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Experimental evaluation of bamboo reinforced concrete beams
Journal Pre-proof Experimental evaluation of bamboo reinforced concrete beams Pankaj R. Mali, Debarati Datta PII:
S2352-7102(19)30347-X
DOI:
https://doi.org/10.1016/j.jobe.2019.101071
Reference:
JOBE 101071
To appear in:
Journal of Building Engineering
Received Date: 2 March 2019 Revised Date:
14 November 2019
Accepted Date: 14 November 2019
Please cite this article as: P.R. Mali, D. Datta, Experimental evaluation of bamboo reinforced concrete beams, Journal of Building Engineering (2019), doi: https://doi.org/10.1016/j.jobe.2019.101071. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.
1
Experimental Evaluation of Bamboo Reinforced Concrete Beams
2
Pankaj R. Mali a, Debarati Datta b a
3 4 5 6
b
Research Scholar, Department of Applied Mechanics, Visvesvaraya National Institute of Technology, Nagpur440010, India. Email- [email protected]
Assistant Professor, Department of Applied Mechanics, Visvesvaraya National Institute of Technology, Nagpur440010, India. Email- [email protected]
7 8
Abstract
9
The paper presents the experimental study on flexural behaviour of concrete beams
10
reinforced with “bamboo strips”. Total 30 beam specimens were tested under four point
11
bending test (pure bending). Three different types of concrete beams were investigated
12
experimentally. They were concrete beams reinforced with bamboo strips, concrete beams
13
reinforced with conventional steel and concrete beams with no reinforcement. The flexural
14
behaviour of these beams was studied through linear stiffness, ultimate load, energy
15
absorption capacity, shear strength and flexural strength.
16
There are two types of BRC (Bamboo reinforced concrete) beams having both longitudinal as
17
well as shear reinforcement (stirrups) in the form of bamboo strips. First is with 2.8% and
18
second with 3.8% longitudinal bamboo reinforcement with respect to the beam cross section.
19
Analysis and comparison of different performance parameters against RCC (steel reinforced
20
cement concrete) as well as PCC (plain cement concrete) beams is carried out. It is observed
21
that both types of BRC beams have shown significantly higher shear as well as flexural
22
strength than PCC beams.
23
However, BRC beams with 2.8% bamboo reinforcement shown less shear and flexural
24
capacity compared to that of RCC beams. The effect of additional 1% bamboo reinforcement
25
on shear as well as flexural strength can be clearly observed in second type of BRC beam.
26
Failure mode observed in both type of BRC beams were different from that of PCC and RCC
27
beams.
28
Keywords: Bamboo reinforced concrete, Flexural behaviour, Reinforced concrete, Bond
29
strength, Semi rectangular groove, Surface treatment.
30
HIGHLIGHTS:
31 • Bond strength enhancement through mechanical action in treated grooved bamboo samples. 32 • Application of newly developed bamboo reinforcement in RC beam specimens. 33 • Effect of bamboo reinforcement percentage on enhancing shear and flexural strength. 1
1
1 Introduction
2
In the present scenario majority of housing and infrastructure projects are built using
3
conventional material i.e. steel and concrete and it has increased in the past two decades.
4
These requirements of conventional construction material has increased manifold. The
5
production of such material like steel and cement causes enormous destruction to the natural
6
atmosphere due to release of CO2 (Approximately 1.83 tonne of CO2 is emitted per tonne of
7
steel produced) and other hazardous fluids. This is one of the major drawbacks of
8
conventional construction material.
9
The research for an alternative material has been there since 1960. Many naturally available
10
fibres have been used along with concrete. The purpose of such materials is to enhance the
11
mechanical properties of the plain concrete. One such naturally available material is bamboo.
12
Bamboo is known to be fast growing, renewable, sustainable, ecofriendly material. During
13
the growth of bamboo, it actually consumes 1-tonne of CO2 per bamboo culm from the
14
surrounding atmosphere. Bamboo is one of the most widely available materials in the tropical
15
regions where most of the developing countries are located. [1-3].
16
The geometry of the typical bamboo culm consists of hollow circular cross section with
17
diaphragms/nodes along the culm height. The wall thickness intermodal distance, diameter
18
and fiber density vary from bottom to top end. Due to the fibrous (along the grain) structure
19
of the culm, the bamboo strip possesses high tensile strength. Compared to conventional
20
reinforcing steel bamboo possesses high strength to weight ratio (about six times higher). A
21
bamboo culm attains its optimum strength around three to four years of age and it matures
22
completely by fifth year. Due to the dense fibrous structure, it can sustain tension as well as
23
compression loading unlike any other natural material, which can only take tension.
24
However, bamboo being organic natural material, durability of the bamboo in a concrete
25
composite possesses limitations on its use. The use of bamboo in the form of full culm or as
26
strips inside the concrete mainly depends on bamboo concrete bond strength. The bonding
27
between bamboo and concrete is majorly influenced by friction between concrete and
28
bamboo surface, adhesion of coating substance attached to exterior bamboo surface and
29
mechanical interlock. Investigations on improving each of these factors have been done by
30
many researchers in last few decades. These treatment procedures are aimed at increasing
31
bamboo concrete bond strength. This includes use of various adhesives on bamboo surface to
32
make the exterior surface water repellant. Wrapping of thin steel wire, use of sand particles 2
1
through sand blasting process at bamboo concrete interface. The modifications in bamboo
2
strip profile using corrugations to incorporate mechanical interlock. [4].
3
The efficacy and performance of such treated bamboo reinforcement in flexural concrete
4
members is investigated further, Experimental investigations carried on such type of BRC
5
members are listed in Table 1.
6
Table 1 Summary of investigations on BRC beams Author
Kankam and OdumEwuakye (2000) [5].
Ghavami (2000) [6].
Ghavami (2005) [7].
Kumar and Prasad (2003) [8]
Bamboo Species and treatment
Beam details (Lxbxd)
Type of test and Response parameters
Babadua bamboo strips. Treated with
100 x 180 x 1500 mm and 135 x 235 x 1800 mm. with varying span to depth ratio and percentage of bamboo reinforcement
3 point bending test, and cyclic loading
Dendrocalamus 300 x 120 x 3000, 2500 giganteous, mm with varying span Treated with The to depth ratio and Nigrolin and percentage of bamboo sand wire reinforcement. treatment 300 x 120 x 3400 mm Dendrocalamus with varying span to giganteous, depth ratio and Treated with The percentage of bamboo Sikadur 32-Gel reinforcement. Loacally available bamboo treated 125 mm x 150 mm x with anti-termite 1000 mm with and then conventional concrete protective and blended concrete. coating (TOP COAT)
Terai and Minami (2011) [9]
Black bamboo and Japanese Timber bamboo.
125 mm x 250 mm x 1500 mm with conventional concrete and blended concrete.
Agarwal et. al. (2014) [10]
Used Muli bamboo strips treated with Sikadur-32 gel to
150 mm x 75 mm x 1000 mm.
Results/ Remark Factor of safety of 1.5 against Cracking and 6.4 against collapse.
3 point bending test, ultimate load, crack initiation and propagation
Bond strength increased by 90%, Ultimate load increased by 400%
4 point bending test, ultimate load, crack initiation and propagation
Bond strength increased by 100%, Flexural strength increased by 400%
3 point bending test, first-crack load and the experimental failure load
Performance of BRC beams with regular concrete and blended concrete is found same
3 point bending test, Longitudinal bar, type of stirrups, spacing of stirrups and shear span to depth ratio. Four point bending test. Failure load, Energy
Fracture behaviour of BRC beams can be evaluated by existing formula of RC beam. Failure load and energy absorption capacity of BRC beams found higher 3
1
prepare BRC absorption. than PCC and RCC beams. beams. L= Total length of beam in mm; b = width of beam in mm; d = depth of beam in mm.
2
Pacheo-Torgal and Jalal [11] reported that use of long fibres of a bamboo culm in structural
3
concrete resulted in high durability. However, mechanical behaviour of bamboo culms still
4
needs detailed investigation.
5
Apart from the above investigations, many other researchers have carried out experimentation
6
on BRC beams to improve its performance. These studies mainly include use of different
7
stirrup materials (bamboo, steel etc.) along with main bamboo reinforcement, variation in
8
spacing of stirrups, and their position with respect to longitudinal reinforcement. Similarly,
9
variation had been made in percentage of main longitudinal reinforcement, type of surface
10
treatment, which has a significant impact on shear as well as flexural strength of these BRC
11
beams. Instead of full bamboo culm or split bamboo, bamboo fibers/pulp in different forms
12
have also been used in concrete at different dosages to improve properties of unreinforced
13
concrete.
14
The effect of corrugations on bamboo surface to enhance bond strength is also studied. The
15
effect of modification in the basic composition of concrete, use of AAC (Aerated autoclaved
16
concrete) blocks placed at tensile zone of BRC beams and its effect at service and ultimate
17
failure is also explored. The study has also been made to understand the stress block
18
parameters of BRC beams with certain assumptions, and the conventional beam theory
19
moment equations of design codes were used to arrive at optimal bamboo reinforcement
20
ratio, stirrup material its spacing etc. [12-16].
21
Mali and Datta [17] investigated bamboo concrete bond behaviour experimentally using pull
22
out tests. Series of pullout tests were conducted on bamboo strips embedded in concrete
23
cylinder. A newly developed grooved bamboo profile was found to enhance the bond strength
24
significantly compared to the conventional plain bamboo strip profile. Among various
25
chemical adhesives (used as a sealant material in surface treatment), explored Bond Tite
26
adhesive along with steel wire wrapping and sand blasting treatment was found most
27
effective surface treatment.
28
Although many publications are available on the technique of using bamboo as main
29
longitudinal reinforcement in concrete beams with respect to behaviour and efficacy,
30
however, it is difficult to predict the performance of BRC beams, since the properties of
31
bamboo vary regionally. Also bamboo concrete bond behaviour has remained a serious issue 4
1
for long. The current research work is aimed at enhancing the bamboo concrete interaction by
2
using surface treatment and incorporating mechanical interlock and then applying this treated
3
and grooved bamboo reinforcement in concrete beams.
4
Although studies have been carried out to understand flexural behaviour of BRC beams, it is
5
limited in number. Most of the research work is pertaining to improving durability of BRC
6
members. Moreover, the research focuses on standardizing the properties and design
7
guidelines available for bamboo.
8
At this point of time, it is difficult to predict the flexural behaviour of BRC beams.
9
Experimental tests were conducted to study the realistic structural performance of B.
10
arundinacea bamboo strips. The design of steel reinforced cement concrete (RCC) as well as
11
BRC beam was done for equal moment capacity, to get the undereinforced section. All
12
concrete beams were subjected to four point bending test. The test results of each BRC beams
13
were compared with the reference PCC and RCC beams.
14
The effect of bamboo (longitudinal) reinforcement percentage, with fixed shear span to depth
15
ratio on the flexural performance was investigated. The load–displacement curves along with
16
failure modes of each beam under flexural loading were studied in detail.
17
2 Experimental Programme
18
The experimentation was carried out in the following steps-
19
•
Characteristics of Bamboo Reinforcement
20
•
Developing Grooved Bamboo profile and its Surface Treatment
21
•
Casting of BRC beams
22
•
Testing Methodology
23
2.1
Characteristics of Bamboo Reinforcement
24
The bamboo species used throughout the study was B. arundinacea (Katang). This species is
25
popularly known for its promising mechanical and physical properties and most widely
26
available in the subcontinent region. Katang is the regional name used for B. arundinacea and
27
its use for construction purposes is cited in National Building code of India (NBC) [18].
28
Before splitting the full bamboo culm into strips, raw bamboo culms were cleaned manually
29
in order to remove any natural dirt and foreign substances. These cleaned bamboo culms
30
were then soaked in 6 % boric acid solution for 72 hrs to prevent the attack of termites and
31
insects. Bamboo Culms were then allowed to dry under moderate (350c) temperature for 5
5
1
days. The moisture content and density of these culms was found to be 25% and 1125 kg/m3
2
[19-21]. The cleaned and air-dried bamboo culms were then converted into strips of uniform
3
thickness and rectangular cross section. IS: 6874 [22] and ISO 22157 [23] have given
4
guidelines to determine the important physical and mechanical properties. Each mechanical
5
property of the selected bamboo specimens were determined in accordance with IS: 6874
6
(2008). The average value of each mechanical property is mentioned in Table 2.
7
Table 2 Mechanical properties of B. arundinacea S.N. 1 2 3 4
8 9
2.2
Type of test Tension Compression Static bending Shear (along grain)
Parameter Modulus of elasticity (MPa) Stress at peak (MPa) Peak displacement (mm) Compressive strength (MPa) Flexural strength (MPa) Shear strength (MPa)
B. Arundinacea 5500 150 2.71 65.10 90.42 7.20
Developing Grooved Bamboo profile and its Surface Treatment
10
The bamboo strips to be used as replacement to conventional steel reinforcement were
11
developed such that adequate bond strength is established at the bamboo concrete interface.
12
The geometry of the bamboo strip used is flat along its length with a substantially rectangular
13
cross section (20 mm x 10 mm), as shown in Fig. 1a and 1b.
14
The parameters like groove shape, size, its spacing, and amount of embedded length were
15
decided based on the results of trial pull out tests. Three types of groove shapes V-notch,
16
rectangular and semicircular were tried before arriving at the most effective shape. Three
17
embedded lengths of 50, 75 and 100% of cylinder height and three different groove size to its
18
spacing ratios (a: S) equal to 1:1, 1:2, 1:3 were tested.
19
From observations, semicircular shape groove pattern with 50% embedded length and a: S
20
ratio of 1:1 was found most effective in enhancing bond strength through mechanical
21
interlock. a
b
L
S
a/2
b
a=10 mm L
6
(a)
(b) Fig. 1. (a), (b) Plain rectangular Bamboo strip reinforcement Specimen
(a)
(b) Fig. 2. (a), (b) Semi rectangular grooved bamboo strip
1 2
The final groove pattern of bamboo reinforcement consists of creating a semicircular shape
3
groove of 10 mm diameter on the edge, i.e. along the thickness of bamboo strip as shown in
4
Fig. 2 with the help of carpentry lathe machine and associated tools, where a, and S are
5
diameter of semicircular groove and clear spacing between the adjacent grooves respectively.
6
(a)
(b)
Fig. 3. (a) Untreated (b) Treated, Plain and Grooved bamboo strip
7 8
In present work, it was observed that for a relatively longer length of bamboo strips (Length
9
more than 1m) making semicircular groove was practically difficult. In search of alternative
10
groove shape, triangular (V notch) and rectangular shapes were tested for their effectiveness
11
in fabrication and bond strength.
12
Among these, rectangular shape groove was found to be equally effective and practically easy
13
to corrugate. Fig. 2 a and 2 b shows the rectangular groove drawing and the actual grooved
14
bamboo strips having length of 1.1 m.
15
The shape and spacing of grooves was studied through different combinations during the
16
pull-out tests. The grooved bamboo strip profile obtained consisted of rectangular grooves of
17
10 mm width and 5 mm depth made in a zigzag manner at 20 mm c/c spacing as shown in
18
Fig. 2 a and 2 b.
19
Surface treatment procedure was adopted to overcome shrinkage of raw bamboo strips inside
20
concrete. Bamboo strips, which were used as reinforcement in concrete, were first treated 7
1
with chemical glue to make the bamboo surface waterproof. Various surface coatings were
2
explored to understand their water repellant properties. The details of these surface treatments
3
were as mentioned in the work of Mali and Datta [17]. Amongst these, Bond Tite chemical
4
adhesive was found most effective. Its coating over bamboo strip, made the surface not only
5
impermeable but also the adhesion helped the sticking of sand particles . It was ensured that
6
chemical action of bond Tite did not influence the internal fibre structure of bamboo. The
7
complete surface treatment was carried out in two-steps at a temperature of 25°c and a
8
humidity of 50%. In the first step, solution of Bond Tite chemical coating was prepared as per
9
the standard proportion mentioned. A thin layer of this coating was applied to the bamboo
10
strips uniformly.
11
A specially prepared mould made of steel and a putty knife (carpentry tool) were used while
12
applying various chemical coatings over the bamboo surface. This ensured that the final layer
13
of adhesive coating was uniform throughout the surface. This coating would ensure that the
14
bamboo strip remained water repellent and helped in chemical adhesion with surrounding
15
concrete.
16
After applying the adhesive coating on the surface of bamboo, a thin circular steel wire of 1
17
mm diameter and 415 MPa yield strength was wrapped throughout the coated bamboo
18
surface in a helical manner (ribbed shape). This wrapped steel wire provided additional
19
mechanical resistance along with that of groove action. In the end, the coated specimens were
20
subjected to sandblasting process; sand particles used in this process were of size 1 mm to 3
21
mm. The final bamboo strips i.e. treated plain ad treated grooved are shown in Fig. 3 a and 3
22
b respectively.
23
2.3
24
2.3.1
25
Mix design procedure of IS 10262 and IS 456 [24-25] was adopted. M20 grade of concrete
26
was used throughout the experimentation.
Concrete Sample preparation Design Concrete mix
27
Table 3 Properties of the concrete Mix Proportion C: S: A 1:2.46:4.07 at water to cement ratio of 0.55
Compression (MPa) Stren gth
Elastic modulus
Design strength
28
24000
20
Tensile Flexural strength strength (MPa) (MPa) 2.35
4.7
Specific weight (kg/m3)
Slump (mm)
2400
45
8
1 2
The BRC members are aimed at structural members to be used in low cost housing projects,
3
considering that cement used in concrete mix was OPC (Ordinary Portland Cement).
4
Concrete used throughout the experiment satisfied the minimum cement content criteria and
5
without any admixtures. It was ensured that concrete was workable enough to be poured in
6
bamboo beam cages. The proportion of coarse aggregate was split into 20 mm and 10 mm
7
size aggregate in 70:30 proportion respectively. After making trial mix proportion the final
8
mix obtained is shown in Table 3. The concrete of this mix was further tested for its
9
compressive strength and other important properties. The average cube strength obtained for
10
each batch of concrete at the age of 7 days and 28 days was 19 MPa and 28 MPa
11
respectively.`
12
2.3.2
13
The design of a BRC beam cross section was carried out with the help of stress block
14
parameters given by Budi et al [26] and flexural beam theory. The design of BRC yielded a
15
size of 140 x 150 x 1100 mm. The details of all types of beams used in present work are
16
given in Table 4.
BRC beam matrix
17
Table 4 Details of Concrete Beams S. Concrete N. Beam 1 2
PCC RCC
3
BRC
Reinforcement (%) Untreated Treated and Plain Grooved Plain Grooved Beam Initial (UP) (UG) (TP) (TG) 0 (PCC) 1.2 (RCC) 2.8 ( BV) 3 3 3 3 3.8 ( BO) 3 3 3 3
18 19
A total of 30 beam specimens were cast as shown in Table 4. Each of these subcategories
20
consisted of three samples. In a subcategory, each single BRC beam was identified with four-
21
letter symbol in capital form followed by corresponding specimen number. The first two
22
letters BV in a beam designation indicate BRC beam with 2.8% bamboo reinforcement while
23
the letter BO stands for beam BRC beam with 3.8% bamboo reinforcement. Whereas the last
24
two letters indicate type of longitudinal bamboo strip used, i.e. untreated plain (UP),
25
untreated grooved (UG) or treated plain (TP), treated grooved (TG) type. The specimens
26
ending with either UP or UG represent control specimens in respective major categories.
27
9
1
2.3.3
Casting of BRC, RCC and PCC beam specimens
10mm x 10mm
140mm
10mm x 10mm
140mm 20 mm
20 mm
120 mm
120 mm
20 mm
150 mm
20 mm
150 mm
10mm x 10mm 30 mm
30 mm 25 mm
20mm x 10mm
25 mm
(a)
20mm x 10mm
(b)
Fig. 4. (a) Cross section details of BRC beam (Ab=2.8%) (b) Cross section details of BRC beam (Ab=3.8%)
2 3
The BRC beams were designed to compare their performance with RCC beams. The analysis
4
and design of RCC and BRC beams were carried out for an equal moment carrying capacity
5
of 12 kNm. Cross section of BV type BRC beam consisted of 2 bamboo strips of size 20 mm
6
x 10 mm x 1000 mm at bottom (tension zone) and 2 bamboo strip of 10 mm x 10 mm x 1000
7
mm at top (compression zone) as shown in Fig. 4a.
Fig. 5. Types of BRC beams with Vertical stirrups (Ab=2.8%)
(a)
(b)
(c)
(d)
Fig. 6. (a), (b), (c) and (d) Cross Section of untreated plain, untreated grooved and treated plain, treated grooved BRC beam respectively.
8 9
Similarly, Fig. 4 b shows the cross section details of BO type BRC beam which consisted of
10
additional 1% bamboo reinforcement. The shear reinforcement was provided in the form of
11
bamboo strips having cross section 10 mm x 8 mm and length 130 mm. Bamboo strips were
12
placed vertically at 100 mm c/c along all four faces. Bamboo reinforcement cage of each BV
13
type BRC beam is shown in Fig. 5. The cross-section details of these beams are shown in 10
1
Fig.6 (a), (b), (c) and (d).
2
Reinforcement cages of BO type BRC beams prepared before casting are shown in Fig. 7.
3
The addition of 1% bamboo reinforcement is carried out by adding two additional bamboo
4
strips of 10 mm x 10 mm x 1000 mm size at bottom as can be seen in the cross section in Fig.
5
8 (a), (b), (c) and (d).
6
The casting of PCC beams was carried out by pouring the concrete mix inside the molds
7
prepared for casting beams. The concrete is placed manually inside the molds in three layers;
8
each layer is then vibrated with the help of needle vibrator for ensuring proper compaction.
9
Fig. 7. Types of BRC beams with Vertical stirrups (Ab=3.8%)
(a)
(b)
(c)
(d)
Fig. 8. (a), (b), (c) and (d) Cross Section of untreated plain, untreated grooved and treated plain, treated grooved BRC beam respectively.
10 11 12
The design of RCC beams was carried in accordance with IS-456 (2000). All dimensions
13
were similar to those of other BRC beams. The longitudinal steel reinforcement of this beam
14
consisted of 2-10 mm dia. bars at bottom and 2- 8 mm diameter bars at top of Fe-415 grade.
15
Shear reinforcement consisted of 2-legged, 6 mm dia. steel stirrups of Fe-250 grade is
16
provided at 100 mm c/c as shown in Fig. 9 (a), (b), and (c). After casting the beams were kept
17
in the laboratory for 24 hrs at room temperature of 280c and humidity of 50% to achieve
18
initial setting of fresh concrete. The samples were then demolded and kept for curing. 11
(a)
(b)
(c)
Fig. 9. (a) Conventional RCC beam reinforcement cage (Ast=1.23%), (b) Side elevation and (c) Cross Section of RCC beam respectively
1 2
2.4
Testing Methodology P/2 L/3
P/2 L/3
LVDT L/3
L P/2
+
SFD -
PL/6 +
+ BMD
P/2
Point loads
+
(a)
(b)
Fig. 10. (a) Schematic representation of Four Point Bending Test, (b) BRC Beam Subjected to four point bending test
3 4
All types of beams were subjected to pure bending action under four point bending test as can
5
be seen from Fig. 10 a. BRC beam was specifically designed as per the stress block given by
6
Budi et al. [26] and guidelines provided by IS 15912 (2017) [27].
7
The test was conducted on a 100 kN capacity flexural testing machine (FTM) which is as per 12
1
the specification of EN 12390-4 (2000) part 4.2 and 4.3 [28]. The two point concentrated
2
loading was applied by the load cell as shown in Fig.10 b. The mid span deformation at each
3
load step captured by a digital LVDT (Linear Variable Displacement Transducer) is shown in
4
Fig. 10 b.
5
The beam was placed on the two supports of the FTM as per the marking shown in Fig. 10 b.
6
The beam was subjected to a displacement controlled loading at the rate of 0.1 mm/sec till
7
failure. The load deformation response was obtained from the calibrated electronic control
8
system attached with the host PC.
9
3 Test Results and Discussions
10
All the concrete beams were tested to failure and the behaviour was obtained in the form of
11
load–displacement curves. The first crack load, ultimate load and corresponding mid-span
12
displacement, ductility, and energy absorption capacity are shown in Table 5. The test results
13
including flexural strength and shear strength are shown in Table 6 and discussed in the
14
following sections.
15
Energy absorbed while undergoing flexural deformations for each beam sample was
16
calculated separately. The energy absorbed by the specimens before failure was considered as
17
the area under entire load deformation curve. This entire area was then calculated by
18
approximating the area between each of the two displacement points in the load-deformation
19
curve (Strips). The area occupied within two consecutive displacement points (energy
20
absorption) was calculated. Finally, all these values of area under the curve were added to
21
obtain a total absorbed energy. The trapezoidal rule used for calculation is given in Eq.1.
22
Energy absorption (Joules) = 0.5 × (d2 -d1) × (F2 -F1)
23
1
24
Where d is the displacement point and F is the force/load (kN) at this displacement (mm)
25
point.
26
Table 5 Experimental Results of Loads and Deflections Beam series
Load at First Crack (kN)
PCC-1
20
Deflection at First Crack load (mm) ∆ 1.800
PCC-2
22
PCC-3
23
Eq.
Ultimate Load (kN)
Deflection at Ultimate load (mm) ∆
∆ ∆
22.0
1.9
1.056
1.100
14.8
1.600
24.0
1.8
1.125
1.091
20.8
2.100
25.0
2.2
1.048
1.087
11.4
Energy Absorption (Joules)
13
Avg.
22 ± 1.5
1.8±0.2
23.7±1.5
2.0±0.2
1.076
1.093
15.7
RCC-1
55
4.200
65.0
8.0
1.905
1.182
356.3
RCC-2
58
4.500
68.0
8.5
1.889
1.172
431.8
RCC-3
59
4.800
69.0
9.0
1.875
1.169
507.1
Avg.
57±2.1
4.5±0.3
67.3±2.1
8.5±0.5
1.890
1.175
431.7
BVUP-1
25
3.200
30.0
7.5
2.344
1.200
193.9
BVUP-2
27
3.500
32.0
7.2
2.057
1.185
182.1
BVUP-3
24
3.800
35.0
7.9
2.079
1.458
203.9
Avg.
25 ± 1.5
3.5±0.3
32.3±2.5
7.5±0.4
2.160
1.281
193.3
BVUG-1
27
2.500
31.0
7.2
2.880
1.148
222.6
BVUG-2
29
3.500
35.0
6.3
1.800
1.207
200.6
BVUG-3
26
2.900
32.0
7.0
2.414
1.231
204.7
Avg.
27± 1.5
2.9±0.5
32.7±2.1
6.8±0.5
2.365
1.195
209.3
BVTP-1
29
2.500
35.0
5.5
2.200
1.207
152.6
BVTP-2
32
2.900
39.0
6.2
2.138
1.219
194.0
BVTP-3
28
3.200
38.0
5.9
1.844
1.357
180.2
Avg.
30± 2.1
2.8±0.3
38.0±2.1
5.9±0.4
2.061
1.261
175.6
BVTG-1
32
2.200
41.0
4.0
1.818
1.281
204.6
BVTG-2
35
3.000
47.0
4.8
1.600
1.343
250.5
BVTG-3
36
2.500
43.0
5.2
2.080
1.194
223.5
Avg.
34 ± 2.1
2.5±0.4
43.7±3.1
4.7±0.6
1.833
1.273
226.2
BOUP-1
31
2.500
42.0
5.3
2.120
1.355
189.5
BOUP-2
32
3.000
39.0
6.9
2.300
1.219
221.2
BOUP-3
38
2.900
45.0
6.8
2.345
1.184
270.8
Avg.
34± 3.7
2.8±0.3
42.0±3.0
6.3±0.9
2.255
1.253
227.2
BOUG-1
36
2.100
45.0
5.0
2.381
1.250
190.1
BOUG-2
38
2.800
48.0
5.9
2.107
1.263
220.3
BOUG-3
31
3.200
40.0
6.3
1.969
1.290
186.7
Avg.
35± 3.6
2.7±0.6
44.3±4.0
5.7±0.7
2.152
1.268
199.0
BOTP-1
37
2.300
55.0
6.3
2.739
1.486
270.0
BOTP-2
39
2.900
62.0
6.9
2.379
1.590
349.3
BOTP-3
43
3.300
58.0
5.5
1.667
1.349
273.0
Avg.
40± 3.0
2.8±0.5
58.3±3.5
6.2±0.7
2.262
1.475
297.5
BOTG-1
45
2.800
63.0
6.9
2.464
1.400
362.7
BOTG-2
39
3.000
63.0
6.5
2.167
1.615
356.0
BOTG-3
42
2.500
70.0
6.0
2.400
1.667
384.5
Avg.
42± 3.0
2.7±0.3
65.3±4.0
6.5±0.5
2.344
1.561
367.7
1 14
1
From Table 5 it can be seen that the first crack load and ultimate load within each BRC beam
2
category increase in a sequence of UP, UG, TP and TG. This is mainly because bamboo-
3
concrete composite action is enhanced in this sequence resulting in a stable load transfer
4
between the two materials in contact. Maximum first crack and ultimate load within each
5
subcategory of BRC beam was obtained in treated grooved beam specimens.
6
The flexural behaviour was assessed through shear and flexural strength of the concrete
7
beams. The shear and flexural strength of the concrete beam were calculated as per IS 456
8
(2000). Shear strength comprises (i) the concrete section alone (Vc); (ii) Shear strength due to
9
confining (stirrups) reinforcement (Vst); and (iii) the concrete section, tension reinforcement,
10
and the (stirrups) (VT).
11
Table 6 Shear and Flexural strength of BRC beams Theoretical Shear Strength (kN) Based Includin Including Concrete on g and Concre Bamboo Bamboo/ te /Steel Steel section Stirrups Stirrups alone Vst Vc VT 6.85 0.00 6.85
Theoretical Flexural Strength (kNm) Including Total Based Longitudinal Moment on Bamboo/ of Concrete Steel Resistan section Stirrups ce alone reinforcement
V E/ VT
Exper iment al Mome nt (kNm) ME
Mc
MR
MT
1.61
3.52
1.05
0.00
1.05
3.35
6.85
1.75
3.84
1.05
0.00
1.05
3.65
0.00
6.85
1.83
4.00
1.05
0.00
1.05
3.80
6.85
0.00
6.85
1.73
3.79
1.05
0.00
1.05
3.60
32.50
13.44
15.63
29.07
1.12
10.40
9.01
1.43
10.44
1.00
RCC-2
34.00
13.44
15.63
29.07
1.17
10.88
9.01
1.43
10.44
1.04
RCC-3
34.50
13.44
15.63
29.07
1.19
11.04
9.01
1.43
10.44
1.06
Avg.
33.67
13.44
15.63
29.07
1.16
10.77
9.01
1.43
10.44
1.03
BVUP-1
15.00
8.40
9.96
18.36
0.82
4.80
4.95
2.15
7.10
0.68
BVUP-2
16.00
8.40
9.96
18.36
0.87
5.12
4.95
2.15
7.10
0.72
BVUP-3
17.50
8.40
9.96
18.36
0.95
5.60
4.95
2.15
7.10
0.79
Avg.
16.17
8.40
9.96
18.36
0.88
5.17
4.95
2.15
7.10
0.73
BVUG-1
15.50
8.40
9.96
18.36
0.84
4.96
4.95
2.15
7.10
0.70
BVUG-2
17.50
8.40
9.96
18.36
0.95
5.60
4.95
2.15
7.10
0.79
BVUG-3
16.00
8.40
9.96
18.36
0.87
5.12
4.95
2.15
7.10
0.72
Avg.
16.33
8.40
9.96
18.36
0.89
5.23
4.95
2.15
7.10
0.74
BVTP-1
17.50
8.40
9.96
18.36
0.95
5.60
4.95
2.15
7.10
0.79
BVTP-2
19.50
8.40
9.96
18.36
1.06
6.24
4.95
2.15
7.10
0.88
BVTP-3
19.00
8.40
9.96
18.36
1.03
6.08
4.95
2.15
7.10
0.86
Beam series
Experi mental Shear (kN) VE
PCC-1
11.00
PCC-2
12.00
6.85
0.00
PCC-3
12.50
6.85
Avg.
11.83
RCC-1
M E/ MT
15
Avg.
18.67
8.40
9.96
18.36
1.02
6.08
4.95
2.15
7.10
0.84
BVTG-1
20.50
8.40
9.96
18.36
1.12
6.56
4.95
2.15
7.10
0.92
BVTG-2
23.50
8.40
9.96
18.36
1.28
7.52
4.95
2.15
7.10
1.06
BVTG-3
21.50
8.40
9.96
18.36
1.17
6.88
4.95
2.15
7.10
0.97
Avg.
21.83
8.40
9.96
18.36
1.19
6.99
4.95
2.15
7.10
0.98
BOUP-1
21.00
20.16
9.96
30.12
0.70
6.72
8.36
2.15
10.51
0.64
BOUP-2
19.50
20.16
9.96
30.12
0.65
6.24
8.36
2.15
10.51
0.59
BOUP-3
22.50
20.16
9.96
30.12
0.75
7.20
8.36
2.15
10.51
0.69
Avg.
21.00
20.16
9.96
30.12
0.70
6.72
8.36
2.15
10.51
0.64
BOUG-1
22.50
20.16
9.96
30.12
0.75
7.20
8.36
2.15
10.51
0.69
BOUG-2
24.00
20.16
9.96
30.12
0.80
7.68
8.36
2.15
10.51
0.73
BOUG-3
20.00
20.16
9.96
30.12
0.66
6.40
8.36
2.15
10.51
0.61
Avg.
22.17
20.16
9.96
30.12
0.74
7.09
8.36
2.15
10.51
0.67
BOTP-1
27.50
20.16
9.96
30.12
0.91
8.80
8.36
2.15
10.51
0.84
BOTP-2
31.00
20.16
9.96
30.12
1.03
9.92
8.36
2.15
10.51
0.94
BOTP-3
29.00
20.16
9.96
30.12
0.96
9.28
8.36
2.15
10.51
0.88
Avg.
29.17
20.16
9.96
30.12
0.97
9.33
8.36
2.15
10.51
0.89
BOTG-1
31.50
20.16
9.96
30.12
1.05
10.08
8.36
2.15
10.51
0.96
BOTG-2
31.50
20.16
9.96
30.12
1.05
10.08
8.36
2.15
10.51
0.96
BOTG-3
35.00
20.16
9.96
30.12
1.16
11.20
8.36
2.15
10.51
1.07
Avg.
32.67
20.16
9.96
30.12
1.08
10.45
8.36
2.15
10.51
0.99
1 2
BVUP beams sustained minimum first crack load and ultimate load amongst all types of BRC
3
beams, because of untreated bamboo strips leading to poor bond strength with concrete. The
4
first crack load of BVTG beam was 54.5% more than that of PCC and 40.3% less than that of
5
RCC beam.
6
On the other hand, ultimate load of BOTG beam was 2.7 times more than that of PCC beams
7
and just 4.4% less than the RCC beams. The maximum ultimate deformation was recorded in
8
the treated plain and treated grooved BRC beam. The highest average deformation for the
9
bamboo reinforced concrete beams was observed in the BVUP beams of 7.5 mm. The
10
deformation ductility i.e. inelastic deformation was maximum in BOTG beam with ratio of
11
2.87.
12
16
25
PCC-1 PCC-2 PCC-3
Load (kN)
20 15 10 5 0 0
1 2 Central Deflection (mm)
(a)
(b)
Fig. 11. (a) Load-deflection response and (b) Crack pattern of PCC beam
1 2
This may be due to the addition of longitudinal bamboo in these beams. The maximum
3
ductility was found similar in BVTP as well as BVTG beams. However, average ductility
4
value of BOTG beam was 18% and 8.3% more than PCC and RCC beams respectively
5
because BRC beams exhibit large deformations before complete failure.
6
The first crack load of PCC beams was 23kN at 2 mm deformation. Up to this load, the PCC
7
beam behaved in a linear elastic manner as seen from Fig. 11 a. After this sudden failure of
8
beam was observed through brittle mode of failure. These PCC beams were found to have
9
least ductility and energy absorption capacity as can be seen from Fig. 11 b. The
10
experimental shear strength and experimental flexural strength were 74% and 245% more
11
than the predicted theoretical capacities.
12
From Table 5 it can be seen that average value of ultimate load sustained by conventional
13
RCC beams was 67.3 kN with 8.5 mm deformation. Initially up to 2 to 3 mm RCC beams
14
describe almost linear elastic behaviour as shown in Fig. 12a. The load after the first crack
15
reaches to a constant value. The failure of RCC beams was due to flexural cracks at middle
16
1/3rd span region as seen in Fig. 12 b.
17
17
80
RCC-1 RCC-2 RCC-3
70
Load (kN)
60 50 40 30 20 10 0 0
1
2
3
4
5
6
7
8
9
10
Central Deflection (mm) (a)
(b) Fig. 12. (a) Load-deflection response of RCC and (b) Beam Crack pattern
1 2
The energy absorption capacity and deformation ductility were found to be maximum in RCC
3
beams amongst all beams considered. However, shear and flexural capacities of RCC beams
4
obtained experimentally were 16% and 3.1% higher than their theoretically predicted values,
5
which can be seen from Table 6.
\
18
Fig. 13. Failure Mode of BRC beams with Vertical stirrups with 2.8% bamboo
50
30 20
BVUG-1 BVUG-2 BVUG-3
40
Load (kN)
40
Load (kN)
50
BVUP-1 BVUP-2 BVUP-3
10
30 20 10
0
0 0
1
2
3
4
5
6
7
8
9 10
0
1
2
3
Central Deflection (mm) BVTP-1 BVTP-2 BVTP-3
1
2
3
4
5
6
7
8
9 10
(b)
Load (kN)
Load (kN)
(a) 50 45 40 35 30 25 20 15 10 5 0 0
4
Central Deflection (mm)
5
6
7
Central Deflection (mm)
8
9 10
50 45 40 35 30 25 20 15 10 5 0
BVTG-1 BVTG-2 BVTG-3
0
1
2
3
4
5
6
7
8
9 10
Central Deflection (mm)
(c) (d) Fig. 14. (a), (b), (c), (d) Load-deflection response of BVUP, BVUG, BVTP, and BVTG Beams respectively.
1 2
The failure of BVTP beams was due to major shear crack as seen from Fig. 13. This may be
3
due to loosening of the confinement of vertical bamboo strips. The deviation in load-
4
deformation curve can be observed at the instance of first crack load and ultimate load. This
5
behaviour can be captured from Fig. 14 (a), (b), (c), and (d) for all BV type BRC beams.
6
Maximum experimental shear strength of 21.83 kN obtained in BVTG beams which is 19 %
7
more than the theoretically predicted value. However, it is 84.5% more than PCC and 54%
8
less than RCC beams.
9
On the other hand, BVTG beam showed average moment carrying capacity of 6.99 kN-m,
10
which nearly, equals to the theoretically predicted flexural strength. Compared to control
11
beams, average flexural capacity of BVTG beam is 1.84 times more than PCC but 35% less
12
than RCC beams.
19
1
BO type BRC beams also had stirrups in the form of bamboo strips tied transverse to the
2
longitudinal bamboo. The BO type BRC beams failed mainly due to the shear crack
3
originating from bottom tensile surface and propagating towards top compressive layer of the
4
beam just below the point load, except BOUG beam, which failed as a result of major
5
flexural crack in middle 1/3rd span as shown in Fig.15.
6
This may be due to loss of bond at bamboo concrete interface and loosening of the
7
confinement joints of vertical bamboo strips. Compared to respective BV type BRC beams
8
BO type BRC beams have shown enhancement in linear stiffness and ultimate load as seen
9
from Fig.16 (a), (b), (c), and (d).
10
Experimentally obtained shear and flexural strength were found to increase in both types of
11
BRC beams. The sequence of increase is UP, UG, TP and TG. Maximum experimental shear
12
strength of 32.67 kN was found in BOTG beams which was 8.4 % more than the theoretically
13
predicted value. However, it is 2.8 times more than PCC and just 3% less than RCC beams.
14
Table 6 shows maximum moment carrying capacity of 10.45 kN-m was developed by BOTG
15
beams and this is more than the value of BVTG beams. The flexural capacity of BOTG beam
16
is 1.84 times more than PCC and compared to RCC beam it is marginally less by 3%.
20
50 45 40 35 30 25 20 15 10 5 0
BOUP-1 BOUP-2 BOUP-3
Load (kN)
Load (kN)
Fig. 15. Failure Mode of BRC beams with 3.8% bamboo
0
1
2
3
4
5
6
7
8
BOUG-1 BOUG-2 BOUG-3
50 45 40 35 30 25 20 15 10 5 0
9 10
0
1
Central Deflection (mm)
2
3
5
6
7
8
9 10
Central Deflection (mm)
(a)
(b) BOTP-1 BOTP-2 BOTP-3
70 60
BOTG-1 BOTG-2 BOTG-3
80 70 60
50
Load (kN)
Load (kN)
4
40 30 20
50 40 30 20
10
10
0
0 0
1
2
3
4
5
6
7
8
9 10
Central Deflection (mm)
0
1
2
3
4
5
6
7
8
9 10
Central Deflection (mm)
(c) (d) Fig. 16. (a), (b), (c), (d) Load-deflection response of BOUP, BOUG, BOTP, and BOTG Beams respectively.
1 2
Fig. 17 compares the average of load deformation response of all the four types of concrete
3
beams. The curves in Fig. 17 distinguish the flexural behaviour of each concrete beam
4
separately. It is observed that flexural strength amongst these beams increases in a sequence
5
of PCC, BV, BO and then RCC beams.
21
70
PCC-avg RCC-avg BVUP -avg
60
BVUG -avg BVTP -avg
50
BVTG -avg BOUP -avg
Load (kN)
40
BOUG -avg BOTP -avg
30
BOTG -avg
20
10
0 0
1
2
3
4
5
6
7
8
9
10
Central Deflection (mm) Fig. 17. Average Load-deflection response of PCC, RCC and all types of BRC Beams.
1
The average values of maximum ultimate load, obtained in these beams are 21kN, 63kN,
2
35kN and 48kN for PCC, RCC, BVTP and BOTG beam respectively. The undereinforced
3
section designed for BV type BRC beam resulted in 67% higher flexural strength than PCC
4
beams, however it is 44% less than the mean flexural strength of RCC beams. Whereas after
5
addition of 1% bamboo in BV type BRC beams flexural strength was found 37% more than
6
BVTP beam but still 24% less than RCC beam.
7
4 Observations and Conclusions
8
The efficacy and performance of BRC beams is investigated in the present research. The
9
concrete beams reinforced with longitudinal as well as shear reinforcement in the form of
10
bamboo strips were tested experimentally. Based on the analysis of test results, the following
11
important conclusions are made.
12
1. There is a significant enhancement in first crack load, ultimate load, ductility, and
13
energy absorption capacity of both type BRC beams (BV and BO) compared to PCC
14
beams. BO type BRC beams have resulted in higher values of these parameters than
15
the respective BV type BRC beams. However, the ultimate load and energy
22
1
absorption capacity of BOTG beam was found close to that of RCC beams, which is
2
3% and 17% less compared to RCC beams.
3
2. The flexural capacity of each BRC beam is more than that of theoretical predicted
4
values. Flexural capacity of BOTG beam is comparable to that of the RCC beam.
5
3. Amongst two type of BRC beams, BO type BRC beams have shown maximum shear
6
as well as flexural strength. Shear strength of BOTG beam is comparable to shear
7
strength of the RCC beam.
8
4. Shear as well as flexural performance of BOTG beam is comparable to that of
9
conventional RCC beam having 1.23 % steel reinforcement, except the mode of
10
failure.
11
The present investigation establishes the efficacy of B. Arundinacea bamboo strip treated
12
with the proposed treatment (i.e. Grooved bamboo profile + Bond Tite coating + steel wire
13
wrapping + sand blasting), which are used instead of conventional steel reinforcement.
14
However, the use of treated bamboo strips inside concrete flexural member needs further
15
experimental studies on full-scale specimens at different ages of concrete to ascertain the
16
long term durability.
17
Conflict of interest
18
It is assured by the authors that this publication does not have any known conflicts of interest.
19
In addition, there has been no significant financial support for this research that could have
20
influenced its findings.
21
Acknowledgement
22
Technical Education Quality improvement Programme -II (TEQIP-II) An initiative of
23
Ministry of Human Resource and Development (MHRD), Government of India funded this
24
research work.
25
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and Wood Products. 71(1):61-7, 2013.
12
21. T. Tan, N. Rahbar, S.M. Allameh, S. Kwofie, D. Dissmore, K. Ghavami, W.O.
13
Soboyejo. Mechanical properties of functionally graded hierarchical bamboo
14
structures. Acta biomaterialia. 7(10):3796-3803, 2011.
15 16
22. Indian Standard Specifications for Method of Tests for Bamboo, I.S. 6874:2008, Bureau of Indian Standards, New Delhi, 2008.
17
23. ISO (International Organization for Standardization). International standard ISO
18
22157–1:2004 (E), bamboo – determination of physical and mechanical properties –
19
part I: requirements. Geneva (Switzerland): ISO; 2004.
20 21 22 23
24. Indian Standard Specifications for Concrete Mix Proportioning Guidelines, I. S. 10262: 2009, Bureau of Indian Standards, New Delhi, 2009. 25. Indian Standard Specifications for Code of Practice for Plain and Reinforced Concrete, IS 456-2000, Bureau of Indian Standards, New Delhi, 1987.
24
26. A. S. Budi, A. P. Rahmadi, E. Rismunarsi, Experimental study of flexural capacity
25
on bamboo ori strip notched v reinforced concrete beams. In AIP Conference
26
Proceedings, 1788,1:030052, AIP Publishing, 2017.
27 28 29 30
27. Indian Standard Specifications for Code of Practice for Structural Design using Bamboo, IS 15912-2017, Bureau of Indian Standards, New Delhi, 2012. 28. Testing of hardened concrete - Part 4: Compressive strength - Specification for testing machines. British Standard. 2000. BS EN 12390-4:2000.
31
25
1
Experimental Evaluation of Bamboo Reinforced Concrete Beams
2
Pankaj R. Mali a, Debarati Datta b a
3 4 5 6
b
Research Scholar, Department of Applied Mechanics, Visvesvaraya National Institute of Technology, Nagpur440010, India. Email- [email protected]
Assistant Professor, Department of Applied Mechanics, Visvesvaraya National Institute of Technology, Nagpur440010, India. Email- [email protected]
7 8
HIGHLIGHTS:
9 • Bond strength enhancement through mechanical action in treated grooved bamboo samples. 10 • Application of newly developed bamboo reinforcement in RC beam specimens. 11 • Effect of bamboo reinforcement percentage on enhancing shear and flexural strength.
1
Declarations of interest
Dear Editor-in-Chief, Journal of Building Engineering
Please find enclosed full-length manuscript, entitled “Experimental Evaluation of Bamboo Reinforced Concrete Beams”, (JOBE_2019_346_R2), by Pankaj R. Mali (corresponding author) and Dr. Debarati Datta, which we would like to submit for publication as a research paper in Journal of Building Engineering, ELSEVIER. We wish to confirm that there are no known conflicts of interest associated with this publication. We also confirm that this manuscript has not been published elsewhere and is not under consideration by another journal. Authors have acknowledged the funding sources in the manuscript. Proper citations to the previously published works is given, and that in case Data/Table/Figures are quoted verbatim from some other publication, the required permission to do so has been obtained. All authors have approved the manuscript and agree with its submission to Journal of Building Engineering, ELSEVIER.
We are ready to help in each step of submission. We appreciate your time and look forward to your response.
Kind regards. P. R. Mali (Corresponding author) E-mail address: [email protected] Contact number: +918806244477
S2352-7102(19)30347-X
DOI:
https://doi.org/10.1016/j.jobe.2019.101071
Reference:
JOBE 101071
To appear in:
Journal of Building Engineering
Received Date: 2 March 2019 Revised Date:
14 November 2019
Accepted Date: 14 November 2019
Please cite this article as: P.R. Mali, D. Datta, Experimental evaluation of bamboo reinforced concrete beams, Journal of Building Engineering (2019), doi: https://doi.org/10.1016/j.jobe.2019.101071. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.
1
Experimental Evaluation of Bamboo Reinforced Concrete Beams
2
Pankaj R. Mali a, Debarati Datta b a
3 4 5 6
b
Research Scholar, Department of Applied Mechanics, Visvesvaraya National Institute of Technology, Nagpur440010, India. Email- [email protected]
Assistant Professor, Department of Applied Mechanics, Visvesvaraya National Institute of Technology, Nagpur440010, India. Email- [email protected]
7 8
Abstract
9
The paper presents the experimental study on flexural behaviour of concrete beams
10
reinforced with “bamboo strips”. Total 30 beam specimens were tested under four point
11
bending test (pure bending). Three different types of concrete beams were investigated
12
experimentally. They were concrete beams reinforced with bamboo strips, concrete beams
13
reinforced with conventional steel and concrete beams with no reinforcement. The flexural
14
behaviour of these beams was studied through linear stiffness, ultimate load, energy
15
absorption capacity, shear strength and flexural strength.
16
There are two types of BRC (Bamboo reinforced concrete) beams having both longitudinal as
17
well as shear reinforcement (stirrups) in the form of bamboo strips. First is with 2.8% and
18
second with 3.8% longitudinal bamboo reinforcement with respect to the beam cross section.
19
Analysis and comparison of different performance parameters against RCC (steel reinforced
20
cement concrete) as well as PCC (plain cement concrete) beams is carried out. It is observed
21
that both types of BRC beams have shown significantly higher shear as well as flexural
22
strength than PCC beams.
23
However, BRC beams with 2.8% bamboo reinforcement shown less shear and flexural
24
capacity compared to that of RCC beams. The effect of additional 1% bamboo reinforcement
25
on shear as well as flexural strength can be clearly observed in second type of BRC beam.
26
Failure mode observed in both type of BRC beams were different from that of PCC and RCC
27
beams.
28
Keywords: Bamboo reinforced concrete, Flexural behaviour, Reinforced concrete, Bond
29
strength, Semi rectangular groove, Surface treatment.
30
HIGHLIGHTS:
31 • Bond strength enhancement through mechanical action in treated grooved bamboo samples. 32 • Application of newly developed bamboo reinforcement in RC beam specimens. 33 • Effect of bamboo reinforcement percentage on enhancing shear and flexural strength. 1
1
1 Introduction
2
In the present scenario majority of housing and infrastructure projects are built using
3
conventional material i.e. steel and concrete and it has increased in the past two decades.
4
These requirements of conventional construction material has increased manifold. The
5
production of such material like steel and cement causes enormous destruction to the natural
6
atmosphere due to release of CO2 (Approximately 1.83 tonne of CO2 is emitted per tonne of
7
steel produced) and other hazardous fluids. This is one of the major drawbacks of
8
conventional construction material.
9
The research for an alternative material has been there since 1960. Many naturally available
10
fibres have been used along with concrete. The purpose of such materials is to enhance the
11
mechanical properties of the plain concrete. One such naturally available material is bamboo.
12
Bamboo is known to be fast growing, renewable, sustainable, ecofriendly material. During
13
the growth of bamboo, it actually consumes 1-tonne of CO2 per bamboo culm from the
14
surrounding atmosphere. Bamboo is one of the most widely available materials in the tropical
15
regions where most of the developing countries are located. [1-3].
16
The geometry of the typical bamboo culm consists of hollow circular cross section with
17
diaphragms/nodes along the culm height. The wall thickness intermodal distance, diameter
18
and fiber density vary from bottom to top end. Due to the fibrous (along the grain) structure
19
of the culm, the bamboo strip possesses high tensile strength. Compared to conventional
20
reinforcing steel bamboo possesses high strength to weight ratio (about six times higher). A
21
bamboo culm attains its optimum strength around three to four years of age and it matures
22
completely by fifth year. Due to the dense fibrous structure, it can sustain tension as well as
23
compression loading unlike any other natural material, which can only take tension.
24
However, bamboo being organic natural material, durability of the bamboo in a concrete
25
composite possesses limitations on its use. The use of bamboo in the form of full culm or as
26
strips inside the concrete mainly depends on bamboo concrete bond strength. The bonding
27
between bamboo and concrete is majorly influenced by friction between concrete and
28
bamboo surface, adhesion of coating substance attached to exterior bamboo surface and
29
mechanical interlock. Investigations on improving each of these factors have been done by
30
many researchers in last few decades. These treatment procedures are aimed at increasing
31
bamboo concrete bond strength. This includes use of various adhesives on bamboo surface to
32
make the exterior surface water repellant. Wrapping of thin steel wire, use of sand particles 2
1
through sand blasting process at bamboo concrete interface. The modifications in bamboo
2
strip profile using corrugations to incorporate mechanical interlock. [4].
3
The efficacy and performance of such treated bamboo reinforcement in flexural concrete
4
members is investigated further, Experimental investigations carried on such type of BRC
5
members are listed in Table 1.
6
Table 1 Summary of investigations on BRC beams Author
Kankam and OdumEwuakye (2000) [5].
Ghavami (2000) [6].
Ghavami (2005) [7].
Kumar and Prasad (2003) [8]
Bamboo Species and treatment
Beam details (Lxbxd)
Type of test and Response parameters
Babadua bamboo strips. Treated with
100 x 180 x 1500 mm and 135 x 235 x 1800 mm. with varying span to depth ratio and percentage of bamboo reinforcement
3 point bending test, and cyclic loading
Dendrocalamus 300 x 120 x 3000, 2500 giganteous, mm with varying span Treated with The to depth ratio and Nigrolin and percentage of bamboo sand wire reinforcement. treatment 300 x 120 x 3400 mm Dendrocalamus with varying span to giganteous, depth ratio and Treated with The percentage of bamboo Sikadur 32-Gel reinforcement. Loacally available bamboo treated 125 mm x 150 mm x with anti-termite 1000 mm with and then conventional concrete protective and blended concrete. coating (TOP COAT)
Terai and Minami (2011) [9]
Black bamboo and Japanese Timber bamboo.
125 mm x 250 mm x 1500 mm with conventional concrete and blended concrete.
Agarwal et. al. (2014) [10]
Used Muli bamboo strips treated with Sikadur-32 gel to
150 mm x 75 mm x 1000 mm.
Results/ Remark Factor of safety of 1.5 against Cracking and 6.4 against collapse.
3 point bending test, ultimate load, crack initiation and propagation
Bond strength increased by 90%, Ultimate load increased by 400%
4 point bending test, ultimate load, crack initiation and propagation
Bond strength increased by 100%, Flexural strength increased by 400%
3 point bending test, first-crack load and the experimental failure load
Performance of BRC beams with regular concrete and blended concrete is found same
3 point bending test, Longitudinal bar, type of stirrups, spacing of stirrups and shear span to depth ratio. Four point bending test. Failure load, Energy
Fracture behaviour of BRC beams can be evaluated by existing formula of RC beam. Failure load and energy absorption capacity of BRC beams found higher 3
1
prepare BRC absorption. than PCC and RCC beams. beams. L= Total length of beam in mm; b = width of beam in mm; d = depth of beam in mm.
2
Pacheo-Torgal and Jalal [11] reported that use of long fibres of a bamboo culm in structural
3
concrete resulted in high durability. However, mechanical behaviour of bamboo culms still
4
needs detailed investigation.
5
Apart from the above investigations, many other researchers have carried out experimentation
6
on BRC beams to improve its performance. These studies mainly include use of different
7
stirrup materials (bamboo, steel etc.) along with main bamboo reinforcement, variation in
8
spacing of stirrups, and their position with respect to longitudinal reinforcement. Similarly,
9
variation had been made in percentage of main longitudinal reinforcement, type of surface
10
treatment, which has a significant impact on shear as well as flexural strength of these BRC
11
beams. Instead of full bamboo culm or split bamboo, bamboo fibers/pulp in different forms
12
have also been used in concrete at different dosages to improve properties of unreinforced
13
concrete.
14
The effect of corrugations on bamboo surface to enhance bond strength is also studied. The
15
effect of modification in the basic composition of concrete, use of AAC (Aerated autoclaved
16
concrete) blocks placed at tensile zone of BRC beams and its effect at service and ultimate
17
failure is also explored. The study has also been made to understand the stress block
18
parameters of BRC beams with certain assumptions, and the conventional beam theory
19
moment equations of design codes were used to arrive at optimal bamboo reinforcement
20
ratio, stirrup material its spacing etc. [12-16].
21
Mali and Datta [17] investigated bamboo concrete bond behaviour experimentally using pull
22
out tests. Series of pullout tests were conducted on bamboo strips embedded in concrete
23
cylinder. A newly developed grooved bamboo profile was found to enhance the bond strength
24
significantly compared to the conventional plain bamboo strip profile. Among various
25
chemical adhesives (used as a sealant material in surface treatment), explored Bond Tite
26
adhesive along with steel wire wrapping and sand blasting treatment was found most
27
effective surface treatment.
28
Although many publications are available on the technique of using bamboo as main
29
longitudinal reinforcement in concrete beams with respect to behaviour and efficacy,
30
however, it is difficult to predict the performance of BRC beams, since the properties of
31
bamboo vary regionally. Also bamboo concrete bond behaviour has remained a serious issue 4
1
for long. The current research work is aimed at enhancing the bamboo concrete interaction by
2
using surface treatment and incorporating mechanical interlock and then applying this treated
3
and grooved bamboo reinforcement in concrete beams.
4
Although studies have been carried out to understand flexural behaviour of BRC beams, it is
5
limited in number. Most of the research work is pertaining to improving durability of BRC
6
members. Moreover, the research focuses on standardizing the properties and design
7
guidelines available for bamboo.
8
At this point of time, it is difficult to predict the flexural behaviour of BRC beams.
9
Experimental tests were conducted to study the realistic structural performance of B.
10
arundinacea bamboo strips. The design of steel reinforced cement concrete (RCC) as well as
11
BRC beam was done for equal moment capacity, to get the undereinforced section. All
12
concrete beams were subjected to four point bending test. The test results of each BRC beams
13
were compared with the reference PCC and RCC beams.
14
The effect of bamboo (longitudinal) reinforcement percentage, with fixed shear span to depth
15
ratio on the flexural performance was investigated. The load–displacement curves along with
16
failure modes of each beam under flexural loading were studied in detail.
17
2 Experimental Programme
18
The experimentation was carried out in the following steps-
19
•
Characteristics of Bamboo Reinforcement
20
•
Developing Grooved Bamboo profile and its Surface Treatment
21
•
Casting of BRC beams
22
•
Testing Methodology
23
2.1
Characteristics of Bamboo Reinforcement
24
The bamboo species used throughout the study was B. arundinacea (Katang). This species is
25
popularly known for its promising mechanical and physical properties and most widely
26
available in the subcontinent region. Katang is the regional name used for B. arundinacea and
27
its use for construction purposes is cited in National Building code of India (NBC) [18].
28
Before splitting the full bamboo culm into strips, raw bamboo culms were cleaned manually
29
in order to remove any natural dirt and foreign substances. These cleaned bamboo culms
30
were then soaked in 6 % boric acid solution for 72 hrs to prevent the attack of termites and
31
insects. Bamboo Culms were then allowed to dry under moderate (350c) temperature for 5
5
1
days. The moisture content and density of these culms was found to be 25% and 1125 kg/m3
2
[19-21]. The cleaned and air-dried bamboo culms were then converted into strips of uniform
3
thickness and rectangular cross section. IS: 6874 [22] and ISO 22157 [23] have given
4
guidelines to determine the important physical and mechanical properties. Each mechanical
5
property of the selected bamboo specimens were determined in accordance with IS: 6874
6
(2008). The average value of each mechanical property is mentioned in Table 2.
7
Table 2 Mechanical properties of B. arundinacea S.N. 1 2 3 4
8 9
2.2
Type of test Tension Compression Static bending Shear (along grain)
Parameter Modulus of elasticity (MPa) Stress at peak (MPa) Peak displacement (mm) Compressive strength (MPa) Flexural strength (MPa) Shear strength (MPa)
B. Arundinacea 5500 150 2.71 65.10 90.42 7.20
Developing Grooved Bamboo profile and its Surface Treatment
10
The bamboo strips to be used as replacement to conventional steel reinforcement were
11
developed such that adequate bond strength is established at the bamboo concrete interface.
12
The geometry of the bamboo strip used is flat along its length with a substantially rectangular
13
cross section (20 mm x 10 mm), as shown in Fig. 1a and 1b.
14
The parameters like groove shape, size, its spacing, and amount of embedded length were
15
decided based on the results of trial pull out tests. Three types of groove shapes V-notch,
16
rectangular and semicircular were tried before arriving at the most effective shape. Three
17
embedded lengths of 50, 75 and 100% of cylinder height and three different groove size to its
18
spacing ratios (a: S) equal to 1:1, 1:2, 1:3 were tested.
19
From observations, semicircular shape groove pattern with 50% embedded length and a: S
20
ratio of 1:1 was found most effective in enhancing bond strength through mechanical
21
interlock. a
b
L
S
a/2
b
a=10 mm L
6
(a)
(b) Fig. 1. (a), (b) Plain rectangular Bamboo strip reinforcement Specimen
(a)
(b) Fig. 2. (a), (b) Semi rectangular grooved bamboo strip
1 2
The final groove pattern of bamboo reinforcement consists of creating a semicircular shape
3
groove of 10 mm diameter on the edge, i.e. along the thickness of bamboo strip as shown in
4
Fig. 2 with the help of carpentry lathe machine and associated tools, where a, and S are
5
diameter of semicircular groove and clear spacing between the adjacent grooves respectively.
6
(a)
(b)
Fig. 3. (a) Untreated (b) Treated, Plain and Grooved bamboo strip
7 8
In present work, it was observed that for a relatively longer length of bamboo strips (Length
9
more than 1m) making semicircular groove was practically difficult. In search of alternative
10
groove shape, triangular (V notch) and rectangular shapes were tested for their effectiveness
11
in fabrication and bond strength.
12
Among these, rectangular shape groove was found to be equally effective and practically easy
13
to corrugate. Fig. 2 a and 2 b shows the rectangular groove drawing and the actual grooved
14
bamboo strips having length of 1.1 m.
15
The shape and spacing of grooves was studied through different combinations during the
16
pull-out tests. The grooved bamboo strip profile obtained consisted of rectangular grooves of
17
10 mm width and 5 mm depth made in a zigzag manner at 20 mm c/c spacing as shown in
18
Fig. 2 a and 2 b.
19
Surface treatment procedure was adopted to overcome shrinkage of raw bamboo strips inside
20
concrete. Bamboo strips, which were used as reinforcement in concrete, were first treated 7
1
with chemical glue to make the bamboo surface waterproof. Various surface coatings were
2
explored to understand their water repellant properties. The details of these surface treatments
3
were as mentioned in the work of Mali and Datta [17]. Amongst these, Bond Tite chemical
4
adhesive was found most effective. Its coating over bamboo strip, made the surface not only
5
impermeable but also the adhesion helped the sticking of sand particles . It was ensured that
6
chemical action of bond Tite did not influence the internal fibre structure of bamboo. The
7
complete surface treatment was carried out in two-steps at a temperature of 25°c and a
8
humidity of 50%. In the first step, solution of Bond Tite chemical coating was prepared as per
9
the standard proportion mentioned. A thin layer of this coating was applied to the bamboo
10
strips uniformly.
11
A specially prepared mould made of steel and a putty knife (carpentry tool) were used while
12
applying various chemical coatings over the bamboo surface. This ensured that the final layer
13
of adhesive coating was uniform throughout the surface. This coating would ensure that the
14
bamboo strip remained water repellent and helped in chemical adhesion with surrounding
15
concrete.
16
After applying the adhesive coating on the surface of bamboo, a thin circular steel wire of 1
17
mm diameter and 415 MPa yield strength was wrapped throughout the coated bamboo
18
surface in a helical manner (ribbed shape). This wrapped steel wire provided additional
19
mechanical resistance along with that of groove action. In the end, the coated specimens were
20
subjected to sandblasting process; sand particles used in this process were of size 1 mm to 3
21
mm. The final bamboo strips i.e. treated plain ad treated grooved are shown in Fig. 3 a and 3
22
b respectively.
23
2.3
24
2.3.1
25
Mix design procedure of IS 10262 and IS 456 [24-25] was adopted. M20 grade of concrete
26
was used throughout the experimentation.
Concrete Sample preparation Design Concrete mix
27
Table 3 Properties of the concrete Mix Proportion C: S: A 1:2.46:4.07 at water to cement ratio of 0.55
Compression (MPa) Stren gth
Elastic modulus
Design strength
28
24000
20
Tensile Flexural strength strength (MPa) (MPa) 2.35
4.7
Specific weight (kg/m3)
Slump (mm)
2400
45
8
1 2
The BRC members are aimed at structural members to be used in low cost housing projects,
3
considering that cement used in concrete mix was OPC (Ordinary Portland Cement).
4
Concrete used throughout the experiment satisfied the minimum cement content criteria and
5
without any admixtures. It was ensured that concrete was workable enough to be poured in
6
bamboo beam cages. The proportion of coarse aggregate was split into 20 mm and 10 mm
7
size aggregate in 70:30 proportion respectively. After making trial mix proportion the final
8
mix obtained is shown in Table 3. The concrete of this mix was further tested for its
9
compressive strength and other important properties. The average cube strength obtained for
10
each batch of concrete at the age of 7 days and 28 days was 19 MPa and 28 MPa
11
respectively.`
12
2.3.2
13
The design of a BRC beam cross section was carried out with the help of stress block
14
parameters given by Budi et al [26] and flexural beam theory. The design of BRC yielded a
15
size of 140 x 150 x 1100 mm. The details of all types of beams used in present work are
16
given in Table 4.
BRC beam matrix
17
Table 4 Details of Concrete Beams S. Concrete N. Beam 1 2
PCC RCC
3
BRC
Reinforcement (%) Untreated Treated and Plain Grooved Plain Grooved Beam Initial (UP) (UG) (TP) (TG) 0 (PCC) 1.2 (RCC) 2.8 ( BV) 3 3 3 3 3.8 ( BO) 3 3 3 3
18 19
A total of 30 beam specimens were cast as shown in Table 4. Each of these subcategories
20
consisted of three samples. In a subcategory, each single BRC beam was identified with four-
21
letter symbol in capital form followed by corresponding specimen number. The first two
22
letters BV in a beam designation indicate BRC beam with 2.8% bamboo reinforcement while
23
the letter BO stands for beam BRC beam with 3.8% bamboo reinforcement. Whereas the last
24
two letters indicate type of longitudinal bamboo strip used, i.e. untreated plain (UP),
25
untreated grooved (UG) or treated plain (TP), treated grooved (TG) type. The specimens
26
ending with either UP or UG represent control specimens in respective major categories.
27
9
1
2.3.3
Casting of BRC, RCC and PCC beam specimens
10mm x 10mm
140mm
10mm x 10mm
140mm 20 mm
20 mm
120 mm
120 mm
20 mm
150 mm
20 mm
150 mm
10mm x 10mm 30 mm
30 mm 25 mm
20mm x 10mm
25 mm
(a)
20mm x 10mm
(b)
Fig. 4. (a) Cross section details of BRC beam (Ab=2.8%) (b) Cross section details of BRC beam (Ab=3.8%)
2 3
The BRC beams were designed to compare their performance with RCC beams. The analysis
4
and design of RCC and BRC beams were carried out for an equal moment carrying capacity
5
of 12 kNm. Cross section of BV type BRC beam consisted of 2 bamboo strips of size 20 mm
6
x 10 mm x 1000 mm at bottom (tension zone) and 2 bamboo strip of 10 mm x 10 mm x 1000
7
mm at top (compression zone) as shown in Fig. 4a.
Fig. 5. Types of BRC beams with Vertical stirrups (Ab=2.8%)
(a)
(b)
(c)
(d)
Fig. 6. (a), (b), (c) and (d) Cross Section of untreated plain, untreated grooved and treated plain, treated grooved BRC beam respectively.
8 9
Similarly, Fig. 4 b shows the cross section details of BO type BRC beam which consisted of
10
additional 1% bamboo reinforcement. The shear reinforcement was provided in the form of
11
bamboo strips having cross section 10 mm x 8 mm and length 130 mm. Bamboo strips were
12
placed vertically at 100 mm c/c along all four faces. Bamboo reinforcement cage of each BV
13
type BRC beam is shown in Fig. 5. The cross-section details of these beams are shown in 10
1
Fig.6 (a), (b), (c) and (d).
2
Reinforcement cages of BO type BRC beams prepared before casting are shown in Fig. 7.
3
The addition of 1% bamboo reinforcement is carried out by adding two additional bamboo
4
strips of 10 mm x 10 mm x 1000 mm size at bottom as can be seen in the cross section in Fig.
5
8 (a), (b), (c) and (d).
6
The casting of PCC beams was carried out by pouring the concrete mix inside the molds
7
prepared for casting beams. The concrete is placed manually inside the molds in three layers;
8
each layer is then vibrated with the help of needle vibrator for ensuring proper compaction.
9
Fig. 7. Types of BRC beams with Vertical stirrups (Ab=3.8%)
(a)
(b)
(c)
(d)
Fig. 8. (a), (b), (c) and (d) Cross Section of untreated plain, untreated grooved and treated plain, treated grooved BRC beam respectively.
10 11 12
The design of RCC beams was carried in accordance with IS-456 (2000). All dimensions
13
were similar to those of other BRC beams. The longitudinal steel reinforcement of this beam
14
consisted of 2-10 mm dia. bars at bottom and 2- 8 mm diameter bars at top of Fe-415 grade.
15
Shear reinforcement consisted of 2-legged, 6 mm dia. steel stirrups of Fe-250 grade is
16
provided at 100 mm c/c as shown in Fig. 9 (a), (b), and (c). After casting the beams were kept
17
in the laboratory for 24 hrs at room temperature of 280c and humidity of 50% to achieve
18
initial setting of fresh concrete. The samples were then demolded and kept for curing. 11
(a)
(b)
(c)
Fig. 9. (a) Conventional RCC beam reinforcement cage (Ast=1.23%), (b) Side elevation and (c) Cross Section of RCC beam respectively
1 2
2.4
Testing Methodology P/2 L/3
P/2 L/3
LVDT L/3
L P/2
+
SFD -
PL/6 +
+ BMD
P/2
Point loads
+
(a)
(b)
Fig. 10. (a) Schematic representation of Four Point Bending Test, (b) BRC Beam Subjected to four point bending test
3 4
All types of beams were subjected to pure bending action under four point bending test as can
5
be seen from Fig. 10 a. BRC beam was specifically designed as per the stress block given by
6
Budi et al. [26] and guidelines provided by IS 15912 (2017) [27].
7
The test was conducted on a 100 kN capacity flexural testing machine (FTM) which is as per 12
1
the specification of EN 12390-4 (2000) part 4.2 and 4.3 [28]. The two point concentrated
2
loading was applied by the load cell as shown in Fig.10 b. The mid span deformation at each
3
load step captured by a digital LVDT (Linear Variable Displacement Transducer) is shown in
4
Fig. 10 b.
5
The beam was placed on the two supports of the FTM as per the marking shown in Fig. 10 b.
6
The beam was subjected to a displacement controlled loading at the rate of 0.1 mm/sec till
7
failure. The load deformation response was obtained from the calibrated electronic control
8
system attached with the host PC.
9
3 Test Results and Discussions
10
All the concrete beams were tested to failure and the behaviour was obtained in the form of
11
load–displacement curves. The first crack load, ultimate load and corresponding mid-span
12
displacement, ductility, and energy absorption capacity are shown in Table 5. The test results
13
including flexural strength and shear strength are shown in Table 6 and discussed in the
14
following sections.
15
Energy absorbed while undergoing flexural deformations for each beam sample was
16
calculated separately. The energy absorbed by the specimens before failure was considered as
17
the area under entire load deformation curve. This entire area was then calculated by
18
approximating the area between each of the two displacement points in the load-deformation
19
curve (Strips). The area occupied within two consecutive displacement points (energy
20
absorption) was calculated. Finally, all these values of area under the curve were added to
21
obtain a total absorbed energy. The trapezoidal rule used for calculation is given in Eq.1.
22
Energy absorption (Joules) = 0.5 × (d2 -d1) × (F2 -F1)
23
1
24
Where d is the displacement point and F is the force/load (kN) at this displacement (mm)
25
point.
26
Table 5 Experimental Results of Loads and Deflections Beam series
Load at First Crack (kN)
PCC-1
20
Deflection at First Crack load (mm) ∆ 1.800
PCC-2
22
PCC-3
23
Eq.
Ultimate Load (kN)
Deflection at Ultimate load (mm) ∆
∆ ∆
22.0
1.9
1.056
1.100
14.8
1.600
24.0
1.8
1.125
1.091
20.8
2.100
25.0
2.2
1.048
1.087
11.4
Energy Absorption (Joules)
13
Avg.
22 ± 1.5
1.8±0.2
23.7±1.5
2.0±0.2
1.076
1.093
15.7
RCC-1
55
4.200
65.0
8.0
1.905
1.182
356.3
RCC-2
58
4.500
68.0
8.5
1.889
1.172
431.8
RCC-3
59
4.800
69.0
9.0
1.875
1.169
507.1
Avg.
57±2.1
4.5±0.3
67.3±2.1
8.5±0.5
1.890
1.175
431.7
BVUP-1
25
3.200
30.0
7.5
2.344
1.200
193.9
BVUP-2
27
3.500
32.0
7.2
2.057
1.185
182.1
BVUP-3
24
3.800
35.0
7.9
2.079
1.458
203.9
Avg.
25 ± 1.5
3.5±0.3
32.3±2.5
7.5±0.4
2.160
1.281
193.3
BVUG-1
27
2.500
31.0
7.2
2.880
1.148
222.6
BVUG-2
29
3.500
35.0
6.3
1.800
1.207
200.6
BVUG-3
26
2.900
32.0
7.0
2.414
1.231
204.7
Avg.
27± 1.5
2.9±0.5
32.7±2.1
6.8±0.5
2.365
1.195
209.3
BVTP-1
29
2.500
35.0
5.5
2.200
1.207
152.6
BVTP-2
32
2.900
39.0
6.2
2.138
1.219
194.0
BVTP-3
28
3.200
38.0
5.9
1.844
1.357
180.2
Avg.
30± 2.1
2.8±0.3
38.0±2.1
5.9±0.4
2.061
1.261
175.6
BVTG-1
32
2.200
41.0
4.0
1.818
1.281
204.6
BVTG-2
35
3.000
47.0
4.8
1.600
1.343
250.5
BVTG-3
36
2.500
43.0
5.2
2.080
1.194
223.5
Avg.
34 ± 2.1
2.5±0.4
43.7±3.1
4.7±0.6
1.833
1.273
226.2
BOUP-1
31
2.500
42.0
5.3
2.120
1.355
189.5
BOUP-2
32
3.000
39.0
6.9
2.300
1.219
221.2
BOUP-3
38
2.900
45.0
6.8
2.345
1.184
270.8
Avg.
34± 3.7
2.8±0.3
42.0±3.0
6.3±0.9
2.255
1.253
227.2
BOUG-1
36
2.100
45.0
5.0
2.381
1.250
190.1
BOUG-2
38
2.800
48.0
5.9
2.107
1.263
220.3
BOUG-3
31
3.200
40.0
6.3
1.969
1.290
186.7
Avg.
35± 3.6
2.7±0.6
44.3±4.0
5.7±0.7
2.152
1.268
199.0
BOTP-1
37
2.300
55.0
6.3
2.739
1.486
270.0
BOTP-2
39
2.900
62.0
6.9
2.379
1.590
349.3
BOTP-3
43
3.300
58.0
5.5
1.667
1.349
273.0
Avg.
40± 3.0
2.8±0.5
58.3±3.5
6.2±0.7
2.262
1.475
297.5
BOTG-1
45
2.800
63.0
6.9
2.464
1.400
362.7
BOTG-2
39
3.000
63.0
6.5
2.167
1.615
356.0
BOTG-3
42
2.500
70.0
6.0
2.400
1.667
384.5
Avg.
42± 3.0
2.7±0.3
65.3±4.0
6.5±0.5
2.344
1.561
367.7
1 14
1
From Table 5 it can be seen that the first crack load and ultimate load within each BRC beam
2
category increase in a sequence of UP, UG, TP and TG. This is mainly because bamboo-
3
concrete composite action is enhanced in this sequence resulting in a stable load transfer
4
between the two materials in contact. Maximum first crack and ultimate load within each
5
subcategory of BRC beam was obtained in treated grooved beam specimens.
6
The flexural behaviour was assessed through shear and flexural strength of the concrete
7
beams. The shear and flexural strength of the concrete beam were calculated as per IS 456
8
(2000). Shear strength comprises (i) the concrete section alone (Vc); (ii) Shear strength due to
9
confining (stirrups) reinforcement (Vst); and (iii) the concrete section, tension reinforcement,
10
and the (stirrups) (VT).
11
Table 6 Shear and Flexural strength of BRC beams Theoretical Shear Strength (kN) Based Includin Including Concrete on g and Concre Bamboo Bamboo/ te /Steel Steel section Stirrups Stirrups alone Vst Vc VT 6.85 0.00 6.85
Theoretical Flexural Strength (kNm) Including Total Based Longitudinal Moment on Bamboo/ of Concrete Steel Resistan section Stirrups ce alone reinforcement
V E/ VT
Exper iment al Mome nt (kNm) ME
Mc
MR
MT
1.61
3.52
1.05
0.00
1.05
3.35
6.85
1.75
3.84
1.05
0.00
1.05
3.65
0.00
6.85
1.83
4.00
1.05
0.00
1.05
3.80
6.85
0.00
6.85
1.73
3.79
1.05
0.00
1.05
3.60
32.50
13.44
15.63
29.07
1.12
10.40
9.01
1.43
10.44
1.00
RCC-2
34.00
13.44
15.63
29.07
1.17
10.88
9.01
1.43
10.44
1.04
RCC-3
34.50
13.44
15.63
29.07
1.19
11.04
9.01
1.43
10.44
1.06
Avg.
33.67
13.44
15.63
29.07
1.16
10.77
9.01
1.43
10.44
1.03
BVUP-1
15.00
8.40
9.96
18.36
0.82
4.80
4.95
2.15
7.10
0.68
BVUP-2
16.00
8.40
9.96
18.36
0.87
5.12
4.95
2.15
7.10
0.72
BVUP-3
17.50
8.40
9.96
18.36
0.95
5.60
4.95
2.15
7.10
0.79
Avg.
16.17
8.40
9.96
18.36
0.88
5.17
4.95
2.15
7.10
0.73
BVUG-1
15.50
8.40
9.96
18.36
0.84
4.96
4.95
2.15
7.10
0.70
BVUG-2
17.50
8.40
9.96
18.36
0.95
5.60
4.95
2.15
7.10
0.79
BVUG-3
16.00
8.40
9.96
18.36
0.87
5.12
4.95
2.15
7.10
0.72
Avg.
16.33
8.40
9.96
18.36
0.89
5.23
4.95
2.15
7.10
0.74
BVTP-1
17.50
8.40
9.96
18.36
0.95
5.60
4.95
2.15
7.10
0.79
BVTP-2
19.50
8.40
9.96
18.36
1.06
6.24
4.95
2.15
7.10
0.88
BVTP-3
19.00
8.40
9.96
18.36
1.03
6.08
4.95
2.15
7.10
0.86
Beam series
Experi mental Shear (kN) VE
PCC-1
11.00
PCC-2
12.00
6.85
0.00
PCC-3
12.50
6.85
Avg.
11.83
RCC-1
M E/ MT
15
Avg.
18.67
8.40
9.96
18.36
1.02
6.08
4.95
2.15
7.10
0.84
BVTG-1
20.50
8.40
9.96
18.36
1.12
6.56
4.95
2.15
7.10
0.92
BVTG-2
23.50
8.40
9.96
18.36
1.28
7.52
4.95
2.15
7.10
1.06
BVTG-3
21.50
8.40
9.96
18.36
1.17
6.88
4.95
2.15
7.10
0.97
Avg.
21.83
8.40
9.96
18.36
1.19
6.99
4.95
2.15
7.10
0.98
BOUP-1
21.00
20.16
9.96
30.12
0.70
6.72
8.36
2.15
10.51
0.64
BOUP-2
19.50
20.16
9.96
30.12
0.65
6.24
8.36
2.15
10.51
0.59
BOUP-3
22.50
20.16
9.96
30.12
0.75
7.20
8.36
2.15
10.51
0.69
Avg.
21.00
20.16
9.96
30.12
0.70
6.72
8.36
2.15
10.51
0.64
BOUG-1
22.50
20.16
9.96
30.12
0.75
7.20
8.36
2.15
10.51
0.69
BOUG-2
24.00
20.16
9.96
30.12
0.80
7.68
8.36
2.15
10.51
0.73
BOUG-3
20.00
20.16
9.96
30.12
0.66
6.40
8.36
2.15
10.51
0.61
Avg.
22.17
20.16
9.96
30.12
0.74
7.09
8.36
2.15
10.51
0.67
BOTP-1
27.50
20.16
9.96
30.12
0.91
8.80
8.36
2.15
10.51
0.84
BOTP-2
31.00
20.16
9.96
30.12
1.03
9.92
8.36
2.15
10.51
0.94
BOTP-3
29.00
20.16
9.96
30.12
0.96
9.28
8.36
2.15
10.51
0.88
Avg.
29.17
20.16
9.96
30.12
0.97
9.33
8.36
2.15
10.51
0.89
BOTG-1
31.50
20.16
9.96
30.12
1.05
10.08
8.36
2.15
10.51
0.96
BOTG-2
31.50
20.16
9.96
30.12
1.05
10.08
8.36
2.15
10.51
0.96
BOTG-3
35.00
20.16
9.96
30.12
1.16
11.20
8.36
2.15
10.51
1.07
Avg.
32.67
20.16
9.96
30.12
1.08
10.45
8.36
2.15
10.51
0.99
1 2
BVUP beams sustained minimum first crack load and ultimate load amongst all types of BRC
3
beams, because of untreated bamboo strips leading to poor bond strength with concrete. The
4
first crack load of BVTG beam was 54.5% more than that of PCC and 40.3% less than that of
5
RCC beam.
6
On the other hand, ultimate load of BOTG beam was 2.7 times more than that of PCC beams
7
and just 4.4% less than the RCC beams. The maximum ultimate deformation was recorded in
8
the treated plain and treated grooved BRC beam. The highest average deformation for the
9
bamboo reinforced concrete beams was observed in the BVUP beams of 7.5 mm. The
10
deformation ductility i.e. inelastic deformation was maximum in BOTG beam with ratio of
11
2.87.
12
16
25
PCC-1 PCC-2 PCC-3
Load (kN)
20 15 10 5 0 0
1 2 Central Deflection (mm)
(a)
(b)
Fig. 11. (a) Load-deflection response and (b) Crack pattern of PCC beam
1 2
This may be due to the addition of longitudinal bamboo in these beams. The maximum
3
ductility was found similar in BVTP as well as BVTG beams. However, average ductility
4
value of BOTG beam was 18% and 8.3% more than PCC and RCC beams respectively
5
because BRC beams exhibit large deformations before complete failure.
6
The first crack load of PCC beams was 23kN at 2 mm deformation. Up to this load, the PCC
7
beam behaved in a linear elastic manner as seen from Fig. 11 a. After this sudden failure of
8
beam was observed through brittle mode of failure. These PCC beams were found to have
9
least ductility and energy absorption capacity as can be seen from Fig. 11 b. The
10
experimental shear strength and experimental flexural strength were 74% and 245% more
11
than the predicted theoretical capacities.
12
From Table 5 it can be seen that average value of ultimate load sustained by conventional
13
RCC beams was 67.3 kN with 8.5 mm deformation. Initially up to 2 to 3 mm RCC beams
14
describe almost linear elastic behaviour as shown in Fig. 12a. The load after the first crack
15
reaches to a constant value. The failure of RCC beams was due to flexural cracks at middle
16
1/3rd span region as seen in Fig. 12 b.
17
17
80
RCC-1 RCC-2 RCC-3
70
Load (kN)
60 50 40 30 20 10 0 0
1
2
3
4
5
6
7
8
9
10
Central Deflection (mm) (a)
(b) Fig. 12. (a) Load-deflection response of RCC and (b) Beam Crack pattern
1 2
The energy absorption capacity and deformation ductility were found to be maximum in RCC
3
beams amongst all beams considered. However, shear and flexural capacities of RCC beams
4
obtained experimentally were 16% and 3.1% higher than their theoretically predicted values,
5
which can be seen from Table 6.
\
18
Fig. 13. Failure Mode of BRC beams with Vertical stirrups with 2.8% bamboo
50
30 20
BVUG-1 BVUG-2 BVUG-3
40
Load (kN)
40
Load (kN)
50
BVUP-1 BVUP-2 BVUP-3
10
30 20 10
0
0 0
1
2
3
4
5
6
7
8
9 10
0
1
2
3
Central Deflection (mm) BVTP-1 BVTP-2 BVTP-3
1
2
3
4
5
6
7
8
9 10
(b)
Load (kN)
Load (kN)
(a) 50 45 40 35 30 25 20 15 10 5 0 0
4
Central Deflection (mm)
5
6
7
Central Deflection (mm)
8
9 10
50 45 40 35 30 25 20 15 10 5 0
BVTG-1 BVTG-2 BVTG-3
0
1
2
3
4
5
6
7
8
9 10
Central Deflection (mm)
(c) (d) Fig. 14. (a), (b), (c), (d) Load-deflection response of BVUP, BVUG, BVTP, and BVTG Beams respectively.
1 2
The failure of BVTP beams was due to major shear crack as seen from Fig. 13. This may be
3
due to loosening of the confinement of vertical bamboo strips. The deviation in load-
4
deformation curve can be observed at the instance of first crack load and ultimate load. This
5
behaviour can be captured from Fig. 14 (a), (b), (c), and (d) for all BV type BRC beams.
6
Maximum experimental shear strength of 21.83 kN obtained in BVTG beams which is 19 %
7
more than the theoretically predicted value. However, it is 84.5% more than PCC and 54%
8
less than RCC beams.
9
On the other hand, BVTG beam showed average moment carrying capacity of 6.99 kN-m,
10
which nearly, equals to the theoretically predicted flexural strength. Compared to control
11
beams, average flexural capacity of BVTG beam is 1.84 times more than PCC but 35% less
12
than RCC beams.
19
1
BO type BRC beams also had stirrups in the form of bamboo strips tied transverse to the
2
longitudinal bamboo. The BO type BRC beams failed mainly due to the shear crack
3
originating from bottom tensile surface and propagating towards top compressive layer of the
4
beam just below the point load, except BOUG beam, which failed as a result of major
5
flexural crack in middle 1/3rd span as shown in Fig.15.
6
This may be due to loss of bond at bamboo concrete interface and loosening of the
7
confinement joints of vertical bamboo strips. Compared to respective BV type BRC beams
8
BO type BRC beams have shown enhancement in linear stiffness and ultimate load as seen
9
from Fig.16 (a), (b), (c), and (d).
10
Experimentally obtained shear and flexural strength were found to increase in both types of
11
BRC beams. The sequence of increase is UP, UG, TP and TG. Maximum experimental shear
12
strength of 32.67 kN was found in BOTG beams which was 8.4 % more than the theoretically
13
predicted value. However, it is 2.8 times more than PCC and just 3% less than RCC beams.
14
Table 6 shows maximum moment carrying capacity of 10.45 kN-m was developed by BOTG
15
beams and this is more than the value of BVTG beams. The flexural capacity of BOTG beam
16
is 1.84 times more than PCC and compared to RCC beam it is marginally less by 3%.
20
50 45 40 35 30 25 20 15 10 5 0
BOUP-1 BOUP-2 BOUP-3
Load (kN)
Load (kN)
Fig. 15. Failure Mode of BRC beams with 3.8% bamboo
0
1
2
3
4
5
6
7
8
BOUG-1 BOUG-2 BOUG-3
50 45 40 35 30 25 20 15 10 5 0
9 10
0
1
Central Deflection (mm)
2
3
5
6
7
8
9 10
Central Deflection (mm)
(a)
(b) BOTP-1 BOTP-2 BOTP-3
70 60
BOTG-1 BOTG-2 BOTG-3
80 70 60
50
Load (kN)
Load (kN)
4
40 30 20
50 40 30 20
10
10
0
0 0
1
2
3
4
5
6
7
8
9 10
Central Deflection (mm)
0
1
2
3
4
5
6
7
8
9 10
Central Deflection (mm)
(c) (d) Fig. 16. (a), (b), (c), (d) Load-deflection response of BOUP, BOUG, BOTP, and BOTG Beams respectively.
1 2
Fig. 17 compares the average of load deformation response of all the four types of concrete
3
beams. The curves in Fig. 17 distinguish the flexural behaviour of each concrete beam
4
separately. It is observed that flexural strength amongst these beams increases in a sequence
5
of PCC, BV, BO and then RCC beams.
21
70
PCC-avg RCC-avg BVUP -avg
60
BVUG -avg BVTP -avg
50
BVTG -avg BOUP -avg
Load (kN)
40
BOUG -avg BOTP -avg
30
BOTG -avg
20
10
0 0
1
2
3
4
5
6
7
8
9
10
Central Deflection (mm) Fig. 17. Average Load-deflection response of PCC, RCC and all types of BRC Beams.
1
The average values of maximum ultimate load, obtained in these beams are 21kN, 63kN,
2
35kN and 48kN for PCC, RCC, BVTP and BOTG beam respectively. The undereinforced
3
section designed for BV type BRC beam resulted in 67% higher flexural strength than PCC
4
beams, however it is 44% less than the mean flexural strength of RCC beams. Whereas after
5
addition of 1% bamboo in BV type BRC beams flexural strength was found 37% more than
6
BVTP beam but still 24% less than RCC beam.
7
4 Observations and Conclusions
8
The efficacy and performance of BRC beams is investigated in the present research. The
9
concrete beams reinforced with longitudinal as well as shear reinforcement in the form of
10
bamboo strips were tested experimentally. Based on the analysis of test results, the following
11
important conclusions are made.
12
1. There is a significant enhancement in first crack load, ultimate load, ductility, and
13
energy absorption capacity of both type BRC beams (BV and BO) compared to PCC
14
beams. BO type BRC beams have resulted in higher values of these parameters than
15
the respective BV type BRC beams. However, the ultimate load and energy
22
1
absorption capacity of BOTG beam was found close to that of RCC beams, which is
2
3% and 17% less compared to RCC beams.
3
2. The flexural capacity of each BRC beam is more than that of theoretical predicted
4
values. Flexural capacity of BOTG beam is comparable to that of the RCC beam.
5
3. Amongst two type of BRC beams, BO type BRC beams have shown maximum shear
6
as well as flexural strength. Shear strength of BOTG beam is comparable to shear
7
strength of the RCC beam.
8
4. Shear as well as flexural performance of BOTG beam is comparable to that of
9
conventional RCC beam having 1.23 % steel reinforcement, except the mode of
10
failure.
11
The present investigation establishes the efficacy of B. Arundinacea bamboo strip treated
12
with the proposed treatment (i.e. Grooved bamboo profile + Bond Tite coating + steel wire
13
wrapping + sand blasting), which are used instead of conventional steel reinforcement.
14
However, the use of treated bamboo strips inside concrete flexural member needs further
15
experimental studies on full-scale specimens at different ages of concrete to ascertain the
16
long term durability.
17
Conflict of interest
18
It is assured by the authors that this publication does not have any known conflicts of interest.
19
In addition, there has been no significant financial support for this research that could have
20
influenced its findings.
21
Acknowledgement
22
Technical Education Quality improvement Programme -II (TEQIP-II) An initiative of
23
Ministry of Human Resource and Development (MHRD), Government of India funded this
24
research work.
25
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26
1. A. Anandamurthy, V. Guna, M. Ilangovan and N. Reddy, A review of fibrous
27
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properties of glubam. Construction and Building Materials. 1(44):765-773, 2013.
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14;168(2):57-67, 2014. 4. S.R. Imadi, I. Mahmood and A.G. Kazi, Bamboo Fiber Processing, Properties, and Applications. In Biomass and Bioenergy, pp. 27-46, Springer, Cham, (2014).
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5. C. K. Kankam, B. Odum-Ewuakye, Flexural strength and behaviour of babadua-
5
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Experimental Evaluation of Bamboo Reinforced Concrete Beams
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Pankaj R. Mali a, Debarati Datta b a
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b
Research Scholar, Department of Applied Mechanics, Visvesvaraya National Institute of Technology, Nagpur440010, India. Email- [email protected]
Assistant Professor, Department of Applied Mechanics, Visvesvaraya National Institute of Technology, Nagpur440010, India. Email- [email protected]
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HIGHLIGHTS:
9 • Bond strength enhancement through mechanical action in treated grooved bamboo samples. 10 • Application of newly developed bamboo reinforcement in RC beam specimens. 11 • Effect of bamboo reinforcement percentage on enhancing shear and flexural strength.
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Declarations of interest
Dear Editor-in-Chief, Journal of Building Engineering
Please find enclosed full-length manuscript, entitled “Experimental Evaluation of Bamboo Reinforced Concrete Beams”, (JOBE_2019_346_R2), by Pankaj R. Mali (corresponding author) and Dr. Debarati Datta, which we would like to submit for publication as a research paper in Journal of Building Engineering, ELSEVIER. We wish to confirm that there are no known conflicts of interest associated with this publication. We also confirm that this manuscript has not been published elsewhere and is not under consideration by another journal. Authors have acknowledged the funding sources in the manuscript. Proper citations to the previously published works is given, and that in case Data/Table/Figures are quoted verbatim from some other publication, the required permission to do so has been obtained. All authors have approved the manuscript and agree with its submission to Journal of Building Engineering, ELSEVIER.
We are ready to help in each step of submission. We appreciate your time and look forward to your response.
Kind regards. P. R. Mali (Corresponding author) E-mail address: [email protected] Contact number: +918806244477