Anti-stripping Additives Research Articles

Experimental evaluation of anti-stripping additives in bituminous mixtures through multiple scale laboratory test results

This paper presents performance changes and material characteristics associated with moisture damage due to anti-stripping additives in asphalt mixtures through various laboratory tests. Two additives (hydrated lime and fly ash) are investigated by adding them into two types of mixes where different asphalt binders and aggregates are used. Two widely-used asphalt concrete mixture performance tests (the AASHTO T-283 and the asphalt pavement analyzer under water) and two mixture constituent tests (the boiling water test and the pull-off tensile strength test) are conducted to characterize the effects of anti-stripping additives on the binder–aggregate bonding potential in mixtures. Results from laboratory tests indicate that the mixes, where high-quality aggregates and polymer-modified binder are used, are fairly self-resistant to moisture damage without treating any anti-stripping additive and do not show any visible sensitivity between additives, whereas the effects of additives and their sensitivity are significant in the mixes that use the unmodified binder and low-quality aggregates. With the limited amount of test data, both hydrated lime and fly ash contribute to reducing moisture damage, which implies potential significant cost savings by the use of fly ash as an alternative additive.

Rheological Evaluation of Warm Mix and Anti-Stripping Additives Modified Performance Grade Binders

ABSTRACT This study evaluated the effects of a warm mix asphalt (WMA) additive, Sasobit®, and a liquid anti-stripping agent, AD-here® HP Plus, onthe rheological properties of a selected performance grade binder (PG 64-22) as per Superpave® specifications. The optimum dosage (mass) of Sasobit®was found to be 1.5%, which was expected to reduce the mixing and the high PG temperatures by 9oC and 4.5oC, respectively. Sasobit® was also found to decrease the fatigue resistance and low temperature resistance of the base binder to some extent. Furthermore, a reduced rolling thin film oven (RTFO) temperature was expected to exhibit significant reduction in the rut resistance of the WMA. While anti-stripping agent was expected to reduce the rutting resistance, it was anticipated to increase low temperature resistance of the WMA. The findings of this study are expected to enhance rheological database and help in implementing WMA mixes in Oklahoma and elsewhere.

Integrated Experimental–Numerical Approach for Estimating Material-Specific Moisture Damage Characteristics of Binder–Aggregate Interface

An integrated experimental–numerical approach is presented for estimating the material-specific moisture damage characteristics of binder–aggregate interfaces. A pull-off test is conducted with a pneumatic adhesion tensile testing instrument to determine the bond strength between asphalt film and the aggregate surface to which various types of antistripping additives are applied with various levels of moisture conditioning. A sequentially coupled moisture diffusion–mechanical analysis is implemented with a finite element technique to model the bond strength and progressive interfacial degradation caused by moisture diffusion, followed by mechanical pulling pressure. To simulate the adhesive fracture at the binder–aggregate interface, a cohesive zone model is incorporated into the approach. The integrated approach results in a degradation function that characterizes interfacial damage caused by moisture uptake with two model parameters representing the remaining bond strength and the degradation trend. With the two model parameters, moisture damage mechanisms and damage resistance potential, both of which are material specific, can be estimated.

Rheological properties and moisture susceptibility of WMA mixture containing moist agregate

The objective of this study was to investigate and evaluate the rheological and moisture susceptibility of the WMA mixtures containing moist aggregates. The experimental design included the utilizations of two aggregate sources, two moisture, two anti-stripping additives, and three WMA additives and control. Several properties of the binders and mixtures were obtained including: viscosity, dynamic shear rheometer, beam bending rheometer of WMA binders, indirect tensile strength (ITS), tensile strength ratio (TSR), and flow values. The experimental results indicate that the WMA additives can result in a slight decrease in viscosity and an increase in failure temperature. In addition, the moisture susceptibility results illustrated that the mixtures containing moist aggregates generally have similar ITS values to other mixtures regardless of HMA or WMA types. Moreover, there were no significant differences in the wet ITS values of WMA mixture amongst four types of mixtures under identical conditions (same moisture and lime contents) except for the mixtures containing liquid anti-stripping additive and Asphamin additive.

Effects of Liquid Anti-Stripping Additives on Rheological Properties of Performance Grade Binders

This study presents a testing protocol for evaluating the viscoelastic properties of selected performance grade (PG) binders using a dynamic mechanical analyzer (DMA). It also presents the effects of amine-based liquid anti-stripping additives on the binders ' rheological properties. Out of total 183 samples tested, 51 samples for three PG binders (PG 64-22, PG 70-28, and PG 76-28) were tested to establish the DMA-based testing protocol. The remaining samples were tested to obtain rheological data of the PO 64-22 binder with different dosages of two anti-stripping (AS) additives. Test results of the DMA were validated by comparing with those obtained from a dynamic shear rheometer (DSR). Test results show that the DMA can be used as an alternative tool for examining the viscoelastic behavior of binders. It was observed that the rutting factor [G*/Sin(δ)] of the binder decreased when the amount of AS additive was increased. The optimum dosage of either of these AS additives was found to be 0.50%. AS additives did not alter the mechanical workability and the linear viscoelastic limit of the binder. Also, a good correlation between the complex modulus of the PG 64-22 binder and the dynamic modulus of the corresponding mix was observed.

Effects of liquid antistrip additives on rheology and moisture susceptibility of water bearing warm mixtures

Warm mix asphalt (WMA) has been gaining increasing popularity in recent years around the world. Rising energy prices, global warming, and more stringent environmental regulations have resulted in an interest in WMA technologies as a mean to decrease the energy consumption and emissions. However, the water absorption and release process caused by water bearing WMA additive (Asphamin) makes the charge re-distribution complex and thus may result in the moisture induced damage of asphalt mixtures. Especially, the liquid antistrip additives (ASAs) blended with the binder and then mixed with aggregate and Asphamin make the issue more complicated. The objective of this study was to investigate and evaluate the rheological properties and moisture susceptibility of the binder and mixture containing ASAs and Asphamin additive. The experimental design for this study included rheological property tests of binders and moisture susceptibility of mixtures. The materials included one binder (PG 64-16), two liquid ASAs and hydrated lime, one water bearing additive, and three aggregate sources. The performed testing included viscosity, performance grade, creep and creep recovery, amplitude sweep, frequency sweep, boiling test, and indirect tensile strength (ITS). The results indicated that the addition of Asphamin can slightly increase the viscosity, failure temperature and G */sin δ values. The mixture containing Asphamin has a lower ITS value than others. Statistical analysis illustrates that there is not significant difference in ITS value between any mixtures containing Asphamin additive and control mixtures. However, significant differences can be found between mixtures containing Asphamin and without any Asphamin additive.

Laboratory Evaluation of Moisture Susceptibility of Hot-Mix Asphalt Containing Cementitious Fillers

Moisture-induced damage has long been recognized as one of the major concerns for asphalt pavements. To mitigate potential moisture damage, one general method is to add mineral antistripping additives or liquid antistripping agents into hot-mix asphalt (HMA) mixtures. In this study, a comparative laboratory experiment was conducted to investigate the effectiveness of cementitious fillers on moisture susceptibility of HMA mixtures. Five types of cementitious fillers were considered: fly ash, cement kiln dust, and three types of hydrated lime with different finenesses. The laboratory performance of HMA mixtures subjected to moisture conditioning was evaluated through the following tests: dynamic modulus test; superpave indirect tensile tests; and tensile strength ratio test. The test results indicate that the cementitious fillers were generally effective in reducing the moisture susceptibility of HMA mixtures. The finer the hydrated lime particle, the more resistant the asphalt mixtures. In addition, dynamic shear rheometer test was conducted on asphalt mastics to explore the stiffening effect of different cementitious fillers.

A Study on the Increase in the Durability of Asphalt Paving Mixtures

A novel approach of increasing the durability of the asphalt-paving mixtures was attempted in this study by pretreatment of the aggregate surface with styrene butadiene rubber (SBR) latex as an antistripping additive (ASA). The boiling water test showed that the pretreatment method could increase the asphalt–aggregate bond strength effectively. This result was confirmed by the indirect tensile test and the stiffness index measurement of the asphalt-paving mixtures. Even though the conventional method of direct addition of ASA to the asphalt could also improve the asphalt–aggregate bond strength compared to the asphalt paving mixtures without ASA, the performance was poorer than the pretreatment method because of its inherent disadvantages of losing the effectiveness of ASA in hot asphalt. Increase of pretreatment drying time, drying temperature, and ASA concentrations could improve the asphalt–aggregate bond strength confirmed by the boiling water test. Increase in pH of the contacting water showed a detrimental effect on the asphalt paving mixtures by dissociation of the acidic functionalities of the asphalt to disrupt the asphalt–aggregate bond.

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

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

Significance Evaluation of Material and Additive Factors Influencing Moisture Susceptibility of Asphalt Mixtures

Abstract Many factors have been identified to have influences on the moisture susceptibility of asphalt mixtures. This research study attempts to evaluate such factors as binder type, aggregate type, mixture type, additive usage, additive type, additive application approach, and additive organic nature. Tensile strength ratio (TSR) was tested on twelve asphalt mixtures of three types, with two binders and three aggregates, and with improving measures as three antistripping additives and two application approaches. Multiple variable statistical analyses were employed on the TSR data in assessing the significance of the factor. Test results and data analyses indicate that the extent of the influence varies considerably from one factor to another. The styrene-butadiene-styrene modified binder is superior to neat petroleum binder for producing asphalt mixtures subject to damp conditions. Granite, basalt, and limestone aggregates make asphalt mixtures that are least, in-between, and most resistant to moisture damage, respectively. Compared with dense graded asphalt concrete (AC) and stone matrix asphalt (SMA) mixtures, porous asphalt macadam (AM) mixtures are more prone to stripping. The usage of inorganic hydrated lime and Portland cement, and organic amine antistripping agent can substantially improve the moisture susceptibility of asphalt mixtures; the wet approach for applying the inorganic additives can result in better effects than the dry approach. Different additives show little difference in improving effects with mixed trends and the inorganic and organic additives are similar in performance with variations that are immaterial.

Evaluation of HMA moisture damage in Wisconsin as it relates to pavement performance

The Wisconsin Department of Transportation (WisDOT) has been using the tensile strength ratio (TSR) test (ASTM D-4867) to predict the potential susceptibility of asphalt mixture to moisture damage and other associated pavement deterioration. The objectives of this paper are to evaluate the relationship between the performance of asphalt pavements in the field and the TSR values measured in laboratory on the original asphalt mixtures used in constructing pavements, and to evaluate the effect of anti-stripping additives on field performance. To assess the moisture damage problem in the field, 21 existing WisDOT pavement sections that were built prior to the adoption of the TSR parameter as a requirement, were selected to cover a wide range of locations and aggregate sources. The TSR and the pavement performance data (pavement distress index or PDI) for these projects were collected from the WisDOT pavement management database. The results indicated no relationship between TSR and field pavement performance as measured by the PDI, and no relationship between TSR and specific pavement distresses that are related to moisture damage (surface raveling and rutting). To evaluate the effect of using anti-stripping additive, a database study and a laboratory study were conducted. The database showed an effect of using anti-stripping additives on the pavement performance and also on the specific pavement distresses that are related to moisture damage. In laboratory testing, anti-stripping additive was not found to change the rheological properties of asphalt binders, nor to improve the rutting and fatigue related properties of asphalt binder as measured by the dynamic shear rheometer (DSR). However, they were found to increase the adhesion of asphalt binder to selected mineral aggregate surfaces, especially when the binder bond is exposed to water. These findings lead to believe that better field performance is achieved by better adhesion between binders and aggregates. The findings also point out that although the TSR testing is sensitive to the use of anti-stripping additives, it does not provide a good simulation of factors playing roles in critical distresses such as rutting and raveling. What could be more effective is a simpler test allowing direct measure of adhesive bond between aggregates and asphalts. Such a test could replace the TSR in making a decision to require or not require the use of anti-stripping additive. The pull-off tensile strength test by the Pneumatic Adhesion Tensile Testing Instrument (PATTI) is also shown to give promising results.

Effect of antistripping additives on environmental damage of bituminous mixtures

The main objective of this study was to investigate the effect of environmental damage (stripping) on the hot mix asphalt (HMA) creep behavior. To achieve this objective, 24 different HMA combinations using different mix parameters were evaluated for their resistance to static creep deformations. The mix parameters include: two types of asphalt cement, three types of aggregate gradation, and two types of antistripping additives (limestone dust and calcium stearate hydroxide). Marshall specimens were prepared at optimum asphalt contents and tested for static creep. Part of the prepared specimens were exposed to freezing–thawing conditioning according to AASHTO T283. The findings of this study indicated that conditioning of HMA specimens has a significant effect on the increase of creep deformation. This is especially true for open graded aggregate gradation mixes. For unconditioned mixes and conditioned mixes, prepared using mid and upper limits of ASTM specification for dense graded aggregate, the creep deformation of mixes prepared using 80/100 asphalt was less than that for mixes prepared using 60/70 asphalt. The opposite trend was noticed for conditioned specimens prepared using open graded aggregate gradation. Antistripping additives showed significant effect on reducing stripping and creep behavior. Mixes which used calcium stearate hydroxide additive showed less stripping and creep deformation than those which contained limestone dust additive.

Characterization of Thermal Degradation of Liquid Amine Anti-Strip Additives in Asphalt Binders Due to RTFO and PAV-Aging

Abstract In this study, thermal degradation of amine-based liquid anti-strip additives was evaluated due to RTFO-aging and PAV-aging according to AASHTO T 240 and AASHTO R 28 test methods, respectively. The surface free energy (SFE) characteristics of asphalt binders before and after aging were used as a tool for this evaluation. Two asphalt binders, namely PG 64-22 and PG 70-28, and two anti-strip additives, namely AD-Here HP Plus and Redicote E-6, were evaluated. It was observed for 0.75 % AD-Here HP Plus in PG 64-22, mixing at 163°C is more effective than mixing at 145°C with respect to increase in SFE. Also, both RTFO and PAV-aging decrease the total SFE of asphalt binders; both the aging processes are more effective in PG 64-22. In addition, the beneficial effect of anti-strip additives in acid-base characteristics of asphalt binders is severely reduced by RTFO and PAV-aging. Finally, the chemical model of asphalt binder, proposed by Wasiuddin et al., was expanded to include the SFE characteristics of asphalt binders due to aging.

Effect of Antistrip Additives on Surface Free Energy Characteristics of Asphalt Binders for Moisture-Induced Damage Potential

Abstract In this study, the effect of antistrip additives on asphalt binders was evaluated by both laboratory tests and a proposed chemical model of asphalt binder based on the surface free energy characteristics. Two performance graded asphalt binders, namely, PG 64-22 and PG 70-28 and two amine-based liquid antistrip additives, namely, AD-Here HP Plus and Redicote E-6 were evaluated at different percentages (0.25 %, 0.75 %, and 1.5 %). It was found that 1.5 %AD-Here HP Plus and 1.5 % Redicote E-6 increased the total SFE of PG 64-22 by 67 % and 208 %, respectively. Also, the acid components of PG 64-22 and PG 70-28 are 2.9 dyne/cm and 2.5 dyne/cm, respectively, whereas, the corresponding base components are 0.4 dyne/cm for both. With the addition of 1.5 %. Redicote E-6 in PG 64-22, the acid component of the binder reduced by 92 % and the base component of the binder increased by 1141 %.

The effects of damage evaluation techniques on the prediction of environmental damage in asphalt mixtures

The main objective of this study was to investigate the effects of evaluation methods on the prediction of environmental damage (stripping) of hot mix asphalt (HMA). To achieve this objective, four different environmental damage evaluation techniques were used to evaluate asphalt mixtures prepared using different mix parameters. The environmental damage evaluation techniques include either percent reduction in indirect tensile strength or Marshall stability or percent increase in static creep deformation due to environmental damage. In addition, theTexas boiling test which is based on visual evaluation of the percent of coated aggregate was used for environmental damage evaluation. The findings of this study indicated that the estimated environmental damage is significantly affected by the method of evaluation. Retained indirect tensile strength and retained stability were found to be less sensitive to environmental damage. Moreover, the static creep test was the only method used that was able to monitor the effect of used asphalt and aggregate gradation on the environmental damage of HMA, while the effect of antistripping additives on reduction stripping was easily monitored by the Texas boiling and static creep test. Finally, it was found that different environmental damage evaluation techniques revealed different results of using calcium stearate hydroxide.

Characterization of Chemical Reactivity of Liquid Antistripping Additives Using Potentiometric Titration and FTIR Spectroscopy

Chemical reactivity of two liquid antistripping additives mixed with two bitumens of diverse acid numbers was evaluated. Additives present in the blends were detected by use of potentiometric tit ...

A Procedure to Quantify Organic Antistrip Additives in Asphalt Binders and Mixes

Stripping is a phenomenon of loss of bond or adhesion between the asphalt binder and the aggregate in asphalt mixes. Stripping frequently results from the presence of water, and most agencies require the use of antistrip additive to control moisture damage. However, there is no simple and quick method for detecting the presence and the amount or percentage of organic antistrip additive in asphalt binders or mixes. This paper presents a procedure based on solid-state spectrophotometry to detect qualitatively and quantitatively the presence of amine-based antistrip additive in asphalt binders and mixes. The developed procedure gives results that are quantifiable and reproducible with low coefficients of variation.

Long-Term Effectiveness of Antistripping Additives

Hydrated lime and liquid antistripping agents are often used as additives in asphalt mixes to improve their resistance to moisture damage. Most laboratory studies have evaluated the effectiveness of these additives on the basis of a short-period intensive moisture conditioning procedure, usually a freeze–thaw cycle. Whether this short-term conditioning sufficiently simulates the actual field conditions is unknown. Questions have arisen about the performance of asphalt mixes exposed to moisture for a long period and the effectiveness of antistripping additives after long-term conditioning. This research was conducted in the laboratory to answer these questions to some extent by two test methods: the indirect tensile strength ratio test and the flexural beam fatigue test. A moisture-sensitive mix was treated with the hydrated lime and liquid antistripping agents, saturated by vacuum, and conditioned in a humid environment for a period of up to 1 year. Mix properties were measured and analyzed every 4 months. It was found that most of the detrimental effects of moisture occurred in the first 4 months, and the reduction of strength or stiffness in the late stages became small. Both tests revealed that the antistripping additives were effective even after 1 year of moisture conditioning. Equivalency between the short-term intensive conditioning and the long-term mild conditioning was also found in this study.

Long-Term Effectiveness of Antistripping Additives: Laboratory Evaluation

Hydrated lime and liquid antistripping agents are often used as additives in asphalt mixes to improve their resistance to moisture damage. Most laboratory studies have evaluated the effectiveness of these additives on the basis of a short-period intensive moisture conditioning procedure, usually a freeze-thaw cycle. Whether this short-term conditioning sufficiently simulates the actual field conditions is unknown. Questions have arisen about the performance of asphalt mixes exposed to moisture for a long period and the effectiveness of antistripping additives after long-term conditioning. This research was conducted in the laboratory to answer these questions to some extent by two test methods: the indirect tensile strength ratio test and the flexural beam fatigue test. A moisture-sensitive mix was treated with the hydrated lime and liquid antistripping agents, saturated by vacuum, and conditioned in a humid environment for a period of up to 1 year. Mix properties were measured and analyzed every 4 months...

A Laboratory Study of the Effectiveness of Various Additives on Moisture Susceptibility of Asphalt Mixtures

Antistripping additives are used routinely to improve water resistance of asphalt mixtures. Different additives have different improvement effectiveness in water resistance. In this study, the effects of various additives on the moisture susceptibility of asphalt mixture are studied with the retained Marshall stability test, Lottman test, and immersion wheel tracking test. Asphalt mixtures were modified with Portland cement, hydrated lime, lime slurry, and liquid antistripping agents. The results show that the lime-slurry-treated asphalt mixtures have better resistance to moisture susceptibility than mixtures treated with other materials, and have better long-term moisture stability than the liquid antistripping agents. The liquid-antistripping-agent-treated asphalt mixtures have better resistance to moisture stability before long-term aging. Portland-cement-treated asphalt mixtures show slightly improved water resistance. Asphalt mixtures become more resistant to moisture damage through short-term aging. It was confirmed that the Lottman and the immersion tracking methods are better methods to evaluate moisture susceptibility than the retained Marshall stability methods.