Flexural Performance of Ferrocement Laminates Containing Silicafume and Fly Ash Reinforced With...

7/30/2019 Flexural Performance of Ferrocement Laminates Containing Silicafume and Fly Ash Reinforced With Chicken Mesh

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International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 6308 (Print),ISSN 0976 6316(Online) Volume 3, Issue 2, July- December (2012), IAEME

130

FLEXURAL PERFORMANCE OF FERROCEMENT LAMINATES

CONTAINING SILICAFUME AND FLY ASH REINFORCED WITH CHICKEN

MESH

K. SASIEKALAA

Professor, Department of Civil Engineering, M.A.M College of Engineering,Trichy- 621 105, Tamilnadu, India. Email: [email protected]

R. MALATHY

Professor & Dean (R&D), Department of Civil Engineering,

Sona College of Technology, Salem- 636005,Tamilnadu,India.Email:[email protected]

ABSTRACT

Ferro cement is a versatile construction material having unique properties of strength and

serviceability that promote low cost technology in both urban and rural applications. The positiveeffects exerted by silica fume and fly ash on properties of Portland cement mortar have been

emphasized. Flexure tests were conducted on ferrocement specimens replacing cement by

silicafume(SF)and fly ash(FA) with superplasticizer.In the present study, slab specimens of size

500mm x150mm x 25mm with the following variables were investigated. i) chicken meshreinforcement with volume fraction 0.943%,1.880%,2.823% and 3.770%.ii) Replacing cement

by 5SF10FA(5%SF&10%FA), 5SF15FA, 5SF20FA, 5SF25FA and 5SF30FA.From the flexure

study parameters such as first crack load, ultimate load, maximum deflection, and crack patternwere observed. From the experimental results it was found that the cement is replaced with the

combination of 5% silica fume, 20% fly ash and 0.6%super plasticizer reinforced with volumefraction 2.823% and 3.770% leads to significantly improved flexural behaviour in terms ofstrength, toughness increased shear resistance and cracking. It can be effectively used for

rehabilitation of reinforced concrete structures particularly with ferrocement composites.

Key words: Ferrocement, silica fume, flyash, Galvanised chicken mesh, mortar matrix, flexural

behaviour.

INTERNATIONAL JOURNAL OF CIVIL ENGINEERING AND

TECHNOLOGY (IJCIET)

ISSN 0976 6308 (Print)

ISSN 0976 6316(Online)

Volume 3, Issue 2, July- December (2012), pp. 130-143

IAEME: www.iaeme.com/ijciet.html

Journal Impact Factor (2012): 3.1861 (Calculated by GISI)www.jifactor.com

IJCIET

I A E M E


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1. INTRODUCTIONIn many countries around the world, silica fume and fly ash are used for producing active

pozzolanic admixtures. These pozzolanic admixtures are used for reducing the Portland cement

content in mortar and concrete production(T Cook DJ et al., 1985).

The combination of silica fume and fly ash in a ternary cement system (i.e. Portland cement

being the third component) should result in a number of synergistic effects, some of which are

obvious as follows (Thomas M.D.A,1999).

o Silica fume compensates for low early strength of concrete with low fly ash.o Fly ash increases long term strength development of silica fume concrete.o Fly ash offsets the increased water demand of silica fume.o Very high resistance to chloride ion penetration can be obtained with ternary blends.o The relative low cost of fly ash offsets the increased cost of silica fume.

Ferciment or Ferro-cemento or Ferrocement is the first invention of the reinforced concrete

(ACI 549R-97; Naaman2000).Ferro cement is thin cement based on composite material. It has

very wide applications due to its unique characteristics/mechanical properties, such as:environment friendly, sound technology; excellent tensile strength, improved toughness, water

tightness, lightness, fire resistance, resistance to cracking and cost, time and material effective

construction technology (Paul B.K and Pama.R.P. 1978).Compared to the reinforced concrete,

ferrocement has homogeneous-orthotropic properties in two directions.It exhibits high tensilestrength, high modulus of rupture and superior cracking performance. In addition, because of the

high specific surfaces of ferrocement meshes, larger bond forces develop with the matrixresulting in smaller crack spacing and width (Naaman AE. 2000).In Ferro cement crack width atworking load remains very small compared to that of the reinforced concrete, thereby leading to

good impermeability, stiffness,and durability.(Onet.T,et al., 1992).The size of the mesh openings

should be within 6-25mm (FMC 2001).

Chloride induced corrosion of steel can be effectively improved by the use of the mineral

admixtures in concrete such as fly ash, blast furnace slag and silica fume (Babu KG et al.,1993).The mineral admixtures such as fly ash, blast furnace slag and silica fume help the

formation of finer and discontinuous pore structures as a consequence of pozzolanic reaction.

The successful application of the ferrocement boats and roofing element is an indication that

ferrocement is relatively resistant to the ingress of water (Akkan MS, et al., 1992).

It is apparent that the ternary cementitious blends of Portland cement, silica fume and fly ash

offer significant advantages over binary blends and even greater enhancements over ordinary

Portland cement. In some cases, price differences between the individual components may allowthe ternary blend to compete with with the ordinary Portland cement on the basis of material

costs (Hariharan A.R et al.,2011).

The availability of materials in most developing countries, and skilled labour required and for

both prefabrication and self help construction could make ferrocement become one of the most

inexpensive and attractive techniques to strengthen and rehabilitate the existing and damaged

concrete structures (Jagannathan A. et al, 2006).


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Limited data exist in the literature on the flexural behaviour of ferrocement with modified

cement matrix.The significant contributions of our paper to the ferrocement work are as follows.

i)To explore the effects of adding silicafume and flyash with super plasticizer to ferrocementlaminates. ii) Tests were conducted to study the flexural characteristics of the ferrocement

laminates of low water binder ratio with the silica fume and fly ash in various proportions in the

presence of a super plasticizer.iii)Ferrocement works demand cement mortars of goodworkability and high strength. It has to be done by including the optimum dosages of SF, FA and

super plasticizer. iv)Furthermore, this paper speaks of the ferrocement panels reinforced with

chicken mesh of volume fraction 0.943%,1.880%,2.823% and 3.770%. and their flexuralperformance was compared with that of the referred ferrocement panel. It considers the

minimization of the manufacturing cost.

2. EXPERIMENTAL PROGRAM

2.1 Materials

All the materials used during this experimental program comply with the standard specifications.2.1.1 CementThe physical and chemicalproperties of the usedOrdinary Portland cement (OPC) are tabulated

in Table 1 and Table 2 respectively.

2.1.2 Fly ash

High calcium fly ash (ASTM classC) from NLC limited, Neyveli, India was used in this

investigation. The physical and chemical compositions of the fly ash are shown in Table1 andTable 2 respectively.

2.1.3 Silica fumeUncompacted silica fume from Elkern, India was incorporated in this study. The physical

properties and chemical compositions of the silica fume are shown in Table 1 and Table 2

respectively.

Table 1: Physical properties of cementitious materials

Description of test ASTM TypeI

Portland cement

Fly ash ASTM

Class C

Silica Fume

Specific gravity 3.15 2.04 2.02

Fineness 94.1 - 85

Initial setting time 150 min - -

Final setting time 265 min - -

Specific surfacem /g 329 - 19

Bulk density kg/m - - 602


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Table 2: Chemical composition of cementitious materials

Description of test ASTM TypeI

Portland cement

Fly ash ASTM

Class C

Silica Fume

SiO2 20.32 60.09 85.72

Al2O3 4.94 18.63 0.06

Fe2O3 3.55 - 0.45

CaO 62.58 - -

MgO 1.18 1.10 -

SO3 3.46 1.54 -

Na2O3 0.19 0.31 -

K2O 0.86 0.05 -

LOI 1.28 2.41 1.96

2.1.4 Fine aggregate

Natural river sand with fraction passing through 2.36mm sieve was used as per

recommendation of ACI 549 IR 93.The specific gravity of fine aggregate was 2.658.

2.1.5 Super plasticizerThe super plasticizer of trade name Fosroc Conplast SP430 conforming to IS 9103-1999

and ASTMC-494 was used as the chemical admixture during this study. It is available asa medium brown coloured aqueous solution and its specific gravity is 1.18.

2.1.6 Water

Good quality drinking water was used for the preparation and curing of specimen.

2.1.7 Meshes

The galvanized chicken mesh was used because it is cheap, user friendly and readily

available in the open market. Salient physical properties of the mesh are evaluated and

given in table 3.


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Table 3: Physical properties of the chicken mesh used in ferrocement

Properties/Description Chicken mesh

Raw material steel

Mesh shape Hexagonal

Width(m) 1

Mesh opening(mm) 15 X 10

Thickness at joint(mm) 1.5

Diameter of wire(mm) 0.5

Unit weight(Kg/m ) 1.85

Density(Kg/m ) 7850

2.2 Preparation of ferrocement test specimens

2.2.1 Mortar for ferrocement

Mix proportion for ferrocement was selected from the results of compressive strength.(sasiekalaa et al.,2012).Table 4 shows the details of the mix proportion of mortar for ferrocement

slab.

Table 4: Mix proportion of mortar for ferrocement slab

Binder: sand 1:2

Silica fume 5% of total binder by weight

Fly ash10%,15%,20%,25% and 30% of total

binder by weight

Water binder ratio 0.35

Super plasticizer 0.6% of total binder by weight

Design compressive strength About 60Mpa

Mesh 1 layer,2 layers,3 layers and 4 layers

2.2.2 Preparation of ferrocement slab

A specimen of ferrocement slabs of size 500x150x25mm with 1:2 mix,0.35 water binder ratio,

partial replacement of cement with 5% silica fume and fly ash content varied from


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10%,15%,20%,25% and 30% by weight of cement were prepared. The dosage of super

plasticizer used is 0.6% by weight of total binder. Thus a total of 72 specimens of the above size

were cast by placing chicken mesh with volume fraction 0.943%, 1.880%, 2.823% and 3.770%.

2.3 Flexural testing of Ferro cement slabs

2.3.1 Instrumentation and loading procedure

All specimens are subjected to flexure under two point loading. The test set up is shown in

Fig.1.The slabs were simply supported with an effective span of 400mmc/c. Two point loadswere applied transversely at one third distance from the support. Dial gauge of sensitivity

0.01mm was used to measure the deflection of the slabs at mid span. The behaviour of the slabs

was keenly observed from the beginning till collapse. The observations were made for: a)Deflection at the midpoint for each 0.5kN increment of loading b) Load at first crack c) Ultimate

load d) Crack formation and its spacing e) Mode of failure of all specimens. The propagation of

the initial cracks owing to the increase of load was also recorded. The loading continued till the

verge of collapse.

Fig.1 Test set up

3. Flexural behavior of the ferrocement panels

The results of the flexural test on ferrocement panels with and without mortar modification for

the chicken mesh are given in table 5.

4. RESULTS AND DISCUSSIONS

4.1 Load Vs Deflection Effect of number of layers

Figure 2 to figure 7 shows the load deflection characteristics of the ferrocement panels with

5SF10FA, 5SF15FA, 5SF20FA, 5SF25FA and 5SF30FA for chicken mesh of volume fraction0.943%,1.880%,2.823% and 3.770%. It is seen that the ferrocement laminates exhibit linear

elastic behavior up to the maximum load, irrespective of number of layers of mesh used. After

reaching the ultimate load, the deflection of the ferrocement panels reinforced with the mesh

tend to decrease gradually. The panels reinforced with volume fraction of 0.943% fail suddenly


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after reaching the maximum load which is essentially due to the deficient bond of the chicken

mesh with the matrix.

4.2 First Crack Load and Failure Load

From the table 5 first crack load and failure load were found to be the maximum for 5SF20FA.First crack load and failure load increase with the increase in the volume fraction of mesh.Themaximum value of the first crack load was found to be 1.9kN and the maximum failure load was

found to be 4kN.Variation of the first crack load and the failure load with % replacement is

shown in figure 8 & figure 9.

4.3 Mode of failure

Flexural failure was observed for all specimens. Most of the cracks were generated near the

centre and on increase in loads multiple cracks were generated at different locations. Averagespacing of cracks was found to be almost equal at higher loads and failure occurred at loading

points.

Table 5 :Details of test results of ferrocement laminates

Mortar mix Volume

fraction(%)

First crack load

(kN)

Ultimate load

(kN)

Maximum

deflection(mm)

Control

specimen

0.943 1.1 1.1 6

1.880 1.3 1.3 8

2.823 1.5 2.1 11

3.770 1.8 3.7 20

5SF10FA

0.943 1.1 1.4 7

1.880 1.2 1.3 8.5

2.823 1.4 2.4 13

3.770 1.5 3.8 21

5SF15FA

0.943 1.1 1.5 7

1.880 1.2 1.4 6.5

2.823 1.3 2.3 12

3.770 1.5 3.7 18

5SF20FA

0.943 1.1 1.6 9

1.880 1.3 1.5 8

2.823 1.7 2.4 11

3.770 1.9 4.0 19


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5SF25FA

0.943 1.0 1.2 8

1.880 1.1 1.2 10

2.823 1.4 1.9 18

3.770 1.6 2.9 24

5SF30FA

0.943 0.9 1.1 6

1.880 1.0 1.0 10

2.823 1.3 1.8 16

3.770 1.6 2.8 25

4.4 Maximum Deflection

In the case of one layer and two layer of reinforcement for various mortar modifications, the

maximum deflection is found to be nearly the same. The maximum deflection is within the

allowable limit as per the codal provisions of ACI 549 IR 93

4.5 Effect of mortar modification

The effect of addition of fly ash and silica fume on the flexural load carrying capacity is found to

be insignificant upto two layers of mesh in the ferrocement panel. It is very effective in

preventing the spalling of the mortar cover at ultimate load. It leads to significantly improvedflexural behavior in terms of strength, toughness, increased shear resistance and cracking. Hence

ferrocement panel with 5% silica fume and 20% fly ash reinforced with chicken mesh of volume

fraction 2.823% and 3.77% is the optimum value.

5. Toughness Index:

Toughness is a measure of the energy absorption capacity of a material and is used to

characterize the materials ability to resist fracture. Energy absorption capacity of the matrix is

increased by increasing the volume fraction of mesh which can be evaluated by determining the

area under the load deflection curve. Variation of toughness index with %replacement of all

ferrocement panels is shown in figure 10. Hence ferrocement panel with 5% silica fume and 20%

fly ash reinforced with chicken mesh of volume fraction 2.823% and 3.77% had the higher

energy absorption capacity.


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Figure 2 :Load deflection plot for specimen without mortar modification

Figure 3:Load deflection plot for specimen with 5% silicafume and 10% fly ash

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 5 10 15 20 25

LoadinkN

Deflection in mm

LOAD VS DEFLECTION

layer 1

layer 2

layer 3

layer4

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 5 10 15 20 25

LoadinkN

Deflection in mm

LOAD VS DEFLECTION

layer 1

layer 2

layer 3

layer4


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0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 5 10 15 20

LoadinkN

Deflection in mm

LOAD VS DEFLECTION

layer 1

layer 2

layer 3

layer4

0

0.5

1

1.5

2

2.5

3

3.54

4.5

0 5 10 15 20

LoadinkN

Deflection in mm

LOAD VS DEFLECTION

layer 1layer 2layer 3layer4


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0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 5 10 15 20 25

LoadinkN

Deflection in mm

LOAD VS DEFLECTION


0

0.5

1

1.5

2

2.5

3

3.54

4.5

0 5 10 15 20 25

LoadinkN

Deflection in mm

LOAD VS DEFLECTION



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Figure 8:First crack load versus % replacement

Figure 9:Failure load versus % replacement

0

0.5

1

1.5

2

2.5

0 5SF10FA 5SF15FA 5SF20FA 5SF25FA 5SF30FA

FirstCrackLoadin

kN

% Replacement

First crack load vs % replacement

1 Layer2 Layer3 Layer4 Layer

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5


Failure

LoadinkN

% Replacement

FAILURE LOAD VERSUS % REPLACEMENT

1 Layer

2 Layer

3 Layer

4 Layer


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Figure 10:Toughness index versus % replacement

6. OPTIMUM RESULT

Based on the load carrying capacity, deflection and crack width, the partial replacement of

cement by 5SF20FA with volume fraction 2.823% and 3.77% is considered as optimum. The

above panels exhibit cracks that are possible to be easily identified by the naked eyes, with theresult that there is slow propagation.i.e progressive cracking behavior. However, brittle failure is

exhibited. The above behavior is clearly due to the contribution of silica fume and fly ash whichhas helped to bridge the cracks that have developed and prevent breaking of specimens.

7. CONCLUSION

Based on the experimental study conducted and the results presented herein, following

conclusions can be drawn.

Ferrocement panels with chicken mesh exhibit linear elastic behavior.(i.e. with respect toload vs deflection),up to the maximum load irrespective of the volume fraction of meshreinforcement used.

It has improved the workability of the mortar. An addition of super plasticizer improvesthe matrix penetration of the mesh system.

There is an increase in the load carrying capacity of the ferrocement panels with theincrease in the volume fraction of the mesh reinforcement.

Thus based on the load carrying capacity, deflection and crack width, the partialreplacement of cement by 5SF20FA with volume fraction 2.823% and 3.770% is

considered as optimum.

The above panels exhibit cracks that can be easily identified with the naked eye, with theresult that there is slow propagation.i.e progressive cracking behaviour. However brittle

0

1

2

3

4

5

6

7

8


ToughnessInde

x

% Replacement

1 LAYER 2 LAYER 3 LAYER 4 LAYER


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failure is exhibited. But the cracked specimen does not separate into various pieces

resulting in the reduction of the crack widths. The above behavior is clearly due to the

contribution of the silica fume and fly ash which has helped to bridge the developedcracks and prevent breaking of the specimens.

From the experimental results it was found that the cement replacement by 5% silicafume, 20% fly ash and incorporation of 0.6% super plasticizer can successfully producemixes of adequate early strength and increased long-term strength development coupledwith excellent flow characteristics. It can be effectively used for the rehabilitation of the

reinforced concrete structures particularly with the ferrocement composites.

8. REFERENCES

1. ACI Committee 549R (1997), State of the Art report on Ferrocement, Manual of concretepractice, ACI, Farmington Hills, Michigan ACI 549R-97.

2. Akkan MS, Mazlum F(1992), A comparative study of natural Pozzolanas used in blendedcement production,Proc fourth international conference on fly ash, silica fume, Slang and

Natural Pozzlanas in concrete,Istanbul, Turkey 1:471 94.

3. Babu KG, Rao GSN, Prakash PVS, (1993),Efficiency of pozzolanas in cementcomposites, concrete2000, published by E & FNSPON497 509

4. Cook DJ (1985), Calcined clay, shale and other soils, Cement replacement materials concrete technology and design, 3:40 70 Survey university press.

5. Ferrocement Model code, January (2001),Reported by International Ferro cement Society(IFS) committee 10, Published by Asian Institute of Technology, International Ferro cement

information centre, Bangkok, Thailand, 89.6. George J,XuZ,Danie F,Watt P,Hudec (1995),Effectiveness of mineral admixtures in

reducing ASK expansion, cement concrete Reseaech,6(25):1225-35.

7. Hariharan.A.R,Santhi.A.S,Mohan Ganesh.G(2011),Effect of ternary cementitious system oncompressive strength and resistance to chloride ion penetration,International J civil and

structural Engineering, (4)8. Jagannathan A,Sundarajan T,(2006),Flexural characteristics of ferrocement panels

reinforced with polymer mesh and polypropylene fibers.Proceedings of eigth Internationalsymposium and workshop on ferrocement and thin reinforced cement composites.06-

08,Bangkok.

9. Naaman, AE (2000), Ferro cement and laminated cementitious composites, Ann Arbor,Michigan, USA: Techno press.

10.Onet.T, Magureanu.C and Vescan.V (1992), Aspects concerning the behavior of Ferrocement in flexure, J ferrocement.22 :1-9

11.Paul B.K and Pama R.P,Ferrocement(1978) published by IFIC,IT,Bangkok,Thailand,149pp.12.Ruiz A(1965),Strength contribution of a Pozzolona to concretes, proc J Amer concrete

Inst 62:315- 24.13.Sasiekalaa K,Malathy R(2012),Behaviour of mortar containing silica fume and fly

ash,Journal of industrial pollution control,28:1-7.

14.M.D.A.Thomas,M.H.Shehata,S.G.Shashiprakash,D.S.Hopkins,K.Cail(1999),Use of ternarycementitious systems containing silica fume and fly ash in concrete,Cement and ConcreteResearch 29:1207-1214.

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