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