Anti-stripping Agent Research Articles

Multi-scale investigation on water stability and anti-aging performance of granite asphalt mixture modified with composite anti-stripping agents

This study aims to improve the water damage resistance of granite asphalt mixtures. Five types of composite modified asphalt were developed using organic anti-stripping agents AMRIII, LQ-2020, ultrafine hydrated lime (HL), and SBS modified asphalt, and the effects of aging on the mechanical properties of these modified asphalt mixtures were evaluated. Fourier Transform Infrared Spectroscopy (FTIR), pull-off tests, and indirect tensile strength tests were the primary analytical methods used. The results indicated that the anti-stripping agents physically mixed with the SBS modified asphalt without any chemical reaction. The SBS modified asphalt containing anti-stripping agents exhibited better mechanical strength compared to unmodified SBS asphalt, with the combined use of multiple anti-stripping agents proving more effective than individual applications. At five freeze-thaw conditions without aging, the enhancement ratios of indirect tensile strength test results of single addition of AMRIII, LQ-2020, HL and combined addition of AMRIII/HL and LQ-2020/HL were 27.27%, 36.36%, 14.29%, 50.91% and 46.41%, respectively. The addition of the anti-stripping agent enhanced the cohesive and adhesive energy. Aging reduced the water stability of the mixtures. Different modified asphalts have various sensitivity to aging, with the combination of AMRIII and HL showing the best aging resistance performance. Additionally, it was found that surface free energy had a strong correlation with water damage indicators, suggesting its potential for verifying the water stability of asphalt mixtures.

Pemanfaatan Limbah Serbuk Kayu dengan Zat Aditif Anti Stripping Agent Terhadap Uji Durabilitas AC-WC (Asphalt Concrete–Wearing Course)

The increasing number of vehicles each year in Indonesia causes excessive repetition of loads that occur on road pavements, as well as extreme weather changes resulting in damage to the pavement layer, especially at the level of durability, especially in the AC-WC layer. The use of sawdust waste in the AC-WC mixture has met the marshall test values/characteristics, but it is necessary to test its durability; a high durability value indicates that the road is more durable and resistant to weather and water. Therefore, it is necessary to improve the quality of road pavement by adding anti-stripping agent additives at levels of 0.3%, 0.4%, and 0.5% to the AC-WC mixture of 25% wood powder waste substitution in order to improve the properties of asphalt in increasing the coating of asphalt with aggregates in a wet state to produce stronger bonds to extend the life of the road. This study aims to determine the effect of adding anti-stripping agent additives in AC-WC mixtures with sawdust waste on durability tests. Experimental tests were conducted using the research method at the Civil Engineering Laboratory of Diponegoro University Vocational School Semarang. The study results obtained a durability value based on the calculation parameters of the Residual Strength Index (IKS) based on the General Specifications of Bina Marga 2018 (Rev 2), which shows the durability of AC-WC asphalt. The results of marshall testing obtained based on averages include VIM 4.11%, VMA 13.15%, VFA 77.33%, Stability 1893.73 Kg, Flow 2.17 mm and MQ 1070.03 kg/mm from 25% wood powder waste variation with anti-stripping agent additives 0.3%; 0.4%; 0.5% in AC-WC wear layer has met the General Specifications of Bina Marga 2018 (Rev 2). The average durability values of IKS with sequential soaking time are 24 hours 92.24%, 48 hours 88.87%, and 72 hours 80.08%.

Laboratory Study of Aging Characteristics of Binder Warm Mix Asphalt Chemical Additive: Rutting, Fatigue Resistance, and Chemical Composition

The research aims to comprehensively assess the impact of anti-stripping agents ZycoTherm (Zyc) and Evotherm M1 (EM1) on Warm Mix Asphalt (WMA). The study employs a range of laboratory tests to investigate the rheological and chemical properties of modified asphalt. Conventional tests such as penetration and softening points are employed alongside advanced techniques including Dynamic Shear Rheometer (DSR), and Linear Amplitude Sweep (LAS) analyses to delve into the rheological properties. Chemical properties (SARA) were analyzed using thin-layer chromatography. Both short-term aging (STA) using The Rolling Thin-Film Oven (RTFO) and long-term aging (LTA) based on the Universal Simple Aging Test are simulated under controlled laboratory conditions. It was found in conventional tests that the value changed, but not significantly. In terms of rutting and fatigue performance, Zyc 0.05% showed positive results. Fatigue behavior shows Zyc has better resistance. The asphalt fractional composition test showed changes in each age condition.

Effects of Resting Conditions on Tensile Properties of Acid Aggregate Hydraulic Asphalt Concrete.

This study addresses the issue of construction stagnation affecting the adhesion and tensile properties of hydraulic asphalt concrete with acid aggregate. It investigates the impact of rest periods on the tensile characteristics of such materials under standard construction conditions. The influence of varying rest durations and asphalt temperatures on the tensile behavior of the concrete is assessed through indoor experiments. The bonding between asphalt and aggregate is examined, along with the tensile property variations of the concrete. The study found that the standstill time significantly affects the adhesion of asphalt, with the adhesion decreasing progressively with increased temperature and rest time, irrespective of the addition of anti-stripping agents. However, the inclusion of these agents can mitigate the reduction in adhesion. Furthermore, the study identified that rest duration has a more substantial impact on adhesion than temperature. The splitting tests demonstrate that the tensile properties of asphalt concrete are considerably affected by the resting time. Over a period of 0, 10, 20, and 30 days of rest, an increase in splitting strength and a decrease in splitting displacement were observed. The findings offer valuable insights for predicting the tensile performance of asphalt concrete in practical engineering applications after a period of rest.

Effects of warm-mix additives, anti stripping agent, and graphene nanoplatelet on the cracking resistance, moisture susceptibility, and cost effectiveness of stone mastic asphalt

Moisture and cracking damages are two of the most common asphalt pavement distresses in the United States. The use of stone matrix asphalt mixture has gained popularity due to its high durability, resistance to permanent deformation and cracking, and reduced noise pollution. Warm-mix additives and nanomaterials have also gained significant interest as promising asphalt binder additives. In order to achieve enhanced resistance to moisture and cracking in extremely wet regions, this study investigated the effects of three warm-mix additives, an anti-stripping agent, and one nanomaterial (graphene nanoplatelet) on the cracking and moisture resistance performance of stone matrix asphalt. Fourier transform infrared spectroscopy and sessile drop tests were used to evaluate the functional groups and moisture susceptibility of the modified asphalt binder blends, respectively. The indirect tensile asphalt cracking test and the modified Lottman tests were used to evaluate the mixtures' resistance to cracking and stripping damage. A cost-effectiveness analysis as well as a two-dimensional performance interaction diagram were employed based on the laboratory performance of the mixtures. Results indicated that the graphene nanoplatelet modification of the asphalt binder had the highest wettability potential, adhesion, and debonding properties, as well as moisture resistance potential compared to other additives. In terms of mixture cracking performance, both the graphene nanoplatelet and a chemical warm-mix asphalt significantly improved the mix cracking performance by 34.1 and 30.0 %, respectively, compared to the control mix. However, the graphene nanoplatelet modification had a tensile strength ratio of 0.76, which is below the acceptance threshold of 0.80 set by AASHTO T 283 for moisture damage resistance of asphalt mixture. Overall, all mixtures with warm-mix additives showed adequate cracking and stripping damage resistance performance and are expected to be cost-effective.

Moisture Sensitivity of Hot Mix Asphalt Modified with Micronized Calcium Carbonate

Moisture sensitivity in an HMA refers to the loss of mastic cohesion and durability between the bitumen and aggregates due to water presence. Various methods exist to mitigate this type of sensitivity, with one of the most important approaches being the incorporation of anti-stripping agents into either the bitumen or aggregate materials. Based on this premise, the current study investigates the impact of using micronized calcium carbonate powder (MCCP or CaCo3) as a modifier for bitumen on moisture sensitivity in HMA. Three types of aggregates with different mineralogical properties (limestone, granite, and quartzite), and PG 64–16 bitumen (along with 2% and 4% MCCP based on the mass of the bitumen) were utilized. The modified Lottman test was performed under 1 to 5 freeze-thaw cycles while measuring surface free energy (SFE) elements for both bitumens and aggregates with Wilhelmy Plate (WP) and Universal Sorption Device (USD), respectively. The results of the moisture sensitivity test on the asphalt mixtures used in this study demonstrate that the addition of MCCP in the modified samples has led to a reduction in the sensitivity of the asphalt mixtures, particularly in multiple freeze-thaw cycles, compared to the control samples. Furthermore, findings from SFE analysis demonstrated that MCCP enhanced cohesion free energy (CFE) which subsequently reduced rupture probability within the bitumen membrane. Additionally, it improved adhesion between acidic aggregates susceptible to moisture-induced sensitivity and bitumens.

Study on the Effect of Asphalt Static Conditions on the Tensile Properties of Acidic Aggregate Hydraulic Asphalt Concrete.

Hydraulic asphalt concrete is known for its excellent seepage control performance and strong deformation resistance. This engineering material has widespread applications in the seepage control structures of hydraulic buildings. Recent projects have investigated the use of acidic aggregates to improve economic efficiency. However, they have also highlighted the weaker adhesion between acidic aggregates and asphalt, which necessitates stringent construction process control. This study investigates the impact of resting conditions on the tensile properties of acidic aggregate hydraulic asphalt concrete. The results of the tensile testing indicate that the storage time significantly affects the performance of asphalt concrete. The tensile strength of the specimens without anti-stripping agents decreased from 1.711 MPa to 0.914 MPa after resting periods of 0, 10, 20, and 30 days. The specimens treated with anti-stripping agents also showed a decrease in tensile strength over time, similar to the trend observed in the previous specimens. Digital specimen simulations indicated a decrease in cohesion between the asphalt and the aggregate from 5.375 MPa to 2.664 MPa after 30 days, representing a reduction of 50.44%. To counteract the effect of the storage time on the bonding between acidic aggregates and asphalt, this study recommends reducing the grading index and maximum size of aggregates, decreasing the coarse aggregate content, and selecting smooth aggregate shapes.

Establishing Strategies to Improve Cracking Resistance of High Recycled Binder Ratio Asphalt Mixtures

This study aims to investigate promising mitigation strategies for improving the cracking performance of high recycled binder ratio (RBR) asphalt mixtures. Moisture-resistant aggregates that do not require anti-stripping agents, reclaimed asphalt pavement (RAP), and recycled asphalt shingles (RAS) were sampled for this study from sources in two climatic zones, south and north. The south-moisture-resistant (SR) mixtures were designed with 0.16 and 0.29 RBRs with RAP, while the north-moisture-resistant (NR) mixtures included 0.21 and 0.37 RBRs with RAP and 0.44 RBR with RAP/RAS. The mitigation strategies evaluated included a softer binder, a different binder source with higher ΔTc, a recycling agent (RA), reduced recycled binder availability (RBA), polymer-modified asphalt (PMA), and hybrid approaches including softer binder + RBA and PMA+RBA. The Indirect Tensile Asphalt Cracking Test (IDEAL-CT) and Disc-Shaped Compact Tension (DCT) test were conducted to capture intermediate-temperature and low-temperature cracking performance, respectively. In addition to the cracking tolerance index (CTindex), an IDEAL-CT interaction diagram analysis was added to further understanding the effect of mixture variables on cracking performance. The findings suggest that while no single strategy works for all RBR mixtures tested, RA, RBA, softer binder, or their combinations yield adequate cracking performance depending on factors including RAP binder stiffness and quantity, RA dose, climatic zone, and RBA.

Feasibility of Using Combustion-Based Methods to Quantify Saline-Based Anti-Stripping Agent in Modified Asphalt Binders

“Anti-stripping Agents” or “adhesion promoters” can enhance the chemical affinity between asphalt and aggregate by increasing their mutual attraction. Various forms of anti-stripping agents have been proposed to mitigate pavement stripping, and siloxane-based Zychotherm is one of them. Choosing the appropriate type and dose of anti-stripping additives is no doubt vital to the intended performance. Therefore, it is critically important to determine the dose of the additives used in the modification of asphalt binders. This research developed a feasible detection method that can closely measure the dose (0.05% and 0.1%) of siloxane-based anti-stripping liquid agents. Related test methods, including heat combustion test, residue visualization, burning, and ignition, were implemented. The heat combustion results showed that with the addition of the Zychotherm anti-stripping additive, the average heat combustion value decreased by 1.34% and 1.72% for 0.05% and 0.1% Zychotherm-modified binder, respectively. In the burning and ignition process, the modified binder left yellowish substances in the residue, which is an indication of the presence of Zychotherm. The weight of the yellowish residue related more to the quantity of Zychotherm in the asphalt binder.

Exploring the Efficacy of Amine-Free Anti-Stripping Agent in Improving Asphalt Characteristics

This research addresses the significant challenge posed by early water damage in highway asphalt pavement, a critical concern affecting pavement service performance. To counteract this issue, the utilization of anti-stripping agents in asphalt is explored as a highly effective technical intervention. In this investigation, a carefully selected amine-free additive was employed to modify the asphalt binder. A comprehensive array of physical and rheological tests, covering aspects such as storage stability, penetration, softening point, ductility, elastic recovery, rolling thin-film oven, retained penetration, the ductility of residue, and rotational viscometer assessments, were conducted to examine the multifaceted impact of the anti-stripping agent on the asphalt binder. Additionally, we assessed the asphalt mixture’s sensitivity to moisture through Marshall stability tests after conditioning for 40 min and 24 h, followed by an enhanced immersion test and moisture susceptibility measurement. The results reveal a nuanced interplay of chemical and physical mechanisms influencing the behavior of the asphalt binder. Notably, the incorporation of an anti-stripping agent at a concentration of 0.25–0.5% (by weight of asphalt binder) led to a substantial improvement in the tensile strength ratio (TSR) to 94.9%, a noteworthy enhancement compared to the 80.6% observed with virgin asphalt mixture. Furthermore, the retained stability index (RSI) exhibited a remarkable increase to 98.1%, surpassing the 87.6% recorded for virgin asphalt. This study not only provides crucial insights into the intricate dynamics of asphalt binder performance but also emphasizes the pivotal role of anti-stripping agents in augmenting the structural integrity and resilience of asphalt pavement.

Laboratory test of physical, rheological, and chemical characteristics of aging binder modified with ZycoTherm and Evotherm

The research aims to comprehensively assess the impact of anti-stripping agents ZycoTherm and Evotherm M1 on Warm Mix Asphalt (WMA). The study employs a range of laboratory tests to investigate the rheological and chemical properties of modified asphalt. Conventional tests such as penetration and ring & ball softening points are employed alongside advanced techniques including Dynamic Shear Rheometer (DSR), and Linear Amplitude Sweep (LAS) analyses to delve into the rheological properties. Chemical properties (SARA) were analyzed using thin-layer chromatography. Both short-term aging (STA) using The Rolling Thin-Film Oven (RTFO) and long-term aging (LTA) based on the Universal Simple Aging Test are simulated under controlled laboratory conditions. It was found in conventional tests that the value changed, but not significantly. In terms of rutting and fatigue performance, Zyc 0.05% showed positive results. Fatigue behavior shows Zyc has better resistance. The asphalt fractional composition test showed changes in each age condition.

Evaluation of Properties of Asphalt Concrete Mixture Using Basalt Aggregate from Jeju Island

In this study, the engineering properties of basalt aggregate used for asphalt road pavement on Jeju Island were evaluated, and the characteristics of the asphalt mixtures used were evaluated to assess the suitability of Jeju Island basalt as road construction material. Chemical composition and surface morphology analysis of the basalt and granite aggregate, engineering characteristics analysis, and filler property evaluation were performed. Mix design was performed, and the basic properties of three asphalt mixtures for the surface, intermediate, and base layers were evaluated. Permanent deformation resistance was evaluated through a wheel tracking test, and moisture resistance was evaluated through a dynamic immersion test and a tensile strength ratio test. The optimum asphalt contents of the asphalt mixture using low-porosity basalt aggregate and high-porosity basalt aggregate were determined to be 5.7% and 5.9% in the surface layer, 5.3% and 5.4% in the intermediate layer, and 4.7% and 5.1% in the base layer, respectively. It was found that the basic properties of the asphalt mixtures satisfied Korean quality standards. The dynamic immersion test results of low-porosity basalt aggregate and high-porosity basalt aggregate were 20% and 10%, respectively, which fall far below the quality standard of 50%. The tensile strength ratios of the basalt asphalt mixtures for the intermediate layer were 0.69 and 0.40, and they were found to increase significantly to 0.87 and 0.80 after the application of a suitable anti-stripping agent. Therefore, it was concluded that in order to apply Jeju Island basalt to asphalt pavement, an appropriate anti-stripping material must be applied.

Water Damage Resistance of Tuff Asphalt Mixtures with Admixtures Based on Surface Energy Theory

At present, tuff aggregates as asphalt pavement mixtures have insufficient water damage resistance; hence, modifying and evaluating the related properties of tuff asphalt mixtures are necessary. In this study, cement and a liquid antistripping agent were selected as admixtures, and tuff and limestone mixtures without admixtures were selected as control. The surface energy for the SBS-modified asphalt polymers and aggregates in the mixtures was evaluated by using surface energy theory. The adhesion work and the spalling work of the polymer–aggregate interface was calculated, and a factor k was proposed to predict the water damage resistance of the tuff mixture with admixtures. The prediction values were compared with those of the macroscopic water stability test for the mixture. The results of this research showed that the factor k after adding admixtures was improved, and the increase range was from 7.14% to 47.62%. The admixture scheme with the best improvement was that with 2% cement content, in which the k value increased by 21.57% and 47.62% compared with that of the limestone and tuff mixtures without admixtures, respectively. The tested water stability indexes and the predicted factor k under different admixture schemes exhibited a good positive correlation, and the correlation equations were obtained by linear fitting. Thus, it was feasible to use the factor k characterizing the water damage resistance of tuff mixtures using surface energy theory.

Evaluation of Bituminous Moisture Damage of High Silica Aggregate

Abstract Moisture damage (Stripping) in Hot Mix Asphalt (HMA) is the loss of adhesive bond between aggregate particles and bitumen due to water action. Most urban roads in Iraq have been exposed to moisture damage failure because of the high silica content in aggregate, this phenomenon led to a decrease in the service life of roads and an increase in maintenance cost. This study used two anti-stripping agents: hydrated lime and Wetfix-BE. Lime was added as a powder to the aggregate in a dosage of 2.0 % of the aggregate weight and Wetfix-BE, a liquid chemical adhesion promoter for hot and warm mix asphalt, was added to asphalt at in dosage of 0.5 % from the total weight of asphalt. The retained Marshall stability, tensile strength ratio, Texas boiling test, and static immersion test are calculated to determine the resistance to moisture damage. The results indicated that both Wetfix-BE and lime could increase Marshall retained stability, tensile strength, and resistance to moisture damage of mixtures, especially at higher condition temperatures. The bitumen modified with Wetfix-BE had better results than bitumen modified with lime for all tests at different temperatures.

Research on the Moisture Stability of Asphalt Mixtures with Three Solid Waste Fillers

Widespread interest has been drawn to the use of solid waste fillers as a partial replacement for natural fillers in high-performance asphalt mixtures in recent years. However, variations in the material properties of solid waste fillers remain a problem for the recycling method. To address this issue, the limestone powder in asphalt mixtures was replaced with three solid waste fillers, including steel slag powder, tailings powder and calcium carbide slag powder in this study. The chemical composition of the fillers was first characterized to assess the homogeneity of the material. Then, a dense-graded asphalt mixture (AC) and a stone matrix asphalt (SMA) mixture were designed, produced and characterized for wet stability. The results show that the asphalt mixtures with solid waste fillers were superior to limestone powder (LP) asphalt mixtures in terms of resistance to water damage, and the steel slag powder showed the best improvement in moisture stability of the asphalt mixtures. The optimum substitution of solid waste filler for limestone filler was 25%. With the addition of anti-stripping agents, the moisture stability of the asphalt mixture with limestone filler was also greatly enhanced. On the contrary, a marginal enhancement was observed in the moisture stability of asphalt mixtures using solid waste fillers. Solid waste fillers can be used in asphalt mixtures and have a similar function as that of anti-stripping agents. In summary, the use of solid waste fillers to replace mineral fillers in asphalt mixtures is a reliable, value-added recycling option.

Performance evaluation of WMA mixtures with RAP

Nowadays, asphalt industries are seeking for new methodologies in order to minimize global warming and emission of greenhouse gases. One of the solutions found out was the use of warm mix asphalt (WMA) technology which allows reduction in asphalt mixing, working and compaction temperature. WMA reduces the desired temperature in comparison with hot mix asphalt by 20–40°C. In addition to this issue, the lack of superior quality natural aggregate resources everywhere around the world, it is essential to use the available natural resources efficiently along with the available construction and demolition waste such as recycled asphalt pavement (RAP) if possible, without compromising in the performance of the mixtures. In this study, reclaimed asphalt pavement was used as partial replacement for conventional aggregates and binder. The RAP contents of 0%, 25% and 50% were considered. Zycotherm was used as warm mix additive which improves the pavement moisture resistance by serving as an anti-stripping agent. The mixtures were prepared with HMA @ 130°C, HMA @ 160°C, WMA @ 130°C and all these three mixtures with partial replacement with RAP. The RAP material with 0, 25 and 50% replacement was adopted for both HMA and WMA for DBM grade 2 course. Zycotherm was added by 0.1% by weight of binder in both HMA and WMA mixes. The prepared test specimens were tested for Marshall and indirect tensile strength (ITS) test. The test results indicated that the WMA blend prepared using 0.1% by the weight of binder content showed good results compared to the hot mix asphalt @ 130°C. The indirect tensile strength ratio (TSR) of mixes containing RAP is found to be higher when compared to the mixes without RAP indicating lower moisture susceptibility of the mixtures. This study demonstrated the possible use of RAP in WMA mixes with better performance than HMA.

Comparative Assessment of Liquid Antistripping Agents and Mineral Admixtures in Asphalt Mix Resistance to Moisture Damage

The main aim of this research was to investigate the effectiveness of liquid antistrips (LASs) as compared with mineral admixtures such as lime and cement in treating moisture sensitivity of asphalt concrete (AC) mixtures produced with aggregates that are severely susceptible to moisture damage. The study involved evaluating the moisture susceptibility of four mix designs that featured two aggregate sources, two asphalt binder types, and both cement and lime as mineral admixtures. Five different liquid antistripping additives were evaluated. Liquid antistrips were directly added to the binder, and the mineral admixtures in the mix were replaced with mineral filler. The experimental plan involved a volumetric assessment of the mixtures after the filler adjustment and baseline characterization of aggregates and mixtures used in the study. A multipoint moisture sensitivity assessment protocol with a moisture conditioning procedure that includes multiple freeze-thaw cycles was used. Moisture susceptibility was evaluated using a fracture experiment and its parameters in addition to the standard indirect tensile strength. The replacement of both mineral admixtures led to a considerable increase in the air voids and the voids in mineral aggregates for all four mixes. Cement and lime were shown to be effective in retaining strength and fracture energy after several conditioning cycles. The performance of the mixtures containing liquid antistrips showed sensitivity to the additive used. While one of the additives showed overall significant deterioration in strength and fracture energy after the first freeze-thaw cycle, a different additive retained 70% of its initial properties after up to three freeze-thaw cycles. Overall, it was shown that a compatible LAS can aid asphalt mixtures’ moisture resistance but not to the same efficiency of lime or cement for the mixtures included in the study.

Waste Plastic Powder Coating on Acidic Aggregates: A New Hydrophobic Coating Technology to Build Moisture-Resistant Asphalt Mixtures

The surface energy of aggregate in asphalt pavements has a huge impact on its moisture susceptibility. The commercial antistripping agents widely used in asphalt may not be effective enough to enhance the moisture resistance if large quantities of acidic aggregates exist in pavements. This is also the reason why moisture damage is still an issue in many U.S. regions primarily supplied with “problematic” aggregates. In this regard, a promising solution is to use waste-plastic-coated aggregate, the surface of which is fundamentally modified and has a high affinity with asphalt because of the hydrophobic nature of plastic. However, it has not been widely promoted in the industry since there needs to be a practical and reliable method for uniform coating and avoiding the agglomeration of fine aggregate. To this end, an entirely new coating technology (thermoplastic polyethylene powder coating [TPPC]) was developed to coat aggregate using polyethylene (PE) powder. This technology utilizes a cheap but highly wettable fluidized bed to stably disperse the hydrophobic PE powder. Then, the dispersion liquid is sprayed onto the hot aggregate where the fluidized bed will evaporate fast while the PE particles stay, melt, and coat the aggregate surface. The microstructures of the coated aggregate were directly observed by scanning electron microscopy. Surface energy-based thermodynamic parameters were used to demonstrate the effect of TPPC on the moisture resistance of asphalt mixtures. This technology can be extended to other types of waste plastic if suitable fluidized beds are developed.

Experimental Study on the Physicochemical Properties of Asphalt Modified by Different Anti-Stripping Agents and Their Moisture Susceptibility with Aggregates.

Erosion and the stripping effect of moisture on asphalt mixtures is one of the main reasons for the shortened service life of asphalt pavements. The common mean of preventing asphalt pavements from being damaged by moisture is adding anti-stripping agents (ASAs) to asphalt mixtures. However, the effect regularity and mechanism of anti-stripping agents on the physicochemical properties of asphalt is not exactly defined. This study compared the physical properties of ASA-modified asphalt (AMAs) to determine the optimal dosage and investigated the rheological and adhesion properties. Based on the roller bottle method and water immersion method, the moisture susceptibility of AMAs with three particle sizes was investigated. The results showed that the modification of asphalt using anti-stripping agents was a physical modification. At the optimum dosage of anti-stripping agents (0.3%), the basic physical properties of AMA1 were the most desirable. ASA2 increased the resistance of asphalt for deformation at high temperature by 46%, and AMA3 had the best low-temperature performance. ASAs enhanced the dispersed and polar components in the asphalt binder, improving the adhesion energy of asphalt. AMA3 had the strongest adhesion to the aggregate, with an increase in adhesion work by 2.8 times and a 45% of increase in ER value. This was attributed to ASA3 containing with a large number of metal cations and polar functional groups. It was shown that ASAs provided the most improvement in the anti-stripping performance of asphalt mixtures with 9.5-13.2 mm particles. The amide ASA, phosphate ASA and aliphatic amine ASA improved the water damage resistance of asphalt by 65%, 45% and 78%, respectively. This study can help engineers realize the effects of different types of ASAs on the physicochemical properties of asphalt and select the most suitable type of ASAs according to the service requirements.

Bio-Modifier: A Sustainable Suturing Technology at the Bitumen–Aggregate Interface

Premature failure at the bitumen–aggregate interface is attributed to the surface chemistry of stone aggregates. Bitumen modifiers with high affinity toward aggregates are often used to change the surface chemistry of aggregates, which in turn changes the type and strength of stones’ interactions with bitumen. Here, the mechanisms of action and the effects of an organosilane and bio-oil separately on the bitumen–aggregate interface, including their binding to aggregates from one side and to bitumen from the other side, were studied and compared. The binding of bio-oils and organosilanes to aggregates is well documented, as well as their efficacy as anti-stripping agents, but their binding to bitumen is not well understood. Using glass beads as a surrogate for siliceous stones, we obtained laboratory measurements of interfacial strength as measured by resistance to shear forces at the interface of bitumen and silica. Our laboratory measurements showed the highest value for the bitumen modified with bio-oil, followed by the control bitumen with no modification, and the lowest value for the bitumen modified with organosilane. Our molecular modeling calculations showed that the adhesion of bitumen molecules to silica coated with bio-oil was notably stronger (up to 72%) than the adhesion of bitumen molecules to silica coated with organosilane. The higher interfacial strength observed for bitumen with bio-oil is attributed to bio-oil having various functional groups with the ability to form hydrogen bonds and π–π interactions with the aromatic and polar components of bitumen. The study outcomes highlight the importance of modifiers’ ability to strongly interact with both aggregates and bitumen. The bio-oil modifier introduced in this work can form a robust bridge between bitumen and siliceous aggregates to improve the adhesive properties, enhancing the sustainability and durability of bituminous composites.