The effects of nanomaterials on the rheology of bituminous cement

In this article, the effects of the addition of different nanomaterials on the rheology of asphalt cement/binder (AC/AB) are discussed.

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CA limits

CA is usually obtained as a residue from the crude oil refining process or from natural sources. It has a semi-solid or solid consistency at room temperature and is used as a binding aggregate for road paving.

However, temperature sensitivity is the main limitation of the use of AC in road construction, as the material takes on a liquid form at high temperatures, causing the asphalt to rut, and becomes brittle at low temperatures. , resulting in low temperature cracking.

Role of nanomaterials to improve the rheological properties of CA

Modifying CA using different nanomaterials can reduce the temperature sensitivity of the material and improve its rheology, leading to higher stability and durability of asphalt mixes.

Nanomaterials have been shown to alter the rheological and physical properties of CA, such as increased softening point (SP), resistance to aging, resistance to rutting and low temperature cracking, viscosity, and decrease in penetration value and ductility.

SP and viscosity of AC increased while ductility decreased when montmorillonite and organ-modified montmorillonite were added to AC separately. These modifiers also increased complex modulus and rutting resistance and reduced phase angle.

Similarly, the addition of nano-clay (NC) and macro-clay to AC increased SP, tensile strength, and kinematic viscosity and decreased the penetration value of the resulting modified AC ( Mac).

Penetration value and ductility decreased, while aging resistance and SP increased when a small percentage of NC was added to AC. Adding the Cloisite-15A NC type to the AC has greatly improved the rutting performance of the MAC.

The MAC obtained after modification of CA with organically expanded vermiculite compounds (OEVMT) and zinc nanooxide (NZnO) demonstrated better resistance to photo-oxidation and thermal oxidation, 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 King Saud University Journal – Engineering Sciencesresearchers added NZnO and NC separately to AC and studied the effects of these modifiers on the rheological properties of AC.

Researchers added 12%, 10%, and 8% NC modifiers and 3%, 2%, and 1% NZnO modifiers to CA and performed a comparative analysis. The optimal percentage of each modifier that would give the best results was also determined.

AC 60/70 penetration grade, surface modified NC with 25-30% octadecylamine montmorillonite clay and 20 µm particle size, and 20-30 nm NZnO particles were used for the study.

The fire and flash points, penetration values ​​and SP of the MAC have been reduced by adding either NZnO or NC to the AC. Complex shear modulus values ​​increased when AC was modified with NZnO or NC, indicating higher stiffness in MAC.

MAC displayed a lower phase angle than AC, indicating less viscosity and more elasticity. Rutting resistance of CA increased when modified with NZnO or NC. In addition, increasing the concentration of either modifier in AC resulted in a corresponding increase in rutting resistance.

Both modifiers reduced the fatigue factor values ​​of the CA, resulting in improved fatigue resistance. MAC demonstrated higher m-value and creep stiffness, indicating significant improvements in AC low-temperature performance after either modifier was added.

3% NZnO and 10% NC were the optimal concentrations of modifiers that led to the greatest improvement in rheological properties. 10% NZnO was considered the optimal concentration due to its higher workability and lower costs than the other two concentrations, while 3% NZnO demonstrated the best improvements for different temperatures.

In another study published in the journal MDPI Nanomaterialsresearchers used high-quality, low-cost graphene to prepare conductive graphene-modified asphalt (GMA) binders with 10%, 8%, 6%, 4%, 2%, and 0% graphene and studied their rheological properties.

The results of this study demonstrated that rutting resistance at higher temperatures, strength and elasticity at temperatures above room temperature were improved in GMA binders.

Percolation of GMAs and formation of graphene networks occurred above 8% graphene concentration, indicating the feasibility of using GMA binders with graphene concentration greater than 8% to prepare graphene. conductive asphalt concrete.

Mechanisms of GMA modification differed after and before the percolation point. Before percolation, graphene with a molecular structure similar to asphaltene improved asphalt by increasing asphaltene components. After percolation, the formation of a graphene network enhanced the asphalt.

Modulus differences between GMA and AB binders were greater at higher temperatures than at lower temperatures. The modifying effect of graphene on asphalt was therefore shown to be greater at higher temperatures than at lower temperatures, since the temperature sensitivity of graphene is considerably lower than that of asphalt.

Addition of graphene improved the viscosity of all GMA samples, and viscosity increased with increasing graphene concentration. The addition of graphene also increased the compaction temperature and the mixing temperature of the modified asphalt samples.

To sum up, adding different nanomaterials, such as NC, NZnO or graphene, to AC/AB can significantly improve their rheological properties. However, further research is needed to investigate the rheological properties of asphalt mixes when modified using multiple nanomaterials, such as NZnO and NC.

Continue Reading: The benefits of using nanoparticles in cement mortar.

References and further reading

Yang, L., Zhou, D., Kang, Y. (2020). Rheological properties of graphene-modified asphalt binders. Nanomaterials10(11), 2197. https://doi.org/10.3390/nano10112197

Khafaja, DA, Imam, R., Taamneh, M., Al-Omari, A., Al-Mistarehi, B. (2021). The effects of the addition of Nano Clay and Nano Zinc Oxide 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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#effects #nanomaterials #rheology #bituminous #cement

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