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Title: Tar as a soil stabilising agent for highway subgrades
Author: Darhouse, M. M.
Awarding Body: University of London
Current Institution: Imperial College London
Date of Award: 1951
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THIS thesis gives an elaborate study of the use of tar as a stabilizing agent for highway subgrades. The study was devoted to the estimation of the two main properties which are of most interest from the point of view of the soil stabilization process; viz, resistance to capillary water absorption and resistance to compressive stresses* In order that study may be of actual useful practical value and of the most possible comprehensive bearing, a very poor soil was chosen as the medium of Investigation: a Brick Earth soil from Harmondsworth, Middlesex; a very fine grained silty clay containing more than 60 per cent, by weight, of fines passing the 200-mesh British Standard sieve. The effect of treating this soil with variable percentages of tar, ungraded, then combined with a high percentage of round grained washed silica sand passing the 7-, and retained on the 14-mesh B.3. sieve, was studied. The purpose of adding this sand, which reduced the percentage of fines passing the 200-mesh down to 43.3 per cent, was to modify and improve the characteristics of the soil, but the results obtained in this investigation proved that grading, with this type of round sand, led to unexpectedly disappointing behaviour of the soil particularly from the point of view of resistance to capillary water absorption. The effect of fluxing the tar with a heavy naphtha with the purpose of studying the possibility of producing a naphtha-tar compound, prepared in the tar works, which may be directly Incorporated with the soil in the field, thus cutting out the costly and laborious heating^process, was also Investigated only to prove that not only the fulfilment of this desire could be accomplished, but that some other unexpected qualities- obtained by fluxing- could be achieved, the most Important of these qualities is the fact, arrived at, that by proper adjustment a fluxed tar compound which may render the tar-soil stabilized mix totally non-absorbent to water, could be designed Trials and studies were also carried out to determine the effect of adding lime to a tar-, or fluxed-tar-stabilized base* This proved lime increased the stability of tar and raised its softening point on heating but its effects on resistance to capillary absorption and resistance to compressive stresses were negative. 'She effect of heat on tar-, and fluxed-tar-stabilized mixes was also investigated only to prove that a stabilized mix loading in compressive resistance, on heating, as soon as it contains a quantity of tar just in excess of what is required to coat every one of, and all, its particles. Finally the whole study led to the conclusion that tar can be safely and adequately recommended as a satisfactory stabilizing agent for highway subgrade built up from this, and other similar, soils. Taking the results obtained in the investigation into account the design of a suitable section of a tar-stabilized highway course was suggested.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available