Experimental Studies on Composite Precast

Roof Panels under Static Flexure

Vasudevan N1

PG Student1,M.E Structural Engineering,

Department of civil engineering,

PSNA College of Engineering and Technology,

Dindigul, Tamil Nadu, India.

vasudevanx1@gmail.com

RanjithBabu B2

Assistant professor2

Department of civil engineering

PSNA College of engineering and technology

Dindigul, Tamil Nadu, India.

ranjithbabucivil@gmail.com

Abstract - Prefabricated composite roof

panels offer a variety of possibilities to be used in

many locations where economy, ease of

construction and speed are of prime importance.

High strength to weight ratio, reduced weight and

thereby attraction of lesser seismic forces and good

thermal insulation are some of the important

characteristics of the panels. Use of light-weight

structural elements in buildings is becoming

popular in the recent years. The sand is replaced

with copper slag with various percentage

0,25,50,75,100.The compression, spilt tensile and

rebound hammer tests were conducted for cubes

and cylinder with varying percentage of copper

slag. Therefore the slabs were casted with 0, 25, 50,

75&100 percentage replacement of copper slag. In

this study the flexural behaviour of precast light-

weight concrete panels under four-point bending is

observed and the variable parameter such as

replacement of copper slag has been studied

Keywords - Precast, Sandwich Panels,

Light-Weight Panels, Copper Slag, Expanded

Polystyrene.

1.INTRODUCTION

Precast concrete structural elements are

manufactured under controlled factory conditions

and therefore concrete structural elements with

good precision in geometry and finishing can be

manufactured. Background information on precast

technology can be found in the literature. Precast

concrete elements besides being structurally and

economically efficient, also have social and

environmental benefits. Precast structural elements

if light-weighted also have advantages such as (i)

less attraction of seismic forces, (ii) ease of

handling and transportation and (iii) cost effective.

Light-weight concrete sandwich panels produced

by replacing core concrete using lesser dense

material consist of two skins of concrete called

wythe, one on either side of the core. Welded wire

mesh or conventional steel rebars may be used to

reinforce the wythes. The core is made of material

that provides significant thermal and sound

insulation. In this study, EPS (Expanded

Polystyrene) is used as the core. In order to achieve

composite action of the panel under flexural load

shear transfer between the two wythes is ensured

by using shear connectors that connect the two

wythes. Experimental studies on the behaviour of

light-weight concrete sandwich panels under

different load conditions can be found in the

literature which have proved the feasibility of using

these panels for floors, roofs and walls of the

buildings. Nevertheless, it is noted that in the

literature no studies are found reported on the

flexural behaviour of light-weight concrete

sandwich panels with wires as shear connectors. In

this paper the results of the experimental study

carried out to determine the flexural behaviour of

prototype precast light-weight concrete sandwich

panels with wires as shear connectors under four-

point bending are presented. Four prototype panels

are tested in the present study to study the effect of

percentage of reinforcement in wythes and the total

thickness of the panel, both of which are directly

proportional to the moment carrying capacity,

ultimate load carrying capacity and the flexural

behaviour of light-weight concrete sandwich panel.

The paper is organized as follows. Section 2

presents the materials used and casting of the

panels, Section 3 presents the experimental work

test set-up details, Section 4 presents the results and

discussions and Section 5 presents summary and

conclusions.

II. MATERIALS DETAILS

2.1 Cement

Cement is largely dependent binder

material in concrete and its quality production must

be ensured with little or no hazard to the

environment. India is one of the largest producers

of cement. For this experimental investigation

RAMCO 53 grade ordinary Portland cement is

used. Specific Gravity of Cement is 3.1.finess of

cement 0.28%.

2.2 Fine aggregate

Sand is an inert occurring material of size

less than 4.75 mm. Specific gravity of fine

aggregate 2.6. Fineness Modulus of Fine Aggregate

= 2.75.

2.3 Coarse aggregate

As explained fine aggregate used for

concrete production is classified as fine aggregate

and coarse aggregate depending on its particle size.

Aggregate of size more than 4.75 mm, is called as

coarse aggregate and is one of the most important

ingredient of concrete. It gives strength to the

concrete and constitutes about 70 to 75 percent

volume of concrete. Crushed stone in general used

as coarse aggregate which is black in colour,

angular and in local name known as black metal. Specific gravity of coarse aggregate is 2.72. Bulk

Density of Coarse Aggregate is1527 kg / m3 Fineness Modulus of Coarse Aggregate is 3.24

2.4 Water

Potable water conforming to the

Requirements of water for concreting and curing as

per IS: 456 2000.

2.5 Copper slag

Copper slag is a by-product material

produced from the process of manufacturing

copper. As the copper settles down in the smelter, it

has a higher density, impurities stay in the top layer

and then are transported to a water basin with a low

temperature for solidification. The end product is a

solid, hard material that goes to the crusher for

further processing. Copper slag used in this work

was brought from Oman Mining Company, which

produces an annual average of 60,000 tons. The

physical properties of copper slag is given in table

.It is an industrial by-product material produced

during the copper smelting and refining process of

manufacturing of copper which can be used for a

surprising number of applications in the building

and industrial fields. This material represents a

popular alternative to sand as a blasting medium in

industrial cleaning. Using blasting or high-pressure

spraying techniques, companies are using copper

slag to clean large smelting equipment or furnaces

.Material like copper slag can be used as one which

can reduce the cost of construction

Physical Properties

Particle shape Irregular

Appearance Black & glassy

Type Air cooled

Specific gravity 3.91.3.68

Percentage of voids 43.20%

Bulk density 2.08g/cc, 1.70 to

1.90 g /cc

Fineness modulus of copper

size 3.47

Angle of internal friction 510 200

Particle size 0.075mm to 4.75

mm

Hardness Between 6 and 7

2.6 Expanded Polystyrene

EPS is a closed cell lightweight cellular

plastics material produced from polystyrene. The

material has been modified by the addition of flame

retardant additives. Polystyrene literally translated

is “polymerised styrene”. That is, the single styrene

molecules are chemically joined together to form a

large molecule which is called the polymer. Styrene

is produced from benzene and ethylene, and

polymerisation is accomplished in the presence of

catalysts, usually organic peroxides. The

expandable form is produced as small beads

containing a blowing agent.

2.7 MIX PROPORTIONS

In this study the copper slag was replaced

instead of fine aggregate with various percentage as

25, 50, 75,100. For M30grade of concrete mix

design was done as per IS: 10262-2009.

2.8 MIX RATIO

III. EXPERIMENTAL WORK

The experimental program includes

preparation and testing of Five slabs with different

proportions of sand by replacing them by copper

slag under four point loading.

3.1 Raw Materials used

Raw materials like Portland cement, fine

aggregate that passes through the 2.36mm sieve,

coarse aggregate 12.5mm,wire mesh with 3mm

diameter and cross section 50mm x 50 mm, sand is

replaced by percentage of 0,25,50,75&100 copper

slag.

Cement

Fine

aggregate

Coarse

aggregate

W/ C ratio

1 1.43 2.33 0.45

3.2 Preparation of Mould

Mould made up of steel, concrete or wood

can be used. Considering the economical condition

wooden mould are used. wooden mould of

dimension 1.3m x 0.5m x 0.075 m is constructed to

obtain a roof panel of required size for the

construction of the precast panel. After hardened

the precast panels are demoulded from the wooden

mould and is undergone for curing.

3.3 Preparation of Mix

Cement, fine aggregate and coarse

aggregate with the ratio of 1:1.43:2.33 is measured

, taken and undergone to normal hand mixing.

Initially dry mix preparation is done and later on

water and mixed together to give flowability to the

mix.

3.4 Casting of specimen

The wooden mould is placed in the plane

surface and the concrete mix poured for 1/3 from

the mould thickness and binded wire mesh and EPS

is placed at the centre of the mould then once again

the concrete is poured in to the mould and let leave

it for hardening.

3.5 curing

Specimens are cast and demoulded after 1

day and then allowed to cure for 28 days. The slabs

were laid to rest vertically in position.

3.6 Testing of slabs

The slab panels were removed from curing

after a period of 28 days. White wash was applied

to the panels in order to get clear indication of

cracks due to bending under service loads. Panels

were tested for flexural strength under universal

testing machine. The panels were placed on support

leaving a space of 50 mm from both ends. Dial

gauge was placed below the panel to record the

deflection in mm each stage of loading. Cracks are

then marked during each loading and

corresponding central deflection is also noted

down.

IV. RESULTS AND DISCUSSIONS

4.1 COMPRESSIVE STRENGTH TEST (28 DAYS)

4.2 SPLIT TENSILE TEST(28DAYS)

TESTING PROCEDURE

Flexure testing is carried out in universal testing machine of 1000tonne capacity.

4.1 Flexural strength on slab

S.NO MIX CS 0 CS 25 CS 50 CS 75 CS 100

1 1:1.43:2.33 5 kN 6.5 kN 8 kN 7 kN 5.5 kN

4.1 TEST RESULTS AND DISCUSSION

• The observed ultimate load for cracking of ratio

1:1.43:2.33 for Slab are 5 KN, 6.5 KN, 8 KN, 7KN

and 5.5 KN for CS 0, CS 25, CS 50 , CS 75 & CS

100.

• The number of cracks developed in slab at first

cracking is 4.5, 6, 7.5,6.5 and 5 for ratio

1:1.43:2.33

• The crack spacing at ultimate load for slab are

45mm, 71mm, 127mm, 97mm and 77mm

respectively for the Static Loading.

• Finally the observation concludes that the

Flexural Behaviour of slab has gained more

strength with mix ratio 1:1.43:2.33

29.4 26.137.6 36.2

30.1

0% 25% 50% 75% 100%

COMPRESSIVE STRENGTH

(MPa)COMPRESSVE STRENGTH

2.33 2.372.79 2.54

2.05

0% 25% 50% 75% 100%

SPILT TENSILE STRENGTH

(MPa)

spilt tensile test

CASTING AND TESTING

4.3 Load–deflection profile for panels

5. ACKNOWLEDGEMENTS

Authors are grateful to the Civil

Engineering Department for their help in

conducting this project and acknowledge the

management of PSNA College of Engineering And

Technology for their moral support.

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EISSN: 2321-9637.

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