EFFECT OF USING THE GRAVEL IN WARM MIXES ASPHALT IN IRAQ

Abstract

There are constantly technological improvements in the asphalt industry that would enhance the performance of materials and increase the efficiency of the pavement and preservation of the resources and the environment. It makes sense that these goals are achieved through reducing the temperatures of asphalt mixes production and hence introduction of the concept of warm mix asphalt over the past few years as a mean to achieve these goals. In this research the asphalt mixes have been produced utilizing gravel commonly used in the construction of roads in Iraq. Necessary tests have been conducted to assess the possibility of using this technology with gravel and their conformity with the Iraqi Standard Specification for Roads and Bridges (SCRB) and American Association of State Highway and Transportation Officials (AASHTO).Gravel is one of the important materials which affects the properties and the quality of the asphalt mix.

There are two types of gravel used depending on the type of road and type of layer to be established. The objective of this research is to study the impact of gravel on the properties of the Warm Mix Asphalt as it affects the strength and durability of the mix. Therefore crushed and non- crushed gravel have been used with different bitumen contents and additive in Warm Mix Asphalt. The asphalt mix design was made using the Marshall Method for aggregates gradation values in the middle of the Iraqi standard specifications. Also, two types of bitumen grade (bitumen 40/50 and 60/70) were used in this research. Results were compared to the corresponding results for Hot Mix Asphalt.

Therefore, the work was divided into different tasks to know the effect of changing the proportion of additives on the asphalt mix as well as the effect of changing the content of bitumen in the asphalt mix. An assessment of the basic engineering properties of the mixes stabilized Marshall requirements was implemented. Also an assessment of the performance of the mix was implemented through the indirect tensile test, loss of stability test and wheel tracking test. The analysis and discussion of the results have been done. This research emphasize the benefits of using Warm Mix Asphalt technology in terms of environmental, economic, production and paving aspects. Test results showed that the temperature could be reduced for processing of these mixes to approximately 130 °C to achieve the required properties that meet standard specifications. In Conclusions this research addresses possibility of using gravel in warm asphalt mixes technology.