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Cold mixtures with bitumen emulsion are produced at ambient temperature, leading to substantial reductions of energy consumption and atmospheric emissions. In cold recycling applications, cement is normally used to improve the mixture performance. Thus, the rheological behavior of cold recycled mixtures is different from that of conventional hot mixtures because it is due to the interaction of fresh bitumen, aged bitumen and cementitious bonds. In this study, we investigated the three-dimensional (3D) linear viscoelastic (LVE) behavior of a cement-bitumen treated material (CBTM) mixture fabricated using bitumen emulsion and cement. For comparison, we also investigated the 3D LVE behavior of hot-mix asphalt containing 25% of reclaimed asphalt and fabricated using polymer-modified binder. Sinusoidal axial tests on cylindrical specimens, were carried out at various temperatures (from 0 °C to 50 °C) and frequencies (from 0.1 to 12 Hz). The complex Young's modulus E∗ and the complex Poisson's ratio v∗ were determined through the measurement of axial and transverse strain. We show that when considering E∗, CBTM mixtures may be considered thermo-rheologically simple and the Huet-Sayegh model can be used to simulate the frequency–temperature dependence. On the other hand, when considering v∗ the behavior of CBTM mixtures is very different from that of hot mix asphalt. In particular, its absolute value is almost constant and very close to 0.15. Keywords: Bitumen emulsion, Cold recycling, Complex modulus, Complex Poisson's ratio, Huet-Sayegh model

This paper focuses on the early age evolution of consistency and rheological properties of fresh bitumen emulsion-cement (BEC) pastes. The tested BEC pastes were fabricated using a Portland limestone cement and an over-stabilized bitumen emulsion and were characterized by water to cement ratio ranging between 0.33 and 1 and by bitumen to cement ratio ranging between 0 and 1. The testing plan included the measurement of sedimentation tendency, setting time and evolution of viscosity with increasing storage time. Rheological measurements were also carried out on bitumen emulsion-filler mastics prepared with a reference filler. Results showed that, regardless of water content, the initial and final setting time of BEC pastes increased when the proportion of bitumen with respect to cement was increased. When the total concentration of the dispersed phases was low, the increase in bitumen concentration with respect to cement led to a reduction in the rate of viscosity increase with storage time; on the other hand, when the total concentration of the dispersed phases was high the increase of storage time led to a change in the physical state of the pastes (from fluid to plastic) due to coalescence of bitumen droplets.

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 Young's 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. Con...

The use of both cold asphalt and cold recycled asphalt mixtures produced with bitumen emulsion is constantly increasing. The failure properties of these low-energy materials are normally improved by using mineral additions or active fillers. These additions are a key component of the bituminous mortar, which binds the coarse aggregate fraction of the mixture. The objective of the present study is to investigate the evolution of the failure properties bitumen-emulsion mortars obtained by using three different types of additions: Portland cement (active filler), hydrated lime and calcium carbonate (inactive filler). The mortars were prepared with standard sand and a fixed bitumen/addition rate. Cylindrical samples were compacted with a shear gyratory compactor, the selected procedure also allowed evaluating the effect of the different additions and water content on workability. The indirect tensile strengths were measured after 7, 14, 28 and 100 days of curing in two conditions: sealed (i.e. no evaporation) and unsealed, at 50 % relative humidity. Each bituminous mortars was also characterized in terms of low temperature fracture resistance. Results showed the influence of the mineral additions on the emulsion breaking and the different curing conditions allowed highlighting the impact of both evaporation and cement hydration on strength and stiffness evolution.

The re-use of pavement materials is an efficient and cost-effective solution in road rehabilitation and construction activities, especially when the availability of high-quality virgin aggregates is limited. In this context, cold recycling of bituminous pavements is becoming one the of most attractive and low environmental impact techniques. The use of cold-recycled pavement mixtures requires a careful assessment of their mechanical properties, which are influenced by both compositional and environmental factors. In particular, regardless of aggregate nature, binder type and dosage, a distinctive feature of cold recycled mixtures is the requirement for a certain curing period to develop the ultimate values of strength and stiffness. In this study, the mechanical behaviour of cement-bitumen treated materials (CBTM), containing high percentage of reclaimed asphalt (RA), was evaluated considering the influence of curing time and temperature. Two CBTM containing 1.0 and 2.5 % cement and 2.0 % of fresh bituminous binder were analyzed. Cylindrical specimens were compacted using a gyratory compactor and cured at 25 and 40 °C; moisture loss and indirect tensile strength (ITS) were measured at increasing curing times. Results showed that the curing temperature and time (curing conditions) significantly affect the moisture loss by evaporation that therefore can be considered a good estimator of the curing process. Moreover, the mechanical characterization indicated that the moisture loss and the cement content control the increase in strength properties of the investigated CBTM. Results also showed that the cement content strongly affects the moisture loss in addition to assure improved mechanical behavior.

In this paper the laboratory curing process of two types of cold recycled mixtures manufactured during the construction of an experimental pavement section along an Italian motorway was investigated. Specifically, a cement–bitumen treated material (CBTM) mixture and a cement treated material (CTM) mixture, produced both on site and in laboratory, were tested. Moisture loss by evaporation (DW), indirect tensile stiffness modulus (ITSM) and indirect tensile strength (ITS) were measured in order to evaluate the curing process. The measured data were analyzed using the nonlinear Michaelis–Menten (MM) model with the aim to characterize the rate at which the mixture properties evolve over time and their values at the long-term cured state. The results showed that the adopted curing variables (DW, ITSM and ITS) gave a comparable description of the curing process, when evaporation was allowed and that the MM model gave an appropriate description of the evolutive behavior of CBTMs and CTMs. Finally, the results showed that in the initial curing stage the effect of cement hydration prevailed on that of emulsion breaking.