Investigation of rheological properties of asphalt emulsions

Rheology is critical issue in the workability, stabilization and engineering performance of asphalt emulsions. The objective of this study is to investigate the rheological properties of asphalt emulsions. To achieve this goal, a preshear protocol was introduced and four kinds of asphalt emulsions were tested base on preshear. Firstly, the necessarity of preshear was analyzed and the suitable range of preshear rate and preshear time of the studied asphalt emulsions were given. Then, the rheological properties of asphalt emulsions were studied after preshear. Finally, the palierne model was modified and the storage/loss modulus of asphalt emulsions was accurately predicted by the modified palierne model. The results showed that it’s necessary to preshear asphalt emulsions before testing rheological properties. The viscosity, zero shear viscosity, storage and loss modulus of asphalt emulsions increase with the increase in solid content. The prediction results of the modified palierne model are better than that of palierne model. The storage/loss modulus of asphalt emulsions can be effectively predicted by the modified palierne model. This study has considerable meaning to the promotion of production and manufacturing of asphalt emulsions.

Structural Contribution of Cold In-Place Recycling Base Layer

Cold in-place recycling (CIR) of asphalt pavements is a process that has successfully been used for many years. The use of CIR for rehabilitation offers many advantages over traditional overlays due to its excellent resistance to reflective cracking and its environmentally friendly impacts. Despite the good performance and positive sustainability aspects of CIR, the structural contribution of the CIR base layer has not been well defined. In this research, CIR mixtures were designed with different asphalt emulsions. The mixtures were then subjected to dynamic modulus, repeated load triaxial, and flexural beam fatigue testing over a range of temperature and loading conditions. The performance test data generated were then used to develop CIR rutting and fatigue performance models used in the mechanistic analysis of flexible pavements. The technique used to develop the performance models leveraged the fact that the rutting and fatigue models for individual CIR mixtures were all within the 95 percent confidence interval of each other. A mechanistic analysis was conducted using the 3D-Move Mechanistic Analysis model. With the laboratory-developed performance models, the structural layer coefficient for the CIR base layer were developed for use in the 1993 AASHTO Guide for the Design of Pavement Structures. This analysis led to the determination of an average structural coefficient of the CIR base layer of 0.25.

Research on the Performance of Regenerant Modified Cold Recycled Mixture with Asphalt Emulsions

In order to study the mechanical properties and effect of a regenerant on a cold recycled mixture with asphalt emulsions (CRMEs), the moisture susceptibility, high-temperature performance, low-temperature performance, dynamic mechanical properties and durability of CRMEs were analyzed and evaluated by immersion splitting strength tests, freeze-thaw splitting strength tests, rutting tests, semi-circle bending tests, uniaxial compression dynamic modulus tests and indirect tensile tests. Scanning electron microscopy (SEM) was used to analyze the micromorphology of CRMEs modified with regenerant. Finally, a comprehensive evaluation system of five different CRMEs was established based on the efficacy coefficient method to quantitatively analyze the comprehensive performance of the CRMEs. The test results showed that the regenerant can significantly improve the water immersion splitting strength, freeze-thaw splitting strength fracture energy density, and fatigue resistance of CRMEs. However, the addition of regenerant affected the high-temperature performance of the cold recycled mixture. The dynamic modulus of the CRMEs first increased and then decreased with regenerant content increasing. When the regenerant content was 8%, the dynamic modulus of the CRMEs was the highest. Adding styrene-butadiene rubber (SBR) latex can improve the high-temperature performance of CRMEs, but the moisture susceptibility, low temperature performance and fatigue resistance of the cold recycled mixture were not significantly improved, and the dynamic modulus of the mixture was reduced. Based on the efficacy coefficient method, the optimal content of regenerant is 8%. Regenerant are potential modifiers for cold recycled mixture that they can significantly improve the dynamic mechanical properties and durability.

Effect of Damage Caused by Site Materials on the Performance of Nonwoven Geotextiles Impregnated With Asphalt Emulsions Used on Paving

A rehabilitation technique for asphalt pavements with geosynthetic is the application of impregnated nonwoven geotextiles between deteriorated and new asphalt overlays. The performance investigation of impregnated geotextiles proves that they are enhancing in mechanical and hydraulic properties. Although, the installation process may cause severe impacts on these materials’ performance. During the installation, the geotextile suffers damage due to the traffic of high load vehicles, as compactors and pavers, and the friction with granular materials found under its layer or poured above it. This paper aims to investigate how the damage caused by granular materials on nonwoven geotextiles impregnated with different asphalt emulsions effect on their strength resistance and permittivity. From two types of nonwoven geotextiles: polypropylene and polyethylene terephthalate, the comparison uses geotextiles in three conditions: not impregnated, impregnated with asphalt emulsion of rapid setting, and impregnated with asphalt emulsion changed by an elastomeric polymer. Part of the samples followed the damage according to ISO 10722 procedure, placed between three different scenarios of granular materials, applying gravel, sand, and clay. After the damage process, the samples were submitted to mechanical and hydraulic properties evaluations.

Performance Characterization of Waterborne Epoxy Resin and Styrene–Butadiene Rubber Latex Composite Modified Asphalt Emulsion (WESAE)

Neat asphalt emulsions have poor physicochemical properties. In order to endow neat asphalt emulsions with excellent physicochemical properties and broaden their application as pavement, this study adopted the composite modification method using waterborne epoxy resin (WER) and styrene–butadiene rubber (SBR) latex. Firstly, a waterborne-epoxy–SBR composite modified asphalt emulsions (WESAEs) with different amounts of WER were prepared, and the storage stability, workability, and residual properties were characterized with a series of tests. Then, the performance of the WESAEs was comprehensively evaluated by multiobjective gray target decision-making method, through which the optimal amount of WER in WESAE was determined. Lastly, the modification mechanism of WER was revealed by Fourier-transform infrared spectroscopy test. The results show that the incorporation of WER improves the high-temperature performance, thermal stability, rheological property, and adhesion of the SBR modified asphalt emulsion (SBRAE) residues. However, an excessive amount of WER will adversely affect the storage stability, particle distribution uniformity, and workability of the WESAE binder. The WESAE with 3% WER showed the best comprehensive performance; thus, the optimal amount of WER is 3% of the weight of the WESAE. Additionally, modification of the SBRAE by WER is a physical blending process, meaning no chemical reaction occurs in the blending process.

Evaluation of Bleeding Resistance in Chip Seal and Asphalt Emulsion Residue Rheology

Chip seal bleeding is influenced by many factors, including design inputs, material properties, and project-specific conditions. It reduces the surface texture of the pavement and thus compromises the safety of the traveling public. Even though factors that bring about premature bleeding are known, currently, no laboratory test methods for evaluating bleeding in chip seals have been specified. The objective of this paper is to present the results of an investigation of the influence factors of asphalt emulsion residue properties measured by the ASTM D7405 multiple stress creep and recovery (MSCR) test, as well as other factors related to chip seal bleeding resistance as measured by the modified loaded wheel test (MLWT). In this study, the MSCR test was used as a tool for evaluating the performance of asphalt emulsions because it has been identified as a potential test related to bleeding in the field. In addition, MLWT was selected as a tool for evaluating chip seal bleeding performance in the laboratory. The results of the MLWT showed that the emulsion application rate (EAR), aggregate gradation, and emulsion properties were significant factors affecting bleeding. The MSCR test was found to be a promising tool for the performance evaluation of asphalt emulsion residue, as the test was able to differentiate between emulsion chemistries and modifications in terms of sensitivity to both temperature and stress. In relation to chip seal bleeding resistance, only the creep compliance (Jnr) obtained from the MSCR test results was identified as a significant property affecting potential for bleeding.

Influence of Binder Property and Mortar Thickness on High-Temperature Performance of Cold Recycled Mixtures with Asphalt Emulsion

Four kinds of cold recycling (CR) mixtures with different asphalt emulsions were studied for their high-temperature performance in both binder properties and internal structures aspects. Digital image processing was introduced to determine the thickness spectrum for the asphalt mortar of the CR mixtures from a mesoscopic perspective. The time–temperature sweep (TTS) test was conducted to obtain the rheological parameters of each corresponding emulsified residue and the permanent deformation performance of each CR mixture was measured by dynamic creep test. A principle component analysis (PCA) was used to compare the typical performance parameters of the CR mixtures and find the factors controlling the rutting resistance of CR mixtures. The results show that the high-temperature performance of the CR mixtures with a modified emulsified asphalt showed improvements relative to the nominal case. Including Marshall stability, several parameters from the rheological properties of binder (G*/sinδ, flow number) and mortar thickness (max, range proportion 0–10 mm) could significantly influence the high-temperature performance and rutting resistance of the CR mixtures.

Bonding Evaluation of Asphalt Emulsions used as Tack Coats through Shear Testing

A poor bond between the layers constituting an asphalt pavement can cause structural problems such as slippage, delamination, and top-down cracking. These are consequences of the pavement being unable to act as a continuous element and to properly transmit the effects of the traffic to underlying layers. The aim of this research was to characterize an asphalt emulsion with low asphalt content using the Mexican standard and to evaluate its performance through the Laboratorio de Caminos de Barcelona (LCB) shear testing. Cationic slow setting (SS) and cationic rapid setting (RS) asphalt emulsions were tested by varying the asphalt contents, dosages, and cure times. The slow set emulsions presented a greater fracture energy than did the rapid set emulsions; a dose of 0.3 L/m2 provided the same level of resistance as a 0.5 L/m2 dose; and a 55% asphalt content provided greater resistance than the 60% asphalt content.

The Influence of Time after Crushing for Cold In-Place Recycling on Compaction and Raveling

Cold in-place recycling (CIR) mills existing bound pavement with a stabilizing agent to remove all surface distresses and some structural distresses. This research investigated the influence of extending the time after crushing, aggregate type, and asphalt emulsion type on four CIR compaction metrics and on the raveling test. Aggregate was crushed in the lab to mimic the milling process of CIR and was mixed with laboratory produced asphalt emulsion at various times after crushing. Three types of aggregate were used, including one field reclaimed asphalt pavement (RAP), a limestone-based laboratory-produced RAP, and a syenite-based laboratory-produced RAP. Two types of cationic medium set (CMS) asphalt emulsions were also used: a proprietary and a commodity asphalt emulsion. One of the compaction metrics, the number of gyrations to 76% Density ( N76), was found to have the most promise for capturing the charge on the RAP, as the limestone aggregate and proprietary asphalt emulsion saw the highest resistance to compaction. These two materials were the most reactive so it was reasonable that they caused the fastest break of the asphalt emulsion. The raveling test did not produce similarly conclusive results. Whereas some trends from the raveling test showed the ability to capture charge on the RAP, perhaps the four-hour cure before the raveling test may have masked any influence of time after crushing and asphalt emulsion type.