ABSTRACT
The present study investigates the effects of the simultaneous use of two additives, an organosilane warm mix asphalt (WMA) agent and a grade-bumping polyolefin compound, on the conventional and high-temperature performance properties of a paving grade 50/70 bitumen and a polymer-modified 45/80-55 bitumen. The WMA agent and polyolefin additive were introduced to the binders at rates of up to 0.3% and 2%, respectively. The base asphalt binders and their blends with the additives were tested before and after aging in a rolling thin film oven test at a temperature of 143 °C. The effects of the investigated additives were found to be dependent on the type of base binder and its aging state. It was generally observed that the WMA additive decreased the performance of the asphalt binders and limited the effects of the other additive, which increased the high-temperature stiffness and non-recoverable compliance of the blends. This interaction amounted to as much as an approx. 20% decrease in high-temperature stiffness and non-recoverable compliance of the binders. The additives caused a small increase in the elasticity of the binders and improved their creep performance when measured in multiple stress creep recovery tests.
ABSTRACT
The present paper investigates the viscoelastic stress-strain responses of laboratory and plant produced warm mix asphalt mixtures containing basalt fiber dispersed reinforcement. The investigated processes and mixture components were evaluated for their efficacy in producing highly performing asphalt mixtures with decreased mixing and compaction temperatures. Surface course asphalt concrete (AC-S 11 mm) and high modulus asphalt concrete (HMAC 22 mm) conventionally and using a warm mix asphalt technique with foamed bitumen and a bio-derived fluxing additive. The warm mixtures included lowered production temperature (by 10 °C) and lowered compaction temperatures (by 15 °C and 30 °C). The complex stiffness moduli of the mixtures were assessed under cyclic loading tests at combinations of four temperatures and five loading frequencies. It was found that the warm produced mixtures were characterized by lower dynamic moduli than the reference mixtures in the whole spectrum of loading conditions, however, the mixtures compacted at the 30 °C lower temperature performed better than the mixtures compacted at 15 °C lower temperature, specifically when highest testing temperatures are considered. The differences in the performance of plant and laboratory produced mixtures were ascertained to be nonsignificant. It was concluded that the differences in stiffness of hot mix and warm mixtures can be attributed to the inherent properties of foamed bitumen mixtures and that these differences should shrink in time.
ABSTRACT
This paper presents the results of an analysis of the changes in the stiffness of asphalt binders modified with a bio-flux additive and subjected to the processes of foaming and short-term ageing. The purpose of the analyses was to determine changes in the rheological properties of asphalt binder as a result of technological processes characteristic of hot and warm mix asphalt technology. Three asphalt binders with similar penetration but varying degrees of polymer modification were tested: 50/70, 45/80-55 polymer-modified bitumen, and 45/80-80 highly modified bitumen. Tests were carried out on four groups of binders: original binders, foamed binders after 14 days of storage, non-foamed binders after Rolling Thin Film Oven Test (RTFOT) ageing, and foamed binders after 14 days of storage subjected to RTFOT ageing. The master curves of the complex shear modulus G* were analysed, and three indexes of binder stiffening were determined, characterising the investigated effects. The tests showed that some of the stiffening indices significantly depended on the degree of polymer modification and the content of the bio-flux additive. Moreover, it was found that the foaming process in the case of paving-grade bitumen and polymer-modified bitumen did not contribute to the additional stiffening of the binders.
ABSTRACT
The study investigated the effects of laboratory ageing on the fluxed and water-foamed asphalt binders in scope of Fourier transform infrared spectroscopic measurements of ageing indicators and changes in their chemical composition. The investigated binders included two paving grades, two polymer modified asphalt binders, and a highly modified asphalt binder. The bio-flux additive was produced from rapeseed methyl esters in an oxidation reaction in the presence of a metal catalyst and organic peroxide. The use of the bio-origin additive, in particular oil derivatives, was aimed at softening and better foaming of asphalt binders. This modification is possible due to the good mixability of vegetable oils with an asphalt binder, which gives a homogeneous product with reduced stiffness. The study involved the rolling thin film oven, short-term, and the pressure ageing vessel, long term, and ageing to induce oxidation on the evaluated asphalt binders. The addition of the bio-flux additive has significantly decreased the measured content of ketone compounds related to oxidation in both non-aged and aged asphalt binders, although this effect after ageing were far smaller in magnitude. Additionally, both ageing processes decreased significantly the absorbances in the ester spectral bands specific to the bio-flux additive. All mentioned effects were similar in magnitude in all tested asphalt binders.
ABSTRACT
The present paper investigates the effects of simultaneous mechanical foaming using water and fluxing with a bio-derived agent on the properties of three distinct asphalt binders: 50/70 paving-grade bitumen, 45/80-55 polymer-modified bitumen, and 45/80-80 highly modified asphalt binder. The testing involved classical tests for assessing binder consistency (penetration at 25 °C, ring and ball softening point, Fraass breaking point, and dynamic viscosity) as well as performance tests (high and low Superpave critical temperatures and multiple stress creep recovery). The tests included assessment directly after asphalt binder foaming and were repeated after a 14-day period. It was shown that bitumen foaming had only short-term effects on the asphalt binders, which did not persist in the repeated tests after 14 days. The fluxing agent that was utilized caused significant changes in the consistency of all asphalt binders. The changes in the performance characteristics of the 50/70 and 45/80-55 binders were severe and amounted to a significant decrease in high-temperature performance of these binders. On the other hand, an improvement in all performance characteristics in the case of the 45/80-80 asphalt binder was observed as a result of the applied processes, particularly when measured 14 days after foaming. This study shows that the simultaneous use of foaming and the fluxing additive decreased the dynamic viscosity of the 45/80-80 binder, while improving its properties relating the pavement performance.
ABSTRACT
The paper investigates the phenomena of adhesion in binder-aggregate systems produced to reflect warm-mix asphalt with water-foamed bitumen. The investigated materials included limestone and quartzite aggregates and a total of four asphalt binders: 50/70 and 45/80-55 bituminous binders obtained from two sources. The adhesive bonding between the asphalt binders and aggregates was evaluated in boiling water stripping tests, which results were quantified using digital image analysis. The bituminous binders were additionally tested for their dynamic viscosities, and their chemical composition was probed using FTIR spectroscopy. The tests were carried out using traditional liquid and foamed bituminous binders on samples prepared at temperatures characteristic of hot-mix asphalt and warm-mix asphalt production (20 °C decrease). The use of foamed binders yielded higher values of residual asphalt binder coverage of the aggregates. Limestone aggregates provided superior adhesion, with the lowest result amounting to approximately 88%, while with quartzite aggregates, the results ranged from approximately 40% to 87%. The refinery from which the asphalt binders were sourced had a significant influence on the results; however, the additional rheological and chemical analyses were insufficient to explain those differences. It was concluded that the process of asphalt binder foaming, per se, may have a beneficial impact on the resistance of the asphalt binder-aggregate system to the action of water.
ABSTRACT
The process of water-based foaming of bitumen produces binders that can be incorporated in cold recycled asphalt mixes and pavement upper structural layers made of half-warm mix asphalt prepared at 100-130 °C. During the foaming process, cold water and air act on hot bitumen (160-170 °C), which results in the explosive vaporization of water leading to changes in the binder structure. The impact of foaming on the properties of bitumen 70/100 was evaluated by investigating the binder characteristics before and after foaming. Determination of two foaming parameters, maximum expansion and half-life, was followed by measurements of penetration at 25 °C, softening point, Fraass breaking point, and dynamic viscosity at 60, 90, and 135 °C. Rheological and low-temperature tests were also performed before and after foaming bitumen 70/100. The Bending Beam Rheometer method was applied to determine the low temperature stiffness modulus. A DHR-2 rheometer was used to determine the dynamic modulus and phase angle of the tested binder. The Black and master curves before and after foaming were plotted in the 2S2P1D model and the model parameters were analysed. Analysis of the test results confirmed the effects of the foaming process on the basic, low-temperature, and rheological characteristics of the bitumen.
ABSTRACT
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.
ABSTRACT
Hot-mix asphalt (HMA) remains the predominant material for pavement surfacing. Mixing is performed at about 180 °C, depending on the bitumen used. Environmental concerns in terms of emissions and energy demand are fostering new sustainable technologies in road construction. Warm-mix asphalt (WMA) and half-warm-mix asphalt (HWMA) mixtures meet current expectations in that they are produced at lower temperatures, 100-130 °C, ensured by foaming the bitumen with water. The extent of temperature reduction requires that the mixture has adequate moisture and frost resistance, which is particularly important in countries that have a low-temperature climate. Asphalt concrete AC 8 S with 50/70-grade foamed bitumen modified with 0.6 wt.% surface-active agent (SAA) was used in the tests. To provide the AC mixture with the required resistance to climatic factors (water, temperature below 0), hydrated lime was added at 0, 15, 30, and 45 wt.% as limestone filler replacement. The influence of the hydrated lime addition on the air void content and resistance to moisture and frost damage was investigated according to the WT-2 2014 methodology based on EN 12697-12: 2008 and to the modified AASHTO T283 method. The optimum content of hydrated lime for filler replacement was determined through statistical analysis of the test results. With the optimum hydrated lime replacement of 30%, the required level of moisture and frost resistance of HWMA concrete with foamed bitumen is achieved. The results of this study confirmed the suitability of HWMA concrete with foamed bitumen for application in road construction practice.
ABSTRACT
The paper aimed at assessing the feasibility of using natural zeolites as a mineral filler substitute for asphalt mixtures produced at around 120 °C temperatures with a water foamed binder and compacted at 100 °C. The tests utilized the AC 16 asphalt concrete mixture intended for the binder and base course with the mineral filler fraction amounting to 4% by wt. comprising limestone dust and zeolites (when added). A reference hot mix and warm mix with foamed bitumen were compared to two mixes with zeolites, with one containing 0.4% of a water-modified (20% moisture content) zeolite and the second containing 1.0% of natural air-dried zeolite. The investigations included: assessment of campactability using a gyratory compactor, air void content, indirect tensile strength before and after conditioning with one freeze-thaw cycle, and the resulting resistance to moisture and frost damage. The mixtures with zeolites exhibited decreased compactability when compared to reference mixes, which the Marshall samples confirmed. The mechanical properties have also deteriorated in zeolite-bearing mixtures, which was partially accounted to the decreased compaction level. It was concluded that the temperature of the mixture production was too low for the zeolite water to significantly improve the compactablity of the asphalt mixture and its mechanical parameters.
ABSTRACT
To ensure the standard properties of half-warm asphalt (HWA) mixes produced with foamed bitumen, the binder needs to have the best possible characteristics. One way to attain this is to modify the bitumen before it is foamed. The 50/70 penetration bitumen used in this study, was modified with a surface active agent (SAA) at different rates (0.2%, 0.4%, and 0.6% by wt.). The effect of the modifier on the bitumen properties (penetration, softening point, the Fraass breaking point, dynamic viscosity at 60 °C, 90 °C, and 135 °C) and on the binder foaming parameters (expansion ratio - ER, half-life - HL, foam index - FI) was investigated and the optimum quantity of foaming water was determined. Statistical analysis of the results showed that the addition of 0.6% SAA had the most beneficial effect on the set of 50/70 bitumen standard properties and foaming characteristics.
