Please use this identifier to cite or link to this item: http://localhost:8081/xmlui/handle/123456789/1404
Authors: Azadani, Masoud Nasr
Issue Date: 1997
Abstract: Due to the rapid increase in allround developmental activities in different parts of the country, the traffic intensity began to increase on the roads as a result the existing pavements are subjected to deterioration at a very fast rate. Critical locations such as round-abouts, bridge decks, intersections and bus stops are subjected to high stresses and need frequent maintenance. Thick rolled bituminous surfacings came into use on heavily trafficked roads. These thick surfacing materials are not only costly and time consuming but also, sometimes fail to resist the stresses imposed by traffic due to tremendous increase in traffic intensity and axle loads. Therefore, the use of new construction materials and innovative technology must be introduced for higher productivity, improved durability, and speedy construction, not only with regard to their structural capacity, but also the functional aspects of travel safety and comfort. Besides polymer modified bituminous mixes, mastic asphalt is another recognised improved alternative for pavement surfacing specially for the above mentioned critical locations. In the present investigation, an attempt has been made to develop new mastic asphalt mixes besides conventional mastic asphalt for surfacing purposes of critical locations as mentioned above as well as locations with extreme climatic conditions like desert areas and also other areas, where suitable ingredients for preparing mastic asphalt are scarce and economically not available. Various methods of testing besides Wilson hardness test which is commonly used, have been evaluated lor design of mastic asphalt. Effects of five ( i ) important variables including type of filler, grade of bitumen, blend of sulphur/bitumen, temperature and rate of loading on strength characteristics of mastic asphalt mixes have been investigated. The first part of the thesis consists of determination of physical characteristics of constituents of mastic asphalt mixes, such as coarse aggregate, fine aggregate, fillers of limestone powder, portland cement, stone dust and hydrated lime, and bitumen and sulphur with a number of widely used asphalt material testing methods. Flow characteristics of blends of filler/bitumen mixes with different types of filler and filler/bitumen ratio as well as blends of sulphur/bitumen, have been measured. Geometric and mineralogical characteristics of different types of fillers have been evaluated by Scanning Electron Microscopic analysis and X-ray instruments. In the second part of the thesis, the methods of design, cooking and preparation of different types of mastic asphalt, have been mentioned. This part of the research work has been divided in three dividual subsections. In the first section, the effect of type of filler on the mechanical strength characteristics of mastic asphalt has been studied. Three types of fillers including limestone powder, portland cement and stone dust were used to prepare of mastic asphalt mixes with hard grade of bitumen, 20/30 pen. The specimens of these mixes were subjected to various methods of testing like triaxial compression, uniaxial compression, Hubbard Field, Marshall, creep and Wilson hardness tests, under different conditions of rates of loading and temperatures. Also the necessity of the long cooking period recommended by IRC and IS codes for preparing mastic asphalt was studied. Samples of hard and soft bitumens were subjected to heat at recommended cooking periods and (i i ) variations in their physical properties were determined. It was found that, when hard bitumen is used as binder, long periods of cooking are not necessary and as soon as the mix becomes homogeneous it may be laid. In the second section of this the second part of thesis, the strength characteristics of mastic asphalt mix prepared with softer grade of 80/100 pen. bitumen and a blend of hydrated lime and limestone powder as filler, have been studied. Specimens from this mix were subjected to various methods of testing as mentioned above. Also, besides tests mentioned above, beam specimens of this mix were subjected to portable skid resistance test under dry and wet conditions. The results of various methods of tests showed that this type of mastic asphalt exhibits not only higher stability than conventional mastic asphalt but also its surface skid resistance is enough and does not require any surface treatment. In the third section of the second part of thesis, the strength characteristics of sulphur-mastic asphalt mix prepared with a blend of sulphur and 80/100 pen. bitumen as binder and limestone powder as filler, have been studied. Sulphur-mastic asphalt was prepared at considerably lower temperatures 130°C - 150°C rather than 200°C used commonly for other types of mastic asphalt mixes. Samples from this mix were subjected to various methods of testing and under the same conditions as mentioned in the above sections. Various methods of introducing sulphur to the mix were studied. Comparison of the tests results on this mix with those of conventional mastic asphalt showed that under all circumstances the strength characteristics of sulphur-mastic asphalt are higher and also this mix does not require any surface treatment. ( i i i ) In the second part of the research work, also based on the results obtained from Uniaxial compression and Hubbard Field stability tests, Multiple linear regression equations were developed to predict maximum stability of mixes under different conditions of rate of loading and temperature. The third part of this investigation consists of evaluation of different types of mastic asphalt mixes, under study in the present research, as a wearing course of steel plate bridge decks. Samples of steel plate surfaced with various types of mastic asphalt mixes were subjected to the three point bending fatigue test under different conditions of load and frequency. Also in order to determine the dynamic stiffness of the mixes, composite specimens of steel/mastic asphalt were subjected to the three point bending test with single pulse loading under different levels of load and frequency. Mid span strain and deflections of mastic asphalt layer were measured, during the tests. These results were used to calculate the dynamic stiffness values of mastic asphalt mixes using composite action theory. (
Other Identifiers: Ph.D
Research Supervisor/ Guide: Vasan, R. M.
metadata.dc.type: Doctoral Thesis
Appears in Collections:DOCTORAL THESES (Civil Engg)

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