Effects of Hydrated Lime as A Filler on Properties and Performance of Mastics and Hot Mix Asphalt
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Date
2018-06
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Addis Ababa University
Abstract
Flexible or asphalt concrete pavement is the paving system most widely adopted all over the world. It has been recognized that there are many different types of factors affecting the performance and durability of asphalt concrete pavement, including the service conditions, such as: variation of temperature from mild to extremes and repeated excessive axle loading as well as inadequate quality of the raw materials. All of these when combined together are going to accelerate the occurrence of distresses in flexible pavement such as permanent deformation and fatigue cracking.as a result proper mix design and appropriate material is a crucial for compromising the distress occurred at the service life of the pavements.
This study is about the effect of hydrated lime as filler on paving grade bitumen under various conditions. The basis of the thesis is to find out change in the rheological properties of the bitumen by modifying it with different fillers type and percentage. The types of fillers used in this research are hydrated lime and crushed Stone dust. Fillers help in filling the voids and change the physical and chemical properties. Fillers modify the properties, increase the performance of, and provide improved durability to various construction materials. The effects of fillers are therefore of vital importance. When bitumen is combined with filler, mastic is formed. This mastic can be viewed as the component of the asphalt mixture that binds the aggregates together and also the component of the asphalt that undergoes deformation when the pavement is stressed under traffic loading. The characteristics of the filler can significantly influence the properties of the mastic, and thus the filler properties can have significant effects on asphalt mixture performance.
Therefore, the main objective of this research is to investigate experimentally effect of using hydrated lime as a fillers on property and performance of asphalt mastic and hot asphalt concrete mixtures.
Different percentage of hydrated lime and crushed stone fillers (25%, 35% & 45% based on Filler to asphalt ratio) is used to modify the bitumen (Penetration grade 60-70). Various physical tests were conducted on virgin and modified bitumen (Mastic) for aged and Unaged samples to evaluate its rheological properties and the results were analyzed and compared.The research evaluated the rheological tests conducted using dynamic shear rheometer (DSR) on mastics prepared from hydrated lime and crushed stone (as controlled Specimen). The major tests performed on DSR were Amplitude sweep test (AST) conducted for determining The visco- elastic region LVE for mastic, Frequency sweep test (FST) conducted to Construct master curve(for complex modulus and phase angle) and backspace diagram. AST & FST conducted for intermediate and high temperature (10oC, 21.1oC, 37.8oC & 54.4oC). Multiple stress and creep recovery (MSCR) test conducted to determine rutting parameter Recovery compliance (Jnr) and Performance Grade (PG) used for checking asphalt binder environmental temperature resistance. MSCR and PG test were conducted at higher temperatures (52oC, 58oC, 64oC, 70oC & 76oC).
The Research conclude that both fillers (Hydrated lime and crushed stone dust fillers) have an effect on asphalt mastic rheology and asphalt concrete properties. When the filler to asphalt ratio increased, the stiffness of asphalt mastic and asphalt concrete increased. As compared to crushed stone filler, asphalt mastic prepared with Hydrated lime had higher stiffness value and improve rutting performance of asphalt mastic at high temperature. Master curves developed from frequency sweep test showed that hydrated lime improves the shear modulus at high temperature and low frequency.
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Keywords
Asphalt Mastics, Performance, Superpave