Asphalt-aggregate Adhesion Research Articles

Quantitative evaluation of cement emulsified asphalt mortar and aggregate adhesion performance with dynamic mechanical analysis

Low adhesion between emulsified asphalt mortar and aggregate can enormously result in poor properties of emulsified asphalt mixture. The adhesion performance can also be directly influenced by the viscosity of cement emulsified asphalt mortar (CEAM). In this work, Brookfield viscometer was used to test the viscosity of CEAM with different cement content, temperature and mixing time. Then, influence degree of each factor on viscosity was determined by gray correlation analysis (GCA) and significance test. Furthermore, dynamic mechanical analysis (DMA) was used to quantitatively evaluate the adhesion between CEAM and aggregate. Besides these, scanning electron microscope (SEM), energy dispersive X-ray (EDX), alkali content test, Fourier transform infrared spectroscopy (FT-IR) were adopted to analyze the interaction between cement and emulsified asphalt. The results show that the viscosity of CEAM increases with the increase of the cement content, mixing time and temperature. The cement content has the highest effect on the viscosity of CEAM, followed by mixing time; and temperature has a lowest effect. When the cement content is less than 50%, hydration products in the mixture can improve the fatigue life of CEAM. While it is higher than 50%, the adhesion is weakened and the fatigue life is shortened. Cement hydration and asphalt emulsion demulsification can mutually promote, which generates a network structure and improves the adhesion performance of CEAM to aggregate.

Molecular dynamics analysis of moisture effect on asphalt-aggregate adhesion considering anisotropic mineral surfaces

The objective of this work is to analyze the effect of moisture on the bonding and debonding behaviors between asphalt and aggregates based on molecular dynamics (MD) simulation, considering the anisotropic characteristics of mineral surfaces. Full atomistic models adopted for MD simulations were constructed using the 12-component asphalt model and two types of representative minerals, α-quartz and calcite. Anisotropic wettability was studied by simulating the dynamic processes of a water nano-droplet spreading on anisotropic mineral surfaces. An improved energy ratio (ER) considering the residual adhesion between asphalt and aggregates in a moist state was established to evaluate the moisture susceptibility of asphalt mixtures. It was found that (1) anisotropic mineral surfaces have a significant influence on the bonding properties and moisture susceptibilities of asphalt mixtures; (2) the concentrated hydroxyl groups on the hydroxylated α-quartz surfaces significantly increase surface hydrophilicity and reduce the resistance to water damage; (3) freshly-cleaved calcite surfaces contribute the most to moisture susceptibility, while un-hydroxylated α-quartz surfaces contribute the least among the mineral surfaces studied. This simulation work provides insights to better understand the moisture damage mechanisms of asphalt mixtures at a microscopic level.

Adhesion characteristics of graphene oxide modified asphalt unveiled by surface free energy and AFM-scanned micro-morphology

Graphene oxide (GO) is a promising nano-material to modify asphalt used in pavement. This work aimed to evaluate the feasibility of GO modified asphalt for the preparation of a high-viscosity asphalt used in open-graded friction course (OGFC). The adhesion characteristics and micro-morphology of the GO modified asphalt were evaluated using the sessile drop method and atomic force microscope (AFM). The addition of no more than 0.2 wt% GO notably increased the surface free energy of an asphalt and its dispersive and polar components and weakened the aging effects on the surface free energy of the asphalt. GO increased the adhesion work between asphalt and aggregate, with minimal influence on the spalling work. Thus, it remarkably enhances the asphalt-aggregate adhesion to improve moisture resistance of asphalt mixture. Limestone and granite aggregates exhibited the highest and lowest asphalt-aggregate adhesion, respectively, and basalt aggregate lied in between. The AFM observations revealed that GO can change the microstructure of asphalt and enhance the asphalt-aggregate adhesion. The adhesion and moisture resistance of styrene–butadienestyrene copolymer (SBS) + GO modified asphalt reached the requirements of high-viscosity asphalt and can be used in OGFC pavement, whereas the GO modified 70# asphalt requires further modification.

Moisture Susceptibility of Asphalt Concrete Pavement Modified by Nanoclay Additive

Durability of hot mix asphalt (HMA) against moisture damage is mostly related to asphalt-aggregate adhesion. The objective of this work is to find the effect of nanoclay with montmorillonite (MMT) on Marshall properties and moisture susceptibility of asphalt mixture. Two types of asphalt cement, AC(40-50) and AC(60-70) were modified with 2%, 4% and 6% of Iraqi nanoclay with montmorillonite. The Marshall properties, Tensile strength ratio(TSR) and Index of retained strength(ISR) were determined in this work. The total number of specimens was 216 and the optimum asphalt content was 4.91% and 5% for asphalt cement (40-50) and (60-70) respectively. The results showed that the modification of asphalt cement with MMT led to increase Marshall stability and the addition of 6% of MMT recorded the highest increase, where it increased by 26.35% and 22.26% foe asphalt cement(40-5) and(60-70) respectively. Also, the addition of MMT led to increase moisture resistance of asphalt mixture according to the increase in TSR and IRS. The addition of 4% and 6% of MMT recorded the highest increase in TSR and IRS for asphalt cement (40-50) and (60-70) respectively, where they increased by 11.8% and 17.5% respectively for asphalt cement (40-50) and by 10% and 18% respectively for asphalt cement (60-70).

Study on improvement of asphalt adhesion by hydrated lime based on surface free energy method

In order to study the improvement of hydrated lime (HL) on asphalt adhesion from mechanism, an asphalt-aggregate adhesion failure model was established based on surface free energy (SFE) method. In the model, the adhesion work Wa was chosen as the main index to evaluate the adhesion between asphalt and aggregate. Adhesion work was studied from two aspects: one was the polarity difference between asphalt and aggregate before and after HL modification, and the other was the variations of asphalt SFE before and after HL modification. The effect of HL on the polarity difference was studied by the changes of the SFE polarity component γap of solid asphalt and contact angle θ between solid asphalt and aggregate, based on SFE theory and sessile drop method respectively. And then, the SFE components between liquid asphalt and aggregate before and after HL modification were measured by improved Wilhelmy plate method. To exclude the effect of binder ageing occurred in the preparation of HL modified asphalt and verify the effectiveness of HL, rolling thin-film oven (RTFO) and pressure ageing vessel (PAV) tests were conducted on asphalt with and without HL modification. The results showed that HL could significantly reduce the polarity difference between asphalt and aggregate and raise the SFE of asphalt. The reduction of polarity difference and the increase of SFE both lead to the raise of adhesion work, resulting in the improvement of the adhesion between asphalt and aggregate. Moreover, the results of RTFO and PAV test illustrated that binder ageing occurred in the whole process of study would have negligible effect on asphalt adhesion. Therefore, it was concluded that SFE method would be a good choice to explain the improvement of asphalt adhesion by HL.

Improvement of Asphalt-Aggregate Adhesion Using Plant Ash Byproduct

The adhesion bonding between asphalt and aggregate significantly influences field performance and durability of asphalt pavement. Adhesion promoters are typically used to improve asphalt-aggregate bonding and minimize moisture-related pavement damage, such as cracking and raveling. This study evaluated the effectiveness of plant ash byproduct as adhesion promoter to improve asphalt-aggregate adhesion performance. Three commonly used aggregate types (granite, basic rock, and limestone) and two asphalt binder types were used in laboratory testing. A modified stripping test method was developed to evaluate test results with image analysis and measurement of asphalt film thickness. The contact angle test and scanning electron microscopy (SEM) with energy disperse spectroscopy (EDS) were conducted. Test results showed that plant ash lixivium significantly improved asphalt-aggregate adhesion. Among three aggregate types, granite yielded the worst asphalt-aggregate adhesion for both control and treated specimens. The effectiveness of adhesion promotion varied depending on the type of asphalt or aggregate and temperature. The SEM/EDS observations showed that the mesh-like crystalline was formed at the interface between asphalt binder and aggregate in the treated specimen, which was believed to enhance the interfacial bonding and prevent asphalt film peeling off from aggregate.

Synergistic Effect of 4A Zeolite from Rice Husk Ash without Aging Time and Silane on the Adhesion Properties of a Warm Mix Asphalt

4A Zeolite was synthesized using rice husk ash (RHA) as a raw material in a microwave-assisted hydrothermal synthesis. Two new procedures were proposed: procedure A, using RHA as the raw material, and procedure B, using the depolymerized RHA. Both procedures were performed using microwave-assisted hydrothermal synthesis, and neither synthesis required an aging time. Crystallinities of over 90 and 80% were reached at 100 oC after 30 min of microwave heating for procedures A and B, respectively. The obtained zeolites were used as warm mix asphalt additives, and the performance of the zeolite obtained from procedure A was better. Additionally, the zeolite obtained from procedure A and commercial silane were used separately as asphalt-aggregate adhesion promoter. An increase in the adhesion percentage from 30% of a blank sample to 94% was observed.

The Effect of Hydrated Lime on the Bond Between Asphalt and Recycled Concrete Aggregates

In this investigation, rolling bottle tests and boiling water tests were performed to evaluate the effect of hydrated lime on the adhesion between recycled concrete aggregates (RCA) and the asphalt binder. RCA from construction and demolition waste (C&DW) were used in this investigation. To generalize the findings, three asphalt penetration grades were analyzed: B40/50, B60/70, and B150/200. The results indicate that the use of hydrated lime does not improve the RCA-aggregate bond. Additionally, the results indicate that a higher asphalt-aggregate adhesion correlates to a lower asphalt penetration grade.

Evaluation of Asphalt-Aggregate Adhesion Using Surface Free Energy Theory

In order to take a precise and objective evaluation on asphalt-aggregate adhesion, this paper analyzed the function at asphalt-aggregate interface using surface free energy theory. Two asphalts and two aggregates were selected and their surface free energy parameters, , and , were measured by the Wilhelmy plate method and the column wicking technique, respectively. Then, the resistance to moisture damage of asphalt mixture was predicted using calculated asphalt-aggregate adhesive bond energy and asphalt cohesive bond energy. The results show that moisture damage is a thermodynamically favorable phenomenon. Asphalt with a great acid-base polar component and a low Lifshitz-van der Waals apolar component always exhibits perfect cohesion.

Modelling and laboratory studies on the adhesion fatigue performance for thin-film asphalt and aggregate system.

Adhesion between asphalt and aggregate plays an important role in the performance of asphalt mixtures. A low-frequency adhesion fatigue test was proposed in this paper to study the effect of environment on the asphalt-aggregate adhesion system. The stress-based fatigue model had been utilized to describe the fatigue behavior of thin-film asphalt and aggregate system. The factors influencing the adhesion fatigue performance were also investigated. Experiment results show that asphalt has more important effect on the adhesion performance comparing with aggregate. Basalt, which is regarded as hydrophobic aggregates with low silica content, has better adhesion performance to asphalt binder when compared with granite. The effects of aging on the adhesion fatigue performance are different for PG64-22 and rubber asphalt. Long-term aging is found to reduce the adhesion fatigue lives for rubber asphalt and aggregate system, while the effect of long-term aging for aggregate and PG64-22 binder system is positive. Generally the increased stress amplitude and test temperature could induce greater damage and lead to less fatigue lives for adhesion test system.

Factors of Adhesion between Asphalt and Mineral Aggregates

The factors of asphalt-aggregate adhesion were studied. Based on the expression of the adhesion work between the asphalt and mineral aggregates, several factors concerning the influence laws on asphalt-aggregate adhesion were analysed. The adhesion work of compatibility among the preparation temperature, aggregate types, and asphalt quality were calculated. The preparation temperature is found to be inversely related to the adhesion work. Among the four kinds of asphalts, the styrene-ethylene/butylene-styrene-modified one has the optimal adhesion with the mineral aggregates. Among the three kinds of aggregates, limestone has the best adhesion with the asphalts.

Study on SBS Modified Asphalt Emulsion and Aggregate Adhesion of CA Mortar

The influence of pH of emulsified asphalt, the kinds and content of emulsifiers and stabilizers on asphalt-aggregate adhesion have been investigated in this paper. Results show that the pH of the emulsified asphalt has great impact on asphalt-aggregate adhesion by way of the effect of pH on asphalt, asphalt-aggregate adhesion is worst when asphalt emulsion at pH≈4, which is close to the isoelectric point of asphalt, the bigger the zeta potential absolute value of emulsified asphalt, the better the asphalt-aggregate adhesion property. Effect of emulsifiers on asphalt-aggregate adhesion is complex, the best dosage is at 0.2%. The addition of organic stabilizers are superior to inorganic stabilizers to improve the asphalt-aggregate adhesion, the best dosage is at 0.4%. Effect of mixing emulsifier and stabilizer is better than single-doped emulsifier and stabilizer.

Triaxial Frequency Sweep Characterization of Asphalt-Aggregate Adhesion in Saskatchewan Asphaltic Mixes

Antistrip additives are commonly used to mitigate loss of asphalt-aggregate adhesion, particularly when siliceous aggregates are used in asphaltic concrete mix. Although both liquid antistrip and lime antistrip additives have shown improved visual based laboratory results, field performance in Saskatchewan has shown the addition of lime provides improved long term climatic durability and structural performance of asphaltic mixes relative to liquid antistrip additives. As a result, improved laboratory characterization is needed to properly quantify the performance-related properties of these antistrip additives. This laboratory study employed triaxial frequency sweep characterization to determine the effect of hydrated lime antistrip and amine liquid antistrip additives on a standard Saskatchewan Type 72 dense graded asphalt mix comprised of siliceous aggregates. This research found that the addition of hydrated lime antistrip to the Saskatchewan Type 72 asphalt mix showed a considerable improvement in the mechanical behavior of the mix, including increased dynamic modulus, decreased strain, and increased phase angle. Although increased phase angle is generally not considered an improved material property in asphalt cement, an increase in phase angle in asphalt mixes may be an indication of improved strain dissipation by the asphalt binder due to more effective stress transfer from the aggregate to the asphalt matrix through improved asphalt-aggregate bonding. This improvement in laboratory mechanical behavior concurs with improved rutting and fatigue performance observed within typical Saskatchewan dense graded asphalt mixes when treated with lime antistrip.

Temperature Sensitivity of Asphalt-Aggregate Adhesion via Dynamic Mechanical Analysis

It is known that the properties of asphalt-aggregate adhesion show great effect on the performance of asphalt pavement, while the temperature plays an important role in determining the fundamental properties of asphalt binder between single aggregate-aggregate contacts surfaces. The temperature sensitivity is considered to be very important on understanding the failures of asphalt pavement, especially on the asphalt-aggregate adhesion. Knowledge the temperature sensitivity of asphalt-aggregate adhesion is very important in asphalt mixture design. The purpose of this paper was to quantify the effect of temperature on the adhesion and cohesion of asphalt film between aggregate and asphalt. The adhesive/cohesive failure of asphalt film between single aggregate-aggregate contacts was investigated using dynamic mechanical analyzer under dynamic tension stress test with force-control mode, then fracture surface were analysis by a Polarizing Microscope. Contrastive experiments were conducted on SBS modified asphalt under different temperatures. Experimental results indicate that the area percentage of adhesive failure was decreased with the increase of test temperature. And the adhesive failure percentage is enhancing with the increase of loading max-stress level.

The Effect of Antistrip Treatments on Asphalt-Aggregate Systems: An Environmental Scanning Electron Microscope Study

The performance of three antistrip additives—a lime-treated aggregate, an amine-treated asphalt and a styrene-butadiene rubber-treated aggregate, was studied with an environmental scanning electron microscope (ESEM). Samples were prepared with the untreated asphalt and aggregate, the treated asphalt with untreated aggregate and untreated asphalt with each treated aggregate. The same asphalt and aggregate sources were used in each test and all samples were run in duplicate. All samples were examined along the asphalt-aggregate interface in the ESEM prior to and following each freeze-thaw cycle. The samples were subjected to a total of ten freeze-thaw cycles. All three additives reduced the potential for moisture damage by maintaining asphalt-aggregate adhesion better than the control samples. Based on ESEM observation of the asphalt-aggregate interface before and after freeze-thaw cycling, the styrene-butadiene rubber-coated aggregate samples performed better than the amine-treated asphalt samples which performed better than the lime-treated aggregate samples.