Polymer-modified Emulsion Research Articles

Investigating the Laboratory Performance of Crumb-Rubber-Modified and High-Float Polymer-Modified Asphalt Emulsions in Chip Sealing

Chip sealing is a widely popular pavement maintenance treatment because of its low initial cost and convenient construction process. Bleeding, loss of aggregate, reduced skid resistance, and aging have been identified as the most common type of distress that lead to the failure of chip sealing. The objective of this study was to evaluate the laboratory performance of a crumb-rubber-modified asphalt emulsion and a high-float polymer-modified asphalt emulsion in chip sealing and to evaluate the effects of crumb rubber as a modifier as well as its utilization as part of the aggregate stone. To achieve this objective, four types of emulsion were evaluated, namely a crumb-rubber-modified asphalt emulsion (CRS-2TR), a high-float polymer-modified emulsion (CHFRS-2P), a polymer-modified emulsion (CRS-2P), and a conventional unmodified emulsion (CRS-2). Based on the results of the experimental program, it was concluded that the aggregate retention properties of polymer-modified and crumb-rubber emulsions were superior to the unmodified emulsion. In addition, the granite aggregate performed better than the granite–crumb-rubber blends regardless of the type of emulsion used. However, a small percentage of crumb rubber may be used in chip sealing without significantly affecting its performance. According to the rheological and physical test results, CHFRS-2P showed the highest useful temperature interval (92.7), followed by CRS-2P (87.8), CRS-2TR (82.6), and CRS-2 (76.7). Based on Fourier transform infrared spectroscopy and saturate, aromatic, resin, and asphaltene test results, both CRS-2TR and CHFRS-2P showed lower carbonyl indices growth as compared to the other emulsions, indicating superior resistance to aging.

Microstructural Properties of Polymer-Modified Bitumen Emulsion-Cement Composites Considering the Production Method

The present study investigated the effect of the polymer-modified bitumen emulsion production method on the properties of cement-polymer emulsion paste. Modified emulsions were made using three methods, including comilling, soap prebatching, and postblending. During comilling, water, acid, styrene-butadiene rubber polymer, emulsifier, and bitumen were added simultaneously to the colloidal mill. In soap prebatching first water, acid and emulsifier were mixed to produce the soap. Then, polymer was added to the soap, and the resulting compound is added simultaneously to a colloidal mill with the bitumen. During postblending, water, acid, and emulsifier were first mixed. Then, this mixture and bitumen were added to the colloidal mill. Next, polymer was added to obtain the polymer-modified bitumen. Portland cement was added to the produced polymer-modified emulsions and cured at 40°C for 72 h. Field emission scanning electron microscopy and energy dispersive X-ray spectroscopy tests were performed on the samples to investigate the weight distribution, dispersion of elements, and hydration rate of cement particles. Using the X-ray diffraction test, cement hydration products were identified, and the particle dispersion of these products was investigated. Moreover, the microstructure, adhesion, and elastic modulus of the samples were examined using atomic force microscopy. Based on the results and analyses, the highest homogeneity in particles distribution due to hydration of cement and the highest elastic modulus in cement samples were related to those made by postblending, whereas the soap prebatching methods resulted in the highest adhesion in cemented samples.

Short-Term Field Performance and Cost-Effectiveness of Crumb-Rubber Modified Asphalt Emulsion in Chip Seal Applications

Chip sealing is a commonly used pavement maintenance technique that aims to delay pavement deterioration by reducing water infiltration and restoring skid resistance. The objective of this study was to evaluate the short-term field performance and cost-effectiveness of chip seals prepared with different types of asphalt emulsion and application rates. A newly introduced crumb-rubber modified asphalt emulsion was evaluated, one that allows chip seal installation at the same temperature as a standard emulsion. Types of emulsion included a crumb-rubber modified asphalt emulsion (CRS-2TR), a polymer-modified emulsion (CRS-2P), and a conventional unmodified emulsion (CRS-2). Application rates were obtained from the Louisiana Department of Transportation and Development (DOTD), the Texas Department of Transportation (DOT) specifications, and from the chip seal design method recommended in NCHRP Report 680. Seven chip seal sections were constructed and monitored regularly over a 12-month period. In the northbound lane, the chip seal section constructed with CRS-2TR (0.37 gal per square yard [gsy]) was the best performer statistically. In the southbound lane, the chip seal sections constructed with CRS-2TR and CRS-2P (0.31 gsy) performed similarly. Furthermore, the maximum Service Life Extension (SLE) was observed for the CRS-2TR (0.31 gsy) chip seal sections, whereas the chip seal sections constructed with CRS-2 had the lowest SLE. In addition, the most cost-effective chip seal section was achieved by the application of CRS-2TR emulsion at the Louisiana DOTD recommended emulsion application rate.

Rheological and performance characterisation of the bitumen recovered from different emulsions for cold mixtures

In recent years, over-stabilized polymer-modified bitumen emulsions have been widely used to improve the mechanical properties of cold bituminous mixtures. However, the effect of the polymer modification process on the emulsion performance have not been investigated. The present paper deals with the analysis of the binders recovered from a reference unmodified bitumen emulsion and two polymer-modified emulsions, respectively including SBR-latex added after bitumen emulsification (post-blending) and SBS added before bitumen emulsification (pre-blending). The laboratory investigation included the linear viscoelastic characterisation and the evaluation of the resistance to permanent deformations and damage. The results showed that the polymer-modified bitumen emulsions have a more pronounced elasticity with respect to the unmodified emulsion, allowing achieving a higher performance against permanent deformations and fatigue. In addition, the SBS modified bitumen emulsion (pre-blending) has better properties than the latex modified emulsion (post-blending), as a consequence of the different chemical structure that the modification process produces.

Effects of emulsion types, application rates, and crumb rubber on the laboratory performance of chip seal

Chip sealing is a commonly used pavement maintenance method that aims to delay pavement deterioration by reducing water infiltration and restoring skid resistance. Loss of aggregate and bleeding are considered the major failure mechanisms in chip seal, and therefore, are the main design criteria for this treatment method. The objective of this study was to evaluate the laboratory performance of chip seals prepared with different types of asphalt emulsions, application rates, and aggregate blends. A newly introduced crumb rubber modified asphalt emulsion was evaluated that allows chip seal installation at the same temperature of a standard emulsion. Types of emulsion included a crumb-rubber modified asphalt emulsion (CRS-2TR), an asphalt rubber (AC20-TR), a polymer-modified emulsion (CRS-2P), and a conventional unmodified emulsion (CRS-2). Application rates were selected based on the Louisiana Department of Transportation and Development (LaDOTD) and the Texas Department of Transportation (TxDOT) specifications as well as from the chip seal design method recommended in NCHRP Report 680. A 90-10 aggregate blend of lightweight aggregate (LWA) and rubber aggregate (RA) was also investigated.The loss of aggregate was measured using two laboratory performance tests: the sweep test (ASTM D 7000) and the Pennsylvania Aggregate Retention Test (PART). The strength of adhesion of the four emulsions was also evaluated using the Bitumen Bond Strength (BBS) test. While asphalt rubber was the best performer in terms of aggregate loss, CRS-2P and CRS-2TR performed similarly followed by the conventional emulsion. Results of the BBS test showed a similar rank for the bond strength of the emulsions. It was also observed that the loss of aggregates in chip seal decreased with the increase in application rate. However, incorporation of rubber as aggregate in chip sealing increased the loss of aggregate in the specimens indicating poor adhesion between the emulsions and the rubber aggregate.

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.

Performance evaluation of fog seals on chip seals and verification of fog seal field tests

With an increasing emphasis on pavement preservation treatments due to economic concerns over the high costs of paving materials, one of the most cost-effective pavement preservation treatments, chip seals, now constitutes a significant proportion of the pavement preservation treatments used in the North Carolina highway network. To mitigate a major problem with chip seals, i.e., the loose aggregate particles, fog seals, which are composed of an emulsified product placed on top of the chip seal, can be used to help control the loose aggregate. For this study, fog seals were applied on top of newly fabricated chip. The surface texture of the fog-sealed chip seals was analyzed using the British pendulum test and a three-dimensional laser. Also, fog seal field test methods that were developed to suggest appropriate traffic opening times after fog seal construction were verified. The main findings presented in this paper are that: (i) the use of polymer-modified emulsions improves fog seal performance in terms of better aggregate retention and bleeding resistance; (ii) the skid resistance problems are not evident once the fog seal is applied on the recommended chip seal type; (iii) the relationship between skid number and mean profile depth can be determined based on three trends that are dependent on traffic loadings, and (iv) although the fog seal field tests were unable to be completed due to safety concerns, it can nonetheless be recommended that approximately 60 min after fog seal construction is an appropriate traffic opening time.

아스팔트 도로포장 유지보수용 표면처리공법의 공용성 평가

PURPOSES : The objective of this study is to evaluate the performance properties of chip seals and fog seals with polymer-modified emulsions. METHODS : The performance of chip seals and fog seals was evaluated on the basis of common issues in surface treatments. Granite aggregate and four types of asphalt emulsions (one of the unmodified and three of the modified emulsions) were used considering the usage in field. A Vialit test was performed to determine the aggregate retention, and the MMLS3 (Third Scale Model Mobile Load Simulator) test was conducted to determine the aggregate retention, bleeding, and rutting. In addition, the fog seal specimens were tested by the BPT (British Pendulum Test) to evaluate skid resistance. RESULTS AND CONCLUSIONS : Overall, the polymer-modified emulsions (PMEs) showed better aggregate retention and bleeding resistance for both chip seals and fog seals. When comparing the performance of the PMEs, the difference was not considerable. In addition, PMEs present significantly better rutting resistance than unmodified emulsions. For skid resistance, if the recommended mix design is applied, the specimens do not cause issues with skid resistance. Although all of the fog seal specimens were over the criteria for skid resistance, the specimen fabricated by the high emulsion application rate (EAR) of the unmodified emulsion was nearly equivalent to the skid value criteria. Therefore, the use of an unmodified emulsion with a high EAR should be carefully applied in the field.

택코트용 폴리머 개질 유화아스팔트 개발 및 성능 평가

PURPOSES: The objectives of this study were to develop a new polymer-modified emulsion for application to tack coats and to evaluate its properties by comparing it with other types of asphalt emulsions, with the goal of providing an enhanced tack coat material for use in construction. METHODS: Modified asphalt binders were developed from using SBS and SBR latex in the laboratory, and their fundamental properties, such as their penetration index and PG grade, were evaluated. Based on the properties, a new tack coat material was developed. To evaluate the newly developed asphalt emulsion, the bonding strength between the two layers of HMA was measured by applying a uniaxial tensile test and shear test. For the tests, a total of four different conditions were applied to the specimens, including the developed asphalt emulsion, latex modified asphalt emulsion, conventional asphalt emulsion, and non-tack coating. RESULTS AND CONCLUSIONS: Overall, the developed asphalt emulsion exhibits the best bonding strength behavior among all of the three types. Also, the two types of polymer-modified emulsions were found to be better for application for use as a tack coat than a conventional emulsion. Especially, at a high temperature (), the conventional asphalt emulsion no longer acts as a tack coating material. Therefore, the polymer-modified emulsion should be considered for application to tack coat construction during the summer.

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.

Evaluation of Reclaimed Asphalt Pavement Materials from Ultra-Thin Bonded Bituminous Surface

Abstract Ultra-thin bonded bituminous surface (UBBS) is a surface treatment that consists of a thin, gap-graded hot-mix asphalt (HMA) layer applied over a thick polymer-modified emulsion membrane. The aggregates and asphalt used in UBBS are of very high quality. The objective of this study is to evaluate whether reclaimed asphalt pavement (RAP) materials from existing UBBS layers can be used in chip seal and Superpave mixtures. UBBS RAP were studied with two different polymer-modified emulsions to assess their performance as precoated aggregates in chip seal using ASTM D7000-04 sweep test. Three different Superpave mix designs were developed for both 12.5-mm and 9.5-mm nominal maximum aggregate sizes (NMAS) using three different percentages (0 %, 10 %, and 20 %) of UBBS RAP materials. The designed Superpave mixes were then tested using the Hamburg wheel tracking device (HWTD) and the modified Lottman tests. Sweep test results showed that UBBS millings did not improve chip retention. Superpave mix design data indicated volumetric properties of Superpave mixes with UBBS millings met all requirements. HWTD and modified Lottman test results indicated all designed mixes performed better with the addition of UBBS RAP materials.

Cracking resistance of thin-bonded overlays using fracture test, numerical simulations and early field performance

Thin-bonded bituminous overlays are becoming an increasingly popular pavement maintenance treatment, which can be used to restore smoothness, seal and renew the pavement surface and increase skid resistance. Thin-bonded overlays (TBOs) are constructed using a specialised type of paving equipment called a ‘spray paver’. A spray paver combines the operation of applying a tack coat and laying down asphalt concrete in a single pass. This allows for the application of a high rate of polymer-modified asphalt emulsion tack coat. Due to reduced thickness, cracking distress is more of a concern in this type of system. This paper describes a new approach for the evaluation of the cracking performance of TBO systems through fracture mechanics-based testing of laboratory and field specimens. Computer simulations and early field performance data are also used in the evaluation. This study is conducted in the context of three field projects which encompass seven different pavement test sections. The test sections allowed a number of variables to be studied, including type and application rate of tack coat emulsion and type of hot-mix asphalt gradation structure (gap graded vs. dense graded). Comparisons are also made between overlays constructed using spray paver and conventional paving process. All seven sections were computationally simulated to evaluate their performance in the context of thermal and reflective cracking potential. Fairly good agreement is observed between laboratory tests, computer simulations and field performance data. The results indicate that good thermal and reflective cracking resistance are expected from TBOs. Furthermore, it was observed that the cracking performance of TBOs depends on the type of gradation for the overlay mixture and the tack coat emulsion type and its application rate.

Methods for Fog Seal Field Test with Polymer-Modified Emulsions

Findings from a laboratory evaluation of fog seal emulsions are presented. Curing time and adhesive behavior of polymer-modified emulsions (PMEs) were compared with those of unmodified emulsions as fog seal materials. The study showed that polymer modification could improve certain properties of emulsions, such as an increase in adhesion. The evaporation test and the pneumatic adhesion tension testing instrument were used to investigate emulsion curing and adhesive behavior. Also, the rolling ball test and the damping test were developed as in situ test methods to determine an appropriate traffic opening time for roadways treated with fog seals. Finally, the third-scale Model Mobile Load Simulator was employed to compare the performance properties of the fog seal emulsions. The following main findings are presented: use of PMEs improved the emulsion bond strength and lessened the time a road was closed to traffic; PMEs showed more effective emulsion curing rates than did unmodified emulsions; strong relationships existed between the bond strength and both the measured rolling distance (from the rolling ball test) and the measured percentage of stained area (from the damping test); field test methods could be used to help determine whether emulsions were fully cured; and PMEs exhibited better aggregate retention and bleeding performance properties than did unmodified emulsions as a fog seal.

Recovery and Laboratory Testing of Asphalt Emulsion Residue

This study involves application of two new test methods to the recovery of asphalt emulsion residue, long-term oxidative aging of the residue, and mechanical testing of the unaged and aged residue to determine low- and intermediate-temperature rheological properties. The new methods are the simple aging test (SAT), which is a thin-film (300 μm) oxidative aging test, and a dynamic shear rheometry technique (commonly referred to as 4-mm DSR), which allows testing to −40°C and requires only 25 mg of material. Three polymer-modified emulsions are recovered by two methods: AASHTO PP 72-11 Method B and use of an SAT plate. Both methods use the same evaporative technique to recover the residue (6 h at 60°C in a forced draft oven). The rheological properties (m-value, G* sin d, and ductility) of the recovered emulsion residues by both methods are reported as well as the rheological properties of the aged emulsion using the SAT. The rheological properties of the unaged emulsion residues recovered are roughly equivalent. The proposed SAT recovery method and application of 4-mm DSR offer significant improvements over Method B and current DSR methodology. The recovery process is simpler with the SAT plate than with Method B, and the SAT plate has been designed so that it can be placed directly in a standard pressure aging vessel (PAV) for long-term aging, and the time required for standard PAV aging is reduced from 20 to 8 h. There is no extrapolation of intermediate-temperature DSR data to low temperature. The error from instrument compliance at low temperature is corrected in the 4-mm DSR procedure.

Evaluation of polymer-modified chip seals at low temperatures

This paper compares the performance of chip seals constructed with polymer-modified emulsion (PME; CRS-2L) versus those constructed with unmodified emulsion (CRS-2). The overall performance evaluation is based on aggregate retention performance. The adhesion of the emulsions is examined using the Vialit test with various curing times and temperature conditions. To evaluate the aggregate retention performance of the chip seals, we used the Vialit test, the flip-over test and the third-scale Model Mobile Loading Simulator (MMLS3). The results from these tests indicate that the PME (CRS-2L) enhances aggregate retention performance, and does so more significantly in the early stages and at low temperatures.

Chip Seal with Lightweight Aggregates for Low-Volume Roads

Chip seal is widely used for preventive maintenance of low-volume roads in many states, including Kansas. Although there are no distinct design guidelines for using lightweight aggregates in chip seals, these aggregates are extensively used in Kansas to limit windshield damage caused by flying chips. Lightweight aggregates were used with polymer-modified asphalt emulsion to determine proper aggregate and emulsion application rates to minimize chip loss in longer-lasting chip seals on low-volume roads. A statistical analysis was conducted to evaluate chip seal performance characteristics that include aggregate retention, aggregate embedment depth, and rutting. Results show that aggregate retention and embedment depth depend on aggregate–emulsion interaction, whereas rutting depends on the type of aggregates used.

Evaluation of Performance and Cost-Effectiveness of Polymer-Modified Chip Seals

Chip seals provide a durable and functional pavement surface and serve as a highly economical highway maintenance option when constructed properly. Data and literature suggest that chip seal sections constructed with polymer-modified emulsions (PMEs) provide better initial and long-term performance than those with unmodified emulsions and extend the overall service life of pavements. Laboratory test results were used to compare the performance of chip seals constructed with PME (CRS-2L) with those constructed with unmodified emulsion (CRS-2). Both types of emulsion are used to fabricate samples in the laboratory. The overall performance evaluation in the study is based on rutting, bleeding, and aggregate retention performance measured by the third-scale model mobile loading simulator (MMLS3). Results from these MMLS3 tests indicate that, because of improved mechanical properties, the CRS-2L PME enhances chip seal performance to extend the service life of the pavement. Life-cycle cost analysis of two scenarios (one rehabilitation technique that uses chip seal over existing hot-mix asphalt pavement and another that uses chip seal as original construction), indicates that PME becomes a cost-effective solution if the polymer modification can extend the service life of the chip seal from 5 years (typical service life of an unmodified chip seal) to 7 years. The limited laboratory performance test results provide strong evidence that this extension is possible with the CRS-2L PME used in the study.