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Accueil du site → Doctorat → Royaume-Uni → 1997 → Premature surface cracking of bituminous pavements in hot arid climates

University of Bristol (1997)

Premature surface cracking of bituminous pavements in hot arid climates

Imbarek, Mohamed Omran

Titre : Premature surface cracking of bituminous pavements in hot arid climates.

Auteur : Imbarek, Mohamed Omran.

Université de soutenance : University of Bristol

Grade : Doctor of Philosophy (Ph.D.) 1997

The stiffness modulus of bituminous binders in hot arid climates was found to increase rapidly with the age of pavement. The stiffness of tested specimens increased by 2.5 times in two years, 6 times in four years and 42 times in eight years. This high increase in bitumen stiffness reflects the rapid loss of volatile compounds from the material in this severe climate. The degree of exposure decreases with the depth of the material under the surface ; this has a significant effect on the hardening and ageing of both bitumen binder and bituminous mix. Viscosity and stiffness values measured for the studied specimens decreased with pavement depths.The viscosity of a bituminous binder, and hence its stiffness, plays a significant role in the susceptibility of the mix stiffness to temperature changes. The current study showed that the mix stiffness of a new pavement falls rapidly with temperature. However, the rate of fall decreases with mix age.The analysis showed that it is possible to predict the binder and mix stiffness of a given bitumen or bituminous mixture for different conditions of loading and temperature from a knowledge of two experimental rheological parameters. The equivalent stiffness (Sme) was defined as the mix stiffness determined at reference values of mix proportions. This equivalent stiffness makes it possible to compare mixes of different mix designs on the same basis and eliminates the influence of mix proportions on the value of mix stiffness. A special calculation technique has been demonstrated to predict the equivalent stiffness.A new model for predicting ageing of bitumen binders and mixtures in hot arid climates was developed. An ageing factor ( ) was introduced. It depends on the rheological origin of the bitumen binder and on the environment in which the pavement is constructed. Special functions were given to calculate this ageing factor for this case study of hot arid climate and bitumen of 60/70 pen.In the analytical part of the study a general method for calculating pavement temperature was presented. The developed procedure is a numerical solution to the fundamental relations of heat transfer process through a solid medium.A procedure for calculating thermal stresses in bituminous pavements in hot arid climates was presented. The models and procedures developed during this study were involved in a general system for predicting thermal cracking of bituminous pavements in hot arid climates. The proposed system can be used in the processes of design and assessment of highway pavements. A number of suggestions are given for minimising the problem of premature thermal cracking of bituminous pavements in hot arid climates.

Annonce : EThOS (UK)

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