Bitumen Bond Strength Research Articles

Performance Evaluation of Chip Seals for Higher Volume Roads Using Polymer-Modified Emulsions: Laboratory and Field Study in North Carolina

Abstract This paper presented a study to evaluate the performance of chip seals for higher traffic volume roads. The evaporation test, bitumen bond strength (BBS) test, and Vialit test were used to investigate curing and adhesive behavior. For the laboratory performance, the third-scale model mobile load simulator (MMLS3) was employed to test for aggregate retention, bleeding, and rutting performance. In field, a total of ten test sections were constructed on three different traffic volume roads using different materials and seal types. Some of the field samples were extracted and moved to the laboratory for performance testing. Also, the field sections were monitored to compare the field performance with the laboratory performance. The main findings presented in this paper were as follows: (1) the laboratory test results indicated that the use of polymer modified emulsions (PMEs) improved the chip seal performance in all areas, i.e., curing and adhesive behavior, aggregate retention, bleeding, and rutting; and (2) the field observations indicated that PME-A (styrene butadiene styrene (SBS) polymer-modified emulsion) performs the best of all the emulsions, regardless of seal type and traffic volume.

Study on Early Adhesive Characteristic of Chip Seals Using a Surface Energy Approach

PURPOSES : The objective of this study is to evaluate the early adhesive characteristic of asphalt emulsions, including polymer-modified emulsions, for chip seals using the surface energy concept, the bitumen bond strength (BBS) test, and the Vialit test. METHODS : Two general methods, the BBS test and Vialit test, were applied to investigate the bond strength and the aggregate loss, respectively. A new theory, the surface free energy (SFE) theory, was used to evaluate the adhesive characteristic between the emulsion and the aggregate. Based on the theory, the contact angles were measured, and then the surface energy components were calculated. Using those components, the work of adhesion (Wa) was calculated for each emulsion. To ensure reliable results, all the tests were performed under the same conditions, i.e., at for 240 minutes of curing time. For the materials, three emulsions (CRS-2, CRS-2L, and CRS-2P) and one aggregate type (granite) were employed. RESULTS AND CONCLUSIONS : Under the same conditions, the modified emulsions showed better adhesive characteristics and curing behaviors than the unmodified emulsions. In addition, there was no significant difference between the various modified emulsions. One of the important findings is that the analysis by Wa presents more sensitive results than other methods. The results of the Wa showed that the CRS-2P emulsion has the best adhesive characteristics. Consequently, the use of modified emulsions for chip seals could prevent aggregate loss and allow open traffic earlier.

Effect of Aging on Adhesion Properties of Asphalt Mixtures with the Use of Bitumen Bond Strength and Surface Energy Measurement Tests

The interaction between asphalt binder and aggregate is fundamental to ensure adequate performance of asphalt mixtures, mainly in the presence of water. The work of adhesion generated between both materials directly affects the resistance of asphalt mixture to moisture damage, because it measures the ease with which water can displace asphalt binder from the aggregate surface. The objective of this study was to characterize the bond strength between asphalt and several aggregate sources. A PG 64-22 neat binder was modified with several additives to determine the effect on adhesion: polymers, nanomaterials, and adhesion promoters. To measure the strength of adhesion, the bitumen bond strength (BBS) test and contact angle measurements between asphalt binder and the aggregate surface by means of goniometry were used. The surface energy of the asphalt and the aggregate, with and without the presence of water, was estimated also. Testing was performed on all binders and on each binder–aggregate combination after ( a) rolling thin-film oven (RTFO) aging and ( b) RTFO and pressure aging vessel aging. The BBS results identified differences in bond strength as a result of moisture conditioning and aging. The differences depended on the aggregate source and binder type. Different failure modes were also observed (i.e., cohesive, adhesive). The results also indicated an increase in strength of adhesion associated with the aging process: the main resistance gain was observed after RTFO aging. Finally, changes in bond strength were compared with functional composition changes associated with the aging process and related to changes in performance.

아스팔트 도로포장 유지보수(표면처리)용 유화아스팔트의 양생 및 점착거동특성 평가

PURPOSES : The objective of this study is to evaluate the curing and adhesive behavior of asphalt emulsions including polymer-modified emulsions for chip seals and fog seals. METHODS : For the laboratory testing, the evaporation test, the bitumen bond strength (BBS) test, and the Vialit test are used. Also, the rolling ball test and the damping test are employed to evaluate the curing properties of the fog seal emulsions. In order to conduct all the tests in controled condition, all test procedures are performed in the environmental chamber. The CRS-2L and the SBS CRS-2P emulsions are used as a polymer-modified emulsion, and then unmodified emulsion, the CRS-2, is compared for the evaluation of chip seal performance. For the fog seal performance evaluation, two types of polymer-modified emulsions (FPME-1 and FPME-2) and one of unmodified emulsion, the CSS-1H, are employed. All the tests are performed at different curing times and temperatures. RESULTS AND CONCLUSIONS : Overall, PMEs show better curing and adhesive behavior than non-PMEs regardless of treatments types. Especially, the curing and adhesive behavior of PMEs is much better than non-PMEs before 120 minutes of curing time. Since all the test results indicate that after 120 minutes of curing time the curing adhesive behavior of emulsions, the early curing time, i.e., 120 minutes, plays an important role in the performance of chip seals and fog seals.

국내 아스팔트 콘크리트 포장용 택코팅제의 기초물성 평가

PURPOSES : The objective of this study is to evaluate the tack-coating material`s properties using the bitumen bond strength(BBS) test and damping test as function of changed curing times. In this study, bonding strength tests were performed according to the curing time of tack coating materials. METHODS : In order to investigate bonding characteristic of tack coating materials, the Pneumatic Adhesion tensile Testing Instrument(PATTI) device is used to measure the bond strength between the tack coating materials and aggregate substrate based on the AASHTO TP-91. Also, damping test as in situ test was used to determine an appropriate traffic openting time for construction vehicle. Four different tack-coating materials were used in this study. The BBS tests were performed a one hour curing and testing temperatures of , , and . Damping test was conducted at 30min, 60min, 90min, and 120 min of curing times with temperatures of and . RESULTS and CONCLUSIONS : The BBS test results show various bond strength as function of tack coat materials. At the same testing condition, A tack coat material shows almost two times higher than D tack coat materials although both materials are satisfied the criteria of material`s physical properties. Also, Dampting test results shows similar trend with BBS test result. The damping test result was significantly changed as function of tack coat materials. Based on this study, the tack coating material`s curing time is very important. Therefore, both curing time and the bond strength`s characteristic has to be considered in standard specification.

Evaluating Adhesion Properties and Moisture Damage Susceptibility of Warm-Mix Asphalts

Through development and evaluation of the warm-mix asphalt (WMA) mixture design process, increased moisture susceptibility has been cited as one of the potential critical failure modes for WMA. Reduced production temperatures can affect the drying of the aggregate before mixing, the development of adhesion at the asphalt–aggregate interface, and binder stiffness. The objective of this research is to identify the significance of these factors and to define their relative contribution to mixture resistance to moisture damage. To evaluate the contribution of asphalt binder–aggregate adhesion, the bitumen bond strength (BBS) test was implemented on dry and moisture-conditioned samples. The effect of production temperature was simulated by heating aggregate substrates to hot-mix asphalt (HMA) and WMA temperatures before applying the asphalt binder. Furthermore, the effect of reduced binder stiffness resulting from lower production temperatures was considered through establishing two controls for mixture performance testing: a conventional HMA and a mixture prepared at WMA temperatures without WMA additives. The relevance of these factors was established through comparison with mixture performance as measured by the reduction in dynamic modulus, as a function of conditioning cycles. Mixture sample preparation allowed for consideration of residual moisture in aggregate that might have been associated with WMA and provided a control HMA sample prepared under standard conditions to establish a performance benchmark. Recommendations were made for incorporation of these new test methods into current WMA mixture design specifications. In summary, both BBS and dynamic modulus testing indicated that specific WMA additives could improve the mixture's moisture resistance and could offset any negative effects from the reduced production temperatures on moisture susceptibility. Therefore, selecting appropriate warmmix additives during the mix design process can help mitigate potential moisture damage associated with WMA.

Development of Emulsion Residue Testing Framework for Improved Chip Seal Performance

To promote sustainability and optimize funding, state highway agencies are integrating pavement preservation strategies into the management of their roadway networks. Chip seals, a prominent pavement preservation alternative, are traditionally being used on low-volume roads with success in many states. However, as advancements in emulsion formulations continue and the use of chip seals on medium- and high-traffic facilities becomes more prevalent, there is a need to improve the methods to select and specify chip seal emulsions. The objective of this study was to develop an emulsion testing framework that captured properties related to critical distresses observed for in-service chip seals and considered the effects of traffic, environment, and aging. The proposed testing framework recommended the use of the dynamic shear rheometer and bitumen bond strength test to evaluate high-, intermediate-, and low-temperature performance. The testing protocols were applied to recovered and pressure aging vessel–aged emulsion residues from six emulsions widely used in Wisconsin, which included two emulsifier chemistries and two types of modification. The base binders before emulsification were also tested to assess the effects of the emulsification process. Results indicated that the proposed test methods could characterize material performance and differentiate between emulsion types and types of modification; however, additional research is needed to establish the relationship between laboratory-measured residue properties and performance of the full chip seal.

Evaluating the Effect of Warm-Mix Asphalt Technologies on Moisture Characteristics of Asphalt Binders and Mixtures

The effect of warm-mix asphalt (WMA) technologies on the moisture susceptibility of a mixture and the adhesion characteristics of the asphalt binder used in it was evaluated. A 9.5-mm Superpave® mixture designed with performance-grade asphalt PG 64-22 was used as the control mixture. Four types of WMA technologies were evaluated: Advera, Evotherm, Sasobit, and SonneWarmix. The Hamburg wheel-tracking device (HWTD) was used to evaluate the effect of each WMA technology on the moisture susceptibility of the mixture at three aging times and three aging temperatures. A liquid antistrip and hydrated lime were added to any mixture that failed the HWTD to determine if they could correct the failure. Because the moisture susceptibility of a mixture is related to failure in the adhesive bond between the binder and the aggregate, a pulloff test, the bitumen bond strength (BBS) test, was used to evaluate the impact of the WMA technologies on the adhesion characteristics of the asphalt binder. The HWTD test results indicated that the moisture resistances of all mixtures improved significantly with an increase in aging time or temperature. Mixtures aged at longer times and at higher aging temperatures exhibited the best performance. The addition of the antistrip agents improved the HWTD results. The BBS test showed that only Sasobit had a significant effect on the pull-off tensile strength of the binder, although only under dry conditions. Overall, no correlation between the BBS and the HWTD was found.

Measuring the Effect of Moisture on Asphalt–Aggregate Bond with the Bitumen Bond Strength Test

Understanding moisture damage mechanisms in asphalt pavements and evaluating the right combination of materials that are resistant to moisture damage are important. Moisture damage is the loss of strength or stiffness in asphalt mixtures caused by a combination of mechanical loading and moisture. Many test methods have been developed to evaluate loss of adhesion and cohesion in binders. However, a simple procedure to address moisture damage in the asphalt–aggregate interface is not available. The feasibility of the newly developed bitumen bond strength (BBS) test for moisture damage characterization was investigated. An experimental matrix that included various binders, modifications, and aggregates to account for the chemical and physical conditions in the aggregate–asphalt interface was completed. A statistical analysis was performed to verify reproducibility of the BBS test. The results indicated that the bond strength of asphalt–aggregate systems was highly dependent on modification and moisture exposure time. Polymers were found to improve the adhesion between asphalt and aggregate as well as the cohesion within the binder. Results from this study indicated that the BBS test was repeatable and reproducible. To further validate the effectiveness of the BBS test, a comparison of the BBS test results and the modified dynamic shear rheometer strain sweep test was conducted. The comparison showed that the BBS test could rank materials similarly to a more sophisticated and time-consuming test.

Correlating Rheological and Bond Properties of Emulsions to Aggregate Retention of Chip Seals

The development of binder stiffness and bond strength is critical for new chip seals: loose aggregates must be minimized once a road enters into service. A new test protocol is presented: called the bitumen bond strength (BBS) test for evaluating emulsion setting behavior, the protocol can be used to evaluate aggregate retention and raveling potential of chip seals. The time required for the asphalt emulsion to gain adequate strength and adhesion to aggregate chips depends on aggregate–binder compatibility, environmental factors, and mechanical action. BBS test results demonstrate bond strength development over a full curing interval for a variety of materials and curing conditions. Results obtained using the BBS test are compared with dynamic shear rheometer strain sweep results to investigate a correlation between bond strength and the rutting parameter G*/sin δ. BBS test results are also correlated to aggregate loss as measured by the sweep test. This research may contribute to the ongoing development of specifications for construction and performance properties of asphalt emulsions used in surface treatments.