“BITUMEN MIXES FOR ROAD”
Dr. Sheetal Agrawal
HOD Civil Department
As per Das et al.(2004); During 1900’s, the bituminous paving technique was first used on rural roads The
term ‘foamed asphalt’ refers to a mixture of pavement construction aggregates and foamed bitumen. The
foamed bitumen, or expanded bitumen, is produced by a process in which water is injected into the hot
bitumen, resulting in spontaneous foaming. The bituminous mix design aims to determine the proportion
of bitumen, filler, fine aggregates, and coarse aggregates to produce a mix which is workable, strong,
durable and economical.
Asphaltic/Bituminous concrete consists of a mixture of aggregates continuously graded from
maximum size , typically less than 25 mm, through the fine filler that is smaller than 0.075 mm. Sufficient
bitumen is added to the mix so that the compacted mix is effectively impervious and will have acceptable
dissipative and elastic properties.
Sufficient bitumen to ensure a durable pavement.
Sufficient strength to resist shear deformation under traffic at higher temperature.
Sufficient air voids in the compacted bitumen to allow for additional compaction by
Sufficient workability to permit easy placement without segregation.
Sufficient resistance to avoid premature cracking due to repeated bending by traffic.
Sufficient resistance at low temperature to prevent shrinkage cracks.
OBJECTIVES OF BITUMINOUS MIX DESIGN
Coarse aggregate (retained on 2.36mm
Fine aggregate (passing 2.36mm sieve but
retained on 75m)
Filler (passing 75m), may be cement.
Binder: Bitumen etc.
CONSTITUENTS OF BITUMEN MIX
Binder: A material used to hold solid particles together,
i.e. bitumen or tar.
A heavy fraction from oil distillation (also occurs as part of natural
Tar: A viscous liquid obtained from distillation of coal or wood.Rarely used
in construction currently in the UK.
Asphalt: A mixture of bitumen and mineral filler.Note that Hot Rolled
Asphalt is a road surfacing material.
Mastic: An adhering asphalt which is placed with
Macadam: A road construction material with binder and coarse
aggregate. Tarmacadam was the first road surfacing material.
ROAD CONSTRUCTION TYPES
Lower Base (Crack
ASPHALT CONCRETE OR (BITUMINIOUS MIXTURE)
Asphalt concrete is a composite material commonly used in construction projects such as road
surfaces, airports and parking lots. It consists of asphalt (used as a binder) and mineral aggregate
Hot mix asphalt concrete (commonly abbreviated as HMAC or HMA) is produced by heating
the asphalt binder to decrease its viscosity, and drying the aggregate to remove moisture from it
prior to mixing
Warm mix asphalt Concrete (commonly abbreviated as WMA) is produced by adding either
zeo-lites waxes, asphalt emulsions, or sometimes even water to the asphalt binder prior to mixing
Cold mix asphalt concrete is produced by emulsifying the asphalt in water with (essentially)
soap prior to mixing with the aggregate
Cut-back asphalt concrete is produced by dissolving the binder in kerosene or another
lighter fraction of petroleum prior to mixing with the aggregate.
Mastic asphalt concrete or sheet asphalt is produced by
heating hard grade blown bitumen (oxidation) in a green
cooker (mixer) until it has become a viscous liquid after
which the aggregate mix is then added.
Natural asphalt concrete can be produced from bituminous
rock, found in some parts of the world, where porous sedimentary
rock near the surface has been impregnated with upwelling
HOT MIX ASPHALT
HMA is a mixture of coarse and fine aggregates and asphalt
binder. HMA, as the name suggests, is mixed, placed and
compacted at higher temperature.
This type of bituminous concrete is a well-graded HMA has good
proportion of all constituents are also called Dense bituminous
Dense graded HMA surface
Dense graded core sample
Stone Matrix Asphalt (SMA)
Stone matrix asphalt (SMA), sometimes called stone mastic asphalt, is a gap-graded HMA originally
developed in Europe to maximize rutting resistance and durability in heavy traffic road.
SMA Lab Sample SMA Surface
Unlike dense-graded mixes and SMA, an open-graded HMA mixture is designed to be water
permeable.Open-graded mixes use only crushed stone (or gravel) and a small percentage of
CHARACTERISTICS OF MATERIAL
USED IN BITUMINOUS MIX
Obtained from different natural sources such as glacial deposits or mines.
A highly cubic shape and rough texture to resist rutting and movements.
A hardness which can resist fracturing under heavy traffic loads.
A high resistance to polishing, and
A high resistance to abrasion.
Generally filler plays an important role in properties of bituminous mixture
particularly in terms of air voids, voids in mineral aggregate. Different types
of mineral fillers are used in the SMA mixes such as stone dust, ordinary
Portland cement (OPC), slag cement, fly Ash, hydrated lime etc
Bitumen acts as a binding agent to the aggregates, fines and stabilizers in bituminous
mixtures. Binder provides durability to the mix.
The main stabilizing additives used in mixes can be classified in to different groups;
Fibres’ (Cellulose Fibres, Mineral Fibres, Chemical Fibres)
Powder and flour like materials (Silicic acid, Special Filler)
Plastics (Polymer Powders or Pellets)
Natural fiber:-Natural fiber classified into 3 category depending upon the part of plant
from where it is extracted
Stem fiber (jute, banana etc.)
Leaf fiber (sisal, pineapple)
Fruit fiber (cotton, coir, oil palm)
Conventional Bituminous Mix Technologies
Hot Mix Technologies-Shortfalls
Heating of binder at 150-170 C
Heating of aggregates at 185-200 C
Production at 150-160 C
Laying at 140 C
Compaction at 120 C
High energy consumption
Limited work year
Cold mix technologies using bitumen
emulsion as binder
COLD BITUMINOUS MIXES
Cold mix technology eliminates heating of
aggregates, bitumen binder, uses cationic
Optimized composition of open graded premix
carpet, semi- dense bituminous concrete,
microsurfacing and bituminous macadam .
It is environment friendly, offer greater social
acceptance, increased paving period, acceptable performance
and cost effective.
Technology has found wide acceptance.
PRODUCTION OF COLD MIXES
Adding Pre-mix Water Adding Emulsion In Drummixer
Cold mix on coneyer belt Discharge of cold to dumper
PREPARATION OF COLD MIX
Charging of Aggregates Wetting of Aggregates
Emulsion for Cold Mix Discharging of Cold Mix
Transportation of cold mix
Cold mix shall be discharged in trolleys/wheel barrow
Cold mix shall be transported to site by wheel barrow/tippers
Avoid newly laid surface or tacky road surface while ferrying
Spreading of cold mix
Spread cold mix in half the road-width
Required thickness with spreader
Cold mix turned black from brown
Cold mix aerated for about one hours
Compacted with 8-10 ton road roller
Wetting of wheels
Preparation of Marshall Specimens
1100g Blended Aggregates
4 % water content Mix for wetting
Addition of emulsion 7,8,9% into
aggregates Mixing for uniform
coating Cold mix in mould
Compaction with 75 Blows on
each face Specimens Marshall
Specimen Curing for 3 days at
400C Testing for Bulk Density,
Stability, flow , Retained Stab. at 250C