Title of Paper-Flexure Behaviour of Ferrocement Strengthened

RC beams

33RD NATIONAL CONVENTION OF CIVIL ENGINEERS,

AHMEDABAD

Author(s) Name-

1. Akshay Dhariwal (14BCL008), Civil Engineering department, Institute of Technology,

Nirma University, Ahmedabad, Gujarat

2. Prof. Sunil Raiyani, Civil Enginnering department, Institute of Technology, Nirma

University, Ahmedabad, Gujarat

Technical Session II

CONTENT

Introduction

Objectives

Literature Review

Experimental Programme

Results and Discussion

Conclusion

References

INTRODUCTION

ACI defines Ferrocement as "a type of thin wall reinforced concretecommonly constructed of hydraulic cement mortar, reinforced withclosely spaced layers of continuous and relatively small diametermesh"[1]

Used for construction of light-weight, hard and strong surfaces inany shapes

Used for retrofitting of structural members

Steel wire mesh induces higher tensile strength, crack resistance andhigh ductility

OBJECTIVES

To understand the behaviour of RC beams under transverse load

To find out the load carring capacity and cracking pattern of

ferrocement beams

To compare the experimental results of normal beams and ferrocement

beams

To compare the experimental results with non linear finite element

solution for the beams

LITERATURE REVIEW

The strengthening of reinforced concrete beam using Ferro-cementonto surface of beams has been done by Paramsivam et al. [2]

Bong and Ahmed [3] have investigated about short term behaviour ofFerro-cement beam and its advantages

Ebead et al. [4] examined the inexpensive strengthening techniquesfor partially loaded reinforced beams where it is not possible toremove entire live load effect

EXPERIMENTAL PROGRAMME

6 Beams are casted as doubly reinforced beam with dimensions

150×150×1300 mm

Reinforcement detailing is given in Fig. 1, Fig. 2 and Fig. 3

Figure 1 Longitudinal section and loading details

(a) BN2-16

(b) BN2-12-10 (c) BN2-10-12

Figure 2 Cross section for Normal beams- (a) (b) and (c)

(a) BF2-16

(b) BF2-10-12(c) BF2-12-10

Figure 3 Cross section for Ferrocement beams- (a) (b) and (c)

Concrete Mix design as per IS: 10262 – 2009[5]

Grade of concrete M25

Maximum nominal size of aggregate 20mm

Slump 75mm

Fine aggregate zone II

Exposure condition Moderate

Specific gravity of cement of OPC 53 grade 3.15

Specific gravity of coarse aggregate 2.69

Specific gravity of fine aggregate 2.7

Table 1 General design data

Material proportionCement 1

Fine aggregate 1.716Coarse aggregate 3.11

Water 0.5

Table 2 Mix proportions

Table 3 Cube Results

Table 4 Properties of wire mesh

Mesh

size(mm)

Wire

diameter(mm)

Yield

stress(MPa)

Ultimate stress

(MPa)

22.5 0.62 650 715

Cubes Compressive Strength at 28 days(MPa)

1 30.25

2 33.36

3 31.25

Average strength 31.62

Motar Mix-

The recommended range of mortar mix proportion for Ferro-

cement is 1:1.5 to 1:2.5 (cement: sand) by weight and water-

cement ratio is about 0.5[6]

In our case the mix proportion is taken as 1:2 (cement: sand)

and water is taken as 0.4

Figure 4 Casting of Ferrocement beams

The casting of beams is done in two stages

1. Normal beams

2. Ferro-cement beams

Instrumentation and Testing setup

Figure 6 Testing SetupFigure 5 Casting of Normal beams

RESULTS AND DISSCUSION

Behaviour of normal beams and ferrocement beams, under transverseloading, were compared with the help of results like central deflection,first crack load and ultimate load

At a regular interval of the load, central deflection of all beams aremeasured up to failure

For understanding the role of ferrocement in flexural strengthening,failure mechanism and failure pattern of all beams were observed

Experimental results are compared with analytical solution carried outwith help of ABAQUS Finite element software

Stress strain relation for concrete and steel derived by Belarbi andHsu[7,8] taken as an input material property to model the RCC beam

Comparison of load – central deflection behavior -

(a) Load – Deflection

behavior: Type of

tension reinforcement 2

– # 16 mm

(b) Load – Deflection

behavior: Type of tension

reinforcement 2 – #12 mm &

2 – #10mm (bottom)

(c) Load – Deflection

behavior: Type of tension

reinforcement 2 – #10 mm

& 2 – #12mm (bottom)

Figure 7 Load v/s Central deflection diagram

Cracking pattern of Ferrocement beam-

Figure 9 BF2-16 after failure Figure 8 BF2-12-10 after failure

Figure 10 Failure pattern for Normal beam and Ferrocement beam

The result of normal beams and ferrocement beams for ultimate loadand cracking load and corresponding deflection are summarized in theTable 5

Beam First crack

load(kN)

Deflection at

Cracking load

(mm)

Ultimate

load(kN)

Deflection at

ultimate

load(mm)

Failure

BN2-16 20 3.10 25.00 4.19 shear

BN2-12-10 20.65 3.40 32.29 6.80 Flexure

BN2-10-12 20.45 3.08 32.81 6.91 Flexure

BF2-16 24.79 3.80 27.55 4.40 1st Crack was

observed in

Ferrocement mould

BF2-12-10 25.00 3.54 33.06 6.36

BF2-10-12 24.50 3.33 35.81 7.10

Table 5 Crack and ultimate load and corresponding deflection

Ductility factor had been found in order to validate the strengtheningeffect of ferrocement mould

The flexural ductility factor defined by

Here,

= ultimate curvature and

= yield curvature

This factor indirectly represent the amount of energy a member canstore during plastic deformations and as such represents the ductility orenergy absorbing capacity of the member [9]

If yield curvature is not distinct properly then by regression analysisderived formula can use to evaluate the ductility factor [9]

u

y

u

y

(1)

0.45 1.25 1.1 310.7( ) [( ) / ] [1 95.2( ) ( ) ]

cck t c bo ck

t

f f (2)

In present case for all the beams the compression steel ratio is smaller than

one quarter of the tension steel ratio. So, last is very close to 1.0

(3) In conventional design the tension steel ratio in reinforced concrete beam

section to not more than 75% of the balanced steel ratio

0.45 1.2510.7( ) [( ) / ]ck t c bof

Total length of Chicken wire mesh (mm) Total no of wires Total area

(mm2)

= 130 (bottom width) + 2×70 (height up to

Neutral axis for tension region on both side) =

270

=12 Nos.

= 12×0.302

= 3.624270

22.5(size)

Table 6 Area of chicken wire mesh in tension

Properties of all tested specimen like dimensions, area of steel and ductility factorare summarized in Table 7 and The ductility factor for the each beam calculated asdefined in above eqution

Beam Cross

Section

(mm2) (MPa)

Area of tensile

reinforcement

(mm2)

Area of

compression

reinforcement

(mm2)

Area of

Chicken

wire mesh

Ductility

factor

(calculated

as per Eq. 3)

BN2-16

31.62

402.12

100.53

- 4.64

BN2-12-10 383.27 - 4.74

BN2-10-12 383.27 - 4.74

BF2-16 402.12 3.624 5.34

BF2-12-10 383.27 3.624 5.47

BF2-10-12 383.27 3.624 5.47

ckf

150 150

Table 7 Ductility factor for all tested beams

CONCLUSION

1. The load – deflection curve of the tested beams shows increase in ultimate

as well as cracking load and deflection

2. The first crack load in the case of ferrocement beam is nearly 25 % higher

compare with normal beam. Initial cracks are observed in Ferrocement

mould and propagate into RCC part of the beam

3. The difference between cracking load and ultimate load is merely 10%. It

may be due to debonding of ferrocement mould was observe after first

crack. It is recommended to provide the tie connector or shear connector

between RCC beam and Ferrocement mould

4. Ductility of all the strengthened beams are higher compare with normal

beams

5. The behavior of ferrocement strengthened RC beam in flexural is predicted

by FE analysis using ABAQUS Software and compared the results with

experimental results. Its shows in good agreement

REFERENCES1. ACI Committee 549 report (1993), “Guide for Design, Construction and

Repair of ferrocement”,ACI 549.1 R-93

2. Paramasivam, P., Lim, C.T.E. and Ong, K. C. G., (1998), “Strengthening

of RC Beams with ferrocement Laminates”, Cement and Concrete

Composites, 20:1, 53 – 65

3. Bong, J.H.L and Ahmed, (2010), “Study the Structural Behaviour of

ferrocement Beam”, UNIMAS e-Journal of Civil Engineering, 1:2

4. Ebead, U. (2015), “Inexpensive Strengthening Technique for Partially

Loaded Reinforced Concrete Beams”, Journal of Materials in Civil

Engineering, 27:10

5. IS 10262:2009, “Indian standard for Concrete mix proportioning”

Bureau of Indian standard

6. Makki, R. F. (2014), “Response of Reinforced Concrete Beams

Retrofitted by ferrocement”, International Journal of Scientific and

Technology research, 3:9, 27 – 34

7. Belarbi, A. and Hsu, T.T.C., (1994) “Constitutive laws of concrete in

tension and reinforcing bars stiffened by concrete”, ACI Structural

Journal, 91:4, 465 – 474.6

8. Belarbi, A. and Hsu, T.T.C., (1995) “Constitutive laws of softened

concrete in biaxial tension – compression”, ACI Structural Journal,

92:5, 562 – 573

9. Kwan, A.K.H, Ho, J.C.M and Pam, H.J. (2002), “Flexural strength and

ductility of reinforced concrete beams”, Proceedings of the Institution

of Civil Engineers Structures & Building, 152:4, 361 - 369

THANK YOU