Experimental Study of Behaviour of Voided (Bubble ... · V APPROVAL FOR SUBMISSION I certify that this project report “Experimental Study of Behaviour of Voided (Bubble) Concrete

I

Experimental Study of Behaviour of Voided (Bubble)

Concrete Slab

STUDENT’S NAME

1-Ali Muhsin Hassan

2-Mohammed Salah Chechan

3-Murtatha Jabbar Salih

Supervisor : Dr. Samir Mohammed Chasib

A project report submitted in partial fulfilment of the

requirements for the award of the degree of

Bachelor of Civil Engineering

Civil Engineering Department

Engineering College

University of Misan

Iraq

2017-2018

II

العظيم صدق اهلل العلي

سورة يوسف

(67)

III

Voided Slab

IV

DECLARATION

I hereby declare that this project report is based on my original work except for

citations and quotations which have been duly acknowledged.

Signature : ____________________

Name : Ali Muhsin Hassan

Date : ____________________

Signature : ____________________

Name : Mohammed Salah Chechan

Date : ____________________

Signature : ____________________

Name : Murtatha Jabbar Salih

Date : ____________________

V

APPROVAL FOR SUBMISSION

I certify that this project report

“Experimental Study of Behaviour of Voided (Bubble) Concrete Slab”

Was prepared by Ali Muhsion , Mohammed Salah, Murtatha Jabbar and has met

the required standard for submission in partial fulfilment of the requirements for the

award of Bachelor of Civil Engineering at University of Misan.

Approved by,

Signature : ____________________

Supervisor : Dr. Samir Mohammed Chasib

Date : ____________________

VI

Dedication

Every Challenging work needs self efforts as well as guidance of elders

especially those who were very close to our heart

Our humble effort ,we dedicate to our sweet and loving

Father& Mother

Whose affection love, encouragement and prays of day and night make

as able to such success and honor

Along with all hard working and respected

Dr. Samir M. Chasib

VII

ACKNOWLEDGEMENTS

I would like to thank everyone who had contributed to the successful

completion of this project. I would like to express our gratitude to my

research supervisor, Dr. Samir Mohammed Chasib for his invaluable

advice, guidance and his enormous patience throughout the development

of the research.

In addition, I would also like to express my gratitude to my loving parent

and friends who had helped and given us encouragement......

VIII

ABSTRACT

Voided slab is a method of virtually eliminating all concrete from the

middle of a floor slab, which is not performing any structural function,

thereby dramatically reducing structural dead weight. High density

polyethylene hollow spheres replace the in-effective concrete in the

center of the slab, thus decreasing the dead weight and increasing the

efficiency of the floor. By introducing the gaps, it leads to 30 to 50%

lighter slab which reduces the loads on the columns, walls and

foundations, and of course of the entire building.

The aim of this project is to introduce a new structural member that's

made from waste materials and to investigate the structural behavior of

it and to determine the best admixture that can improve the flexural

strength of the voided slab that we created.

Our results shows that the best admixture that improved the flexural

strength of the voided slab was the Sika Latex that gives an average

ultimate load of (15831.333) N .

IX

TABLE OF CONTENTS

APPROVAL FOR SUBMISSION V

DECLARATION VI

ACKNOWLEDGEMENTS VII

ABSTRACT VIII

TABLE OF CONTENTS IX

LIST OF SYMBOLS / ABBREVIATIONS XI

CHAPTER

1 INTRODUCTION 1

1.1 General 1

1.2 Type of slabs 4

1.3 Types of voided flat slabs 5

1.4 Materials 9

1.5 Applications of Voided Slab 12

2 LITERATURE REVIEW 13

3 EXPERIMENTAL WORK 16

3.1 General 16

3.2 Materials used 16

3.3 mixing 18

4 RESULTS AND DISCUSSION 22

4.1 flexural strength " Case 1" 22

X



5 CONCLUSIONS AND RECOMMMENDATIONS 31

5.1 Conclusions 31

5.2 Recommendations 32

REFERENCES 34

XI

LIST OF SYMBOLS / ABBREVIATIONS

S.F.B: Super plastizer, Sika Fibers with bubbles.

S.S.B: Super plastizer, Sika Latex with bubbles.

S.N.B: Super plastizer, normal with bubbles.

S.N.W: Super plastizer, normal without bubbles.

Chapter One Introduction

1

Chapter One

Introduction

1.1 General

For decades, several attempts have been made to create biaxial slabs

with hollow cavities in order to reduce the weight. Most attempts have

consisted of laying blocks of a less heavy material like expanded

polystyrene between the bottom and top reinforcement, while other types

included waffle slabs and grid slabs.

Due to the limitations in hollow-core slabs, primarily lack of structural

integrity, inflexibility and reduced architectural possibilities, focus has

been on biaxial slabs and ways to reduce the weight. Several methods

have been introduced during the last decades, but with very limited

success, due to major problems with shear capacity and fire resistance as

well as impractical execution.

Of these types, only waffle slabs can be regarded to have a certain use in

the market. But the use will always be very limited due to reduced

resistances towards shear, local punching and fire. The idea of placing

large blocks of light material in the slab suffers from the same flaws,

which is why the use of these systems has never gained acceptance and

they are only used in a limited number of projects.

Bubble eliminates up to 35% of the structural concrete. When coupled

with the reduced floor thickness and facade, smaller foundations and

columns, construction costs can be reduced by as much as 10%.

With virtually no formwork, no downturn beams or drop heads, and fast

coverage of typically 350ft2 per panel, using Bubble means floor cycles


2

up to 20% faster than traditional construction methods. Regardless of

project size, shape or complexity; simply shore, place, and pour to

quickly install concretes .The Bubble system offers a wide range of

advantages in building design and during construction. There are a

number of green attributes

including reduction in total construction materials, use of recycled

materials, lower energy consumption and reduced

CO2 emissions, less transportation and crane lifts that make Bubble

more environmentally friendly than other concrete construction

techniques. Bubble can achieve larger spans as compared to a site cast

concrete structure without the need for post-tensioning or pre-stressed

sections. The total construction time for the structure was reduced and

allowed the consultants to fast track the design without the interior

design finalized.

The Bubble, on the other hand, creates such a cushion of air between

layers of concrete with the reinforcement of both the metal grid and the

weight distribution across the plastic spheres. Now that’s a rather

innovative concept that you don’t often see. True enough, you might not

initially see many differences between a building that has been

constructed using in-situ casting and one that uses Bubble technology,

but the differences are significant.

One notable difference about Bubble technology is that it allows for

stronger, and often thicker, slabs of concrete that span larger areas, as

well as the opportunity to architecturally design larger cantilevers.

According to the Bubble Group, the hollow spheres at the core of this

technology allow for an approximately 35% reduction of dead weight

from the building’s concrete slabs. When those slabs cover a larger area,

there is also no requirement for supporting columns, walls, and down

stand beams. These latter elements can often generate great limitations


3

for an architect, not allowing them to create wide, open spaces with

minimal supporting features.


4

1.2 Type of Slabs

Structural two way slabs may be classified as follows:

1.2.1 Flat Plate: Span not exceeding 6.0 to 7.5 m and live load not

exceeding 3.5 to 4.5 kN/m2

Advantages

1. Low cost formwork

2. Exposed flat ceilings

3. Fast

Disadvantages

1. Low shear capacity

2. Low Stiffness (notable deflection)

3. Need of special formwork for drop panels and capitals

1.2.2 Waffle Slab: Span up to 14 m and live load up to 7.5 kN/m2

Advantages

1. Carries heavy loads

2. Attractive exposed ceilings

Disadvantages

1. Formwork with panels is expensive

1.2.3 Slab with beams: Span up to 10 m

Advantages

1. Versatile

2. Framing of beams with columns

Disadvantages

1. Visibility of drop beams in ceilings

1.2.4 Voided slab: Span up to 14 m and live load up to 7.5 kN/m2


5

1.3 Types of voided flat slabs

1.3.1 Air Deck

The Air concept was patented in 2003 and comprises an inverted plastic

injection moulded element which is vibrated into the lower slab during

the production process by a robotic arm. The advantage of this system is

that no retaining mesh is required to hold down the voiding elements

during on site pouring of the second layer. As the boxes can be nested

there are transport advantages versus other voiding systems.

Figure (1.1) Air deck box Figure (1.2) section in air deck box

1.3.2 Cobiax

The Cobiax system makes use of the same voided slab principles of

creating voids within the concrete slabs to lighten the building structures.

Elliptical and torus shaped hollow plastic members, termed as void

formers, are held in place by a light metal mesh for easy installation

between the top and bottom reinforcement layers of a concrete slab.

Figure (1.3) Cobiax system


6

1.3.3 U-BOOT BETON

In 2001 an Italian engineer, Roberto Il Grande, developed and patented a

new system of void formers, in order to decrease the transportation costs

and CO2 production. The product is U-Boot Beton, and its biggest

advantage is that it is stackable. A truck of U-boot means approximately

5000 m2 of slab, once void formers are laid down at building site. The

second innovation is the shape: U-Boot Beton creates a grid of

orthogonal "I" beams, so the calculation of the reinforcement can be

effected by any static engineer according to Eurocode, British Standards

or any local standard.

U-Boot Beton is a recycled polypropylene formwork that was designed

to create two-way voided slabs and rafts. The use of U-Boot Beton

formwork makes it possible to create mushroom pillars, with the

possibility to have the mushroom in the thickness of the slab.

Thanks to the conic elevator foot, immerging the U-Boot Beton

formworks in the concrete casting will create a grid work of mutually

perpendicular beams closed from the bottom and the top by a flat plate

that is created with a single casting; this results in considerable reduction

in the use of concrete and steel. U-Boot Beton is used to create slabs

with large span or that are able to support large loads without beams.

Light and quick and easy to position, thanks to their modularity the

designer can vary the geometric parameters as needed to adapt to all

situations with great architectural freedom. U-boot earliest projects were

executed in 2002 and since that time it has been used all over the world.

Figure (1.4) U-Boot Beton


7

1.3.4 BUBBLE

In the 1990s, a new system was invented, eliminating the above

problems. The so-called Bubble technology invented by Jorgen

Breuning, locks ellipsoids between the top and bottom reinforcement

meshes, thereby creating a natural cell structure, acting like a solid slab.

A voided biaxial slab is created with the same capabilities as a solid slab,

but with considerably less weight due to the elimination of superfluous

concrete.

Bubble slab is a biaxial hollow core slab invented in Denmark. It is a

method of virtually eliminating all concrete from the middle of a floor

slab not performing any structural function Figure (1.5), thereby

dramatically reducing structural dead weight.. Void forms in the middle

of a flat slab by means of plastic spheres eliminate 35% of a slab's self-

weight, removing constraints of high dead loads and short spans. It’s

flexible layout easily adapts to irregular and curved plan

configureurations. The system allows for the realization of longer spans,

more rapid and less expensive erection, as well as the elimination of

down-stand beams. According to the manufacturers, Bubble slab can

reduce total project costs by three percent. Bubble slab is a new

innovative and sustainable floor system to be used as a self-supporting

concrete floor. The application of the Bubble slab floor system in the

Netherlands is manifested as the world-wide first application. The

Bubble slab floor system can be used for storey floors, roof floors and

ground floor slabs. A Bubble slab floor is a flat slab floor, therefore

without beams and column heads. The principal characteristic is that

hollow plastic spheres are incorporated in the floor, Clamped in a

factory-made reinforcement structure. This reinforcement structure

constitutes at the same time the upper and lower reinforcement of the

concrete floor.


8

Figure (1.5): Section of Bubble slab

The reinforcement structure with spherical shapes and possibly a thin

concrete shell as precast slab floor are supplied to the construction site in

factory-made units with a maximum width of 3 meters; they are installed

on site and are assembled by installing connecting rods and by pouring

concrete. After the concrete has set, the floor is ready to be used. The

ratio of the diameter of the plastic spheres to the thickness of the floor is

such that a 35 % saving is achieved on the material or concrete

consumption for the floor in comparison with a solid concrete floor of

the same thickness. The saving on weight obtained in this way has the

result that a Bubble slab floor can provide the required load-bearing

capacity at a smaller thickness this leads to a further advantage, resulting

in a saving of 40 to 50 % of the material consumption in the floor

construction. This is not the last of the advantages of the Bubble slab

floor system: because of the lower weight of the floor system itself, also

the supporting constructions such as columns and foundations can be

less heavy. This can results eventually in a total weight or material

saving on the building construction of up to 50 %. Since the weight of

the structure reduced, this type of structure can useful to reduce

earthquake damage.


9

1.4 MATERIALS

Bubble slab is composed of three main materials; they are steel, plastic

spheres and concrete:

1.4.1 Concrete

The concrete is made of standard Portland cement with max aggregate

size of 20 mm. Tests have proved that the characteristic compressive

strength of concrete is achieved by bubble slabs in the same manner as

that of solid slabs. In certain type of bubble slab a thin layer of concrete

at the bottom is precast at the manufacturing plant. This is done so as to

place the bubbles as per the specifications. These are achieved by

placing concrete in platforms and lowering the bubbles into concrete.

This concrete will be compacted by platform vibrator or formwork

vibrator. The remaining concreting is done at site, and it can be

compacted with needles vibrators and surface vibrators.

1.4.2 Steel

The steel reinforcement is of grade 60 (Fy =60ksi) strength or higher.

The steel is fabricated in two forms -meshed layers for lateral support

and diagonal girders for vertical support of the bubbles. Figure 4.1 shows

the arrangement of steel and bubbles in a Bubble slab. Steel

reinforcement is mainly arranged as soon as the bubbles are prepared.

Proper locking of bubbles are only possible by placing them in

reinforcements. The spherical shape makes it non-stackable. Thus the

bubbles are held in place in the lattice by proper steel reinforcement.

Generally reinforcement is provided in mesh type along the top and

bottom. The top and bottom reinforcements are then held together by

welding with the help of diagonal short length bars.The steel

reinforcement is designed as per the design procedure. Suitable extra

bars and shear reinforcements are to be provided as and when required.


10

Figure (1.6): Construction of Biaxial hollow core slab 1.4.3 Plastic spheres

The hollow spheres are made from recycled high-density polyethylene or

HDPE. Figure (1.7) shows the hollow plastic spheres which are ready to

be transported to site. Plastic bubbles are available in different sizes

based on the size of stucture and it is tabulated in Table 1.1. The main

disadvanatge of bubbles is dat it is not stackable. These HDPE bubbles

can be slavaged and reused again or recycled. This conctributes to the

Green properties of bubble slab.

Figure 1.7: Plastic spheres along with reinforcement


11

Table 1.1: Different types of Plastic Bubbles available in market

Version

Slab

thick ness, mm

Bubbles diameter

Mm

Cantilever-

maximum length

m

Span, m

Completed slab mass

KN/m2

Site

concrete quantity m3/m2

BD230 230 180 < =2.8 5-6.5 4.26 0.112

BD280 280 225 < =3.3 6-7.8 5.11 0.146

BD340 340 270 < =4.0 7-9.5 6.22 0191

BD390 390 315 < =4.7 9-10.9 6.92 0.219

BD450 450 360 < =5.4 10-

12.5 7.85 0.252

BD510 510 410 < =6.1 11-

13.9 9.09 0.298

BD600 600 500 < =7.2 12-

15.0 10.30 0.348


12

1.5 Applications Of Voided Slab

Figure (1.8) bubble slab.

Figure (1.9) Cantilever bubble slab.

Chapter Two literature revie

13

Chapter Two

LITERATURE REVIEW

In the 1990's, Jorgen Breuning invented a way to link the air space and

steel within a voided biaxial concrete slab. The Bubble technology uses

spheres made of recycled industrial plastic to create air voids while

providing strength through arch action. See Figure 2.1 for a section cut

of a Bubble. As a result, this allows the hollow slab to act as a normal

monolithic two-way spanning concrete slab. These bubbles can decrease

the dead weight up to 35% and can increase the capacity by almost 100%

with the same thickness. As a result, Bubble slabs can be lighter,

stronger, and thinner than regular reinforced concrete slabs.

Figure 2.1: Cut through section of Bubble slab

Currently, this innovative technology has only been applied to a few

hundred residential, high-rise, and industrial floor slabs due to limited


14

understanding. For this investigation, the structural behavior of Bubble

under various conditions will be studied in order to gain an

understanding on this new technique and to compare it to the current slab

systems. This technology will then be studied about the applicability to

create lightweight bridge s since a significant portion of the stress

applied to a bridge comes from its own self-weight. By applying the

knowledge gathered during the behavioral analysis, a modular

component for pedestrian bridges that is notably lighter but comparable

in strength to typical reinforced concrete sections will be designed.

A study has been conducted by Amer M Ibrahim, Nazar K Ali, Wissam

Di Salman in2012 on the flexural capacities of reinforced two way

Bubble slabs. A Bubble slab has a two dimensional arrangement of voids

within the slabs to reduce self-weight. The behavior of Bubble slabs is

influenced by the ratio of bubble diameter to slab thickness. To verify

the flexural behavior of Bubble slab such as ultimate load, deflection,

concrete compressive strain and crack pattern, two dimensional flexural

tests were tested by using special loading frame. Results have shown that

the crack pattern and flexural behavior depend on the void diameter to

slab thickness ratio. The ultimate load capacities for Bubble slabs having

bubble diameter to slab thickness of0.01 to 0.64 were the same of solid

slabs, the ultimate capacities were reduced to about 10%.

From the studies conducted by Sergui Calin, Roxana Gintu and Gabriela

Dascalu on the tests of Bubble slab inferred that Bubble slab is

conceived to omit a significant volume of concrete in the central core

where the slab is principally un-stressed in flexure. In slabs, the depth of

compressed concrete is usually a small proportion of the slab depth and

this means that it almost always involve only the concrete between the

ball and the surface, so there is no sensible difference between the

behavior of a solid slab and Bubble slab.


15

In 2012, Prabhu Teja, P Vijay Kumar studied the durability of Bubble

slab and is explained on the basis of creep and shrinkage. A Bubble

element with two spherical hollows was compared with a solid concrete

block of the same dimension and of the same concrete. The difference

between the shrinkage strains of these two was measured. The results

show that Bubble element has a negligible larger marginal shrinkage

strain than a solid slab with equivalent dimensions and the same concrete

performances, under the same exposure to environmental conditions.

The influence of carbonation shrinkage can be neglected in the design of

concrete structures with Bubble system, because only a small part of the

concrete cross- section is exposed to this kind of shrinkage.

In 2010 S Anusha, C.H Mounika and Purnachandra conducted studies on

the fire resistance of Bubble slabs. The analysis was first done on a

hollow core slab without fire, for two charges one that leads to elastic

dynamic response and the other that causes plastic behavior and severe

concrete cracking. The same blast analysis had been subjected to fire.

There were many difficulties in obtaining a reliable result. A discussion

of the experimental setup and experimental results are compared with

simplified numerical models solved with the software LS-DYNA. Fire

does not change the material and structural properties that fast as

compared to an explosion. The most important conclusion of the analysis

is that crack patterns and blast load dynamic responses are indeed altered

by fires with temperature up to 4500C.

In 2009, Tina Lai discussed about the acoustic behavior of Bubble slabs

in“Structural behavior of Bubble slabs and their applications” and

found that Bubble performs acoustically in a better way than any other

hollow or solid floor surfaces.

Chapter three experimental work

16

Chapter Three

Experimental work

3.1 General

This project has been working in the laboratories of the college of

Engineering, University of Maysan. The objective of this project was

toreducing structural dead weight. High density polyethylene hollow

spheres replace the in-effective concrete in the center of the slab, thus

decreasing the dead weight and increasing the efficiency of the floor. By

introducing the gaps.

3.2 Materials used

The materials used in this investigation were commercially available

materials, which include cement, sand, water, Sika latex, Sika Fiber

(PPM-12): Polypropylene Fibers and superplasticizer.

3.2.1 Cement

Ordinary Portland cement was used throughout this investigation. The

whole quantity required was brought to the laboratory and stored in a dry

place. The setting time test is conducted according to ASTM C191. The

compressive strength test is accomplished according to ASTM C109.

3.2.2 Sand

Passing from sieve 1.18 mm according ASTM C 128

3.2.3Water

Ordinary potable water was used for mixing and curing.


17

3.2.4 Sika latex: water resistant, bonding agent for mortar. Figure

(3.1)

Advantage

1. Extremely good adhesion

2. Reduced shrinkage

3. Greater flexibility

4. Excellent water resistance

5. Improved chemical resistance

3.2.5 Sika Fiber (PPM-12): Polypropylene Fibers for mortar and

concrete. Figure (3.2)

Advantage

1. Reduces tendency for plastic and drying shrinkage cracking

2. Save and easy to use

3. Reduces water migration

4. Improved durability

5. Increased impact resistance of young

6. concrete

Use 600 g for 1 cubic meter

Figure (3.1) Sika latex Figure (3.2) Sika Fiber (PPM-12)


18

3.2.6 Superplasticizers 1. increases workability of freshly mixed concrete without increasing

water cement ratio

2. The function of water reducing admixture is to reduce the water

content of the mix, usually by 5 to 10%.

3. High strength can be obtained with the same cement content by

reducing water cement ratio.

3.2.7 Plastic Covers.

3.3 mixing

All the samples have been mixed with 1:1 cement to sand ratio and the

water –cement ratio was 30% with the Superplasticizer for all samples.

We used waste material (plastic water bottle's covers) in our project

instead of plastic balls as shown in Figure 3.3and we used two layers of

iron mesh shown in Figure 3.4. The wooden mold with a distance of 50 *

50 cm and a thickness of 4 cm was used in our project as shown in

Figure. (3.5)

Figure. (3.3) Top and bottom wire mesh


19

Figure. (3.4) Wire mesh Figure. (3.5) Wooden mold

Four ferrocement mixes were used through the whole investigation as

shown in Table (3-1).Three samples were mixed from each mixes of the

(S.F.B), (S.S.B),(S.N.B) and one sample was (S.N.W). During casting

of each mixture, three 50 x 50 x 50 mm cubes from each mix were made

to predict the compressive strength of mix. As shown in Figure (3.6),

(3.7),(3.8),(3.9).

Table 3.1 Mixing

content S.S.F. S.S.L. S.N.B S.N.W.

Cement to

sand ratio 1:1 1:1 1:1 1:1

% super from

cement wt. 1% 1% 1% 1%

Sika fiber

(gm.) 100 - - -

% Sika latex

from cement

wt.

- 12.5% - -

% w/c 30 30 30 30


20

Figure (3.6) Wire mesh and the mold Figure (3.7) The shaker

Table 3.2 compression test results.

Spicemans Compression

strength (Mpa)

Average

Compression

strength (Mpa)

S.F.B-1 58.2

58.3 S.F.B-2 58

S.F.B-3 58.7

S.S.B-1 81.3

81.46 S.S.B-2 82.1

S.S.B-3 81

S.N.B-1 41.3

41.16 S.N.B-2 41.2

S.N.B-3 41

S.N.W 42 42


21

Figure (3.8) Holding the wire mesh

Figure (3.9) Mixing

Chapter four results and Conclusion

22

Chapter Four

Results and Conclusion

4.1 flexural strength "Case 1"

4.1.1 Ultimate Load Capacity The ultimate load capacity and the other results are tabulated in Table 4.1.

The two-way Bubble slab with the plastic sphere showed good ultimate

load and ductility compared with the solid specimen. The ultimate total

load of solid slab (S.N.W) were (9270.4 N) with the deflections of

(6.95mm). (S.F.B, S.S.B, and S.N.B) specimens showed (10001 N, 14038

N,7416.3 N) with (6.3mm, 5.52mm, and 0.92mm).

Table 4.1 shows the ultimate load and deflection of the bubble slab samples and the

solid sample.

Slab

Name Weight(kg)

Decrease

in

weight

%

First

crack

load

Pc/Pcsolid

Ultimate

load

Pu (N)

Δu,(mm),

Ultimate

defection

Pu/Pu

solid

S.F.B-1 20 13 5155.1 0.85 10001 6.3 1.08

S.S.B-1 19.6 14.8 5513.2 0.918 14038 5.52 1.514

S.N.B-1 19.8 14 3973 0.66 7416.3 0.92 0.8

S.N.W

(solid) 22.4 - 6003.7 1 9270.4 6.95 1


23

4.1.2 Load versus Deflection Relationship

Figure 4.1 shows the load versus mid-span deflection relationship of the

Slabs.Its noticed that (S.N.B) specimen has failed in the earlier stages

because of decreasing in stiffness of sample while the other bubble

samples that contain admixtures (Sika latex,Sika fiber) showed better

results comparing with the soild sample as shown in Figure (4.1). From

Figure (4.1) it noticed that the (S.S.B) gives the higher flexural strength.

Table 4.2 shows the ratio between the ultimate deflection of the bubble slab samples

and the solid sample.

Figure (4.1) Load Vs Deflection

Slab

Name

Ultimate load

Pu (N)

Δu,(mm),

Ultimate

defection

Δu / Δu solid

S.F.B-1 10001 6.3 0.9

S.S.B-1 14038 5.52 0.79

S.N.B-1 7416.3 0.92 0.13

S.N.W

(solid) 9270.4 6.95 1


24

4.1.3 Crack Patterns

Figure (4.2),(4.3),(4.4) and (4.5) illustrates the specimens’ crack patterns

and failure mode under ultimate load. All specimens showed flexural

failure mode with diagonal flexural cracks.

Figure. (4.2), (S.S.B) Figure (4.3) ,(S.N.B)

Figure (4.4), (S.F.B) Figure (4.5), (S.N.W)


25


4.2.1 Ultimate Load Capacity

The ultimate load capacity and the other results are tabulated in Table 4.3.




(6.95mm). (S.F.B, S.S.B, and S.N.B) specimens showed (10315 N, 10016

N, 7455.6 N) with (6.6mm, 5.95mm, and 1.15mm).

Table 4. Shows the ultimate load and deflection of the bubble slab samples and the

solid sample.


Figure (4.6) shows the load versus mid-span deflection relationship of the

Slabs.Its noticed that (S.N.B) specimen has failed in the earlier stages



results comparing with the soild sample as shown in Figure(4.6)

The (S.F.B) showed the higher flexural strength .

Slab

Name Weight(kg)

Decrease

in

weight

%

First

crack

load

Pc/Pcsolid

Ultimate

load

Pu (N)

Δu,(mm),

Ultimate

defection

Pu/Pu

solid

S.F.B-2 20 11 5066.8 0.84 10315 6.6 1.112

S.S.B-2 19.6 12.5 6337.2 1.05 10016 5.95 1.08

S.N.B-2 20 11 4076 0.678 7455.6 1.15 0.804

S.N.W

(solid) 22.4 - 6003.7 1 9270.4 6.95 1


26





Figure (4.7),(4.8),(4.9) and (4.10) illustrates the specimens’ crack

patterns and failure mode under ultimate load. All specimens showed

flexural failure mode with diagonal flexural cracks.

Slab Name

Ultimate

load Pu (N)

Δu,(mm),

Ultimate

defection

Δu / Δu solid

S.F.B-2 10315 6.6 0.95

S.S.B-2 10016 5.95 0.85

S.N.B-2 7455.6 1.15 0.165

S.N.W (solid)

9270.4 6.95 1


27

Figure(4.7), (S.F.B) Figure(4.8), (S.N.B)

Figure(4.9) (S.S.B) Figure(4.10 ),(S.N.W)


4.3.1 Ultimate Load Capacity

The ultimate load capacity and the other results are tabulated in Table 4.5.




(6.95mm). (S.F.B, S.S.B, and S.N.B) specimens showed (9927.7 N,

23440 N, 10702 N) with (5 mm, 5.8mm, and 3.35mm).


28

Table 4.5 shows the ultimate load and deflection of the bubble slab samples and the

solid sample.


Figure (4.11) shows the load versus mid-span deflection relationship of

the Slabs.Its noticed that (S.N.B) specimen has failed in the earlier stages



results comparing with the soild sample as shown in Figure (4.11).

The (S.F.B) showed the higher flexural strength.



Slab

Name Weight(kg)

Decrease

in

weight

%

First

crack

load

Pc/Pcsolid

Ultimate

load

Pu (Kg)

Δu,(mm),

Ultimate

defection

Pu/Pu

solid

S.F.B-3 19.9 11.16 4905 0.816 9927.7 5 1.65

S.S.B-3 19.19 14.33 5626 0.937 23440 5.8 3.9

S.N.B-3 19.5 13 5768.2 0.96 10702 3.55 1.78

S.N.W

(solid) 22.4 - 6003.7 1 9270.4 6.95 1

Slab Name

Ultimate load

Pu (N)

Δu,(mm),

Ultimate

defection

Δu / Δu solid

S.F.B-3 9927.7 5 0.71

S.S.B-3 23440 5.8 0.83

S.N.B-3 10702 3.55 0.51

S.N.W

(solid) 9270.4 6.95 1


29



Figure (4.12),(4.13),(4.14) and (4.15) illustrates the specimens’ crack

patterns and failure mode under ultimate load. All specimens showed

flexural failure mode with diagonal flexural cracks.

Figure (4.12) ,(S.F.B) Figure (4.13),(S.N.B)


30

Figure (4.14),(S.S.B) Figure(4.15),(S.N.W)


31

Chapter Five

Conclusions and Recommendations

5.1 Conclusions

1. Reducing material consumption made it possible to make the

construction time faster, to reduce the overall costs. Besides that, it

has led to reduce dead weight about 16%, which allow creating

foundation sizes smaller.

2.The technology is environmentally green and sustainable. Avoiding

the cement production allows to reduce global CO2 emissions.

3. The results shows that the best admixture that improve the flexural

strength was the Sika Latex where the average ratio of the ultimate

load of the S.S.B to the S.N.W was (1.707) ,average ratio of the

ultimate load of the S.F.B to the S.N.W was (1.087), and the

average ratio of the ultimate load of the S.N.B to the S.N.W was

(0.95)

4.The failure of all samples were flexural failure not shear failure.

This means that the admixture that we added can improve the shear

resistance

5.The type of failure in all of the samples was elastic failure not brittle

failure because these kind of samples can fail because of the brittle

failure.

Chapter Five Conclusions and Recommendations


32

5.2 Recommendations

1. Increase the dimensions of the bubbles to reduce more weight.

2. Change the boundary conditions.

3. Change the dimensions of the column (point load).

4. Increase the dimensions of the slab.

Chapter Five Conclusions and Recommendations


33

References

[1] SERGIU CALIN ˘ ∗ and CIPRIAN ASAVOAIE,2009, "

METHOD FOR BUBBLEDECK CONCRETE SLAB WITH GAPS"

[2] Tina Lai,2011, " Structural Behavior of Bubble Deck Slabs And Their

Application to Lightweight Bridge Decks"

[3] Mr. Muhammad Shafiq Mushfiq1, PG Student, Asst. Prof .Shikha

Saini2 and Asst. Prof. Nishant Rajoria3,2017, " EXPERIMENTAL

STUDY ON BUBBLE DECK SLAB"

[4] P. Prabhu Teja1, P. Vijay Kumar1, S. Anusha1, CH. Mounika1,

Purnachandra Saha2,2012, " Structural Behavior of Bubble Deck Slab"

[5] Shivani Mirajkar1, Mitali Balapure1, Asst. Prof. Trupti

kshirsagar2,2017, " STUDY OF BUBBLE DECK SLAB"

Website

[6] http://www.bubbledeck.com/.

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