Anti-stripping Additives Research Articles

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.

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.

The Effect of Wetfix and Nanohydrated Lime Additives on Bitumen Aging and the Cohesion and Adhesion Failure Mechanisms of Hot Asphalt Mixtures

Aging due to sunlight and the passage of time is an effective element in the occurrence of moisture damage in hot asphalt mixtures. Still, the effects of this parameter are scarcely considered in the experiments examining the moisture damage potential. Accordingly, this study investigated the effect of aging on the performance of hot asphalt mixtures and examined the improvement of moisture damage performance by using antistripping additives via mechanism and functional tests. Two types of aggregates (limestone and granite) with different degrees of moisture sensitivity, two types of bitumen (PG64-16 and PG58-22) with different performances, and two additives (Wetfix liquid additive and nanohydrated lime) as bitumen modifiers were used. Bitumen samples and asphalt mixtures were subjected to short- and long-term aging. The pull-off test was performed to explore the aging effect on different failure mechanisms (cohesion and adhesion), and the indirect tensile stiffness modulus (ITSM) test was conducted to study the asphalt mixture’s performance against moisture damage. The results specify that aging, in terms of hot asphalt mixture hardening in dry and wet conditions, decreased the MSR (resilient modulus wet to resilient modulus dry ratio), and this decline was greater in long-term aging. The pull-off test results exhibited that aging, especially in the long term, decreased the asphalt mixture’s adhesive strength in dry and wet conditions; this decline in adhesion was greater in the wet than in the dry state, and this difference decreased the wet-to-dry adhesion strength ratio (the pull-off ratio). The additives relatively improved the yield modulus of the asphalt mixture, but their effect was greater in the wet state. A comparison of the pull-off test results in cohesion and adhesion failure demonstrated that Wetfix was more effective in improving bitumen–aggregate adhesion, whereas nanohydrated lime was more effective in enhancing bitumen adhesion. The resilient modulus (Mr) ratio in wet-to-dry conditions indicated that nanohydrated lime had better effects on the overall performance of the aged asphalt mixture against moisture damage. To investigate the effect of additives on the performance of asphalt mixtures, a t-test was performed in all modes of control, short-term aging, and long-term aging. The findings showed the effect of Wetfix and nanohydrated lime on increasing the modulus of elasticity of the samples.

Effect of Crumb Rubber on the Moisture and Rutting Behavior of Low-Energy Asphalt and Determining the Best Flow Number Model

The advancement of technology and the increasing growth of environmental threats have led experts in the field of transportation to find alternatives for hot mix asphalts (HMAs). One of these alternatives is low-energy asphalt (LEA) mixtures. LEA mixture consists of hot asphalt binder and coarse aggregates and wet sand, which, having a lower mixing temperature, has caused a significant reduction in energy consumption and pollutants emitted from asphalt binder. According to previous studies, the influence of crumb rubber (CR) on the rutting and moisture performances of LEAs has not been investigated so far. In this regard, due to the softness of this type of asphalt mixture and its weakness against rutting and moisture, in this study, as an innovation, CR was used to modify LEA mixtures in three weight percentages of 10, 15, and 20. Considering the high moisture sensitivity of LEA mixtures due to the presence of water, the ability of CR to overcome this weakness and its potential to be replaced with antistriping additives were also investigated using the indirect tensile strength (ITS) test. In addition, in order to evaluate the rutting resistance, LEA mixtures were subjected to the dynamic creep test at a temperature of 54.4°C and at two stress levels of 270 and 310 kPa. According to ITS test results, it was found that although the modified LEA mixtures with 10 and 15% CR met the minimum requirement, the tensile strength ratio (TSR) value recorded for mentioned mixtures was still lower than that for HMA. Therefore, it is recommended to use antistripping additives in the use of LEA-containing CR, especially in areas with a high probability of moisture damage. The results of creep curves and flow numbers (FNs) extracted from four different models of three-stage, Fnest, Francken, and stepwise showed that although the LEA sample without additive had lower rutting resistance than HMA, the modification of this mixture to 15% CR significantly increased the rutting resistance. Moreover, considering the variety of variables in the process of making LEA compared to HMA, the comparison of FN determination models and the introduction of the most stable model were conducted in this research. According to the laboratory and statistical analysis results, it was found that the Francken model had less sensitivity to the variables, so it is suggested to determine FN for LEA mixtures.

Stripping propensity detection of HMA Mixes: With focus on image processing method

• The incorporation of anti- Stripping in hot mix asphalt was investigated. • The effects of anti- Stripping agents on the specimens by image processing were evaluated. • The performance of specimens under different working conditions was analyzed. • Anti-stripping agent improved of adhesive property of HMA asphalt mixtures. Infiltration of water into Hot Mix Asphalt (HMA) can cause performance degradation and service life reduction of the asphalt concrete pavements. Moreover, it can lead to adhesion failure at the binder-aggregate interface and/or cohesion failure within the binder or binder-filler mastic. In this paper, three aggregate types, three anti-stripping additives, and one bitumen type were selected to study this phenomenon. Based on the results of chemical analysis, selected aggregates were categorized into two groups: non-stripping and stripping aggregates. Then, the stripping propensity of loose and compacted mixes was assessed through boiling water, retained compressive strength, and indirect tensile tests. The chemical analysis was showed the importance of amphoteric and alkaline oxides in moisture sensitivity in silicate rocks. The results emphasize the detrimental effect of moisture in HMA mixes even in the non-stripping mix. All selected anti-stripping additives improve the tensile strength ratio (TSR) of specimens, however, the stripping propensity of some treated mixes was maintained. In the next step, cohesion loss and adhesion loss surfaces of loose mixes and ITS specimens was determined under the wet conditions by the image processing technique in ENVI and MATLAB software packages. Based on image processing results, the higher retained bitumen coating in loose mixes leads to less stripping propensity of compacted specimens and the tensile strength ratio of modified Lottman specimens is decreased by an increase in the percentage of broken aggregates and adhesion loss. Image processing data were subjected to nonlinear regression and multiple analysis of variance (MANOVA) to investigate this phenomenon.

Effect of Antistripping Additives on the Cohesion, Adhesion, and Performance of Different Asphalt Mixtures in Dry and Wet Conditions

Most available tests of asphalt mixture performance against moisture damage or the effect of additives examined the asphalt mixture’s overall performance. Considering the different mechanisms of moisture damage, studying antistripping additives’ effect on failure mechanisms might provide a better view of the asphalt mixture’s performance against moisture. Accordingly, herein, the effects of various antistripping additives, including a liquid antistripping additive (dodecylamine) and a nano-magnesium hydroxide additive, each at two bitumen weight percentages, with two types of aggregates with different mineralogical properties and a PG 64-16 bitumen on moisture damage mechanism were investigated. The cohesion and adhesion mechanisms of moisture damage were examined using the pull off test, and the asphalt mixture’s overall performance was assessed using the indirect tensile strength (ITS) test in multiple dry and wet conditions (1, 2, and 3 freeze-thaw cycles) according to the modified Lottman test. The results revealed that the use of 0.4% dodecylamine and 1% nano-magnesium hydroxide in the mixtures made with lime aggregates increases the tensile strength ratio (TSR) from 62.67% to 85.4% and 84.8%, respectively. In mixtures made with granite aggregates, TSR increased from 54.45% to 72.49% and 71.35%, respectively. The failure mechanisms’ assessment showed that the use of 1% nano-magnesium hydroxide in mixtures made with granite aggregate elevated the pull off in the adhesion failure mechanism by 80%, and the pull off increased by 70% in the cohesion failure mechanism. Moreover, the pull off increased by 63% for limestone mixtures in the cohesion failure mechanism and by 56% in the adhesion failure mechanism. The dodecylamine additive with the highest pull off and ITS ratio in all freeze-thaw cycles was more suitable than nano-magnesium hydroxide to promote the asphalt mixtures’ overall performance against moisture. The statistical analysis also indicated the significant effect of dodecylamine and nano-magnesium hydroxide additives on asphalt mixtures’ moisture sensitivity reduction at a 95% confidence level. The findings show that some additives have a stronger effect on adhesion strength and some effect on cohesion strength, but the additive that better improves the overall asphalt mix performance depends on mix design characteristics and aggregate and bitumen type.

Evaluation of Stripping Problem in Terms of Additive Types and Ratios in Asphalt Pavements

Stripping in asphalt mixtures is the one of foremost distress mechanisms. To prevent stripping, fatty acids (AS) and hydrated lime (HL) additives are often used as anti-stripping additives. The determination of the correct usage ratios of these additives and the storage stability of bitumen constitutes important research topics for anti-stripping additive applications. Three surfactants and hydrated lime were used in three ratios to evaluate the effect of additive ratio and type. Indirect tensile strength (ITS) values obtained from samples with one and three cycle modified Lottman conditioning and indirect tensile strength ratios (ITSRs) were interpreted in the context of water damage. The load-carrying capacity of the conditioned mixtures increased significantly. Even if the degree of damage was considerably increased at the end of three cycles, the integrity of the mixtures was maintained. Both AS and HL significantly increased water damage resistance. Modified Lottman conditioning has an observable level of damage. Additives remained functional and maintain their mechanisms of benefit, especially in the event of a high degree of damage.

Prediction of moisture resistance of asphalt mastics modified by liquid anti stripping based on support vector regression, artificial neural network and Kernel-based support vector regression methods

Commonly referred to as stripping, moisture sensitivity is described as the stripping of bitumen from the surface of aggregates. This phenomenon occurs when adhesion bonds between asphalt mastics and the surface of aggregates are fractured mainly due to cohesion failures in the asphalt cement. For evaluating the effect of bitumen-aggregates adhesion and also asphalt mastic cohesion, the bitumen bonding strength (BBS) test on wet and dry conditions was implemented, with regard to a few studies in this field. The experimental program for this study consists of using one binder source Flint Hills PG 64-22, three liquid anti stripping additives (ASA), and two aggregate substrate (limestone and granite). This research aimed to examine the effect of various ASA and mineral fillers on moisture failure resistance in asphalt mastic by the use of BBS experiment. The findings indicated that in dry condition, samples with no additive and containing limestone filler had higher pull-off tensile strength (POTS) than those with granite. While, by addition of ASA, all specimens containing granite had higher POTS compared to those with limestone. In addition, the failure of most of the asphalt mastics was cohesive, except asphalt mastics containing granite filler and the one with limestone filler and additive C.

Effectiveness of Liquid Antistripping Additive for Emulsion‐Treated Base Layer Using Reclaimed Asphalt Pavement Material

In the new global economy, getting natural aggregates (NA) has become a central issue for constructing flexible pavements due to the scarcity of aggregates and the ban on mining in various states in India. This research is an attempt to achieve sustainability by using a liquid antistripping additive for emulsion‐treated base layer to improve the performance of Reclaimed Asphalt Pavement Material (RAPM) inclusive aggregates. RAPM was evaluated, with inclusion percentages of 50 and 70 percent, whereas, the control mix was prepared using 100 percent natural aggregate (NA). The effect of inclusion of liquid antistripping additive (ASA) with different RAPM percentages on various properties of ETB mixes, such as maximum dry density, indirect tensile strength, moisture resistance and resilient modulus, was studied. Furthermore, when compared to RAP‐ETB mixes without ASA, RAP‐ETB mixes with ASA were found to preserve many of their qualities. The present study aimed to propose the laboratory design of optimum bitumen emulsion content (OBEC) for ETB in a simpler manner. For 50 RAP, obtained OBEC was at 4.4%, whereas for 70 RAP, OBEC was obtained at 3.8%. However, for 100 % NA, calculated OBEC was 7.0% as there was 0% RAP in it, hence binder absorption was more. The strength parameter was assessed using the Indirect Tensile Strength (ITS) test. At the same time, the pavement response was measured in terms of Resilient Modulus (MR). MR of 70 RAP mixes was higher than that of 50 RAP mixes, and 100 NA mixes with antistripping additive. Test results were encouraging, and significant improvement in strength was caused by cement filler and antistripping additive.

Effects of Additional Antistrip Additives on Durability and Moisture Susceptibility of Granite-Based Open-Graded Friction Course

AbstractThis study aimed to evaluate the effects of additional antistrip additives on the durability and moisture susceptibility of granite-based open-graded friction course, referred to as FC-5 as...

Improvements of TPS-Porous Asphalt Using Wax- Based Additives for the Application on Malaysian Expressway

Porous asphalt provides a sustainable approach to reduce traffic noise at source, while at the same time offering storm-water management systems which promote infiltration and often reduce the need for a detention pool. However, porous asphalt is prone to premature deteriorations, in terms of ravelling, and air voids clogging, rendering its unpopularity as the road surfacing material for expressways construction. In this research, the comparative influences of Tough Fix (TF) and Tough Fix Hyper (TFH) additives incorporation were evaluated on the performance of Tafpack-Super modified porous asphalt mixtures (TPS-PA). The Tafpack-Super (TPS) as a modifier at 20%, and anti-stripping additives (TF and TFH) with dosages used in this study were 0.3%, and 0.15% based on the weight of asphalt binder, respectively. Initially, the PA mixtures were prepared according to a predetermined mix design, and verified based on the percentage of air voids, permeability, and connected air voids. Comprehensive experimental tests of Marshall stability, permeability, Cantabro loss, rutting resistance, and moisture induced damage resistance were performed to assess the mechanical performance of the TPS-PA mixtures. Moreover, the Texas boiling test was employed to assess the stripping potential of loose TPS-PA mixtures. The experimental results revealed that both TF and TFH are capable of improving the PA resistance against rutting, ravelling, and moisture damage. In addition, the porous asphalt with TFH anti-stripping agent incorporation exhibited a superior overall performance as compared to the PA with TF.

Durability of Asphalt Concrete (ACWC) Mixed with Antistripping Additive

In pavement structures that are often submerged by water, the damage to pavement is often caused by the loss of bonds or adhesions between the aggregate and asphalt, the type of damage that occurs due to the loss of adhesion between the aggregate and asphalt is the exfoliation of asphalt granules so that the road is cracked and corrugated. To reduce the release of aggregate granules and improve the bond between aggregates and asphalt can be made with the addition of anti-exfoliating additives or antistripping agent additives. This study aims to analyze the performance of wear-coated concrete asphalt mixture (ACWC) with the addition of antistripping additives. Antistripping agents used in this study were Zycotherm, Morlife and Adhebit with variations of 0.1% addition, 0.3% and 0.5% of the weight of asphalt mixture. The results of this study showed that ACWC mixture with the addition of Zycotherm additives resulted in optimum Marshall stability and increased durability at 0.5% and Adhebit additives at 0.3% levels, while in Morlife additives although at 0.3% levels were able to show optimum marshall analysis in terms of increased durability did not show expected performance.

The effect of nanomaterials as anti-stripping additives on the moisture sensitivity of glasphalt

Despite the environmental and economic benefits of using glasphalt, it suffers from a number of disadvantages. The most common damage in glasphalt is the effect of water on bitumen-aggregate adhesion and the occurrence of moisture damage. One way to improve the resistance of glasphalt against the moisture damage is to use anti-stripping additives. Accordingly, the effect of two types of nanomaterials including nano hydrated lime (NHL) and nano calcium carbonate (NCC) as bitumen modifiers on the moisture sensitivity of glass asphalt has been investigated in this study. The moisture sensitivity of asphalt mixtures was assessed by the AASHTO T283 test and surface free energy (SFE) method. Indirect tensile strength (ITS) results show that the use of waste glass cullet increases and decreases the resistance of asphalt mixture in dry and wet conditions, respectively. An increase in the number of freeze–thaw cycles causes a decrease in the ITS of the glasphalt. The obtained results showed that using both nanomaterials in glasphalt significantly improved the resistance to moisture sensitivity. Bitumen modification using NHL and NCC, which was added in 2% bitumen, reduced the SFE of cohesion, which resulted in improving the bitumen coating on the aggregate surface and the adhesive between bitumen and aggregate.

Examination of Significant Binder Aging Due to the Use of Different Anti-Stripping Additives in Polymer and CRM Asphalt Mixtures Using GPC

Abstract As an anti-stripping agent (ASA), hydrated lime (HL) has been widely used for many years in the world. Many brands of liquid-type ASA (LA), which properly provided the anti-stripping function, have been also developed and marketed. Because HL was found to provide anti-aging function of the binder in the mix, in addition to anti-stripping function, its use was known to have many advantages of other beneficial functions to the asphalt pavement. However, because the anti-aging function of LA is in question, it will be important to recognize if the anti-aging function is presented by the LAs too. Therefore, this study investigated the anti-aging effect of HL and three LAs in normal, crumb rubber–modified and polymer-modified asphalt mixes, in terms of absolute viscosity (AV) estimated from the large molecular size (LMS) measured by gel permeation chromatography (GPC), a scientific equipment. It was found that HL provided a significant retardation of age hardening, compared with the binder of the mix without any ASA. However, unlikely the anti-stripping function, most of the LAs did not show age retardation effect. The anti-aging function of liquid additives was not proved in this study, and therefore, the significant difference in binder aging was present due to the use of different ASA.

Laboratory performance and modelling behaviour of hot-mix asphalt with recycled crushed glass

In South Africa research is currently under way to determine the suitability of using locally available recycled crushed glass as a partial fine aggregate substitute in the production of asphalt mixes. This paper characterises the laboratory performance of a dense-graded asphalt wearing course mix consisting of 15% recycled crushed glass. The influence of selected antistripping additives on moisture susceptibility was specifically assessed as a variable in the performance evaluation of the glass-asphalt mix as follows: (a) the effect of 1% hydrated lime, (b) the effect of 0.5% liquid antistripping additive, and (c) the effect without the addition of antistripping additive. The effect of these variables on the moisture susceptibility of the glass-asphalt mix was evaluated using the tensile strength ratio parameter supported with a microscopic imaging analysis. Additionally, the stiffness and permanent deformation properties of the glass-asphalt mix that demonstrated optimum resistance to moisture damage was compared to the same mix without crushed glass. The performance properties were evaluated using the Huet-Sayegh model and a polynomial model respectively, which were used particularly to develop performance characterisation models for the glass-asphalt mix. The findings of this study revealed that an anti-stripping additive is essential to meet moisture susceptibility criteria and alleviate moisture damage in dense-graded glass-asphalt mixes. In particular, moisture susceptibility was improved using hydrated lime rather than the liquid antistripping additive. Furthermore, the selected constitutive models were able to effectively characterise the laboratory performance of both mixes, with the glass-asphalt mix demonstrating improved resistance to permanent deformation when compared with the conventional asphalt mix.

Influence of Antistripping Additives and Rejuvenators on Healing Performance of Moisture‐Damaged HMA

This study aims to evaluate the effect of different rejuvenators and antistripping agents on the healing performance of hot mix asphalt (HMA). Two damage HMA series (e.g., moisture damage and aged damage) were subjected to either induction or microwave heating. A PG64‐22 virgin and aged binder were used and modified with several additives. Three long‐term aged binders (e.g., PAV5, PAV15, and PAV20) were conducted by pressure aging vessel (PAV) test. The moisture damage series fabricating with a new binder was further categorized into four different freeze‐thaw (FT) cycles (e.g., 0FT, 1FT, 3FT, and 5FT). Also, the aged series was fabricated with three different aged binders. A total of eight damage‐healing cycles were applied to all asphalt mixtures, examined by the three‐point bending test. The moisture resistance of modified asphalt mixture was examined by indirect tensile strength test. Overall, asphalt mixtures modified with either antistripping additives or rejuvenators not only obtained higher moisture resistance but also gained better healing performance under moisture damage. In addition, the study showed a probable correlation between moisture damage and long‐term aging in terms of healing performance, such as PAV15 and 3FT cycles and PAV20 and 5FT cycles.

SYSTEMATIC TESTING METHODOLOGY TO PREDICT STRIPPING OF ASPHALT CONCRETE MIXTURE

The stripping of asphalt cement still the most significant reason that causes the deterioration of asphalt concrete pavement. This study aims to compare and develop a systematic method for the results of stripping tests: Texas boiling, resilient modulus, and fatigue. Three types of aggregates and two types of anti-stripping additives were used. Texas boiling test, and then Marshall specimens with (6-8%) air voids subjected to medium or high moisture conditioning were used. The stripping potential evaluated by suggesting sequence tests steps for asphalt coating retained (60-80%) visually and by the resilient modulus (MR). The visual assessment of the boiling test and the rolling test is not enough to predict stripping. The degree of saturation had a very significant effect on the resilient modulus values. The use of the resilient modulus test for Marshall specimens is a reliable test to predict stripping. For the results of less than the range; add additives and re-evaluate the stripping. For results above the range; run a fatigue test with high saturation. In general, it found that the dosage of lime needed is between 1.5 to 2.0% by weight of aggregate, where for polyamine, it was between 0.75 to 1% by weight of asphalt binder. Lime additive showed better effects on stripping potential than polyamine (liquid) additive. The proposed methodology which organized by a flow chart is a sound step-by-step and practical procedure for predicting the stripping. It could be used as a guideline to assess the water susceptibility for any aggregate type

Utilization of fatigue test to predict stripping of asphalt concrete mixtures

Stripping is the separation of the asphalt cement film from the aggregate surface due to the action of moisture. Three types of aggregate: crushed limestone, uncrushed valley gravel, and crushed basalt, asphalt cement, and two anti-stripping additives: hydrated lime and a polyamine liquid additive were used. The stripping potential is evaluated by a Fatigue test using the Universal Testing Machine. Marshall specimens were prepared with optimum asphalt and 6-8% air voids, with; no additive, hydrated lime dosages of (1.5-2.0%) by weight of aggregate and the polyamine dosage of (0.75-1.0 %) by weight of asphalt. High saturation degree 60 - 80% of the air voids volume was used. It was concluded that aggregate type is the most significant variable that affects the stripping. The anti-stripping agents are effective in cases where the potential of stripping is high. All aggregates types have shown a tendency for stripping at a high degree of saturation. Limestone showed the best stripping resistance, better than valley gravel and basalt. The results indicated that cycles to failure at a given strain (1000 micro-strain) were improved as the accumulated strain for all mixtures. The use of the fatigue test gives a necessary indicator of the performance of moisture potential and additive effects.

Relationship between microscopic analysis and quantitative and qualitative indicators of moisture susceptibility evaluation of warm-mix asphalt mixtures containing modifiers

Given the defects of bitumen in asphalt mixtures particularly exposed to moisture, this study mainly aims to investigate the relationship between qualitative and quantitative results of moisture susceptibility tests on asphalt mixtures modified by ZycoTherm, nanoclay, nanosilica and SBS. The Marshall stability, modulus of resilience and indirect tensile strength tests are carried out. Boiling water and SEM qualitative tests are also used. Eventually, the qualitative tests results are digitalized through image processing by MATLAB and compared with the moisture susceptibility results of indirect tensile strength test. For modulus of resilience testing, the results show that this modifier has the maximum impact on Marshall stability, improving it by about 23%. For moisture susceptibility testing, the nanosilica-modified mixture has the maximum effect among anti-stripping additives, with an improvement by about 20%. An investigation into the results of SEM images and boiling water test via MATLAB indicates the high accuracy of SEM images and their results show the most compatibility with the results of quantitative data.

Determination of moisture damage mechanism in asphalt mixtures using thermodynamic and mix design parameters

The shortcoming of the available laboratory methods for determining the moisture susceptibility of asphalt mixtures has led researchers to think about providing new methods based on effective parameters on moisture damage process. Accordingly, this research is an attempt to provide a prediction model using thermodynamic and mix design parameters that can predict and analyze the performance of asphalt mix against moisture. T he results of this study indicate that the use of anti-stripping additives can generally improve the performance of asphalt mixtures against moisture; however, the type and percentage of these additives should be determined according to the type of aggregate, the type of bitumen and the properties of the mixing plan of the asphalt mix. Based on the proposed model, it can be stated that an increase in cohesion free energy, adhesion free energy, aggregate wettability by bitumen, surface area of aggregates, and apparent asphalt film thickness on the aggregate surface improve the moisture resistance of mixtures. On the other hand, debonding energy, saturation percentage, and permeability negatively affect the asphalt mixture’s resistance to moisture damage.