Abstract
For asphalt concrete preparation in laboratory mix-design operations, bitumens are usually mixed with micrometer-sized particles (filler), sand and centimeter-sized crushed stones in a gyratory press at a temperature of about 140–155 °C depending on the bitumen viscosity, until adequate homogenization and compaction take place (air voids optimum). This requires energy consumption. To minimize it, the process needs to be optimized and is usually made empirically. The aim of this manuscript is to gain a comprehension of the physico-chemical mechanisms involved in the process by exploring: (i) the rheological properties (viscosity, activation energy) of a neat and RTFOT-aged bitumen, in presence and in absence of a filler, (ii) the volumetric and resistance behavior under the compaction in a standard Gyratory Compactor (GC) of their blends with aggregates and (iii) the mechanical properties (Indirect Tensile Strength, compression and tensile deformation) of the final products. Correlations between activation energy and pre-exponential factor of the viscosity on a side, and between viscosity, workability and final mechanical properties on the other side allowed to provide a rational interpretation of the physico-chemical processes involved in the framework of the physics of complex fluids. The scientific clues will be of help in optimizing the workability in asphalt concretes productions with obvious repercussions in terms of energy savings, useful for economic and environmental issues.
Highlights
Asphalt is a well-known material used for road paving all around the world.It is a mixture of crushed stone materials, sand and a fine powder bound together by a small amount of a viscoelastic binder called bitumen [1,2]
To highlight the rheological properties of bituminous materials used in this study, viscosity (ŋ) was measured as a function of temperature for both neat and RTFOT-aged as they are and mixed with filler
The first aim of this study is to understand the macroscopic behavior in terms of molecule-based physics, so it must be pointed out that viscosity is a synthetic indicator concisely yielding information on the total amount of energy that the system absorbs under shear conditions
Summary
Asphalt (asphalt concrete) is a well-known material used for road paving all around the world It is a mixture of crushed stone materials (aggregates), sand and a fine powder (filler) bound together by a small amount (about 5% w/w) of a viscoelastic binder called bitumen [1,2]. These components need to be properly mixed together, and this is usually made at relatively high temperatures (140–155 ◦ C). The mechanical and thermal energy consumption to complete this job unavoidably implies high costs To face this problem, mechanical properties of bitumens are tuned by small amounts of additives [3]. This can be useful to reduce the temperature at which the asphalt is prepared [8]
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