This paper discusses the effects of the addition of different nanomaterials on the rheology of asphalt / binder cement (AC / AB).
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Limitations of AC
CA is usually obtained as a residue from the refining process of crude oil or natural sources. It has a semi-solid or solid consistency at room temperature and is used as an aggregate binder for paving roads.
However, temperature susceptibility is the main limitation of the use of AC in road construction, as the material takes liquid form at high temperatures, causing the asphalt to roll, and it becomes brittle. at low temperatures, resulting in low temperature cracks.
Role of nanomaterials in improving the rheological properties of AC
Modification of the AC with different nanomaterials can reduce the temperature susceptibility of the material and improve its rheology, leading to greater stability and durability of asphalt mixtures.
Nanomaterials have been shown to alter the rheological and physical properties of AC, such as increased softening point (SP), aging resistance, low temperature cracking resistance, and viscosity. , and decreased penetration value and ductility.
SP and AC viscosity increased while ductility decreased when organ-modified montmorillonite and montmorillonite modified by organs were added to AC separately. These modifiers also increased complex modulus and rut resistance and reduced phase angle.
Similarly, the addition of nanoclay (NC) and macro clay to the AC increased the SP, tensile strength, and kinematic viscosity, and decreased the resulting modified AC (MAC) penetration value.
Penetration value and ductility decreased, while aging resistance and SP increased when a low percentage of NC to AC was added. The addition of the Cloisite-15A NC type to the AC significantly improved the performance of the MAC.
MAC obtained after modification of AC with compounds of organically expanded vermiculite (OEVMT) and zinc nanoxide (NZnO) demonstrated improved resistance to photooxidation and thermal oxidation, a lower complex modulus and a higher phase angle.
Recent studies investigating the effect of nanomaterials on AC rheology
In a recent study published in the Journal of King Saud University – Engineering Sciences, researchers added NZnO and NC separately to AC and investigated the effects of these modifiers on the rheological properties of AC.
The researchers added 12%, 10%, and 8% NC modifiers and 3%, 2%, and 1% NZnO modifiers to the CA and performed a comparative analysis. The optimal percentage of each modifier that can give the best results was also determined.
For the study were used NC of penetration degree 60/70, NC modified to the surface with 25-30% octadecylamine montmorillonite clay and a particle size of 20 µm and NZnO particles of 20- 30 nm.
Fire and flash points, penetration values, and MAC SP were reduced by adding NZnO or NC to the AC. The shear modulus complex values increased when the AC was modified with NZnO or NC, indicating higher stiffness in the MAC.
The MAC showed a lower phase angle than the AC, indicating less viscosity and more elasticity. The breaking strength of the AC increased after modification with NZnO or NC. In addition, increasing the concentration of any modifier in the AC resulted in a corresponding increase in breaking strength.
Both modifiers reduced AC fatigue factor values, leading to an improvement in fatigue strength. The MAC showed a higher m and creep stiffness value, indicating significant improvements in low temperature AC performance after the addition of any modifiers.
3% NZnO and 10% NC were the optimal concentrations of modifiers that led to the highest improvement in rheological properties. 10% NZnO was considered the optimal concentration due to the higher work capacity and lower costs than the other two concentrations, while 3% NZnO showed the best improvements for different temperatures.
In another study published in the journal MDPI Nanomaterials, researchers used high-quality, low-cost graphene to prepare graphene-modified asphalt binders with conductive graphene (GMA) with 10%, 8%, 6%, 4% , 2% and 0% graphene and investigated its rheological properties.
The results of this study showed that the tensile strength at higher temperatures, the strength and elasticity at higher ambient temperatures were improved in GMA binders.
GMA percolation and graphene network formation occurred above 8% graphene concentration, indicating the feasibility of using GMA binders with more than 8% graphene concentration to prepare conductive asphalt concrete .
The mechanisms of GMA modification differ after and before the percolation point. Prior to percolation, graphene with an asphalt-like molecular structure improved asphalt by increasing asphalt components. After percolation, the formation of a graphene network improved the asphalt.
Module differences between GMA and AB binders were more significant at higher temperatures compared to lower temperatures. Therefore, it was indicated that the modifying effect of graphene on asphalt was higher at higher temperatures compared to lower temperatures, as the temperature susceptibility of graphene is considerably lower than that of asphalt.
The addition of graphene improved the viscosity of all GMA samples and the viscosity increased with increasing graphene concentration. The addition of graphene also increased the compaction temperature and mixing temperature of the modified asphalt samples.
In summary, adding different nanomaterials, such as NC, NZnO or graphene, to AC / AB can significantly improve their rheological properties. However, more research is required to investigate the rheological properties of asphalt mixtures when modified using various nanomaterials, such as NZnO and NC.
Continue reading: The advantages of using nanoparticles in cement mortar.
References and additional reading
Yang, L., Zhou, D., Kang, Y. (2020). Rheological properties of graphene-modified asphalt binders. Nanomaterials, 10 (11), 2197.
Khafaja, DA, Imam, R., Taamneh, M., Al-Omari, A., Al-Mistarehi, B. (2021). The effects of the addition of nanoclay and zinc nanoxide on the rheology of asphalt cement. King Saud University Journal – Engineering Sciences. https://doi.org/10.1016/j.jksues.2021.03.010.
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