In this paper, the authors have discussed about the replacement of aggregates by discarded tyre rubber. This type of concrete is known as “Rubcrete”. It will cover the problems with the natural aggregate and also the reasons behind the use of rubber. The types of tyre rubber that are used, influence of size and content of rubber on concrete, effect of surface texture are discussed. Change in the properties of rubcrete over the conventional concrete, in hardened and fresh state such as slump, unit weight, air content, plastic shrinkage, mechanical strength been discussed. Paper covers the mechanisms behind the strength change, impact resistance, heat and sound insulation, freezing and thawing resistance of rubcrete. At the last, discussion on applications of rubcrete.

1. USE OF RUBBER TYRE INSTEAD
OF AGGREGATE IN CONCRETE
MIX
bangalore INSTITUTE OF TECHNOLOGy
Presented by -
rahul das biswas
SADASHIV S MAKKOJI
M.Tech (Structural Engineering)

2. INTRODUCTION
• The scarcity and availability at reasonable rates of sand and aggregate .
• Banning of excavation of Natural aggregates
• Huge environmental problems.
•Contamination of water
•Landslides
•Sound Pollution due to Blasting
•Air Pollution due to Grinding
Best way to overcome this problem :
• Find alternate aggregates for construction in place of conventional
natural aggregates.
• Use of Rubber tires

3. JUSTIFICATION of USING RUBBER TYRES
• Discarded tyres are potential threat to the environment.
• Fire hazards.
• Breeding grounds for mosquitoes.
• Rapid depletion of available sites for waste disposal.

4. TYPES OF RUBBER TYRE :
TWO TYPES
CAR TYRES TRUCK TYRES
BROAD CATAGORIES OF DISCARDED TYRES
CHIPPED RUBBER CRUMB RUBBER ASH RUBBER

6. RUBBER TYRE AS CONCRETE AGGREGATE :
♦ Recycled tyre rubber in concrete might improve the weak characteristics of
concrete like- low tensile strength, low ductility, low energy absorption, and shrinkage
and cracking associated with hardening and curing .
♦ For the purpose of using it as aggregate the rubber tyres are first cut
into pieces. There are two major processing categories of rubber size reduction .
(i)Mechanical grinding
(ii)Cryogenic reduction

7. PROCESS OF MAKING RUBCRETE CONCRETE :
• The tyres are cut into small pieces.
• Irregular texture of ground rubber particles are preferable as it tends to create a
better bond between cement matrix and rubber granules.
•Steel components are removed by a magnetic separator (sieve shakers and
conventional separators such as centrifugal separator, air classification, density, etc.
are also used).
• The fibre components are separated by magnets, air classifiers, or other separation
equipment.
•Then it is mixed with the cement and proper mixture is prepared.

9. Properties of RUBCRETE CONCRETE :
The following points are to be considered:-
♦ Slump Value
♦ Unit Weight
♦ Air Content
♦ Plastic Shrinkage
♦ Mechanical Strength
♦Impact Resistance, Heat and Sound Insulation
♦Freezing and Thawing Resistance
♦Effect of Rubber Content and Particle Size
♦Effect of Surface Texture of Rubber Particles
♦ Mechanisms of Strength Reduction
Some of the main reasons will be described now

10. SLUMP VALUE :
♦Decrease in slump with increased rubber content by total aggregate volume.
♦ Rubber contents of 40% by total aggregate volume, the slump is near zero and the
concrete is not workable by hand.
♦ Mortars containing rubber shreds achieved
workability comparable to or better than a control
mortar without rubber particles.

11. UNIT WEIGHT :
Due to the low specific gravity of rubber, the unit weight of rubcrete mixtures
decreases.
The decrease is almost negligible for rubber
contents lower than 10 to 20% of the total
aggregate volume.
Plastic Shrinkage :
• The addition of rubber shreds to mortar reduces plastic shrinkage cracking
compared to a control mortar.
• Multiple cracking occurs over the width of mortar specimens compared to a single
crack ,but total crack area is decreased.
• It also prevents cracks from propagating.
•The higher the content of rubber shreds, the smaller the crack length and crack width.
• The crack width in this case is 0.3-0.4 mm whereas in normal case it is 0.9 mm.
• The onset time of cracking is also delayed due to mixture of rubber shreds.

12. Air Content :
♦ The air content increases in rubcrete mixtures with increased amounts of ground tyre
rubber although no air entraining agent is used.
♦ The higher air content is due to the nonpolar
nature of rubber particles
♦ When the nonpolar rubber is added to the
concrete mixture, it may attract air as it repels water.
♦ Since rubber has a specific gravity of 1.14, it is
expected to sink rather than float. But as air gets
entrapped in the jagged surface of rubber particle.
So it floats when added with water.

13. Mechanical Strength
• Depends on:
• Size
• Surface Texture
• Content
• Type of Cement

14. Effect of Rubber Content and Particle Size :
• Coarse grading of rubber granules lowered the compressive strength of mixtures
more, than fine grading.
• About 85% reduction in compressive strength and 50% reduction in tensile strength
when the coarse aggregate is fully replaced by coarse rubber chips.
• Specimens lost up to 65% of their compressive strength and up to 50% of their tensile
strength when the fine aggregate is fully replaced by fine crumb rubber .

16. Effect of Surface Texture of Rubber Particles:
• Rougher the rubber particles -- better the bonding -- higher the compressive strength
• To achieve enhanced adhesion, it is necessary to pre-treat the rubber.
• Pre-treatments vary from merely washing rubber particles with water to acid etching,
plasma pre-treatment, and various coupling agents.
• Due to the treatment a microscopic increase in surface roughness of the rubber,
which improves its attachment to the cement paste.

17. Impact Resistance, Heat and Sound Insulation :
• The impact resistance of concrete and ability to absorb energy and insulate sound
during impact increased when rubber aggregates are added to the mixture.
• Flammability of rubber in rubcrete mixtures is also reduced.

18. USES OF RUBCRETE MIX :
 Where vibrations damping is needed (i.e rail station).
 Where resistance to impact or blast is required such as in railway buffers, jersey
barriers and bunkers.
 For trench filling and pipe bedding, pile heads and paving slabs.
 Light unit weight may be suitable for architectural works.
 Shock absorber, in sound barriers .
 Also in buildings as an earthquake shock-wave absorber.
Further researches are being going on …

19. CONCLUSION :
 Rubber recycling saves natural resources also it has few desirable characteristics-
 Lower density, higher impact and toughness resistance
 Enhanced ductility and
 Better sound insulation etc.
 Using magnesium oxychloride cement improves the performance of rubcrete.
 Experimentally proved fact is that they are substantially resistant to the combined
action of frost and de-icing salts, making them very promising.
 Its strength can also be improved by pre-treating.

20. REFFERENCE:
1) K. Rechner: Scrap Tire Recycling: A Summary of Prevalent Disposal and Recycling Methods,
Berlin, Germany, www.entire-engineering.de
2) R. Siddique, Waste Materials and By-Products in Concrete, Scrap Tires, Chapter 4, Springer;
1edition, (2007), pp. 121-145.
3) Khatib, Z.K. and F.M. Bayomy, 1999. Rubberized Portland cement concrete. J. Mater. Civil. Eng.
ASCE,11: 206-213.
4) Raghvan, D., Huynh, H., and Ferraris, C.F., ―Workability, mechanical properties and chemical
stability of a recycled tire rubber-filled cementitious composite, Journal of Materials Science, Vol. 33,
No. 7, pp. 1745-1752.
5) IS:383-1970- “Specifications for coarse and fine aggregates from natural sources for concrete”
(Second revision) BIS, New Delhi.
6) Kishore Kaushal - “Concrete Aggregates From Discarded Tyre Rubber”
7) Sharma Nimesh- “Tyre Recycling”, The New Business on the Block March, 2010.
8) Nehdi Moncef And Khan Ashfaq- “Cementitious Composites Containing Tire Rubber” Cement,
Concrete and Aggregate Vol. 23 No. 1 June 2001. pp 3-10.
9) Topeu I.B.“The properties of rubberized concrete”.