Investigation and improvement of temperature and moisture sensitivity of bituminous mixtures

It is known that temperature and moisture, which are environmental factors, play an important role in the occurrence of deteriorations observed in flexible pavements. Within the scope of this thesis study, firstly, the resistance of hot and warm asphalt mixtures, which are the most preferred bituminous mixture types for the construction of flexible pavements, to temperature and moisture sensitivities were investigated. Then, it was aimed to improve the engineering properties of both types of mixtures, which were observed to be inadequate in the face of these environmental factors, by means of various methods. In the first stage, the behaviours of hot asphalt mixtures produced with 50/70 and 70/100 penetration grade bituminous binders were determined under the influence of low and high temperature and moisture. Subsequently, in order to enhance the resistance of the mixtures to these factors, nano expanded vermiculite was incorporated into hot asphalt mixtures through the utilisation of two distinct methods (wet and dry). In the wet method, both reference bituminous binders were modified with nano expanded vermiculite at specific ratios (1, 2 and 3%) by weight. In the dry method, the filler in the aggregate gradations of hot asphalt mixtures prepared for both reference bitumen grades were replaced with nano expanded vermiculite in certain ratios (0.5, 1 and 1.5‰). In the second stage, in order to production of warm asphalt mixtures, 50/70 and 70/100 penetration grade bituminous binders were modified with chemical (warm mix additive – 2, 3 and 4‰) and organic (filtered waste fat – 1, 3 and 5%) additives, respectively. And then, the temperature and moisture sensitivities of warm asphalt mixtures were ascertained on the samples prepared with the mentioned modified bituminous binders. In order to overcome the deficiencies of the warm asphalt mixtures against these factors, the filler in the aggregate gradations of both warm asphalt mixtures were replaced with nano expanded vermiculite at ratios of 0.5, 1 and 1.5‰. For all hot and warm asphalt mixtures, the experimental methods for the evaluation of temperature and moisture sensitivities are common. The properties of the reference and modified bituminous binders used were determined by the help of chemical characterisation methods and conventional bitumen tests. Also, the behaviours of loose mixtures prepared using these binders and aggregates under temperature and moisture exposure were investigated by means of stripping tests. The actual effects of these factors have been determined by various tests on compacted mixtures, which are the actual form in which the material is used in the field. However, since more than one material and/or method is used at the same time in the study, the number of mixture combinations is quite considerable. Therefore, in order to minimise the loss of material and time occurred during the preparation of samples, some evaluations were conducted only on specific mixture combinations. Statistical methods were used both to reduce the number of samples and to model the relationships between the results obtained from the tests and the variables by means of the derived mathematical equations. A simple cost – benefit analysis was conducted in order to evaluate the mixtures produced from an economic standpoint. After all the assessments, it is concluded that the resistances of hot and warm asphalt mixtures to temperature and moisture sensitivities can be improved by the use of nano expanded vermiculite. This thesis study will make a significant contribution to the existing literature in terms of the usage types and purposes of additives, the mixture design method in which treatments are performed and the results obtained. Furthermore, the steps taken to examine the impacts of temperature and moisture on two distinct types of bituminous mixtures and improve the engineering properties of them will facilitate the construction of more resistant, cost – effective, and sustainable pavements capable of withstanding the effects of temperature and moisture in our country and globally.