Foaming Water Content Research Articles

Characterization of Residual Moisture Distribution in Cold-Recycled Mixtures with Foamed Asphalt Using Hyperspectral Technology

Cold-recycling technology with foamed asphalt is used widely because it has the incomparable advantages of environmental protection and resource conservation. In this study, cold-recycled mixtures with foamed asphalt were prepared with different gradation types, mixing water contents, and curing times to study the distribution characteristics of residual moisture. An optimum foaming water content of 2.5% and foaming temperature of 165°C were determined for producing the foamed asphalt that was used for the cold-recycled asphalt mixtures. Hyperspectral imaging tests and spectral processing technology were used to obtain the image information and spectral information of residual moisture from 44 specimens; the moisture content of all specimens ranged from 0.25% to 4.70%. Pseudocolor-coding technology was utilized to realize visualization of moisture distribution. In addition, the residual moisture content prediction model was established based on the partial least-squares regression (PLSR) model. Correlations of the residual moisture distribution characteristics and moisture damage resistance evaluation indicators were developed. The residual moisture distribution characteristics and moisture damage resistance are affected significantly by aggregate gradations, mixed water content, and curing time. After 3 days of curing, the strength of the recycled mixture tends to be stable, and the moisture damage resistance can reach the specification requirements, and is suitable for open traffic. It was confirmed that there is a certain correlation between the internal residual moisture content value distribution range and the moisture damage resistance of the cold-recycled mixtures with foamed asphalt. This study could contribute to a better application of cold-recycled asphalt pavement for environmental protection and carbon stabilization.

Optimization of Bentonite Bar Soap Formula with Combination of Coconut Oil and Soybean Oil Using Simplex Lattice Design Method

Muslim population in Indonesia reaches 87% and is one of the countries with the largest muslim population according to the 2010 population census. Thaharah is one of the things that Muslims pay much attention to, especially in worship. One of thaharah is washing up from najis mughallazah. Soap is skin cleansing preparations that has become a public basic needs so that the innovation of soap formulation containing bentonite as a component that can washed the najis mughallazah to make it easier for Muslims to thaharah. This study optimizes the formula for bentonite bar soap with combination of coconut oil and soybean oil using the Simplex Lattice Design method. The optimum formula obtained was then verified using the one sample T-test method. To determine the optimum formula, it is necessary to test the physical and chemical properties such as foaming power and foam stability and follows the parameters of the Standar Nasional Indonesia such as foaming water content, pH, total fat, insoluble substance in ethanol, free alkali/ free fatty acid and unsaponifiable fat. Bentonite soap with the optimum formula was then tested for consumer acceptance. The optimum formula from the prediction consisted of 76.58% coconut oil and 23.42% soybean oil. The test results of the formula produced soap with hard properties and good foaming and met several requirements of SNI 3532:2021.

Foaming Performance and FTIR Spectrometric Analysis of Foamed Bituminous Binders Intended for Surface Courses.

This study explores the effects of foaming on three selected bituminous binders: 50/70 paving grade bitumen, 45/80-55 polymer modified bitumen and 45/80-80 HiMA binder. The first part of the investigations included the evaluation of the foaming performance in terms of foaming temperature and foaming water content with the utilization of desirability functions and based on the equality of maximum expansion ratio and bitumen foam half-life. The second part of the study investigated the effects of foaming on the chemical structure of the binders using Fourier-transform infrared spectroscopy. The results of the spectroscopic measurements permitted calculation of structural indices specific to functional groups associated with bitumen oxidation, as well as those indicative of elastomeric modification. The results have shown that the different types of bitumen exhibited different foaming characteristics, which was most evident in bitumen foam half-lives, with the HiMA binder performing the best. The spectrometric measurements did not show any significant effects of foaming on the chemical structure of the evaluated binders related to oxidative stress, neither were any major changes in the PmB-specific regions found.

Effects of Asphalt Foaming on Damage Characteristics of Foamed Warm Mix Asphalt

In the asphalt foaming process, the foaming water content (FWC) controls the formation and characteristics of water bubbles. These water bubbles are expected to be expelled from the foamed warm mix asphalt (WMA) during mixing and compaction. However, foaming water may not be completely expelled, rather some of the microbubbles may be trapped in the foamed WMA even after compaction. These microbubbles, or undissipated water, can diffuse over time and cause damage to the foamed WMA. To this end, this study has determined the effects of foaming on the fatigue, moisture damage, and permanent deformation characteristics of foamed WMA. Foamed asphalt and mixtures were designed with varying FWCs and they were tested using linear amplitude sweep, multiple stress creep recovery, four-point flexural beam, and Hamburg wheel tracking tests. Primarily, asphalt foaming dynamics were assessed with a laser-based non-contact method. A simplified viscoelastic continuum damage concept and a three-phase permanent deformation model were used for damage evaluation. The study reveals that foaming softens the binder, which results in slightly higher rutting and moisture susceptibility, though an equivalent or slightly improved fatigue characteristic compared with the regular hot mix asphalt.

Glass transition temperature and low temperature performance for foam warm mix asphalt

In order to study the glass transition temperature and low temperature performance of foam warm mix asphalt (FWMA), we have prepared the FWMA samples with different asphalt types and different foaming water contents (FWC). Glass transition temperatures of the samples are determined by using dynamic mechanical analyzer (DMA) and differential scanning calorimetry (DSC) methods, and their low temperature performancesare evaluated by using bending beam rheometer (BBR) method. Results show that for different asphalt types and FWC, the behaviors of glass transition temperatures determined by DMA and DSC are different, but their changing trends are similar.With the increase of FWC, the glass transition temperature of asphalt increases gradually.The addition of foam water damages the low temperature cracking resistance of asphalt to a certain extent.Foaming water with a mass fraction of 6% could not meet the low temperature requirement below -12 °C, and could not satisfy the application scope of the non-foaming asphalt at low temperature.In order to ensure good pavement performance of FWMA, the low temperature cracking resistance must be taken as the priority consideration for choosing the optimal FWC.

Investigation of Moisture Dissipation of Water-Foamed Asphalt and Its Influence on the Viscosity.

Water-foamed asphalt is capable of improving the workability of asphalt mixture. It has been extensively used for its energy-saving and emission-reducing features. Water plays an essential part in improving the workability of water-foamed asphalt mixture. However, there is still lack in profound studies of moisture dissipation of the water-foamed asphalt over time and its influence on workability. In this study, the evolutions of residual water content and rotational viscosity of the water-foamed asphalt with time were respectively measured by the analytical balance and modified rotational viscometer (RV). The atomic force microscopy (AFM) analysis was conducted to discuss the mechanism of viscosity reduction of water-foamed asphalt. The results showed that moisture evaporation is significantly influenced by the foaming water content and ambient temperature, which results in the different stabilizing time of water-foamed asphalt. When water-foamed asphalt was stabilized, the residual water inside the asphalt was less than 0.01% relative to the asphalt mass. The AFM analysis showed that the foaming process changed the distribution of wax in the water-foamed asphalt resulting in reduction of viscosity. The viscosity reduction of asphalt is highly related to the initial foaming water content. After the foaming process, the viscosity keeps stable and is independent of moisture dissipation.

Analysis of moisture susceptibility of foamed warm mix asphalt based on cohesion, adhesion, bond strength, and morphology

Although foamed warm mix asphalt (FWMA) offers several benefits, concerns exist regarding the potential moisture damage that can be produced within it. Boiling water tests, the surface free energy (SFE), the binder bond strength (BBS), and atomic force microscopy (AFM) morphologies are all used to analyse the moisture damage of asphalt. These methods were evaluated and compared in this study. The results indicate that some residual moisture remains trapped in asphalt after foaming and that the foaming states for base asphalt and SBS modified asphalt attain stability after 6 min and 15 min, respectively. Boiling water tests are unsuitable for evaluating the adhesion of FWMA. SFE and BBS tests demonstrated that the residual foaming water undermines the bond strength of FWMA by reducing the cohesion energy. The Scanning Electron Microscope (SEM) and AFM methods were used to identify differences between morphologies by investigating the various foaming water contents. The results of SFE, BBS, and AFM morphologies were observed to be in agreement. Although cohesive failure modes were observed in the BBS experiment, foaming water aggravates the adhesion failure and causes moisture damage owing to the participation of external water. Furthermore, the results indicate that less water damage resistance is associated with substantial amounts of foaming water. These findings provide a clearer understanding of the moisture susceptibility of FWMA.

Characterization of foaming attributes to binder tribology and rheology to better understand the mechanistic behavior of foamed asphalt

In the asphalt foaming process, water is encapsulated inside asphalt binder in the form of numerous small to large size water bubbles. Though larger water bubbles dissipate shortly after foaming, smaller bubbles or micro-bubbles take a longer time to dissipate and hence, a fraction of added foaming water content (FWC) might remain undissipated in the form of micro-bubbles or diffused water. The study speculates that these water bubbles or undissipated water might be related to tribological and rheological characteristics, rather than binder viscosity only. As such the study characterizes FWC and associated foaming attributes to tribological, and rheological characteristics to better understand the foaming effects on mechanistic behavior of foamed asphalt. Tribological and rheological tests were conducted on foamed asphalts with varying FWCs and on a controlled un-foamed asphalt binder. A ball-on-three-plates apparatus assembled in a dynamic shear rheometer (DSR) was utilized for the tribological test. In addition, foaming characteristics were evaluated by various foaming parameters utilizing a laser-based non-contact method. The results yield a better understanding of foaming effects on mechanistic behavior of foamed asphalt in terms of foam expansion, stability, lubrication, frictional resistance, and viscoelastic responses.

Impact of Additives on the Foamability of a Road Paving Bitumen

Because of the needs for the increased efficiency and environmental concerns that now emerge environmentally friendly techniques are more sought for and more commonly utilized in the road paving industry. Typical asphalt mixes are produced in temperatures exceeding 150˚C depending on the type of asphalt binder used, but new techniques are being developed, permitting decreased production and paving temperatures. One of the most effective techniques that are being studied are the Warm Mix Asphalt and Half Warm Mix Asphalt methods utilizing water based bitumen foaming that allow production of asphalt mixes at temperatures as low as 100˚C. Due to the extremely low processing temperatures, it is often difficult to obtain satisfactory results regarding the physical and mechanical properties of the resulting mixes, specifically the resistance to moisture the damage and resistance to the permanent deformation being in concern. As these issues were found to be originating in the inadequate coating of aggregates, a surface active agent in amounts of 0, 2% - 0, 6% and synthetic wax in amounts of 1, 0% - 2, 5% were added to 50/70 paving bitumen to improve its foamability and coating potential. Foaming characteristics were established in terms of bitumen foam expansion ratio ER and its half-life HL as a function of foaming water content ranging from 1, 5% to 4, 0%. It was found that the addition of surface active agent in the amount of 0, 6% resulted in the most favourable foaming performance at 2, 5% foaming water content, resulting in a doubling in expansion ratio and more than a 2, 5 times increase in half-life compared to the base bitumen. It is believed that the improved foaming characteristics of the bitumen would significantly benefit the performance of a subsequent warm or half-warm asphalt mix.

Tribological Evaluation for an In-Depth Understanding of Improved Workability of Foamed Asphalt

Asphalt binder acts as a lubricant between two aggregates during mixing and compaction. The frictional behavior of asphalt binder as a lubricant in an asphalt-aggregate system plays an important role in mixing and compaction (workability) of warm-mix asphalt (WMA). This study evaluates the frictional behavior of foamed WMA through tribological characterization using a ball-on-three-plates apparatus assembled inside a dynamic shear rheometer (DSR). The tribological test was conducted on six foamed asphalts with varying foaming water contents (FWCs) and on a controlled unfoamed asphalt binder at four different temperatures: 25°C, 60°C, 100°C, and 135°C. These binders were also characterized for rheological and chemical properties. Test results show that the foaming process alters the frictional resistance of the foamed asphalts; specifically, the foaming process reduces the coefficient of friction in elastohydrodynamic and hydrodynamic lubrication regimes. Reduced frictional resistance helps in the formation of a better coating during mixing and improves the sliding ability between aggregates during compaction at reduced temperature.

Influence of foaming on tribological and rheological characteristics of foamed asphalt

The frictional characteristics of asphalt binder as a lubricant film in an asphalt-aggregate interaction play a major role in workability of warm-mix asphalt (WMA). However, no WMA research considered the frictional characteristics of asphalt to demonstrate the workability of WMA, rather most of the previous studies are limited to foaming and some of the rheological properties. Frictional evaluation can be conducted on asphalt binder through the tribological experimentation with a ball-on-three-plates apparatus assembled inside a dynamic shear rheometer (DSR). This study aims to evaluate the effect of foaming on tribological and rheological characteristics of foamed asphalt binder. The tribological and rheological tests were conducted on six foamed asphalts with varying foaming water contents (FWCs) and on a controlled un-foamed asphalt binder at different temperatures. These binders were also characterized by foaming and chemical properties. Test results show that the foaming process alters the frictional resistance of the foamed asphalt binders, specifically the foaming process reduces the coefficient of friction in the elasto-hydrodynamic and hydrodynamic lubrication regimes. The tribological characteristics are more relevant to the improved workability of foamed WMA over rheological characteristics.

Influence of base asphalt aging levels on the foaming characteristics and rheological properties of foamed asphalt

Foamed asphalt technique is widely used in road construction due to its environmental and economic effects. The various characteristics of foamed asphalt and mixtures have already been investigated; however, few studies focused on what happened on the properties of foamed asphalt when the base asphalt was aged at different degree. In this study, the foaming characteristics and rheological performance of foamed asphalt prepared by different aging levels for base asphalt and foaming water content were determined. The rheological properties such as failure temperature, Zero shear viscosity @60 °C, temperature sensitivity, and fatigue resistance were evaluated by DSR tests. The results show that the deeper aging degree of asphalt for foaming process needs higher temperature and more foaming water content. And aging process of asphalt has better for high-temperature performance and temperature sensitivity, and adverse for fatigue resistance performance.

Influence of foaming water and aging process on the properties of foamed asphalt

Foamed asphalt is a good technique to reduce energy consumption and protect environment by decreasing the construction temperature of asphalt mixture. Many efforts have focused on the original foamed asphalt such as foaming characteristics and rheological properties, but how the performance of samples at different aging stages changing has been few studied. Therefore, foamed asphalts sampales with different foaming water (0wt%, 1.0wt%, 2.0wt% and 3.0wt%) at three stages (unaged, short-term aging and long-term aging) are investigated in this study. The high-temperature performance, low-temperature performance, temperature susceptibility, fatigue performance and microstructure of foamed asphalt were evaluated by Brookfield viscosity tests, dynamic shear rheology (DSR) tests, bending beam rheometer (BBR) tests and Fourier Transform Infrared spectroscopy (FTIR) tests. The results show that the foaming water content and aging process have great influence on the rheological properties and microstructure of non-foamed and foamed asphalt. Foaming water decreases the failure temperature, ZSV@60°C, low temperature performance, and fatigue resistance while it could improve temperature sensitivity. Aging process has better for viscosity, rutting resistance factors and temperature sensitivity of non-foamed and foamed asphalt. Meanwhile, less foaming water has better effect on the anti-aging properties of asphalt.

A closer scientific look at foam bitumen

In the asphalt industry, a substantial interest is observed to find possibilities to reduce the production temperature of asphalt mixtures. In the context of this research, new methods for the visualisation of unstable bitumen foam, such as dynamic X-ray radiography, computed tomography (CT) and high-speed camera investigations, have been developed. Moreover, characterisation with empirical methods such as expansion ratio and half-life was determined accurately using ultrasonic measurements. This opens new possibilities to characterise bitumen foam (foaming process) for practical applications. Examination of the foam bitumen stream using a high-speed camera revealed that the foam bitumen contains fragmented pieces of bitumen, which resemble more a liquid than foam. This indicates that the foam is formed afterwards and not, as assumed, within the expansion chamber of the foam generator. In situ thermal imagery of the surface, during the hot foaming process, showed that the temperature distribution depends on the foaming water content (W.C.) and bubble size distribution. Higher W.C. results in more inhomogeneous temperature distribution as compared to lower W.C. (<2 wt%). The dynamic X-radiography results indicated that as the foam decays, the bubble size distribution becomes progressively larger with time for 160°C bitumen temperature. Furthermore, at the beginning of the foam formation, majority of the bubbles is small in cross-section size (0.2–10 mm2). At a later stage, the bubbles become polydisperse. Moreover, theoretical investigations based on the 3D X-ray CT scan data set of bubble merging show that the disjoining pressure increases as the foam film gets thinner with time and finally undergoes rupture. The speed of the bubbles also increases with time when the bubbles are getting closer to each other.

Rheological and microstructural properties of foamed epoxy asphalt

Epoxy asphalt has been extensively used in the bridge deck pavement. The main concerns during the construction process of epoxy asphalt are including high construction temperature, high viscosity to deal with and limited construction time which finally affects the service performance of the pavement. In this study, foamed epoxy asphalt is proposed to solve these construction challenges. The foamed epoxy asphalt samples were prepared by foaming machine at different foaming water content in the laboratory. The viscosity-temperature performance, failure temperature, ZSV@60°C, temperature sensitivity and storage stability were evaluated by rotational viscometer, temperature sweep, frequency sweep and storage tests. Fluorescence microscope and Infrared spectroscopy were utilized to characterize the morphology and chemical reaction change of non-foamed and foamed epoxy asphalt with different foaming water content. The results show that the addition of foaming water could improve the workability of foamed epoxy asphalt binder mixtures and prolong the allowable reserved time of construction process. Compared to non-foamed epoxy asphalt, foamed epoxy asphalt compromise failure temperature and viscosity@60°C and improve the temperature sensitivity and storage stability. With the increase of foaming water content, the failure temperature, viscosity@60°C and storage stability of foamed epoxy asphalt decrease at some extent, while the temperature sensitivity of foamed epoxy asphalt increases. According to the change of microstructure, the foaming water is beneficial to enhance the epoxy resin dispersion in the asphalt and promote the chemical reaction between epoxy resins and curing agent, which could improve the pavement performance of epoxy asphalt.

Mix design procedure for foamed asphalt mixtures

Mechanical foaming is the most popular method for producing warm mix asphalt in the United States; yet, a standard mix design procedure for foamed asphalt mixtures has not been established. Currently, the design of foamed asphalt mixtures consists of determining the optimum binder content by following a standard hot mix asphalt (HMA) design procedure and then estimating the foaming water content based on the foamer manufacturer's recommendation, engineering judgement, or previous experience. This practice fails to account for the effect of foaming on binder and mixture properties, and therefore may not ensure desirable foamed mixture performance. To overcome this shortcoming, additions to the standard mix design procedure were proposed in this study in order to accommodate foamed asphalt mixtures, which included optimisation of foaming water content and evaluation of foamed mixture performance. In addition, the proposed procedure was verified using materials procured from two field projects. The optimum foaming water content (Wopt%) was first determined by comparing the workability results of foamed mixtures at various foaming water contents. Afterwards, the foamed mixture at Wopt% was tested for coatability and performance evaluation, and all laboratory test parameters complied with established American Association of State Highway and Transportation Officials or agency specifications or were equivalent to or better than the control HMA test results. Therefore, the proposed foamed mix design procedure seemed a viable alternative for designing foamed mixtures with adequate pavement performance.

Effect of laboratory foamer on asphalt foaming characteristics and foamed mixture properties

In the United States, mechanical foaming is the most popular method for producing warm mix asphalt, which is the latest technology implemented to reduce the production temperature and/or enhance the compactability of asphalt mixtures. Three commonly used commercially available laboratory foamers to produce asphalt foams include the Wirtgen WLB 10S (Wirtgen foamer), the InstroTek Accufoamer (InstroTek foamer) and the Pavement Technology Inc. Foamer (PTI foamer). Though these foamers have been widely used in research studies and construction practice, it is still unknown whether they produce asphalt foams with the same quality and quantity. In this study, asphalt foaming characteristics produced by these three laboratory foamers were measured using a non-contact test set-up consisting of a laser device and a digital camera, and compared in terms of instantaneous volume expansion, foam stability and surface area evolution of foam bubbles. Additionally, the workability, coatability and mechanical performance of foamed mixtures prepared using these same laboratory foamers were compared against the conventional hot mix asphalt (HMA). Test results indicated that foamed asphalts produced by the Wirtgen foamer had the largest volume expansion and greatest foam stability, followed by those produced by the InstroTek foamer and the PTI foamer. The optimum foaming water content (Wopt) was determined for each laboratory foamer based on the workability and coatability results of the corresponding foamed mixtures. In addition, the performance evaluation of the foamed mixtures produced at Wopt values indicated equivalent mixture stiffness but greater moisture susceptibility as compared to the conventional HMA.

Performance Characteristics Comparisons of Various Asphalt Mixture Technologies

Abstract A laboratory investigation was carried out to study the effects of various compaction technologies on moisture susceptibility, rutting resistance, and fatigue characteristics of various asphalt mixtures. The methodologies used in this study included three technologies such as common hot mix asphalt (HMA), warm mix (WMA), and half-warm mix asphalt (HWMA) technologies. In addition, in terms of WMA and HWMA mixtures, a foaming technology was used to produce the samples. The experimental design for WMA and HWMA included one aggregate moisture contents (∼0.5 % by weight of the dry mass of the aggregate), three lime contents (0 %, 1 % and 2 % lime by weight of dry aggregate), and 2 % foaming water content. For HMA, 1 % lime content and completely dried aggregate were used. Three aggregate sources (designated as A, B, and C) and one PG 64-22 binder were used in this study. A total of 9 Superpave mix designs and 21 mixtures were completed. A total of 84 indirect tensile strength (ITS) samples, 126 asphalt pavement analyzer (APA) samples, and 30 fatigue beams were tested in this research. The major properties such as gyration number, ITS, tensile strength ratio (TSR), rut depth, deformation, toughness, as well as fatigue life were measured and computed for all mixtures. The test results indicated that various compaction technologies would slightly affect the Superpave mix design and obviously have an influence on gyration number, ITS values, rut depth, flow, toughness, and fatigue life of various mixtures regardless of aggregate source and lime content. In addition, the aggregate source significantly affected the ITS and rutting resistance in this study.

Application of synthetic wax for improvement of foamed bitumen parameters

The aim of the research was to evaluate the properties of foamed bitumen, produced from a Fischer–Tropsch synthetic wax modified 50/70 penetration grade bitumen for use as a binder in road construction layers. The binders were subjected to conventional tests (including penetration, softening point, Fraass breaking point and dynamic viscosity) as well as bitumen-foam-specific testing (including expansion ratio, half-life and foam index at different foaming water contents). Optimum amounts of foaming water and Fischer–Tropsch wax were identified and the binders were classified as relevant for different low-energy bitumen mix production techniques.

Effect of Water Content on Binder Foaming Characteristics and Foamed Mixture Properties

Mechanical foaming has become the most popular method for producing warm-mix asphalt in the United States. The process of mixing cold water with hot binder results in volume expansion and subsequent viscosity reduction of the binder, which is likely to produce a better coating of the aggregates along with improved overall mixture workability. Although mechanical foaming has been widely used in recent years, questions persist regarding the effects that different amounts of water have on binder foaming characteristics and foamed mixture properties. This study developed a novel, noncontact method to measure the expansion and collapse of foamed binder during the foaming process and the evolution of the size and amount of foam bubbles over time. Two parameters were proposed for evaluating the effect of water content on binder foaming characteristics. In addition, the effect of water content on the foamed mixture properties of workability and performance was investigated. The test results indicated that the amount of water used in the foaming process had a significant effect on binder foaming characteristics and foamed mixture properties. The optimum foaming water content could be determined through evaluation of the workability of foamed asphalt mixtures produced at different foaming water contents. Compared with hot-mix asphalt mixtures, equivalent or better performance in laboratory tests was observed for plant-produced and laboratory-produced foamed mixtures at the optimum water content.