use of plastic in formwork -...

259 Abhishek Balvir Patil, Akhilesh Anil More, Akshay Ashok Patil, Akshay Sunil Lohar,

Mikaj Shahajhan Sutar, Sayali Kiran Shirgave, Prof. Dr. G. M. Malu

International Journal of Engineering Technology Science and Research

IJETSR

www.ijetsr.com

ISSN 2394 – 3386

Volume 4, Issue 4

April 2017

Use of Plastic in Formwork

Abhishek Balvir Patil

Student, (U.G.)

Dr. J.J. Magdum College of

Engineering, Jaysingpur

Akhilesh Anil More

Student, (U.G.)



Akshay Ashok Patil

Student, (U.G.)



Akshay Sunil Lohar

Student, (U.G.)



Mikaj Shahajhan Sutar

Student, (U.G.)


Engineering, Jaysingpur.

Prof. Dr. G. M. Malu

Head of Departments

Civil Engineering



Sayali Kiran Shirgave

Student, (U.G.)



Abstract

In this paper, has been discussed plastic formwork system has been introduced and all the aspects of plastic

formwork. The large amount of deforestation has occurred in recent past causing environmental imbalance to our

ecosystem. As a preventive measure to stop deforestation we should find alternative to wood formwork. In this point of

view ‘PLASTIC FORMWORK’ is only possible solution to this problem as it is recyclable, reusable and eco-friendly

alternative. That’s why the plastic formwork introduced to replace the traditional formwork. Plastic formwork is a new

innovation is formwork industry, it is famous for its light weight, speedy construction and in accuracy in work. Today

almost over 350000 sq m of formwork is being used for construction purpose all over the world. In our country plastic

formwork has been used on many construction projects and it has been proved to be economical. Plastic formwork has

been widely used in Gulf countries, Europe, Asia as well as all other parts of world. This technology is mostly suitable

for huge housing projects to be completed in short period of time, where columns, beams, slab sizes are standard. This

technology gives more accurate results and good quality of construction in optimum cost and minimum time.

Keywords:Plastic formwork, Joist, Props, Ligaments and Joints.

INTRODUCTION

Formwork is the temporary structure that enables molding of concrete into desired shape, holds it in the

correct position until it has hardened sufficiently and is able to support the loads imposed on it. The structural

system of temporary supports that holds the formwork in position is termed as false work. Formwork is also

an effective means of curing when it is left in place. The operation of removing the formwork is known as

stripping. Stripped formwork can be reused. Reusable forms are known as panel forms and non-usable ones

are called stationary forms.

The erection of formwork is a time consuming process and cost of formwork (material + labour) could

sometimes be as high as 50% of the cost of the concrete structure. The failure of formwork systems during

construction, causing monetary and time loss, sometimes grave injuries and death, are not uncommon.

Efficient design of these temporary structures play critical role in reducing the cost and ensuring safety. [1]




IJETSR

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April 2017

Formwork, which holds and supports wet concrete till such time it cures, is a very vital element in concrete

construction. With the globalization of Indian economy and introduction of multinationals in India for the

construction and nations pride program of golden quadrilateral, it has become foremost to have speedy

construction and timely completion of projects. Now days, low waste modern formwork systems for

superstructure construction are commonly adopted. Formwork system affects on the cost, time, and quality of

project delivery. But still these formwork systems are not much used in India and most of the contractors do

not like to shift to the latest technology as they have the doubt of facing losses in the project and they are very

much familiar with the existing formwork type, the conventional type. At the same time they believe that

these formwork systems are bit expensive.[2]

1. CLASSIFICATION OF FORMWORK AND FORMWORK SYSTEMS

Different types of construction require the use of different types of formworks. The strength of the building

components, the speed at which building is constructed, and the cost of construction will depend to a great

extent upon the appropriateness of formwork used in the construction. Formwork can be classified according

to a variety of categories, relating to the differences in sizes, location of use, construction materials, nature of

operation, or simply by the brand name of the products. Major formwork systems are as follows:

1. Traditional Timber Formwork Systems

2. Re-Usable Plastic/PVC/Aluminium Formwork Systems

3. Table form/Flying form systems

4. Jump form Systems

5. Slip form Systems

6. Permanent Insulated Formwork Systems

2. CONVENTIONAL FORMWORK AND NEED FOR MODERN FORMWORK

2.1 Conventional Formwork

This usually consists of standard framed panels tied together over their backs with horizontalmembers called

waling. The waling is provided with the basic function of resisting the horizontal force of wet concrete. One

side of the wall formwork is first assembled ensuring that it is correctly aligned, plumbed and strutted. The

steel reinforcement cage is then placed and positioned before the other side of the formwork is erected and

fixed. Plywood sheet in combination with timber is the most common material used for wall formwork. The

usual method is to make up wall forms as framed panels with the plywood facing sheet screwed on to studs on

a timber frame. This allows for the plywood to be easily removed and reversed and used on both sides so as to

increase thenumber of reuses. The wall forms are susceptible to edge and corner damage and must be

carefully handled. Special attention must be given to comers and attached piers since the increased pressures

applied by wet concrete could cause the abutments to open up, giving rise to unacceptable grout escape and a

poor finish to the cast wall.

2.2 Need For Modern Formwork Systems

The earliest formwork systems made use of wooden scantlings and timber runners as it enabled easy forming

and making at site. But these wooden scantlings and timber runners tend to lose their structural and

dimensional properties over a period time and after repeated usage thus posing safety problems. Many of the

accidents take place in Reinforced Cement Concrete (RCC) construction because of inferior formwork and

scaffolding. Now focus has to be shifted to other key factor “Formwork”, to face the challenges for the

completion of fast track projects. By going in for system formwork, substantial savings are possible by faster

return on investments.

2.3 Plastics Used For Design Of Formwork

ABS (Acrylonitrile Butadiene Styrene)




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HIPS (High Impact Polystyrene)

HALENE PP

PP (Polypropylene)

2.4 Features And Limitations Of Plastic Formwork

The System is extremely light in weight as compared to wood and steel formwork system which requires

heavy lifting equipment’s.

Fast construction is achieved, and mainly suitable for large construction projects.

Locking system is very easy having nylon handles that lock with simple 90degree turn.

System components are durable and can be used several times without sacrificing the quality or

correctness of dimensions and surface.

Installation and dismantling is very easy and fast saving much more time.

System is extremely flexible as more number of combinations are possible.

Concrete does not stick to plastic which makes dismantling easy and less timing consuming.

System has extreme temperature tolerance of -30°C to 70°C.

System is fungus and termite resistance unlike traditional formworks hence improving life of formwork.

Cleaning is extremely easy. Just water is enough no requirement of any oil or lubricant.

2.5 Comparison Between Various Types Of Formwork

There are different types of formwork which are using for construction of building. But now a days

conventional formworks are not feasible to use according to cost, time and handling. Table below gives

comparison between various types of conventional formworks and modern formworks.

Table 1: Comparison between various types of formwork

Sr.

No Item

Wood

Formwork Steel Form Work

Plywood with Steel

formwork

Aluminium

Formwork

Plastic Formwork

(Geo-Plast)

01 Strength (kN/ Sq.m) 30 65 50 60 80

02 Difficulty Easy Difficult Average Easy Easy

03 Efficiency Low Quite High Average High

More than

aluminium

Formwork

04 Application

Wall, Column,

Beam, Slab,

Bridge.

Wall, Column,

Beam, Slab.

Wall, Column,

Beam, Slab, Bridge.

Wall, Column, Beam,

Slab.

Wall, Column,

Beam, Slab.

05 Recovery Value Rough Smooth Like Dry

Wall Smooth Finishing Smooth Finishing

Smoother finishing

than aluminium

Formwork

06 Maintenance Cost Low High Low Low Very Low

07 Durability Low Average Average High Very High

08 Life Span Short Long Long Long Used for 100 times

09 Speed of Construction Low Moderate Moderate High High

10 Labour Unskilled Semi-skilled Semi-skilled Skilled Semi-skilled

11 Recycle No Yes Yes/No Yes Yes

12 Self-Weight Light Heavy Heavy Light Light

13 Initial Cost Low High High High Moderate

14 Handling Average Difficult Difficult Easy Easy




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3. DESIGN OF MEMBERS

Design of different components of plastic formwork are discussed below.

Notation:

a= Weight of the formwork itself and the scaffold = Density x thickness of plate

b= Weight of fresh concrete (normal weight (heavy reinforced) X Thickness of slab

c= Uniform distributed load of runways for concrete transport and impact loads of the crowding of

crewmen(panel design)

d= Concentrated load form weight of work crews and transport equipment:= one crew member that carries

loads + wheel barrow/ buggies for concrete transport

q = uniformly distributed load pre unit length

σe = applied bending stress;

σa= allowable bending design stress;

M = bending moment [Nmm];

I = moment of inertia of the cross section [mm4];

W = section modulus of the cross- section [mm3].

h = Thickness of Plate [mm]

3.1 Slab Plate[3]

Sample calculations for Verification for Bending Stress.

The calculation is made for a width of b=1m.

𝑞 = 𝑎 + 𝑏 + 𝑐 × 1.00 + 𝑑 𝑙 ……(N/ m2)

For ABS type of plastic:

a = 10300.5 X 0.06 = 618.03 N/ m2

b= 25000 X 0.15 = 3750 N/ m2

c = 2500 N/ m2

d = 1300 + 2800 = 4100 N/ m2

𝑞 = 𝑎 + 𝑏 + 𝑐 × 1.00 + 𝑑 𝑙

q = (618.03 + 3750 + 2500) x 1.00 + 4100/0.252

q = 23137.87 N/m

Now, 𝜎𝑒 = 𝑀 𝑊 < 𝜎𝑎

Where, 𝑀 = 𝑞𝑙2 8

= 23137.87 X 0.2522 / 8

M = 183668.4 N-mm

𝑊 = 𝑏 × 𝑕2 6

= 1000 × 602 / 6

W= 6,00,000 mm3

𝜎𝑒 = 𝑀 𝑊 < 𝜎𝑎

= 183668.4 / 600000

𝜎𝑒= 0.3061N/ mm2<σa ………(σa= 70 N/mm

2)




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Table 2: Result of Critical Bending Stress

Sr. No. Composition of Plastic

Critical Bending Stress (MPa)

For

30 c.m. width Panel 60 c.m. width Panel

For Depth

(mm) Applied

Allowab

le

For Depth

(mm)) Applied Allowable

01 Halene PP M312 6 29.86 33 6 26.86 33

02 PP(Polypropylene Impact

Copolymer) 7033 6 29.86 37.65 6 26.86 37.65

03 ABS 4 67.15 70 4 60.40 70

04 HIPS 6 29.87 35 6 28.87 35

Sample calculations for Verification for deflection,

The calculation is made for a width of b=1m.

𝑞 = 𝑎 + 𝑏 × 1.00 + 𝑑 𝑙 …..(N/ m2)

For ABS type of plastic,

a = 10300.5 X 0.06 = 618.03 N/ m2

b= 25000 X 0.15 = 3750 N/ m2

q = (618.03 + 3750 ) x 1.00

q = 4.368 N/mm

For a rectangular beam subjected to bending the applied deflection can be calculated form the following

equation:

𝑓𝑒 = 5 384 × 𝑞 × 𝑙2 𝐸𝐼 < 𝑓𝑎

where, 𝐼 = 𝑏𝑕3 12 = 18 X 106 mm

4

E = 2600 MPa

fe= (5/ 384) X (4.368 x2524)/ 2600 X 18 X 10

6

fe= 0.00490 mm

fa = l / 300 = 0.84

𝒇𝒆 < 𝒇𝒂 …Hence OK.

Table 3: Result of Critical Deflection

Sr. No. Composition of Plastic

Critical Deflection (mm)

For

30 c.m. width Panel 60 c.m. width Panel

For Depth

(mm ) Applied

Allowabl

e

For Depth

(mm) Applied

Allowabl

e

01 Halene PP M312 15 0.724 0.84 14 0.889 0.92

02 PP(Polypropylene

Impact Copolymer) 7033 15 0.717 0.84 14 0.88 0.92

03 ABS 11 0.703 0.84 11 0.703 0.92

04 HIPS 13 0.743 0.84 10 0.894 0.92




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3.2Design of joist

Sample Calculations for Design of Joist for 1m

Notification:

a = Weight of the formwork itself

= Density × Plate Thickness

= 10300.5 × 0.015 = 154.5075 𝑁 𝑚2

b = Weight of fresh concrete (reinforced)

= 25000 × 0.15 = 3750 𝑁 𝑚2

c = Uniform distributed load of runways for concrete transport and impact loads of the crowding of

crewmen

= 1500 𝑁 𝑚2

𝑎 + 𝑏 + 𝑐 = 154.5075 + 3750 + 1500 = 5404.5075 [𝑁 𝑚2]

d = Concentrated load from weight of work crews and

transport equipment

= One crew member that carries load + wheel

barrow/buggies for concrete transport

=1300 + 2800

= 4100 N

l =𝑐/𝑐 distance between props = 0.2507 m

W= total UDL

𝑊 = 𝑞 = (𝑎 + 𝑏 + 𝑐) × 1 + (𝑑 ÷ 𝑙)

𝑊 = 5404.5075 + (4100/0.2507)

= 21804.5075 𝑁/𝑚

M = Maximum Bending moment

𝑀 =𝑤𝑙2

8 =

21804.50275

8 = 2725.56 𝑁𝑚

𝑀/𝐼 = Ϭ/𝑦

𝐼 = 𝑀𝑂𝑀𝐸𝑁𝑇 𝑂𝐹 𝐼𝑁𝐸𝑅𝑇𝐼𝐴 = 𝑑4/12

𝜎 = 𝑓𝑙𝑒𝑥𝑢𝑟𝑎𝑙 𝑠𝑡𝑟𝑒𝑠𝑠 = 70𝑀𝑃𝑎

𝑌 = 𝑒𝑥𝑡𝑟𝑒𝑚𝑒 𝑓𝑖𝑏𝑟𝑒 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑓𝑟𝑜𝑚 𝐶𝐺 = 𝑑/2

𝐸 = 𝑦𝑜𝑢𝑛𝑔’𝑠 𝑚𝑜𝑑𝑢𝑙𝑢𝑠 = 2600𝑀𝑃𝑎

𝑑3 = 2725.56 × 12

2 × 70 × 106

𝑏 = 𝑑 = 0.061588 𝑚

So, Joist is square in size, hence required size of joist should not be less than 𝟔. 𝟏𝟓𝟖𝟖 𝒄. 𝒎. 𝑿 𝟔.𝟏𝟓𝟖𝟖 𝒄. 𝒎.




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Table 4: Dimensions of Joist

3.3Design of Props [4]

Sample calculations for Design of Props

Name of plastic: ABS

𝐷𝑒𝑛𝑠𝑖𝑡𝑦 = 10300.5𝑁/𝑚3

𝑇𝑕𝑖𝑐𝑘𝑛𝑒𝑠𝑠 𝑜𝑓 𝑝𝑙𝑎𝑡𝑒 = 0.015𝑚

𝑇𝑕𝑖𝑐𝑘𝑛𝑒𝑠𝑠 𝑜𝑓 𝑠𝑙𝑎𝑏 = 0.15𝑚

DISCRIPTION

a = Weight of the formwork itself

= Density × Plate thickness

= 10300.5 × 0.015 = 154.5075𝑁/𝑚2

b = Wight of fresh concrete (reinforced)

= 25000 × 0.15 = 3750𝑁/𝑚2

c = uniform distributed load of runways for concrete transport and impact loads of the crowding of crewmen

= 1000𝑁/𝑚2

3.3.1 Design of Solid Props (for 3m)

𝑎 + 𝑏 + 𝑐 = 154.5075 + 3750 + 1000 = 4904.5075𝑁/𝑚2

𝑃𝑛 = (𝑎 + 𝑏 + 𝑐) × 𝑖𝑛𝑓𝑙𝑢𝑒𝑛𝑐𝑒 𝑎𝑟𝑒𝑎 = 4904.5075 × 0.3

𝑃𝑛 = 1471.35 𝑁

E = Flexural modulus.

𝑙𝑒 = 𝐸𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒 𝐿𝑒𝑛𝑔𝑡𝑕 = 0.7 × 3 = 2.1𝑚

𝑃𝑛 = 𝜋2𝐸𝐼 𝑙𝑒2

𝐼 = 𝜋 4 × 𝑑4

1471.3525 =𝜋3 4 × 2600 × 106 × 𝑑4

0.7 × 3 2

𝑑 = 23.82 𝑚𝑚

So, Diameter required should not be less than 𝟐𝟑. 𝟖𝟐 𝒎𝒎.

Types of plastic

Design values Actual values

Width

(cm)

Depth

(cm)

Width

(cm)

Depth

(cm)

ABS 6.154 6.154 10 5

HIPS 7.816 7.816 10 8

PP 7.673 7.673 10 8

HALEN PP 8.018 8.018 10 8




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Table 5: Dimensions of Solid Props

3.3.2 Design of Hallow Props (for 1.5m)

𝑊𝑒𝑖𝑔𝑕𝑡 𝑜𝑓 𝑠𝑜𝑙𝑖𝑑 = 𝜋 4 × 0.023822 × 3 × 10300.5

= 13.7710 𝑁

𝑎 + 𝑏 + 𝑐 = 154.5075 + 3750 + 1000 = 4904.5075𝑁/𝑚2

𝑃𝑛 = (𝑎 + 𝑏 + 𝑐) × 𝑖𝑛𝑓𝑙𝑢𝑒𝑛𝑐𝑒 𝑎𝑟𝑒𝑎 = 4904.5075 × 0.3

𝑃𝑛 = 1471.35 + 13.7710 = 1485.12 𝑁

E = Flexural modulus.

𝑙𝑒 = 𝐸𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒 𝐿𝑒𝑛𝑔𝑡𝑕 = 0.7 × 1.5 = 1.05 𝑚

𝑃𝑛 = 𝜋2𝐸𝐼 𝑙𝑒2

𝐼 = 𝜋 4 × 𝐷4 − 𝑑4

1485.12 =𝜋3 4 × 2600 × 106 × 𝐷4 − 𝑑4

0.7 × 3 2

𝑑 = 25.19 𝑚𝑚

So, Diameter required should not be less than 𝟐𝟓. 𝟏𝟗 𝒎𝒎

Table 6: Dimensions of Hallow Props

4. CONCLUSION

In traditional formwork system mainly wood and steel are being used as a material for formwork system. In

wooden formwork system, time delay and less accuracy are main constrained. Installation and dismantling

period is very high in wooden system. In steel formwork system accuracy is in work can be achieved but due

to its heavy weight it requires crane for lifting purpose as a result it proves to be time consuming. Also the

repetitions for wood and steel formwork have 10 and 60 repetitions respectively, while ABS plastic can be

used over 100 times. Due to its light weight ABS plastic formwork is easy to handle and easy to transport on

site, which increases labour productivity.

Type of

Plastic P E 𝑷 × 𝒍𝒆

𝟐 𝒅𝟒 d

ABS 1471.35 2.6E+09 6488.665 3.22E-07 0.023822

HIPS 1472.67 1.5E+09 6494.504 5.59E-07 0.027339

PP 1464.73 1.01E+09 6459.462 8.25E-07 0.03014

HALEN PP 1464.73 1E+09 6459.462 8.33E-07 0.030215

Type of Plastic P E 𝒅𝟒 𝑫𝟒 𝑫

ABS 1485.12 2.6E+09 3.22E-07 4.03E-07 0.0252

HIPS 1491.33 1.5E+09 5.59E-07 7.00E-07 0.02893

PP 1483.62 1.01E+09 8.25E-07 1.03E-06 0.031888

HALEN PP 1483.72 1E+09 8.33E-07 1.04E-06 0.031966




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April 2017

As deforestation is a major issue worldwide, these days use of ABS plastic as a alternative material for

formwork purpose might be possible solution against deforestation.

Thus it can concluded that the ABS plastic formwork technology is economical when used on large projects.

Increases Speed of construction. It enhanced labour productivity. Repetitions are much more than traditional

formwork techniques giving more than 100 repetitions and also ecofriendly alternative to wooden formwork

system as it is recyclable.

REFERENCES [1] Manual of TECHALTRA(2013), published by Ultratech, Vol.03, PP:02.

[2] Karke S. M. &Kumathekar M. B.(2002),“Comparison of the use of Traditional and Modern Formwork Systems”,

Civil Engineering Systems and Sustainable Innovations , Vol.04,PP:348-355.

[3] Octavian George Ilinoiu,Civil Engineering Dimensions, Vol. 8, No. 1, 47-54, March2006 (ISSN 1410-9530)

[4] Biggest Library of Free PDF and Product Manyal,CE 405: Design of Steel Structures, A. Varma

use of plastic in formwork -...

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