Abstract
Asphalt mixes encounter different distress during the life cycle of asphalt pavements, among which rutting and fatigue failure are prominent. Moreover, the addition of environmentally friendly modifiers into the asphalt binder to increase the performance of asphalt mixes has been a challenging phenomenon for researchers. Calcium lignosulfonate (CL) is a waste material that is a by-product of the wood industry. In this paper, the impact of the calcium lignosulfonate on the rutting and fatigue performance of the asphalt binder was investigated. For this purpose, the Dynamic Shear Rheometer (DSR) was utilized to run the Multiple Stress Creep Recovery (MSCR) test and evaluate G ∗ /sinδ and G ∗ ·sinδ indices for the asphalt binder containing different percentages of CL. The elastic recovery test was also conducted on the asphalt binder. In order to analyze the thermal storage stability of CL-modified asphalt binders, the storage stability test was considered. The Field Emission Scanning Electron Microscope test showed that using CL as a binder modifier makes the texture of the asphalt binder spongy and porous. The conventional test results indicated that increasing the CL amount in the asphalt binder led to an increase in the stiffness of the asphalt binder. The rheological test results showed that the rutting resistance of the asphalt binder improved by adding up to 15% of the CL powder; however, the fatigue performance and the elasticity of the asphalt binder declined by increasing the CL content in the asphalt binder. The storage stability test revealed that the dispersion of CL in the asphalt binder was uniform; moreover, the presence of CL in the asphalt binder could not adversely affect the thermal storage stability of the modified asphalt binder.
Highlights
Calcium lignosulfonate (CL) is an amorphous yellow powder, which is made of wood lignin
The kraft lignin dwindled the penetration degree and increased the modified asphalt binder’s hardness [13]. e viscosity of the asphalt binder increases by almost 50% when the CL content is increased. e increase of viscosity may result in a dramatic increase in the mixing and compaction temperature of the asphalt mixes
(ii) e conventional test results showed that the viscosity and softening point of the asphalt binder increased, and the penetration declined by increasing the CL content, which emanated from the stiffening effect of the CL powder on the asphalt binder
Summary
Calcium lignosulfonate (CL) is an amorphous yellow powder, which is made of wood lignin. Wood lignin is a byproduct of the wood industry that consists of phenylpropane units [1]. Erefore, finding a way to reuse this material in the industry is a major concern to the researchers. To this aim, this material is used as an additive in concrete and asphalt mixes. It is shown that the use of this material in the asphalt industry improves some of the performance characteristics of asphalt binder and mixes. It provides environmental benefits [2, 3]. Previous findings showed that the use of biomass materials in the construction process of asphalt mixes lessens the need for harsh chemical materials, which leads to minimizing health risks of humans and reducing chemical pollutions of aquatic environments located near the asphalt pavements [4, 5]
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