Daniel Perraton

Complex modulus characterisation of cold-recycled mixtures with foamed bitumen and different contents of reclaimed asphalt

Cold-in place recycling with foamed bitumen (FB) is currently employed for the rehabilitation of road pavements, from local roads to heavy-duty motorways. The mechanical properties of FB mixtures may vary from that of an improved granular material to that of an asphalt concrete, depending on their composition. The objective of the present study was to characterise the linear viscoelastic (LVE) response of FB mixtures with different contents of reclaimed asphalt (50%, 70% and 0%). This objective was tackled by measuring the complex Youngs modulus by means of uniaxial cyclic compression tests, in a range of temperatures (from −20°C to 55°C) and frequencies (from 0.03 to 10 Hz). The thermo-rheological behaviour was modelled using the Huet–Sayegh model, commonly used for bituminous mixtures. In order to focus on the influence of reclaimed asphalt content, the same grading and FB content were used for all the mixtures. In addition, an effort was made to produce mixtures with similar volumetric properties. Considering all the tested mixtures, the stiffness modulus ranged between 171 and 4075 MPa, whereas the phase angle ranged between 4° and 18°. Though these values are well below those normally measured on asphalt mixtures, the frequency and temperature variations clearly highlight a typical asphalt-like behaviour. In addition, the time–temperature superposition principle can be considered valid, regardless of the reclaimed asphalt content. Overall the experimental results showed that it is possible to characterise the LVE response of cold-recycled FB mixtures using the same experimental and analytical approach adopted for asphalt mixtures.

On the Optimization of the Aggregate Packing Characteristics for the Design of High-Performance Asphalt Concretes

ABSTRACT In the framework of a partnership between the European EIFFAGE Travaux Publics Group and the Ecole de Technologie Supérieure (ETS) from Montreal (Québec), some basic concepts associated with granular combinations and aggregate packing characteristics enabled the development and design of high-performance self-blocking asphalt concretes. The aggregate packing methods first developed in the field of high-performance cement concretes were successfully transposed to the field of asphalt concretes. Laboratory assessment in both laboratories of the ETS and EIFFAGE Travaux Publics consisted in the evaluation of the compactin g ability using the French gyratory shear compactor (GSC), the resistance to moisture using the so-called Duriez test, the resistance to rutting thanks to the French wheel tracking tester at 60°C, the secant stiffness modulus at 15°C and the fatigue resistance at 10°C. The paper concludes that the grading analysis concepts allow the design engineer new insights into the structure of aggregates. The proposed principles can be used to develop more specific guidelines for aggregate structure selection of high-performance asphalt concretes.

Contraction and expansion of partially saturated hot mix asphalt samples exposed to freeze–thaw cycles

This paper analyses the physical impacts over hot mix asphalt subjected to freeze–thaw (FT) cycles (−18°C to +10°C) under dry and partially saturated conditions, with water or brine at different salt concentrations. Specifically, axial strain and temperatures at surface and in the heart of samples are measured during FT cycles. These measurements allow the quantification of the: (i) linear coefficient of thermal expansion (LCTE), (ii) dilation generated by formation of ice, (iii) contraction by melting of ice and (iv) freezing points variation with the degree of saturation and content of salt in brine. Under FT cycles, elongation, dilation and contraction generated by formation and melting of ice are much more significant for sample partially saturated with water (PSW). In addition, between +10°C and +23°C, LCTE value of samples PSW or brine is higher than that of sample in the dry state.

Evaluation of the impact of recycled glass on asphalt mixture performances

The goal of this research was to verify the possibility of using recycled glass particles in an asphalt mixture while maintaining equivalent properties and performance in lieu of a conventional mixture. First, one type of asphalt mixture (ESG14) with different glass contents was tested according to the Ministère des transports du Québec’s mix design method. Next, the performances (resistance to thermal cracking, mixture stiffness and stripping resistance) of an asphalt mixture with optimal glass content were evaluated and compared to a reference mixture. Overall, it was found that using recycled glass in an ESG14 asphalt mixture reduces the binder content, increases the mixture workability and decreases the rutting resistance. It was also found that using 10% recycled glass in an ESG14 asphalt mixture does not impact the resistance to thermal cracking as well as the mixture stiffness. On the other hand, the stripping resistance is negatively affected by the presence of glass.

Degradation of hot mix asphalt samples subjected to freeze-thaw cycles and partially saturated with water or brine

In the province of Quebec, during winter and spring, hot mix asphalt (HMA) is subjected to freeze-thaw cycles (FTCs). This paper presents a part of a general research programme which aims to characterise damage generated on HMA samples by FTCs, under dry and partially saturated (PS) conditions, with water (PSW) or brine (PSB). The samples were subjected to complex modulus (E*) test after different number of FTCs, which allowed us to assess the evolution of the damage due to freeze-thaw sequences. Rheological model, 2S2P1D, was used to simulate the behaviour of the HMAs. The 2S2P1D model well simulates the linear viscoelastic behaviour of the HMAs. Over the FTCs, damage is observed for all samples. But is seen to be much higher for the PSW sample. For PS samples, the time–temperature superposition principle (TTSP) is less valid over the FTCs. A different shift factor evolution could be observed below and above the ice formation temperature. Damage due to FTCs seems to have a greater impact at high temperatures and low frequencies.

New conceptual model for filler stiffening effect on asphalt mastic of microsurfacing

AbstractThis research focused on the stiffening effect of the filler on the asphalt mastic of microsurfacing. One challenge that researchers are faced with in the field of bituminous materials is the interaction between the filler and binder. In this study, a new conceptual model for filler stiffening of the mastic was developed that allows the asphalt mix designer to establish the minimum and maximum filler concentration to incorporate in the asphalt mixture. The proposed model has only one parameter that can be determined using the filler and asphalt emulsion selective properties, such as D10 and pH of the filler and the asphaltene content of the emulsion. A new mechanism for the stiffening effect of filler on mastic was developed based on the physicochemical interaction between filler and bitumen. Based on the model, the increase in mastic stiffness (G*) as a function of the increase in filler concentration can be divided into three regions: diluted region, optimum concentration region, and concentrate...

Mechanical Testing of Bituminous Mixtures

This chapter focuses on permanent deformation, which is at the origin of pavement rutting. First experimental laboratory tools and associated analyses related to permanent deformations are presented. It is either material tests, that can be homogeneous or giving a simple empirical characteristic, or non-homogeneous Structural/Specimen tests.

Comparison of Some Pavement Design Methods from a Fatigue Point of View: Effect of Fatigue Properties of Asphalt Materials

ABSTRACT The paper presents a comparison between the principle international flexible pavement design methods based on fatigue material properties. Four methods were studied for the design of two pavement sections. Laboratory tests showed an enormous difference between the fatigue and the complex modulus results for the two asphalt mixes used in the base course (Stone Matrix Asphalt: SMA, and EB14: reference mix). The required thickness of the base course changes depending on the pavement design method used. Despite the laboratory results, certain methods showed no difference in thickness of the base course for the two asphalt base mixes while others showed an important difference and proves the benefit of the materials fatigue performance. Discussions underlined that the complex modulus of an asphalt material should not be used as a performance indicator to predict the fatigue life of that material.

Deterioration of HMA partially saturated with water or brine subjected to freeze-thaw cycles

In the province of Quebec, during winter and spring, hot mix asphalt (HMA), constituting the pavement, is subjected to freeze-thaw cycles (FTC). This paper presents a part of a general research program aimed at characterizing damage generated on bituminous mixes by thermal tests, including FTC, under dry (D) and partially saturated (PS) conditions, with water (PSW) or brine (PSB). The samples were subjected to mechanical testing and the complex modulus test is used to assess the evolution of their damage after different sequences of FTC. The test results and rheological model 2S2P1D were used to simulate the behaviour of the HMA according to the various states. The 2S2P1D model simulates the linear viscoelastic behaviour of the asphalt mix following different states very well. Over FTC, damage is observed for all samples, but is seen to be much higher for the PSW sample. Moreover, for PS samples, the principle of equivalent temperature-time is less valid over the FTC, and a double behaviour is observable: below and above the ice formation. Indeed, damage to the asphalt mix seems to have a greater impact at high temperatures and low frequencies.

In-situ permeability of the outermost layer of asphalt and cement concrete road materials water permeability evaluated with gas flow

ABSTRACT A permeability cell was developed by applying Carman and Klinkenberg principles to measure the permeability of a porous medium to gas. The method applied concentrates gas flow on a better well-defined area on the surface of the material tested. Both the cell and the calculations used are explained in detail in this paper. The permeability was measured on three hot-mix asphalt mixes (HMA), which were compacted into 125x400x600 mm3 slabs in order to allow the simulation of in-situ conditions. The permeability cell test results show a higher variability in the permeability values of HMA as compared to those obtained from cement concrete measurements. The permeability to gas, when transformed to water permeability, found in this research is comparable to the results found in the literature.