Asphalt

Presented By:Presented By:

Engineer LATIF HYDER WADHOEngineer LATIF HYDER WADHO

Mehran University of Engg: & Technology Khairpur Mehran University of Engg: & Technology Khairpur

CIVIL ENGINEERING MATERIALSCIVIL ENGINEERING MATERIALS

11STST Term 1 Term 1STST Year B.E.Civil Year B.E.Civil

ASPHAT,BITUMEN,

TAR

BITUMEN:Bitumen is a hydrocarbon in composition

containing 85% carbon, 12%hydrogen and 3% oxygen. It is a product derived during the distillation of petroleum from the residue left behind. It may occur in gaseous, liquid, semi-solid or solid form. When in liquid form, it is designated as naphtha of petroleum. The solid form is commonly designated as Bitumen. Being a hydrocarbon it is completely dissolved by carbon disulphide.

Characteristics:Following are the main characteristics of Bitumen:(i) Its colour is black.(ii)Often it is in solid or semi-solid form.(iii)It is a sticky substance.(iv)It is a light material with specific gravity 1.10.(v)It is completely dissolves in carbon disulphide.

Uses of Bitumen:

The main large-scale use of bitumen is for the making of flexible pavements, i.e. roads and high ways. It is also used as water proofing agent in building construction. Due to flexible and water proof material, it is also used for filling joints between concrete slabs.

Types of Bitumen:The main types of bitumen are given as under:(1) Straight-Run Bitumen:This is the bitumen obtained straight from the petroleum distillation. It is an oily substance with comparatively lesser viscosity and can be even sprayed.

(2) Blown Bitumen:This variety is comparatively thick and elastic. It is obtained by blowing air through bitumen at a high temperature. In doing so, the bitumen is partly oxides and becomes thick and elastic. It has high binding power; therefore it is extensively used in the constructional works.

(3) Bitumen Emulsion:

This type of bitumen is a liquid with aqueous medium containing 50 to 60 % bitumen in a finely divided form. It is prepared by stirring and mixing vigorously the mixture of hot water, molten bitumen and some resinous substances which acts as the emulsifying agent. It is used for making and repairing roads. It is also used for coating cast iron pipes (being water proof).

(4) Cut-back Bitumen:

This is a solution of the bituminous material in a volatile solvent. Actually the volatile products are removed by distillation of petroleum. In this case the volatile component called cut is added back to the solid bitumen. It contains about 20% solvent and 80% bituminous materials. The solvents used include kerosene oil, petrol. It is used for road making, more commonly for road repair work.

(5) Plastic Bitumen:It is mix consisting of bitumen, inert filler and a thinner. It is suitable for filling joints in the concrete slabs as it has a good binding power and it has a good binding power and it is water repellent.

ASPHALT:Asphalt is a solid or semi-solid product left behind during the distillation of petroleum. In composition, it is actually a mixture of bitumen and certain inert mineral matter, like silica, alumina and lime. As such, it is only partly soluble in carbon disulphide.

Characteristics of Asphalt:Main characteristics of Asphalt are as under:(1) It has a brownish-black colour.(2) It is solid or semi solid material.(3) It is moderately elastic.(4) It is partly soluble in carbon disulphide.(5) It does not absorb water.(6) It has resistance to acids.(7) It is soft, plastic, and workable when heated.(8) It has high binding power.(9) It is good insulator for heat, electricity and sound.(10) It is never solid hard and brittle.

Uses:Main uses of Asphalt are as under:It is mainly used for the construction of flexible pavements i.e. Roads (highways).To give ling to the swimming pools and other water tanks.As D.P.C in the building construction works.It is used as water - proof cover for the roofs.It is also used in the preparing of paints.

Types:There are two main types known as Natural Asphalt and Residual Asphalt.Natural Asphalt:It is the asphalt that occurs in nature. It is just collected and used. If at all any purification is required, it is done by simple melting and boiling. At some places it is found in the lakes, as in South Africa, described as Lake Asphalt. It contains as much as 70% bitumen and some water and other impurities. It is easily purified by heating and boiling. In doing so, the water content escapes, the impurities rise up, leaving the bituminous matter beneath. This refined asphalt is suitable for making flexible pavements.

Another type of natural asphalt is known as rock asphalt, found in the rocks. It is a mix of rocky matter and bitumen. The %age of bitumen is about 10 to 15 %. It can be used as such for road making. The rock asphalt is just crushed and spread along the road. It is then heated and processed by rolling.

(2) Residual Asphalt:This is the solid or semi-solid material left behind after the distillation of petroleum. It is commonly known as artificial asphalt.In addition to the above two types on the basis of mode of occurrence, there are few more types which are actually the finished products prepared from raw asphalt. These include:

(i) Asphaltic Emulsion,(ii)Asphaltic Cement,(iii)Mastic Asphaltic,(iv) Cut-back Asphalt, and (v) Bituminous Paints.

TAR:Tar is a highly viscous black coloured sticky substance derived from coal, wood or shales. It contains 70 % to 95% bituminous matter. However, its characteristics depend upon the raw material from which it is extracted and the amount of residual matter present in it. The method of distillation is used for the extraction of tar from its raw materials.This is also used for the making of roads (flexible pavements), also used as a preservative for the timber.

Types:Depending upon the raw materials from which the tar is derived, there are three types described as:Coal Tar,Wood Tar,Mineral Tar.

THE PLEASANT END