 9 the cross-section of the bridge

deck Bourg-lès-Valence (France) is shown. Ten prestressed

beams form the main structure of the bridge. Additional plates

are used as the lost shuttering for ordinary concrete cast

in situ with ordinary reinforcement and covered with road pave-

ment. The prestressed beams and plates are made with DuctalÒ.

Thanks to 3 vol.% of dispersed microfibres in DuctalÒ, there are

neither stirrups no other mild steel reinforcement needed

against shearing and local stresses in the beams and consider-

able economy was obtained in time and cost of labour. Another

example of prestressed concrete beams with 3 vol.% of fibres is

shown in Fig. 10. This is certainly a new and important direction

of future application of fibres in structural elements without anyother reinforcement.

6. Main directions of development of FRC

Extension of application of FRC with development of technology

in construction is ensured. Further investigations in a few selected

directions are needed, aimed particularly at

– development of reliable and relatively simple methods of calcu-

lation of FRC elements for strength and stiffness and their intro-

duction to the recommendations and standards available for

professional engineers;

– use of modern test methods of FRC in general practice, particu-

larly in civil engineering structures, in view of ensuring thequality control and improving their durability;

– solution of a few problems for special structures where high

performance is required, e.g. concerning hybrid reinforcement,

compatibility between various components, and optimization

in material design to determine the best mixture proportions.

7. Conclusions

The development of various kinds of high performance and ul-

tra-high performance concretes, reinforced with dispersed fibres,

results in creation of a group of very important building materials.

At present, for many outstanding structures or for construction in

special conditions, application of FRC is considered as necessary,

and this situation will be extended in the future.

Successful use of various high performance materials based on

cement matrix has a considerable positive influence on production

of ordinary concretes. New components and technologies devel-

oped for special purposes are now, at least partly, applied in every-

day production in ready-mix-concrete plants. Large variety and

better quality of admixtures, improved precision of executionand adequate curing are the bases for ordinary concretes that are

becoming inexpensive, strong and ensured improved durability

of buildings and civil infrastructure.

In general, concrete and particularly concrete with dispersed fi-

bre reinforcement is becoming a high-tech material that provides

excellent performance but requires competent design and execu-

tion. Various experimental and theoretical methods that are suc-

cessfully applied will certainly be used in further research and

development.

Acknowledgements

This work was supported by Project No. R04 013 01 coordinated

by IFTR PAS and sponsored by The Ministry of Science and Higher

Education(MniSW), Warsaw,Poland,to which theauthoris grateful.

References

[1] Biryukovich KL, Biryukovich YuL, Biryukovich DL. Glass-fibre-reinforcedcement. Kiev: Budivelnik; 1964 [CERA Translation, 1965, No. 12].

[2] Majumdar AJ, Ryder JR. Glass fibre reinforcement of cement products. GlassTechnol 1968;9(3):78–84.

[3] Romualdi JP, Batson GB. Mechanics of crack arrest in concrete. J Eng Mech DivASCE Proc 1963;89(EM3):147–68.

[4] Romualdi JP, Mandel JA. Tensile strength of concrete affected by uniformlydistributed and closely spaced short lengths of wire reinforcement. J ACI1964:657–70.

[5] Brandt AM. Cement-based composites: materials, mechanical properties andperformance. London: E&FN Spon; 1995. p. 470.

[6] Sujivorakul C, Naaman AE. Modeling bond components of deformed steel fibersin FRC composites. In: Reinhardt HW, Naaman AE, editors. Proceedings of the

international RILEM workshop ‘High performance fiber reinforced cementcomposites’ HPFRCC4, Ann Arbor; 2003. p. 35–48.

Fig. 9. Cross-section of the bridge deck in Bourg-lès-Valence (France) made with

FRC, V f = 3%, after Behloul [12].

Fig. 10. Cross-section of prestressed FRC bridge beams without mild reinforcement,

V f = 3%.

LOAD

DEFLECTIONO

D E F

A

B

C

3 5.5

I5 = OABE/OAD

I10 = OABCF/OAD

δ δ δ

Fig. 8. Computation of the flexural toughness indices, after ASTM [14].


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[7] Brandt AM. Structural image analysis in investigation of concrete. In: AMASworkshop No. 3, IFTR Warsaw; 2002. p. 149–74.

[8] Betterman LR, Ouyang C, Shah SP. Fiber-matrix interaction in microfiberreinforced matrix. Adv Cem Bas Mat 1995;2:52–61.

[9] Rossi P. Ultra-high-performance fiber-reinforced concretes. In: Concreteinternational, December 1982. p. 46–52.

[10] Naaman AE. Strain hardening and deflection hardening fiber reinforcedcement composites. In: Reinhardt HW, Naaman AE, editors. Proceedings of the international RILEM workshop ‘High performance fiber reinforced cementcomposites’ HPFRCC4, Ann Arbor; 2003. p. 95–113.

[11] Ramakrishnan V, Zellers R, Patnaik AK. Plastic shrinkage reduction potential of a new high tenacity monofilament polypropylene fiber. In: Malhotra VM,editor. 9th CANMET/ACI international conference on recent advances inconcrete technology, 2007, ACI SP-243. p. 49–62.

[12] Behloul M. HPFRCC field of applications: DuctalÒ recent experience. In:Reinhardt HW, Naaman AE, editors. Proceedings of the international RILEM

workshop ‘High performance fiber reinforced cement composites’ HPFRCC5,Mainz; 2007. p. 213–22.

[13] Kucharska L, Brandt AM. Pitch-based carbon fibre reinforced cementcomposites. A review. Arch Civ Eng 1997;43(2):165–87.

[14] ASTM C 1018 Standard Test Method for Flexural Toughness and First-CrackStrength of Fiber Reinforced Concrete. ASTM Int.; 1997.

[15] Standards for Test Methods of Fiber Reinforced Concrete, SF-4: Method of Testfor Flexural Strength and Flexural Toughness of Fiber Reinforced Concrete.

Japan Society of Civil Engineers; 1984.[16] Vandewalle L. RILEM TC 162-TDF, Test and design methods for steel fibre

reinforced concrete: r–e design method. Final Recommendation. Mater Struct2003;36(October):560–7.

[17] Coutts RSP. A review of Australian research into natural fibre cementcomposites. Cement Conrete Res 2005;27:518–26.

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