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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 2, February 2014)

233

Experimental Investigations on The Flexural Strength of

PET Reinforced Concrete

M. L. Anoop Kumar

1

, Dr. I. V. Ramana Reddy

2

, Dr. C. Sasidhar

3

1

Lecturer in Civil Engineering, Govt. Polytechnic, Dept. of Technical Education, A.P., India.

2Professor, Dept. of Civil Engineering, S.V.University College of Engineering, Tirupati, India.

3Professor, Dept. of Civil Engineering, JNT University College of Engineering, Anantapuramu, India

Abstract— Due to the rapid industrialization taking place globally, the problems generated are acute shortage of construction material and increasing in productivity of wastes. The production and consumption of plastic and the rate at which solid plastic waste (SPW) are created have increased considerably. Plastics constitute 12.3% of total waste produced most of which is from discarded water bottles. The present research studies concentrate on resolving the above issues in a beneficial way. By the usage of PET bottle waste at suitable scale as concrete reinforcement for constructional works, the present research aims at waste management, by use of PET waste in improvement of concrete. The non-biodegradable PET bottle waste is used as reinforcement for concrete and the flexural strength of hardened concrete at 28days was tested and compared with conventional concrete and steel reinforced concrete. In this study, there are four types of concrete beam specimens with steel reinforcement, without steel reinforcement, with PET reinforcement and combined steel and PET reinforcement tested for 28 days flexural strengths and the detailed analysis of the results are reported.

Keywords— Concrete, Flexural Strength, PET waste concrete, PET Bottle waste

I. INTRODUCTION

Plastic, one of the most significant innovations of 20th century, is a ubiquitous material. A substantial growth in the consumption of Plastic is observed all over the world in recent years, which also increased the production of plastic related waste. The plastic waste is now a serious environmental threat to modern civilization. Plastic is composed of several toxic chemicals, and therefore plastic pollutes soil, air and water. Since plastic is a non-biodegradable material, land-filling using plastic would mean preserving the harmful material forever. Land-filling of plastic is also dangerous due to its slow degradation rate and bulky nature and also the waste mass may hinder the ground water flow and can also block the movement of plant roots.

Burning of plastics releases a variety of poisonous chemicals into the air, including dioxins, one of the most toxic substances.

Plastic waste can also be used to produce new plastic based products after processing. However it is not an economical process as the recycled plastic degrades in quality and necessitates new plastic to make the original product. Although these alternatives are feasible except for land-filling, recycling of plastic waste to produce new materials, such as cement composites, appears as one of the best solution for disposing of plastic waste, due to its economic and ecological advantages[2][3].

Work has already been done on the use of plastic waste such as polyethylene terephthalate (PET) bottle, poly vinyl chloride (PVC) pipe, high density polyethylene (HDPE), shredded and recycled plastic waste, polyurethane foam, polypropylene fiber etc. as an aggregate, as filler or as fiber in the preparation of concrete.

Polyethylene Terephthalate (PET) is one of the most important and extensively used plastics in the world, especially for manufacturing beverage containers [1]. The current worldwide production of PET exceeds 6.7 million tons/year and shows a dramatic increase in the Asian region due to recent increasing demands in China and India. In 2007 the world’s annual consumption represented 250,000 million PET bottles (10 million tons of waste) with a growth increase of 15%. In the United States 50,000 million bottles are land filled each year.

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 2, February 2014)

234

II. ABOUT THE RESEARCH

A.Objective Of The Present Research

To study the flexural behavior of concrete reinforced with recycled PET bottle in various forms such as bars, bunch of long strips and shorter strips in comparison to non-reinforced concrete and concrete reinforced with steel reinforcement.

B.Need Of The Present Study

The enormous production of PET bottle wastes is posing a threat to the environment. Even though a little portion of it is recycled, most of it is being land filled and incinerated which leads to potential imbalance of the eco system especially in Asian countries like India. The increased rate of annual production of PET bottle waste, their cost of recycle and disposal became a global issue creating menace to the wellbeing of our environment and its components. To abate the risk and finance involved in recycling and disposal of these PET bottles alternative techniques are in progress in using the PET bottles waste as a constituent of concrete in the construction industry. Though few research works were taken up for using the recycled PET bottles as a constituent of concrete, the flexural behavior of concrete when reinforced with recycled PET hollow bars, PET strips and comparison with plain concrete and Steel Reinforced concrete were not widely reported. Hence, the present study has been taken up to assess the flexural behaviour of concrete reinforced with recycled PET bottles in the form of hollow bars and strips.

C.Significance Of Research

DoraFoti reported that addition of a very small amount of fibers from recycled and shredded PET bottles can have a large influence on the post-cracking behavior of plain concrete elements [4]. Ramadevi et al. reported that Flexural strength increased up to 2% replacement of the fine aggregate with PET bottle fibers and it gradually decreased for 4% and remains the same for 6% replacements[5]. Akcaozoglu et al. determined the ratios between flexural strength and compressive strength values of cement mortar and found that average values of flexural strength similar to those of normal weight mortar.

This paper examines the flexural properties of concrete reinforced with recycled post consumer PET bottles in various forms such as hollow bars, bunch of long strips and discrete shorter strips in comparison to non-reinforced concrete and concrete reinforced with steel reinforcement.

D. Methodology

In the present research, experimental investigations were conducted for assessing the flexural strength of concrete provided with PET reinforcement in various forms like hollow bars and strips. Also the recycled PET were incorporated in the tension zone, providing PET reinforcement in the form of bars and bunch of strips. In addition 1% fine aggregate was replacement by PET bottle material cut in dimensions of 40mm x 4mm x 0.6mm and flexural strength tests were conducted and the results were reported.

Totally 7 types of concrete beam specimens of size 50 x 10 x 10 cm were used for the research. Control beams are those which were made with plain concrete without any reinforcement are the first type designated as CB. Concrete beams reinforced with steel bars of 8mm diameter and 48cm long were the second type of specimens designated as RSB. Concrete beams reinforced with PET hollow bars of 24mm external diameter, 22.8mm internal diameter and 48cm long with a single bar or with two bars in the tension zone of the beam were used which are third and fourth types designated as RP1B and RP2B respectively. Also, Beams with combination of steel and PET reinforcement in the tension zone were made which are designated as RSPB and the beams with steel and PET long strips were made designated as RSPSB and finally the beams with PET short strips were made which are prepared by replacing 1% fine aggregate with PET short strips while mixing concrete, designated as PC.

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 2, February 2014)

235

The details of various types of test specimen used are listed in TABLE I.

TABLEI DETAILS OF BEAMS USED

S.No. Constituent Designation

1. Control specimens CB

2. Concrete beams reinforced with steel bars

RSB

3. Concrete beams reinforced with one PET bar

RP1B

4. Concrete beams reinforced with two PET bars

RP2B

5. Concrete beams reinforced with steel and PET bars

RSPB

6. Concrete beams reinforced with steel and PET long strips

RSPSB

7. PET concrete( with short strips) PC

E. Materials Used

The materials used for the present research are: 43-Grade Ordinary Portland Cement (OPC) sand confirming Zone II

Coarse Aggregate Water

Recycled PET Steel bars of 8mm dia

The properties of PET material used are given in Table.II.

The following types of PET reinforcement was used for the purpose of investigation.

TABLEII

PROPERTIES OF PETMATERIAL

1. Hollow PET Bars: A hollow PET bar is prepared by cutting four PET bottles longitudinally, folded and pinned together to the dimensions of 48cm long hollow bar, with outer diameter of 24mm and the inner diameter of 22.8mm so that the effective cross section almost similar to the 8 mm dia. Steel bar. The making of hollow PET bars is shown in Figures 2&3.

2. PET Long Strips: PET long strips are made of PET bottle material by cutting and placing plastic layers in the dimensions of 8cm long, breadth of 0.5cm, 11 such strips are placed over one another to a thickness of 6.6mm, in which each strip is 0.6mm.These layers are bound together by tying with plastic strings that are prepared by cutting the PET bottle nearly to the size of threads as shown in Figure.4.

3. PET Short Strips:PET short strips are similar to that of long strips. They are prepared by cutting the PET bottles into pieces of 4cm long, width of 0.4cm and thickness of 0.6mm as shown in Figure.6.

Concrete used for the testing programme is of M25 grade

with the proportions given in TABLE III obtained by IS method of mix design as per IS 10262:1993.

Molecular formulae (C10H8O4)n

Density

1.38 g/cm3 (20 °C), amorphous: 1.370 g/cm3; single crystal: 1.455 g/cm3

Melting point > 250 °C,260 °C Boiling point > 350 °C (decomposes)

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 2, February 2014)

236

TABLEIII PROPORTION OF M25 GRADE

Material Content(Kg/m3)

Cement 415.524

Sand 639.256

Coarse Aggregate

1086.128 Water 203.255

E. Test Programme

The beams were tested for flexural strength after curing for 28 days in a Digitalized universal testing machine, the deflection in the beam is noted at regular intervals from the deflection dial gauge and the load at the point of failure is noted.

The bearing surfaces of the supporting and loading rollers are wiped clean, and any loose sand or other material removed from the surfaces of the specimen where they are to make contact with the rollers. The specimen is then placed in the machine in such a manner that the load is applied to the uppermost surface as cast in the mould, along two lines spaced 20.0 or 13.3 cm apart. The axis of the specimen is carefully aligned with the axis of the loading device. No packing is used between the bearing surfaces of the specimen and the rollers. The load is applied without shock and increasing continuously at a rate such that the extreme fibre stress increases at approximately 0.7 kg/sq cm/min that is, at a rate of loading of 400 kg/min for the 15.0 cm specimens and at a rate of 180 kg/min for the 10.0 cm specimens. The load is increased until the specimen fails, and the maximum load applied to the specimen during the test is recorded. The appearance of the fractured faces of concrete and any unusual features in the type of failure is noted.

The flexural strength of the specimen is expressed as the modulus of rupture fb which if ‘a’ equals the distance

between the line of fracture and the nearer support, measured on the centre line of the tensile side of the specimen, in cm, is calculated to the nearest 0.05 MPa as follows:

When ‘a’ is greater than 20.0 cm for 15.0 cm specimen or greater than 13.3 cm for a 10.0 cm specimen, then

When ‘a’ is less than 20.0 cm but greater than 17.0 cm for 15.0 specimen, or less than 13.3 cm but greater than 11.0 cm for a 10.0 cm specimen

Where

b = measured width in cm of the specimen,

d = measured depth in cm of the specimen at the point of failure,

l = length in cm of the span on which the specimen was supported, and

p = maximum load in kg applied to the specimen. The test setup is shown in Figure.1.

Figure.1 Test Beam placed in UTM

Figure.2 Making of PET Hollow bars

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 2, February 2014)

237

Figure.3 PET Hollow bars as Beam reinforcement

Figure.4 PET Long strips

Figure.5 PET Long strips as reinforcement along with steel

Figure.6 PET Short strips

Figure.7 Concrete with PET Short strips filled in beam mould

The Flexural strength of each type of beam was obtained and the load-deflection characteristics of the beam up to the point of failure are reported in this paper.

F. Test Results and Discussion

The results of the experimental investigations carried out on all the 7 types of concrete beams with respect to the flexural strength and load deflection characteristics are presented in tabular and graphical forms.

1. Comparing CB, RSB, RP1B:

Figure7.Load Deflection Curves of CB, RSB and RP1B

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 2, February 2014)

238

2. Comparing CB, RSB, RP2B:

Figure.8 Load Deflection Curves of CB, RSB and RP2B

In the above Figure.8, a comparison between control beam(CB), beam reinforced with steel(RSB) and beam reinforced with only two PET hollow bars (RP2B) is done, which depicts the deflection of these beams under their corresponding loading. The deflection of RP2B has similar variation compared to RSB in exhibiting a large deformation before failure than the control beam which exhibited sudden failure. The load at failure for RSB is greater than that of CB and RP2B. Just before failure, the RP2B exhibited a little ductile nature like RSB. Due to improper bonding between concrete and PET, micro cracks would have propagated in concrete and the failure has occured in earlier stage itself, but the post cracking behaviour of RP2B shows the ductile nature of PET in the beam offering a little resistance even after the failure of beam preventing sudden failure.

3. Comparing RSB& RSPB

Figure.9 Load Deflection Curves of RSB and RSPB

In the graph shown in Figure.9 it can be observed that the load at failure of RSB for the given load is considerably greater compared to RSPB, which has both steel and PET reinforcement in the tension zone. The load at failure for RSB is greater than that of but the post cracking behavior of the RSPB shows brittle nature contrary to the previous case. Also, it was observed that the deflection was same up to some point of load and the deflection was decreasing in the RSPB when compared to RSB. But finally exhibited sudden failure. This may be due to the improper bonding between the PET hollow bars and concrete present in the tension zone. So, due to improper bonding between concrete and PET, micro cracks would have propagated in concrete as a result, even before the stress was transferred to steel, failure of the beam occurred.

4. Comparing RSB & RSPSB

Figure.10 Load Deflection Curves of RSB and RSPSB

From the graph in Figure.10, it is observed that there is exceptionally large increase of load at failure in RSPSB than that of RSB. RSB exhibited ductile nature due to presence of steel in it, and the graph shows continuous increase of strain with almost marginal increase of stress, results in maximum deflection. While the load-deflection curve of RSPSB shows greater increase of load at failure than that of RSB. And at some point, the deflection of RSPSB decreases compared to RSB. The post cracking behavior of RSPSB exhibited greater resistance to sudden failure which is even better than that of RSB.

5. Comparing RSB & RSPSB

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 2, February 2014)

239

But the post cracking behaviour of the PC shows binding of PET short strips with the hardened concrete offering resistance even after the failure of the beam preventing sudden failure.

6. Flexural Strength Test Results:

The variations of flexural strength results of all the 7 different types of concrete beams are given in TABLE IV. Figure.11 displays a bar chart clearly showing the variation of strength in flexure for different types of beams.

TABLEIV

FLEXURE STRENGTH TEST RESULTS

S.No. Constituent Designation Flexural

Sterngth

(N/mm2)

1. Control specimens CB

8.4

2. Concrete beams reinforced

with steel bars

RSB

18.3

3. Concrete beams reinforced with PET one bar

RP1B

6.7

4. Concrete beams reinforced with PET two bars

RP2B

7.5

5. Concrete beams reinforced with steel and PET bars

RSPB

18.9

6. Concrete beams reinforced with steel and PET long strips

RSPSB

23.96

7. PET concrete( with short strips)

PC

7.39

Figure.10 Bar Chart showing Flexural Strength Test Results

From the above bar chart it can be understood that there is not much difference in flexural strength of control beam is compared to that of PET concrete beam RP1B and concrete beam reinforced with two PET bars RP2B, whereas the flexural strength of concrete beam reinforced with one PET bar (RP1B) is slightly less than that of the control beam. The flexural strength of concrete beam reinforced with steel bars (RSB) is almost similar to that of concrete beam reinforced with steel and PET bars (RSPB) and the flexural strength of beams reinforced with both steel and PET long Strips (RSPSB) exhibited exceptionally higher strength in flexure and flexural strength of these beams is far greater than that of control beams(CB), PET concrete beam (PC), concrete beams reinforced with only PET bars(RP1B). The maximum flexural strength is attained by concrete beam reinforced with steel and PET long strips (RSPSB) above all the beams casted in the present investigation i.e. nearly 25 N/mm2

III. CONCLUSION

Flexural strength comparison between control beam and other types of beams casted for the present investigation is illustrated as follows:

CB (vs) RSB

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 2, February 2014)

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CB (vs) RP1B& RP2B

The flexural strength of control beam (CB) and the concrete beams reinforced with one and two PET bars i.e. RP1B, RP2B is almost same, further the ductility property is enhanced for PET reinforced concrete over control beam. More over post cracking behavior shows the binding nature of PET material with hardened concrete offering more resistance even after the failure preventing sudden failure

CB (vs) RSPSB

The flexural strength of concrete beams reinforced with steel and PET long strips (RSPSB) is far greater than that of control beams. The load at failure is also comparatively more for RSPSB.

CB (vs) PET CONCRETE

The flexural strength and the loads at failure of CB &PET concrete beams (PC) are almost the same. And the post cracking behavior of the PET concrete beam shows the nature of PET fibres with hardened concrete offering little more resistance even after the failure.

In concrete beam reinforced with steel (RSB), the increase in load causes transfer of stress from concrete to steel, which bears the load and resists the failure of beam, whereas in the case of concrete beams reinforced with PET bars, with the increase in load micro cracks are developed in the concrete, causing failure of the hardened concrete before the stress transfer taking place from concrete to PET bars. This might be due to improper bonding at the interface of concrete and PET bars. The concrete beam reinforced with steel and PET strips (RSPSB) has shown considerable increase in flexural strength compared to that of concrete beams reinforced with steel bars (RSB).

In environmental perspective, there is dire need for safe disposal of PET waste, which otherwise causes pollution. As there is marginal difference in flexural strength of control beam (CB) compared to other PET reinforced concrete beam, the PET reinforced concrete can be used for less important works by which PET waste can be effectively mitigated. Thus the present investigation suggests the scope for safe disposal of PET waste as a constituent of construction material.

IV. FUTURE SCOPE

If proper bonding is present at the interface of concrete and PET bars, the increase in load causes stress transfer from concrete to PET bars, preventing early failure of the beam. Therefore further investigation can be performed to develop effective techniques to improve the bonding between concrete and PET bars in the PET reinforced concrete beams.

REFERENCES

[1] Bandodkar.L.R., Gaonkar.A.A, Gaonkar N. D., Gauns Y. P., Aldonkar S. S., Savoikar P. P., Pulverised PET Bottles as Partial Replacement for Sand., International Journal of Earth Sciences and Engineering., Volume 04, No.06 SPL, October 2011, pp. 1009-1012 [2] Sivaraja.M, Kandasamy.S, Thirumurugan.A, Mechanical strength of

fibrous concrete with waste rural materials., Journal of engineering and applied science, vol. 69, April,page: 308 – 312, 2010

[3] Sivaraja.M and Kandasamy.S, Reinforced concrete beams with rural composites under cyclic loading., Journal of engineering and applied science 2 (11), page: 1620 -1626, 2007.

[4] Dora Foti, Use of recycled waste PET bottles fibers for the reinforcement of concrete., Composite Structures 96,pp.396–404, 2013

[5] Ramadevi.K, Manju.R., Experimental Investigation on the Properties of Concrete With Plastic PET (Bottle) Fibres as Fine Aggregates., International Journal of Emerging Technology and Advanced Engineering Volume 2, Issue 6, June 2012

[6] Bhogayata, Shah.K.D, vyas.A, Arora.N.K., Performance of concrete by using Non recyclable plastic wastes as concrete constituents., International Journal of Engineering Research & Technology (IJERT) Vol. 1 Issue 4, June – 2012

[7] Batayneh M, Marie I, Asi I., Use of selected waste materials in concrete mixes., Waste Manage 2007;27(12):1870–6.

[8] Marzouk OY, Dheilly RM, Queneudec M., Valorization of post-consumer waste plastic in cementitious concrete composites. Waste Manage 2007;27:310–8.

[9] Choi Y-W, Moon D-J, Chung J-S, Cho S-K., Effects of waste PET bottles aggregate on the properties of concrete. Cem Concr Res 2005;35(4):776–81.

[10] Ochi T, Okubo S, Fukui K., Development of recycled PET fiber and its application as concrete-reinforcing fiber., Cement & Concrete Composites 35;29:448–55., 2007.

[11] Kim SB, Yi NH, Kim HY, Kim JHJ, Song Y-C. Material and structural performance evaluation of recycled PET fiber reinforced concrete. Cement & Concrete Composites;32:232–40, 2010 [12] IS 456-2000 -Code of practice for plain & reinforced cement

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References

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