partial replacement of discarded rubber tyres with coarse aggregate

Partial replacement of discarded rubber tyres with coarse aggregate

ABSTRACT

The disposal of waste tyres is becoming a major waste management problem in the world at the

moment. It is estimated that 1.2 billions of waste tyre rubber produced globally in a year. It is estimated

that 11% of postconsumer tyres are exported and 27% are sent to landfill, stockpiled or dumped illegally

and only 4% is used for civil engineering projects. Hence efforts have been taken to identify the

potential application of waste tyres in civil engineering projects. In this essence, our present study aims

to investigate the optimal use of waste tyre rubber crumbs as coarse aggregate in concrete composite.

A total of 6 cubes are casted of M25 grade by replacing 20 percent of tyre aggregate with coarse

aggregate and compared with regular M25 grade concrete. Fresh and hardened concretesuch as

workability, compressive strength were identified.

1


Introdution:

The scarcity and availability at reasonable rates of sand and aggregates lead to invent the new

materials with their replacement. The new materials should not be much expensive than what we have

now or else it would be somewhat again cannot be replaceable because every cannot use it. The material

should be economical and affordably available.

So, from number of years the experiments have been going on to replace partially or completely

by the solid wastes which cannot harm the construction and gives same strength as the regular

aggregate.

Discarded rubber tyres, plastic waste, rice husk, fly ash etc, are some of the waste materials can

partially replaced by the coarse or fine aggregate. The rubber aggregate from discarded tyre rubber is

one of the waste material which can be used to partially replace natural aggregate in sizes 20-10mm, 10-

4.75mm and 4.75 down can be partially replaced.

About one crore ten lakhs all types of new vehicles are added each year to the Indian roads. The

increase of about three crores discarded tyres. The disposal of which each year pose a potential threat to

environment.

2


preview

3


Materials:

Rubber aggregate:Rubber aggregate of 20mm are taken from lorry tyres of MRF make partially replacing the coarse

aggregate of concrete with some quantity of small waste tyre material. These materials are cut into

20mm size manually. The research has shown that material improves qualities such as low unit weight,

high resistance to abrasion, absorbing the shocks and vibrations and so on to the concrete more over

inclusion of rubber in to concrete results in higher durability and elasticity.

Discarded tyres as concrete aggregates:Earlier studies in the use of worn-out tyres in asphalt mixes were very promising, they showed that

rubberized asphalt had better skid resistance, reduced fatigue cracking and achieved longer pavement

life than conventional asphalt. So far very little work have been done in the use of rubber from scrap

tyres in Portland cement concrete mixture. The work done so far in the use of tyre rubber as aggregate

in concrete is given below.

Slump:It was observed slump decreases with increase rubber content by total aggregates volume, the results

show that at rubber content 20% by total aggregates volume. The slump was normal and the concrete

was workable. This mix was properly compacted because rubber having low unit weight and low

interlocking capacity without proper mixing rubber cannot paired up with the concrete as natural

aggregate.

Density: The general density reduction was to be expected due to the low specific gravity of the rubber

aggregates with respect to that of the natural aggregates. The reduction in density can be a desirable

feature in a number of application, including architectural application such as nailing concrete, false

facades, stone backing and interior construction as well as precast concrete, light weight hollow and

solid blocks, slabs etc.

Air content:The air content increases in rubber concrete mixture with increase amount of ground tyre rubber.

4


Plastic shrinkage:The addition of rubber shreds to mortar reduced plastic shrinkage cracking compared to a control

mortar. Despite their apparently weak bonding to the cement paste, rubber shreds provided sufficient

restrain to prevent micro cracks from propagating.

Effect of surface texture of rubber particles:Various studies show that the rougher the rubber particles used in concrete mixtures the better the

bonding they develop with the surrounding matrix and, therefore, the higher the compressive strength of

rubber concrete may be obtained by improving the bond between rubber particles and the surrounding

cement paste. Pretreatment to improve bond of rubber aggregates vary from merely washing them with

water to acid etching. The treatment increase in surface roughness of the rubber, which improves its

attachment to the cement paste. Upon loading weak bonding of rubber aggregates to surrounding cement

paste is one of the main cause of lower compressive strerngth of rubber concrete. There are various

methods by which rubber aggregates bonds may be improved. The waste rubber recycling factories

should supply the rubber aggregates in pretreated and specified gradings for their better performance.

This will build confidence to users and improve the mass sale of rubber aggregates as a new

construction material of cement concrete construction. Quality rubber aggregates should be

manufactured and supplied by waste rubber recycling factories in grading 20-10 mm, 10-4.75 mm and

4.75 mm down sizes.

Toughness, impact resistance, heat and sound insulation: Rubberized concrete has ability to with stand large tensile deformations, the rubber particles act as

springs, delaying the widening of cracks and preventing full disintegration of the concrete mass.

Rubberized concrete will give better performance than conventional concrete where vibration damping

is required, such as in building as an earthquakes shock-wave absorber, in foundation pads for

machinery, and in Railway stations.

When rubber aggregates were added to the mixture, the impact resistance of concrete is increased,

Rubber aggregates in concreter also make the material a better thermal insulator, which could be very

useful especially in the wake of energy conservation requirements. From fire test it was observed that

flammability of rubber in rubber concrete mixture was much reduced by the presence of cement and

aggregates. It is believed that fire resistance of rubber concrete mixture is satisfactory. In this connection

more testing is needed.

5


Coarse aggregate:Coarse aggregate of angular shape 20mm and 10mm sizes are mixed to increase the interlocking

capacity. The most desirable fine-aggregate grading depends on the type of work, the richness of the

mixture, and the maximum size of coarse aggregate. In leaner mixtures, or when small-size coarse

aggregates are used, a grading that approaches the maximum recommended percentage passing each

sieve is desirable for workability. In general, if the water-cement ratio is kept constant and the ratio of

fine-to-coarse aggregate is chosen correctly, a wide range in grading can be used without measurable

effect on strength. However, the best economy will sometimes be achieved by adjusting the concrete

mixture to suit the gradation of the local aggregates.

Type of material: 20mm c.a

Wt. of sample taken for testing: 2kg

IS sieve wt.of aggregate retained pecentage retained cumulative % retained % passing

observed As per IS-38340mm 0 0 0 100 10020mm 0.22 11 11 89 85-10010mm 1.63 81.5 92.5 7.5 0-204.75mm 0.15 7.5 100 0 0-5

Type of material: 10mm c.a

Wt. of sample taken for testing: 1kg


observed As per IS-38312.5mm 0 0 0 100 10010mm 0.1 10 10 90 85-1004.75mm 0.8 80 90 10 0-202.36mm 0.1 10 100 0 0-5

Fine aggregate:

6


The shape surface texture, angularity and grading of the fine aggregate used in Portland cement concrete

mixtures significantly effect the workability, strength and performance of the concrete mixtures in

service. Shape,surface texture, angularity are the results of the interaction of the nature, structure, and

texture of the rock of which the particles consist and the forces to which they were subjected during and

after formation of the particles.

1.when rock is crushed it generally breaks along the inter faces between the mineral crystals making up

the rock.this is where the binding is weakest.

2.it is difficult to produce particles having a cubical shape from astrong homogeneous rock such as fine

graned trap rock (or) basalt. Homogeneous rock trends to disintegrate into flakes. Sedimentary rocks

commonly are laminated and the strength of the material is lower in one direction than in others.

3.the rock tends to form slabby particles. Rock having closely spaced partings (or) cleavages in one of

two directions produce flat or elongated particles.

Type of material: sand fine aggregate

wt. of sample taken for testing: 0.5kg


observed As per IS-38310mm 0 0 0 100 1004.75mm 0.017 3.4 3.4 96.6 90-1002.36mm 0.021 4.2 7.6 92.4 75-1001.18mm 0.066 13.2 20.8 79.2 55-90600micron 0.201 40.2 61 39 35-59300micron 0.104 20.8 81.8 18.2 80-30150micron 0.091 18.2 100 0 0-10

7


Portland pozolana cement(ppc of 43 grade)

The Portland Pozzolana Cement is a kind of Blended Cement which is produced by either intergrinding

of OPC clinker along with gypsum and pozzolanic materials in certain proportions or grinding the OPC

clinker, gypsum and Pozzolanic materials separately and thoroughly blending them in certain

proportions.

Pozzolana is a natural or artificial material containing silica in a reactive form. It may be further

discussed as siliceous or siliceous and aluminous material which in itself possesses little, or no

cementitious properties but will in finely divided form and in the presence of moisture, chemically react

with calcium hydroxide at ordinary temperature.

M25 concrete mix design with partial replacement of rubber

Stipulations for proportioning:

Grade designation – m25

Type of cement – pcc 43grade

Maxmimum nominal aggregate size – 20mm

Minimum cement concrete – 280kg/m3

Maximum water cement ratio – 0.5

Workability – 25mm to 50mm

8


Exposure condition – extreme

Type of aggregate – crushed angular aggregate

Maximum cement content -445.58kg/m3

Replacement of rubber aggregate – crushed square aggregate

Test data for materials:

Cement used - ppc 43grade

Specific gravity of cement – 3.15

Specific gravity of water – 1.00

Specific gravity of 20mm aggregate – 2.6

Specific gravity of 20mm rubber aggregate – 1.14

Specific gravity of a sand – 2.6

Target strength for mix proportions:

Target mean strength = fck + 1.65*standard deviation

Where fck characteristics strength at 28days = 25n/mm2

Fck = fck + 1.65* standard deviation =24+1.65*4

=31.6n/mm2

Selection of water cement concrete:

From graph of relation between free water cement ratio and concrete strength for different cement strength. The water cement ratio required for target mean strength of 31.6n/mm2 is 0.5.

Adopt water content is 0.50

9


Selection of water content: selection of w/c from curves

For 20mm maximum size aggregate

sand conforming to grading zone 11

water content per cubic metre of concrete = 186kg

10


sand content as percentage of total aggregate by obsolute volume = 35%

adjustment is regular.

change in condition percent adjustment water content required sand in total aggregatefor decrease in water cement ratio by (0. 0 -1(0.60-0.50) that is 0.10for increase in compacting factor 3 0(0.9-0.8) i.e, 0.1for sand conforming to zone 3 of 0 -1.5table 4, IS 383 - 1970

TOTAL 3 -2.5

Therefore required sand content as percentage of total aggregate by absolute volume

= 35 – 4.9

= 30.1%

Required water content

= 186 + 5.58

=191.6 l/m3

Determination of cement content:

Water cement ratio = 0.45

Water = 191.6

Cement = 191.6/0.45

= 445.58 kg/m3

Determination of coarse and fine aggregate contents:

11


0.98 = [191.6 + 445.58/3.15 + 1/0.301 * fa/2.6] *1/1000

0.98 = [191.6 + 141.45 + 1.277fa] * 1/1000

980 = 333.05 + 1.277fa

fa = 506.61 kg/m3

ca = (1-0.301/0.301) * 506.61 * (2.6/2.6)

ca = 1101.67 kg/m3

The mix proportions has become:

cement fine aggregate coarse aggregate445.58 506.61 1101.67

1 1.13 2.47

For one cube of size 150mm*150mm*150mm

Fine aggregate=1.709kg

Coarse aggregate=3.718kg

Cement=1.5kg

Rubber aggregate=0.32kg

Coarse aggregate=2.96kg

12


13


14


15


16


17


18

partial replacement of discarded rubber tyres with coarse aggregate

Documents