Moisture Resistance Of Asphalt Mixture Research Articles

Research on Improving Moisture Resistance of Asphalt Mixture with Compounded Recycled Metallurgical Slag Powders.

The utilization of steel slag as an alternative material in asphalt mixtures is considered the solution to the problem of the shortage of natural aggregates. However, asphalt mixtures with steel slag show susceptibility to damage caused by moisture, especially in powder form. Therefore, blast furnace slag powders were used to compound with steel slag powders as fillers to improve the moisture resistance of asphalt mixtures. The characteristics of the steel slag powders and blast furnace slag powders were investigated initially. Subsequently, the adhesion properties of the asphalt mastics with the powders to the aggregates were evaluated. Finally, the moisture resistances of the asphalt mixtures were identified. The results indicate that the steel slag powder exhibited a notable prevalence of surface pores, which had a more uniform size distribution. In contrast, the blast furnace slag powder exhibited a greater average pore size. The larger specific surface area of the steel slag powder was over 30% larger than that of the blast furnace slag powder, and the superior gelling activity of the blast furnace powder enhanced the adhesion property. Both the steel slag powder and blast furnace slag powder were found to enhance the adhesion properties of the asphalt mastics, while the effect of the steel slag powder was more pronounced, the maximum force difference of which exceeded 200 N. The antagonistic effect of the steel slag powder and blast furnace slag powder on the resistance of the adhesive interface to moisture damage was confirmed by the contact angle test. The incorporation of the blast furnace slag powder markedly enhanced the moisture resistances of the asphalt mixtures. The phenomenon of dynamic moisture damage to the asphalt mixtures was more pronounced under the multicycle times, obviously severer than that in a stable water environment. As the dynamic moisture cycles increased, the degree of destruction gradually approached a steady state.

Investigating the Influence of Mineral Fillers at Australian Asphalt Mixtures

Abstract It is commonly known that mineral fillers significantly affect the asphalt mixture's performance. Superior flexible pavement performance can be ensured by gaining a deeper understanding of the function of filler. This research investigates the influence of three different fillers: granite dust, cement, and hydrated lime, at Australian asphalt mixtures. The testing program includes Marshall testing, moisture damage resistance, indirect tensile strength (ITS), and indirect tensile stiffness modulus (ITSM) tests of asphalt mixtures. Analysis of variance (ANOVA) was used to statistically assess the results obtained, besides damage analysis. The results indicate that using natural granite dust yields the highest resistance to moisture, while cement produces the highest stability, ITS, and ITSM. Unexpectedly, using hydrated lime filler decreases the stability/stiffness and moisture resistance of asphalt mixtures. ANOVA tests indicate that the type of filler affects ITS, TSR, and ITSM results (i.e., the p-value <0.05). The damage analysis shows that the design life of the asphalt mixture made with cement filler is higher than that of mixtures made with natural granite dust and hydrated lime fillers respectively. The findings indicate the important role of nontraditional fillers at the performance of Australian asphalt mixtures.

Organic expanded vermiculite as an alternative to filler for improving aging resistance of asphalt mixture

The organic expanded vermiculite (OEVMT) is a good anti-aging agent for asphalt binder due to its excellent heat and oxygen barrier properties. However, the application form of OEVMT is usually limited to being as a modifier for asphalt binder while seldom research takes it as an alternative to filler in asphalt mixture. Using the OEVMT as an alternative to filler has the potential to further improve the aging resistance of asphalt mixture in comparison with using the OEVMT as an asphalt binder modifier, because the amount of OEVMT in asphalt mixture can be largely increased in this case. In present study, different proportions of fillers in asphalt mixture were replaced by OEVMT to produce asphalt mixtures with better aging resistance. The effects of using OEVMT as an alternative to fillers on road performance and aging resistance of asphalt mixture were investigated. The results indicate that replacing a large proportion of fillers in asphalt mixture can lead to a poor moisture resistance of asphalt mixture. In comprehensive consideration of moisture, cracking and rutting resistances, the optimal proportion of filler that should be replaced by OEVMT is 12.5 %. In comparison with the form of using OEVMT as a modifier for asphalt binder, using an appropriate amount of OEVMT to replace limestone fillers in asphalt mixture can further enhance the aging resistance of asphalt mixture by increasing the amount of OEVMT in asphalt mixture.

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.

Mitigating Stripping in Asphalt Mixtures: Pretreatment of Aggregate by Thermoplastic Polyethylene Powder Coating

Thermoplastic polyethylene (PE) powder coating is proposed as a new technique to pretreat the aggregate of asphalt mixtures and improve the corresponding moisture resistance. In this paper, ethanol solution is investigated as a fluidized bed to disperse the PE powder. The surface tension of the solution, indicating the wettability of the liquid phase, decreases with increasing ethanol concentration and temperature. The PE powder could be stably dispersed into the solution when 15% ethanol solution heated to 40 to 50°C is used to reduce the surface tension of liquid to less than 40 mN/m. The suspension carrying the PE particles could be uniformly sprayed onto a hot aggregate surface (180–190°C) where the liquid phase evaporates fast while the PE powder melts and stays. The powder coating technique could prevent the aggregate from lumping and achieve a high-quality and efficient coating for aggregate. The PE monolayer model considering a hexagonal close packing of PE on aggregate surface is tentatively proposed to determine the theoretical amount of PE required to perfectly coat the aggregate. The predicted PE content was reasonably lower than that determined by the experimental results considering the ideal monolayer coating was hard to achieve. However, the modeling results could be used to determine the lower bound of the required PE content. The optimum PE content significantly increased with increasing particle size of PE and specific surface area of aggregate. The use of high-density polyethylene (HDPE) powder with a smaller particle size was more effective in the coating process. In addition, excessive PE could not further enhance the moisture resistance of asphalt mixtures efficiently. This study can contribute to both the recycling of waste plastic and the construction of durable asphalt pavements.

Experimental Analysis to Evaluate the Impact of Styrene-Butadiene-Styrene and Crumb Rubber on the Rutting and Moisture Resistance of Asphalt Mixtures

The most severe distresses in asphalt pavement are rutting, fatigue, and low-temperature cracking; therefore, to solve these problems, it is essential to modify asphalt binders in asphalt concrete mixtures. In this study, a comparison between using styrene-butadiene-styrene (SBS) and crumb rubber (CR) as modifiers for asphalt binders to overcome distress issues was conducted. Base and SBS or CR-modified binders were subjected to all conventional and Superpave binder tests. Engineering tests such as the Hamburg wheel tracker and indirect tensile strength ratio were also run to evaluate the engineering properties. The used SBS percentages were 1, 2, 3, 4, and 5%, while CR percentages were 3, 6, 9, 12, and 15% by total weight. The results showed lower penetration, higher softening point, viscosity, and elastic recovery for both additives. In addition, dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests showed increasing values of both high and low temperatures of modified asphalt performance grade (PG) with increasing SBS or CR percent. The tensile strength ratio and Hamburg wheel tracker results showed the best engineering properties at 3% SBS or 9% CR, the optimum percent. A triple percentage of CR is needed to get the same effect of SBS for the asphalt mixture.

Biomass valorization toward sustainable asphalt pavements: Progress and prospects

To cope with the global climate crisis and assist in achieving the carbon neutrality, the use of biomass materials to fully or partially replace petroleum-based products and unrenewable resources is expected to become a widespread solution. Based on the analysis of the existing literature, this paper firstly classified biomass materials with potential application prospects in pavement engineering according to their application and summarized their respective preparation methods and characteristics. The pavement performance of asphalt mixtures with biomass materials was analyzed and summarized, and the economic and environmental benefits of bio-asphalt binder were evaluated. The analysis shows that pavement biomass materials with potential for practical application can be divided into three categories: bio-oil, bio-fiber, and bio-filler. Adding bio-oil to modify or extend the virgin asphalt binder can mostly improve the low temperature performance of asphalt binder. Adding styrene-butadienestyrene (SBS) or other preferable bio-components for composite modification will have a further improved effect. Most of the asphalt mixtures prepared by using bio-oil modified asphalt binders have improved the low temperature crack resistance and fatigue resistance of asphalt mixtures, but the high temperature stability and moisture resistance may decrease. As a rejuvenator, most bio-oils can restore the high and low temperature performance of aged asphalt and recycled asphalt mixture, and improve fatigue resistance. Adding bio-fiber could significantly improve the high temperature stability, low temperature crack resistance and moisture resistance of asphalt mixtures. Biochar as a bio-filler can slow down the asphalt aging process and some other bio-fillers can improve the high temperature stability and fatigue resistance of asphalt binders. Through calculation, it is found that the cost performance of bio-asphalt has the ability to surpass conventional asphalt and has economic benefits. The use of biomass materials for pavements not only reduces pollutants, but also reduces the dependence on petroleum-based products. It has significant environmental benefits and development potential.

Effect of warm mix asphalt (WMA) technologies on the moisture resistance of asphalt mixtures

Moisture damage has been identified as a major concern for asphalt pavements. This concern becomes more critical when the asphalt mixtures are prepared at lower mixing and compaction temperatures using technologies such as warm mix asphalt (WMA). In this study, the effect of different WMA technologies on the moisture resistance of asphalt mixtures was studied using a variety of experimental investigations including bond strength ratio (BSR), percentage coating, retained Marshall stability (RMS), and tensile strength ratio (TSR). Two aggregate sources (granite and dolomite), two base asphalt binders (VG30 and PMB40), and five WMA additives categorized under organic, chemical, and foaming technologies were used. Moisture damage in WMA mixtures was found to be a function of aggregate type and base asphalt binder. Rediset, a chemical WMA additive, showed higher moisture resistance in comparison to other technologies. Appreciable correlations were found between BSR and TSR (R2 ranged from 0.61 to 0.72). This study suggests a minimum BSR of 0.7 for satisfactory performance against moisture damage.

Effects of recycling agents and methods on the fracture and moisture resistance of asphalt mixtures with high RAP contents

The design guidelines for recycled asphalt mixtures recommend rejuvenating the oxidized binder by adding recycling agents, which are viscosity and, consequently, temperature-reducing additives. As it is a component of recent use in pavement and its variety, there has yet to be a consensus on the determination of the recycling agent content or the ideal moment of its addition in the recycled asphalt mixture production process. This study aimed to analyze the fracture and moisture performance of asphalt mixtures with the addition of high contents of RAP (25%, 50%, 75%, and 100%) and two recycling agents (ADCAP WM and residual engine oil) in stages distinct from the production of recycled asphalt mixture (directly to the RAP and directly to the virgin asphalt binder). The recycling agents were added at 12%, 15%, and 18% residual engine oil by mass of RAP and 2%, 2.5%, and 3% of ADCAP WM by the total mass of asphalt binder. The asphalt mixtures were submitted to mechanical tests of tensile strength, resilient modulus, ice and thaw cycles, bending fracture, and fatigue life. The results showed that adding residual engine oil in the asphalt binder enables using up to 75% of RAP. In the case of ADCAP WM additions, identical additions of RAP can be performed. Mixtures with ADCAP WM showed higher consumption of fracture energy, while blends with residual engine oil showed a lower slope of the post-peak curve. Conditioning by the freeze–thaw (F-T) cycle method increased the susceptibility of mixtures to the deleterious effect of water. Statistical analyzes showed that the parameters RAP content, recycling agent, and time of addition of the recycling agent presented adequate significance for the analyzed tests. The maximum RAP content to be applied should be 75%, and adding ADCAP WM directly to the binder showed slightly better results than the other combination.

Recent Advances in Basalt Fiber Reinforced Asphalt Mixture for Pavement Applications

This paper conducts a thorough review of the literature on the feasibility and current state-of-the-art incorporation of basalt fiber (BF) into asphalt pavement materials, focusing on fiber characteristics, dosage, incorporation methods, mixture properties, and surface modification techniques. The optimum basalt fiber dosage should be determined based on engineering performance parameters such as asphalt type, fatigue cracking, thermal cracking, rutting, and moisture resistance of asphalt mixtures. Basalt fibers are added to asphalt mixes by dry method or mixed method to achieve better dispersion. Adding BF to asphalt mixtures increased performance characteristics like cracking resistance, rutting resistance, and fatigue resistance. Overall, incorporating BF into asphalt mixtures would lower costs while increasing pavement service life. More research is needed to fully understand the effects of different sizes of BF on pavement performance and the possible environmental and economic repercussions of fiber surface alteration.

Feasibility Study for Evaluating the Moisture Resistance of Asphalt Mixtures Containing RAP Using Pull-Off Test

Abstract Binder adhesion has an important effect on the properties of asphalt mixtures. In asphalt mixtures containing reclaimed asphalt pavement (RAP), rejuvenating agents have been used to restore the adhesive properties of an aged binder. In this study, a new rejuvenator was investigated to discover whether it can improve the moisture susceptibility of mixtures containing RAP. For this purpose, first, the effects of a new rejuvenator on the moisture resistance of binder compounds containing different percentages of aged binder were evaluated. Second, the moisture susceptibility of asphalt mixtures with different RAP contents (25, 50, 75, and 100 %) were investigated with and without rejuvenator utilization. The pull-off test was performed to evaluate the adhesion of binder compounds; indirect tensile strength and resilient modulus tests were utilized for evaluating the moisture susceptibility of the asphalt mixtures. Meanwhile, for the first time, the relationship between the pull-off test and the moisture susceptibility parameters of asphalt mixtures was established. The results indicate that the use of the rejuvenating agent improved the moisture resistance of the asphalt mixtures containing RAP as compared with the control mixture and mixtures without a rejuvenator. According to the obtained correlations, the pull-off test can be used as a rapid and economic test to estimate the moisture sensitivity of asphalt mixtures.

The effects of nano zinc oxide (ZnO) and nano reduced graphene oxide (RGO) on moisture susceptibility property of stone mastic asphalt (SMA)

Moisture damage is one of the most common and main distresses in asphalt pavements. Using Nanomaterials due to their unique and outstanding properties in the asphalt pavement industry has received much attention in recent years. This paper investigated the effects of Nano Zinc Oxide (ZnO) and Nano Reduced Graphene Oxide (RGO) on moisture susceptibility resistance of Stone Mastic Asphalt (SMA) mixtures. SMA mixtures are a type of hot mix asphalt (HMA) containing two main parts of coarse aggregates and bitumen-filled mortar (bitumen, stabilizing additives, and filler aggregates). There is a wide range of test methods for evaluating the moisture resistance of asphalt mixtures; this study used the immersion Marshall test, indirect tensile strength test, boiling water test, static creep test, pull-off adhesion, and Semi-circular bending (SCB) fracture test for this aim. The pure bitumen was modified with three content of Nano ZnO and Nano RGO (0.2 %, 0.4 %, and 0.6 % by weight of asphalt binder). The experimental results obtained in this research indicated that the addition of Nano RGO in pure binder increases the softening point and viscosity and decreases the penetration and ductility properties of pure bitumen. Also, the addition of Nano ZnO in bitumen can increase the ductility, softening point, and viscosity, and decrease the penetration properties of pure bitumen. The mechanical test results showed that an increase in the percentage of Nano ZnO and RGO lead to a rise in Marshall Stability, indirect tensile strength, accumulated strain, pull-off adhesion strength, and fracture energy and improve the bitumen coating on aggregates in SMA mixtures. According to calculated moisture susceptibility indices of the mentioned tests above, the Nano ZnO and Nano RGO can significantly improve the resistance of stone mastic asphalt mixtures against moisture susceptibility. Examination of the test results showed that the ITS, pull-off, and Semi-circular bending (SCB) fracture test can give a good estimation of the moisture susceptibility of asphalt mixture. In addition, the results of the ANOVA test depicted that in ITS, Pull-off, and SCB fracture tests, Nano ZnO has a more significant effect on improving moisture susceptibility than Nano RGO.

Laboratory comparative assessment of warm and hot mixes Asphalt containing reclaimed Asphalt pavement

Warm mix Asphalt (WMA) could be mixed and used in paving at low temperatures to minimize the consumption of energy and the emissions of greenhouse gas. Recycled Asphalt pavement (RAP) could save Asphaltic cement and aggregate, which could achieve the better effects of recycling. However, both of the two WMA and RAP technologies have some deficiencies. Warm mix Asphalt and Reclaimed Asphalt pavement (WMA-RAP) technique may solve these issues and deficiencies when they are utilized together. This study investigated the implementations of WMA-RAP and its impacts on the performance of the Asphalt mixture. Under the framework of this study, four percentages of RAP (0%, 20%, 30%, and 40%) were added to the hot mix Asphalt (HMA) and WMA containing 4% Sasobit to study the impact of increasing RAP content on Marshall stability and moisture resistance of Asphalt mixtures. In summary, the Marshall stability of HMA and WMA mixtures is higher than the control mixtures. A small decrease in moisture resistance of both (HMA and WMA) containing RAP comparing to control mixtures Asphalt was observed, as shown by reduced the tensile strength ratios (TSR), but it is still much higher than the minimum of 80%.

New achievement in moisture sensitivity of nano-silica modified asphalt mixture with a combined effect of bitumen type and traffic condition

Moisture damage is a critical problem of asphalt pavements. Some factors affecting the moisture sensitivity of asphalt mixtures include bitumen properties, air void content, and the type of anti-stripping additive. This study investigated the use of nano-silica for improving the properties of different bitumens and to increase the moisture resistance of asphalt mixtures at different traffic loading conditions. Two types of bitumen (60–70 and 85–100 pen grade) were modified with various percentages of nano-silica (0, 0.2, 0.4, 0.7, and 0.9% by the weight of the bitumen), and physical and rheological tests were conducted to determine the optimum nano-content. Then, the optimal content was used to prepare asphalt mixtures at three different air void contents (4, 5, and 6%) to simulate the heavy, medium, and low traffic loading conditions. Indirect tensile strength (ITS) and compressive strength tests were performed on the specimens in dry and wet conditions, and the effect of air void content and the type of bitumen on the moisture sensitivity and compressive strength of unmodified and nano-silica-modified asphalt concrete was investigated. The results showed that nano-silica improved the moisture sensitivity of asphalt mixtures with 60–70 and 85–100 pen grade bitumens at all air void contents and the effect of nano-silica was higher on the moisture sensitivity of asphalt mixtures with 60–70 than 85–100 pen grade bitumen.

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.

Investigation of Moisture Sensitivity and Conductivity Properties of Inductive Asphalt Mixtures Containing Steel Wool Fiber

The construction of suitable roads in rainy areas has created problems in the construction process due to the low resistance of asphalt to moisture. To solve this problem, materials are commonly used that make mixtures resistant to moisture; however, these materials may reduce the dynamic resistance of asphalt. Therefore, materials should be used that, in addition to increasing the dynamic resistance, also increase the moisture resistance of asphalt mixtures. One of these materials used in this research is steel wool fiber (SWF), which in addition to creating conductive roads also could have a significant effect on moisture resistance. In this study, the impact of 2%, 4%, 6%, 8%, and 10% SWF on the Marshall stability and moisture sensitivity of mixtures was investigated using the Marshall stability and indirect tensile strength (ITS) tests, respectively. Moreover, using SWF as a conductive fiber, the conductivity properties of asphalt mixtures were explored to find the optimal amount of electrical conductivity. The results of the Marshall stability test indicated that by increasing SWF contents, the stability of mixtures increased, compared with the base sample, and greater amounts of 6% SWF resulted in the reduction of the Marshall stability. The results of ITS showed that modification of bitumen by SWF increased ITS and tensile strength ratio (TSR) amounts of mixtures. 6% SWF was the optimal amount for enhancing the resistance of asphalt mixtures to moisture sensitivity. The results of the electrical resistivity test showed that the resistivity had three phases: high resistivity, transit, and low resistivity. Mixtures containing less than 4% SWF illustrated an insulating behavior, with electrical resistivity greater than 7.62 × 108 Ω.m. At the transit phase, the resistivity of mixtures had a sharp reduction from 7.62 × 108 Ω.m to 6.17 × 104 Ω.m. Finally, 8% SWF was known as the optimal content for the electrical conductivity of mixtures.

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).

Investigating the effect of amorphous carbon powder on the moisture sensitivity, fatigue performance and rutting resistance of rubberized asphalt concrete mixtures

In recent years, the significant importance of solid waste management, increase in the cost of bitumen and polymer modifiers have encouraged the pavement engineers to use reusable alternative sources. Ground tire rubber (GTR) and amorphous carbon powder (ACP) are considered as two industrial waste which their using in asphalt mixture prevents their releasing in the environment. This study aims to analyze moisture sensitivity, fatigue performance, and rutting resistance of asphalt mixture influenced by using GTR (8, 12, and 16% of bitumen weight) as the modifier of bitumen properties, and ACP (25, 50, and 75% of filler weight) as filler. The results of this study shows that the ACP increases the resilient modulus and indirect tensile strength of rubberized asphalt concrete (RAC) mixtures. The results revealed that despite the negative effect of GTR on the moisture resistance of asphalt mixture, ACP improves the moisture performance. The results of fracture energy also implies that using ACP decreases the fracture energy, but using the GTR improves the fatigue resistance of asphalt mixture. Furthermore, the results of dynamic creep and wheel track tests indicates that 16GTR + 50ACP has the lowest permanent deformation and highest rutting resistance. The results of ANOVA analysis demonstrates that using GTR and ACP has a considerable effect on the performance properties of asphalt mixture. Finally, the results of this study illustrate the simultaneous use cleaner production and wasted materials decreases the environmental damages in addition to improvement of physical properties of the asphalt mixture.

Investigating the Effect of Modifying Aggregate Surface by Micronized Calcium Carbonate on Increasing the Moisture Resistance of Asphalt Mixtures

The adhesion between aggregate and asphalt binder in dry conditions, and the amount of its reduction in wet conditions are amongst fundamental indicators that moisture sensitivity amount of asphalt mixtures is dependent to. Among different methods to increase adhesion, modification of aggregates surface with anti-stripping materials is known as an effective method. Therefore, the effect of covering aggregates surface with micronized calcium carbonate as a proper and inexpensive anti-stripping material was investigated. Accordingly, in order to evaluate mixes, first, mechanical methods were used, and then thermodynamic methods were employed to determine the mechanism of the effect of calcium carbonate on increasing asphalt mix resistance to moisture damage. In order to conduct this research, three types of aggregates including limestone, granite, and quartzite, for their different degrees of hydrophilic, and two types of asphalt binder 60–70 and 85–100 were used to produce mixtures. Results obtained by mechanical methods show that modification of aggregates surface causes an increase in the tensile strength ratio (TSR) in the samples made by both two types of asphalt binder. In addition, results of surface free energy method indicate the increase of adhesion energy (except in granite samples) and reduction of debonding energy in all modified samples. Generally, evaluations conducted by the use of both methods show that covering aggregates by micronized calcium carbonate has a positive effect on reducing moisture sensitivity of asphalt mixes.

Evaluation of Moisture Resistance of Hot-Mix Asphalt Mixture Containing Refined Air-Cooled Slag for Road Pavements

Recently, potholes have drawn attention as a major pavement distress. In Korea and other countries, slaked lime is used to improve the moisture resistance of asphalt mixtures in order to prevent road damages by moisture. The present study was conducted to evaluate the moisture resistance of asphalt mixtures containing air-cooled slag having a chemical composition similar to that of slaked lime. To evaluate the moisture resistance of asphalt mixtures containing air-cooled slag, a moisture resistance test that is applied in Korea and other countries was performed. The evaluation of the moisture resistance of asphalt mixtures containing air-cooled slag showed that the coverage ratio measured by the dynamic immersion test was about 80%, which was similar to that of the asphalt mixtures containing slaked lime. In the case of the indirect tensile strength test, the TSR value tends to increase with increasing the air-cooled slag content of the specimens. But the indirect tensile strength was slightly lower in the specimen containing 3% air-cooled slag. The Hamburg wheel tracking test showed that the moisture resistance of the specimens produced in a laboratory and in a plant was good but that of the specimen containing 3% air-cooled slag was slightly lower. The laboratory experiment performed in the present study showed that the moisture resistance was improved by the addition of air-cooled slag, which has a similar composition with slaked lime, to asphalt mixtures. However, when the entire filler of the asphalt mixture was replaced by air-cooled slag, the strength was slightly decreased, indicating that an appropriate amount of air-cooled slag should be added. The applicability of air-cooled slag to asphalt pavement material may need to be studied through a microstructure analysis and a long-term pavement performance test to investigate the mechanism more accurately.