flexural behaviour of reinforced concrete beam …

www.tjprc.org SCOPUS Indexed Journal [email protected]

FLEXURAL BEHAVIOUR OF REINFORCED CONCRETE BEAM USING BASALT

FIBER

P. MANIBALAN1, R. BASKAR2& N. PANNIRSELVAM3

1Research Scholar, Department of Structural Engineering, Annamalai University, Tamilnadu, India

2Professor, Department of Structural Engineering, Annamalai University, Tamilnadu, India

3Associate Professor, Department of Civil Engineering, SRM Institute of Science and Technology, Tamilnadu, India

Highlights

The eco-friendly fiber called the basalt fiber is chosen for the research to enhance the flexure behaviour of

concrete.

The optimum percentage of 0.9% basalt fiber is added and the flexure results Load-Deflection, Moment-

Curvature, ductility and stiffness are discussed.

The test results proved that the basalt fiber plays an effective role in enhancing the flexure behaviour of

concrete beam specimen.

ABSTRACT

The use of basalt fiber in the concrete structure is a recent research due to its high tensile strength, high modulus, strain

to failure, fire resistance, impact load resistance, good resistance to chemical attack and non-toxic. In this paper, the

effectiveness of basalt fiber in the flexural strength of concrete beam is experimentally investigated. The basalt fiber is

added at the volume fraction of 0.9% in the beam which is the optimum percentage of fiber from its mechanical proper-

ties. The flexural response of basalt fiber reinforced concrete beam and control concrete beam are analyzed by static

loading test. This paper compares the flexural behaviour of BFRC and controlled concrete beam by using the result of

Load Deflection, Moment Curvature relationship, stiffness, flexural rigidity and its ductility factor. The number of shear

cracks and flexural cracks are observed which shows the effective bridging action of basalt fiber of the tested beam. The

dispersion and bonding behaviour of basalt fiber in the concrete matrix are confirmed by its SEM image. According to

the experimental research, basalt fiber beams proved its effective flexural properties such as load carrying capacity, mo-

ment curvature, ductility, stiffness, flexural rigidity and crack resistance compared to controlled beams.

KEYWORDS: Basalt, optimum, Load-deflection, Moment-curvature, Stiffness & Resistance

Received: Jun 08, 2020; Accepted: Jun 28, 2020; Published: Oct 13, 2020; Paper Id.: IJMPERDJUN20201522

1. INTRODUCTION

Concrete is a composite material made primarily with aggregate, cement and water. There are many formulation of

concrete, which provide varied properties and concrete is the most used man-made product in the world. Concrete

can be formulated with high compressive strength but always has lower tensile strength. Fiber reinforced concrete

is one of the recent researches, to increase the tensile strength of concrete.[1] Presently, several organic and inor-

ganic fiber are available in the market, but many of them either lack structural strength or durability are extremely

costly for use in moderate loadings.

Orig

inal A

rticle International Journal of Mechanical and Production

Engineering Research and Development (IJMPERD)

ISSN(P): 2249–6890; ISSN(E): 2249–8001

Vol. 10, Issue 3, Jun 2020, 16055-16064

© TJPRC Pvt. Ltd.

16056 P.Manibalan, R.Baskar & N.Pannirselvam

Impact Factor (JCC): 8.8746 SCOPUS Indexed Journal NAAS Rating: 3.11

Basalt fiber is one of the inorganic and natural fiber with high modulus, thermal resistance, salt and alkali re-

sistance, high strength, eco-friendly and inexpensive.[2] Basalt fiber is obtained after extrusion from basalt based molten

igneous volcanic rock, which is found in flowing lava. Basalt rock having silica content more than 46% are suitable for

fiber production. The extrusion process of basalt fiber popularity as a potential competitor in concrete reinforcing applica-

tion due to its excellent mechanical properties and environment friendly manufacturing process.[3] Applicability of basalt

fiber as a strengthening for concrete structural materials has been studied for durability, mechanical and flexural properties.

The understanding of fracture mechanism of RC structure is vital and under this study it’s focussing the crack and

deflection behaviour for RC beam under static loading. However, basalt fiber rod has many advantages; it is good alterna-

tive for steel due to its low modulus of elasticity.[4] Glass fiber and carbon fiber rod are having low modulus of elasticity

compared with basalt fiber rod. So the addition of fiber in volume has greatly influence the flexural behaviour of concrete.

[5] Although, many researches has been conducted to investigate the flexural behaviour of fiber reinforced concrete, basalt

fiber has some unique properties to enhance it.[6] This paper presents an experimental study of deflection, moment-

curvature and stress-strain relationship of basalt fiber reinforced concrete compared with controlled concrete. Based on the

experimental result of this paper and collected literature, basalt fiber concrete has significant improvement load-deflection

and moment-curvature than the controlled concrete.

2. EXPERIMENTAL PROGRAM

2.1 Material and its Property

The material used in the concrete mixes are ordinary Portland cement, river sand, crushed aggregate, super-plasticizing

admixture and basalt fiber. OPC 53 grade cement is tested as per the Indian standard specification BIS 12269 – 1987. Fine

aggregate is river sand conforming to zone II of BIS: 383 – 1970 having specific gravity of 2.72 and fineness modulus of

2.74. Coarse aggregates of size 20mm having specific gravity of 2.79 and fineness modulus of 6.15. Water reducing agent

based on the salt of polymetric naphthalene sulphonate is used as a chemical admixture. The dosage of super plasticizer is

vary to obtain the desired level of workability in the concrete. The mix proportions are kept constant for target mean

strength of 48MPaand 0.40 as W/C ratio. Basalt fibers are multifilament type with 6mm length and 0.05mm diameter.

2.2 Specimen Design

This study consists of three basalt fiber reinforced concrete beam and three control concrete beam specimens. The beam

mould of size 150mm wide, 250mm deep and 3200mm long is made up of with wood to cast the concrete that has target

strength of 48 MPa. Concrete are mixed in a mixer machine for uniformity to cast the beam specimens and the Figure 1

illustrated the casting of beam specimen.

Flexural Behaviour of Reinforced Concrete Beam using Basalt Fiber 16057


a) Wooden Mould

b) Reinforcement Cage

c) Placing and Leveling of

Concrete

Figure 1: Casting Process

The beam specimen is divided into two phases, namely phase I and phase II. Three beams are built and tested in

each phase. The first phase is plain concrete without any fibers, the second is beams reinforcing with basalt fiber of 0.9%

in the volume of concrete. A 20mm concrete cover is used in the beams. The beams are designed to fail by yielding of

steel. This is accomplished by using reinforcement ratio lesser than the balance reinforcement ratio. Fe-500 steel is used for

longitudinal reinforcement and stirrups. The controlled concrete beams are called CB1, CB2 and CB3, while beams with

basalt fiber are BF1, BF2 and BF3. After casting al beams are cured at normal temperature in a water bath for 28 days.

2.3 Test Setup and Protocol

Test of six simply supported beams subjected to four – point bending are carried out as per ASTM D6272 standards in the

laboratory of Annamalai University. The beam spanning 3200mm are subjected to flexural testing and its loading span of

1000mm. Schematic arrangement of test setup and loading configuration are shown in figure 2. Three dial gauge are fixed,

one at mid-span and two are at loading point to monitor the mid span deflection and curvature of the beam. The beams are

statically tested for failure at 2.5kN increment of load by means of hydraulic jack and it is measured with load cell. At

cracking and at the end of each 2.5kN load, cracks are sketched and a near mid-span crack width is measured using a mi-

croscope.

Figure 2: Experimental Test Setup



3. ANALYSIS OF TEST PROTOCOL

3.1 Crack Pattern

Cracking pattern of control beams and basalt fiber beams are shown in figure 3 and 4 respectively. During loading, vertical

cracks in the flexural span are propagated towards the compression face as the load increased. Cracks are formed similar to

the flexural cracks at the outside of bending zone. Further loading, shear stress are formed and induced the shear cracks.

Shear cracks began from the bottom face of the beam and diagonally propagated up towards the top support. It is clearly

shown that the number of flexural cracks is higher in the normal concrete than the basalt fiber concrete. This crack pattern

proved that the basalt fiber is active in arresting the cracks. It is mainly contributed by bonding behaviour between concrete

complex and basalt fiber.[7]

Figure 3: Crack pattern for CC Beam

Figure 4: Crack pattern for BF Beam

Scanning electron microscope provides a valuable information about the cause of deterioration in concrete due to

cracks.[8,9] In order to study the effect of basalt fiber in the microstructure of concrete, fractured surface of basalt fiber con-

crete at the age of 30 days are investigated by scanning electron microscope. SEM images as shown in Figure 5 reveals that

the perfect scattering of basalt fiber in concrete. It also showed that the boning behaviour of cement matrix and basalt fiber.

The major crack formation are reduced by the basalt fiber in the concrete and it is proved by the SEM images.



Figure 5: SEM Image

3.2 Load – Deflection

The load – deflection behaviour of six beams are traced experimentally as shown in following figure 6. Table 1 presents

the maximum mid-span deflection of the tested beam. A distinct difference in the shape of load deflection plots at post

cracking load. Both basalt fiber and normal concrete beam are similar in pre-cracking load – deflection behaviour. The

ultimate load – Carrying capacity of the beams are noted.

Table 1: Load – Deflection for the Beam Specimens

Specimen Id

First Crack Stage Ultimate Stage

Load

(Kn) Deflection (Mm)

Load

(Kn)

Deflection

(Mm)

CB 1 15.00 1.45 52.50 16.80

CB 2 15.00 2.03 50.00 17.40

CB 3 17.50 1.17 52.50 16.42

BF 1 20.00 3.22 62.50 19.98

BF 2 20.00 3.29 62.50 20.84

BF 3 17.50 2.80 65.00 20.78

Table 1 shows the increase in ultimate load value for basalt fiber beam than the normal concrete beam. BF1 beam,

which is added with the basalt fiber, first cracked at 20kN and the ultimate load at 62.5kN. The maximum deflection of

BF1 beam is 19.98mm. CB1, which is control concrete beam, first cracked at 15kN And the ultimate load at 52.5kN. The

maximum deflection of CB1 beam is 16.8mm. BF2 beam shows the increase in ultimate load and deflection as 4.12% and

19.77% % than CB2 beam. BF3 beam shows the increase in ultimate load and deflection as 23% and 26.55% than CB3

beam.



Figure 6: Load - Deflection Plot

As we observed from load deflection curve that all the basalt fiber beam has initial stiffness similar to control

concrete beam. After cracking, the stiffness increased for all the basalt fiber beam than the normal concrete beam

3.3 Moment – Curvature

In this study, a parametric analysis of moment – curvature relation on controlled and basalt fiber reinforced beams at first

crack load level and ultimate load level are taken into consideration. The moment – curvature values for the beams under

consideration is tabulated in table at two specified load levels. Loads were applied continuously and their corresponding

strain gauge readings were recorded until complete failure of the beam occurred. The moment – curvature behaviour of the

controlled and BF beams with different proportions of BF were illustrated in Table 2.

Table 2: Moment – Curvature for the Beam Specimens

Specimen Id First Crack Stage Ultimate Stage

Moment

(Kn.M)

Curvature

(X106/M)

Moment

(Kn.M)

Curvature

(X106/M)

CB 1 7.50 0.244 26.25 2.102

CB 2 7.50 0.209 25.00 2.018

CB 3 8.75 0.200 26.25 2.053

BF 1 10.00 0.431 31.25 2.129

BF 2 10.00 0.391 31.25 2.116

BF 3 8.75 0.289 32.50 2.204

Figure 7 shows the variation in moment-curvature behaviour on controlled and the basalt fiber concrete.



Figure 7: Moment - Curvature Plot

It is observed that, initially all the BF beams behave in a similar way as that of the controlled beam before the

steel yields. When the reinforcing steel reaches its limiting state, it undergoes plastic deformation thereby increasing the

curvature of the beam. The curvature of BF1, BF2, BF3, fiber reinforced concrete decreased by 1.28%, 4.86%, 7.36% that

of CB1, CB2, CB3 controlled concrete. Also, the moment carrying capacity of the BF1, BF2, BF3 fiber reinforced concrete

has been increased by 19.04%, 25%, 23.81% CB1, CB2, CB3 compared to controlled beam. This clearly indicates the ad-

vantage of using BF in upgrading the RC beams.

3.4 Ductility

Ductility is the ability of the material to undergo large deformation without rupture before the failure of material. Accord-

ing to Committee Euro-International Du Beton, 1996, the ductility factor is defined by the ratio between ultimate deflec-

tions to yield deflection.[10] The yield deflection is measured from the assumed bilinear of load-deflection curve of a spec-

imen. i.e, it is the lateral displacement at 80% of ultimate load at the ascending part of the curve while the maximum de-

flection is lateral displacement at 80% of ultimate load at the descending part of the curve as shown in the Figure 8.

Figure 8: Ductility Curve

The ductility factor can be formulated as,

https://www.sciencedirect.com/topics/engineering/lateral-displacement



Ductility Factor = Ultimate Deflection / Yield Deflection

Ductility of concrete structure also represents the energy absorption capacity of the beam. The energy absorbed is equal to

the area under the load defection curve. The energy ductility of the tested beams is calculated by finding the ratio of energy

at ultimate load to energy at yield load.

Table 3: Ductility Factor for the Beam Specimens

Specimen ID Ultimate Deflection (mm) Yield Deflection (mm) Ductility Factor

CB 1 16.80 12.36 1.36

CB 2 17.40 12.67 1.37

CB 3 16.42 12.26 1.34

BF 1 19.98 14.72 1.36

BF 2 20.84 14.9 1.40

BF 3 20.78 15.28 1.36

Table 3 shows the ductility factor for both the controlled and the basalt beams. The ductility factor for basalt fiber

reinforced concrete beam has an average of 1.37 and that is 0.74% greater than the controlled concrete beam. This indi-

cates that, on addition of basalt fiber, the deflection of the beam increases thereby increasing its ductility.

3.5 Flexural Rigidity

Flexural rigidity is the resistance offered by a beam while under loading. The deflection of beam is mainly affected by the

magnitude of loading, type of loading, span of beam, beam type, material properties (E) and moment of inertia (I). If the

deflection in a beam is beyond the permissible limit, there will be a loss of rigidity causing undesired deflection and slopes

and also the smooth operation of a flexural member becomes impossible. By using the relationship between curvature and

bending moment, the deflection equation for a simply supported beam under two point load is given below,

∆ = 𝑃𝑎

24𝐸𝐼 (3𝐿2 − 4𝑎2)

The above equation is used to calculate the flexural rigidity by substituting the experimental values of ultimate deflection

and ultimate load.

Table 4: Flexural Rigidity for the Beam Specimens

Specimen ID Ultimate Load

(kN) Maximum Deflection (m)

Flexural Rigidity EI

(kN m2)

CB 1 52.5 16.8 2994.79

CB 2 50 17.4 2753.83

CB 3 52.5 16.42 3064.10

BF 1 62.5 19.98 2997.79

BF 2 62.5 20.84 2874.08

BF 3 65 20.78 2997.67

Table 4 showed the flexural rigidity of basalt fiber beam reached as a high value while compared with other beam

specimen. Basalt fiber beam have an average flexural rigidity value as 2956.51kNm2 which is 0.64% higher than the con-

trol beam. The results showed that the addition of basalt fiber is enhanced the flexural rigidity by arresting the propagation

of micro cracks in the beam.



4. CONCLUSIONS

The flexural behaviour of controlled concrete beam and fiber reinforced concrete beam has been analysed in this paper.

The crack pattern, load carrying capacity, mid-span deflection, moment and curvature were predicted experimentally. The

following are the conclusions drawn from the above results:

Incorporating basalt fiber on to the concrete will arrest the crack than the controlled concrete shown by its crack

pattern.

The first cracking load for basalt fiber concrete beams is 21.27% higher than the control concrete beam. Hence,

this study proved the contribution of BF in cracking zone.

The measured strain for BF beams was less than those of controlled beams under the same load.

The addition of BF showed the higher ultimate load carrying capacity of tested beams than the control concrete

beam. Moreover, the deflection at ultimate load for BF beam is higher than the control concrete beam.

Addition of BF in RC beam leads to increase in its flexural strength compared with control concrete beam and its

load carrying capacity prolonged by 15.39% than controlled beam.

The calculated flexural moment and curvature has been increased and decreased by 22.61% and 4.5% respectively

under the influence of basalt fiber.

The deflection of beam increases thereby increasing its ductility by the addition of basalt fiber.

The inclusion of basalt fibers increases the flexural rigidity by arresting the cracks.

By considering the above result, flexural properties for basalt fiber concrete beam is higher than the controlled

concrete beam.

REFERENCES

1. American Concrete Institute Committee 544, State of Art report on fiber reinforced concrete – ACI manual of concrete prac-

tices, Vol.5 (ACI 544.12-86), Detroit, 1987

2. V. Dhand, G. Mittal, K.Y. Rhee, S.J.Park, D. Hui , A short review on basalt fiber reinforced polymer composites, Composite

Part B Engineering 73 (2015), 166-180

3. Cory High, Hatem M. Seliem, Adel El-safty, Sami H. Rizkalla, Use of basalt fibers for concrete structure, Construction and

Building Materials 96 (2015), 37-46

4. J. Sim, C. Park, Characteristic of basalt fiber as a strengthening material for concrete structures, Compos. Part B Eng. 36 (6)

(2005), 604-512

5. T. Deak, T. Czigany, Chemical composition and mechanical properties of basalt and glass fibers: A comparision,

Text.Res.J.79 (7) (2009), 645-651

6. Kan. Z.B, Li. Y. R, Analysis of mechanical and durability of basalt fiber reinforced concrete, Advanced material research,

Vol.598 (2012), PP:627-630

7. Huatiay Lice, Junzhi Zhanj, Zhaagii Fu, Shengbing Zhou, Experiment on chopped basalt fiber, J. Concrete, 1(2011), 14-15 (In

Chinese)



8. F. Sarasini, J, Tinillo, L. Kerrante, M. Valente, L. Lampani, P. Gaudinzi, S. Cioffi, S. Larnace, L. Sorrentino, Drop- weight

impact behaviour of woven hybrid basalt- carbon lepoxy composites, Composite Part B Engineering, 159 (2014), 204-220

9. X. Wary, B. Wu, Y. Fey, F.Liay, J. Mo. J. Xioy, Y. Qiu, Low velocity impact properties of 3D noven basalt/aramid hybrid com-

posites, Compos. Sci, tech, 68 (2) (2008), 444-450

10. Wenjun Qu, Xiaoliany Zhany and Haiaun Huay, Flexural behaviour of concrete beams reinforced with hybrid bar, J. Compos.

Construction, 13 (5) (2009), 350-359

flexural behaviour of reinforced concrete beam …

Documents