Mineralization of flocculated bitumen emulsions allows producing bitumen powders, also referred to as Bitumen@SiO2 hybrid particles, that can resist storage in hard conditions, with a load up to 8 kPa at 50 °C during 20 hours, without alteration of their morphology or release of their bitumen core. Thanks to the flocculation, final Bitumen@SiO2 powders are not highly pulverulent and allow transportation and handling of bitumen at ambient temperature without the need of water as it is the case for bitumen emulsions. This "water free" storage particularity exhibits the double advantage of reducing the cost of transport and of avoiding inhibition of bitumen adhesion at mineral aggregates through the presence of water, therefore rendering the bitumen its high quality of binder. The silica shell is responsible for the high storage stability and, when mixed with aggregates for end use of asphalt, as for example in pavement applications, serves as mineral charge to the bitumen, modifying the bitumen flow properties. Indeed, when heated at 100°C and crushed, the capsules break releasing thus the bitumen. This suspension made of bitumen and silica shell fragments exhibits an interesting
The oxidative aging of bituminous binders affects the performance and durability of pavements. In the case of polymer-modified binders, aging involves both bitumen and polymers and has a strong impact on the whole architecture of the material. Rheology may help in understanding these structural changes, and interesting information may be obtained by analysing the evolution of apparent molecular weight distributions. This was demonstrated with a bituminous binder modified with a poly(styrene-butadiene) block copolymer and subjected to prolonged artificial aging. Isothermal frequency sweep tests were used to construct master curves of the phase angle and magnitude of the complex modulus. The master curves were then used to calculate relaxation spectra and apparent molecular weight distributions of the binders, as well as simulated temperature sweep tests. A comparison of the behaviour of the base and modified bitumen highlighted the role of the polymer in aging. Polymer degradation significantly damages the elastomeric network, yet the residual polymer chains still interact with the bitumen molecules and reduce their oxidative aging. The apparent molecular weight distributions were deconvoluted to create an aging index specifically developed for polymer-modified bitumen.
Due to budget constraints in Europe, sustainability of pavement materials is taking an increasing part in the construction and maintenance policy of road networks. The aging properties of bituminous binders are known to have a direct impact on the durability of road pavement and must be properly assessed. The measurement of in-situ bituminous binder and asphalt mix performances is the most reliable way to appreciate and measure the consequence of aging and oxidation on materials. However, accelerated test methods provide a cost-efficient, predictive assessment of the aging behavior, provided that these methods are representative of the aging phenomenon in the field. The present study is focused on the low-temperature and the aging properties of various bituminous binders in relation to the corresponding properties of asphalt mixes. In a first publication, investigations were devoted to different binder's characterization method (Fraass, BBR, ABCD) as potential predictive tool to thermal cracking of asphalt mixtures (TSRST). This paper focuses on analyzing the sensitivity of these test methods to the degree of aging of different binders (paving bitumen, crosslinked elastomer-modified binder and physical blend elastomer-modified binder) and asphalt mixes. Based on original investigations, noticeable trends are pointed out aging impact on binders and both methods.
International audienceThe preparation of functional nanocomposites by dispersion of a synthetic lamellar α-ZrP within a styrene/butadiene random copolymer during melt compounding is described. It is shown how the physical and chemical incompatibility of filler and polymer can be overcome, and problems arising from the low viscosity ratio between slurry and polymer matrix are discussed. The aqueous phase can easily be eliminated at the end of the process. The dispersion of the ZrP requires the use of intercalants, and alkylamines were used for this purpose. XRD and TEM are used to characterize the degree of organization of ZrP in the slurries and in the matrix. DMA helps to understand the origin of the limited reinforcing effect
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