SPECIFIC GRAVITY OF COMPACTED SPECIMEN OF BITUMINOUS MIX

The specific gravity values of the different aggregates, filler and bitumen used are determined first. The theoretical specific gravity G_t of the mix is given by-

 Where,

W₁ = percent by weight of coarse aggregate

                        W₂ = percent by weight of fine aggregate

                        W₃ = percent by weight of mineral filler

                        W₄ = percent by weight of bitumen

                        G₁ = apparent specific gravity of coarse aggregate

                        G₂ = apparent specific gravity of fine aggregate

                        G₃ = apparent specific gravity of mineral filler

            G₄ = apparent specific gravity of bitumen

MIX DESIGN METHOD OF BITUMINOUS MIXES

Various methods of designing the mix proportions of dense bitumen concrete have been evolved. The most widely used methods are the following:

i) The Marshall method.
ii) The Hubbard-field method.
iii) The Hveem method.
iv) The Smith triaxial method

INTRODUCTION OF BITUMINOUS MATERIAL

Bituminous mixes are most commonly used all over the world in pavement construction. They were being used as a mortar and water proofing agent; as early as 3800 B.C. Early bitumen was of natural origin, found in pools and lakes. Many of these pools and lakes exist even today. The bitumen lake on the Trinidad island and the Bermudez deposit in Venezuela, are the largest known sources of bitumen supply. Most of the roads are constructed in Bangladesh by bituminous materials.

In different parts of the world, bitumen is also found in porous rocks such as sandstone and limestone. These bitumen-impregnated rocks have been of limited commercial value, because of the range of bitumen content. Gilsonite is another form of natural bitumen rock and is related to rock asphalt. It is a form of asphalt or bitumen occurring in rock crevices or veins.

Many theories have been put forward to explain the formation of petroleum and bitumen. But it has now been accepted that these materials were produced by decomposition of Dead Sea organisms such as Alge, molluscs, radiolaria, and probaly fish also. The organic matter changed chemically to^, hydrocarbons, which constitute crude petroleum. Due to distortion in earth's crust, crude petroleum deposits got exposed to evaporation. On exposure, lighter oils and gases were driven off, leaving behind a residue called natural asphalt which may be in the form of lake asphalt or rock asphalt. Crude petroleum is obtained by tapping the under ground reservoir by drilling.

There has been some confusion in regard to the terms `Asphalt' and `Bitumen’. In U.S.A. the term `asphalt' is used to refer to both the products manufactured from crude petroleum in the refinery and also to the natural or artificial mixture in which it is associated with inert mineral matter. But else-where in the world including India, the refinery product is termed bitumen and the mixture of bitumen and inert mineral matter as `asphalt'.

OBJECTIVE OF THE MODIFICATION OF BITUMEN

A lot of efforts have been made for the modification of bitumen. But the cost of the modified binder is high because of the high price of the polymers. Considering this problem our endeavor was to use reclaimed polyethylene to fulfill the following objectives:

• To get high strength bituminous mix.
• To achieve economic goal by saving some portion of bitumen. 
•  To find out the changing properties of bitumen after mixing of polyethylene and kerosene.
• To sure the bituminous admixture is suitable or not for construction.
• To measure benefit from the project.
• To save the environment from pollution by using waste polyethylene.

INTRODUCTION OF BITUMINOUS MIXES

Bituminous mixes are most commonly used all over the world in pavement construction. Under normal circumstances, conventional bituminous materials if designed and executed properly perform quite satisfactorily. But for special applications like roundabouts or where traffic is extremely heavy, stiffer mixes are required which can have larger fatigue life and more resistance to permanent deformation. It has been found from many researches that the strength of the paving mixes can be enhanced by use of a binder formed by modifying available bitumen with certain additives like sulphur and organic polymers. The modified polymers also improve temperature susceptibility and viscosity characteristics and help alleviating some common problems like bleeding of binder during peak summer temperature and stripping of aggregate in moisture prone areas. The polymers used for modification of bitumen for paving purposes are generally styrene­-butadiene-styrene copolymer, styrene-butadiene rubber, latex, ethylene vinyl acetate copolymer, polyethylene, polypropylene, etc. Most of these polymers, besides being costly, are not available very commonly. Due to these reasons reclaimed rubbers mainly in the form of used tires have been found to perform satisfactorily for years. Keeping the above things in mind, it was felt that an effort can be made to use some material which besides being available easily, is very cheap, or even better, if it is waste material. From this point of view, low density polyethylene carry bags have been used for modification of bitumen in the present investigation. Moreover another reason for choosing this topic is that very little papers are found published with this theme.