Experimental characterization of the 3D linear viscoelastic behavior of cold recycled bitumen emulsion mixtures

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

The evolution of the mechanical behaviour of cold recycled mixtures stabilised with cement and bitumen: field and laboratory study

from the demolition of old asphalt pavements. Recycling allows environmental and economic benefits to be achieved, by reducing the consumption of natural resources. These advantages are maximised with cold-recycling, in particular when full depth reclamation (FDR) is adopted as road rehabilitation technique. The aim of this research was to compare different FDR techniques, which produce cement-treated material and cement–bitumen treated material (CBTM) combining the use of cement and bitumen emulsion or foamed bitumen. The FDR was applied in a trial section built along an in-service highway and monitored with annual falling weight deflectometer (FWD) surveys in order to evaluate the performance evolution. Results highlighted that, because of the effect of temperature, the FWD deflections were not suitable to accurately evaluate the evolution of the mechanical behaviour of the cold recycled mixture (CRM) layers. However, the temperature-corrected FWD moduli allowed to conclude that the performance of the CRM layers was similar

Instrumented test section for analyzing the curing process of cold-recycled mixtures

An instrumented pavement section was realized during the widening of an Italian motorway in order to evalu-ate the curing process and performance of two types of cold-recycled mixtures: a cement treated material (3% of cement) and a cement-bitumen treated material (2% of cement and 3% of bitumen emulsion). The mixtures were fabricated in place by full-depth reclamation and, before the construction of the upper courses; the recy-cled layer was instrumented with pressure cells, asphalt strain gauges, time domain reflectometer probes and temperature sensors. After construction, part of the recycled layer was sealed with bitumen emulsion in order to evaluate the effect of free or prevented water evaporation on the curing process. This paper describes the site preparation, the pavement construction phases, sensor installation and the setup of the data acquisition system. The moisture data recorded by the time domain reflectometer probes during 90 days are presented. Results show that moisture loss was higher for the cement treated material that was characterized by higher cement content. In addition, covering the layer with a bitumen emulsion membrane (i.e. preventing water evaporation) induced a marked reduction (around 50%) of the initial curing rate

Cyclic Approach to Airport Pavement Management Based on Non-Destructive Deflection Testing

The Authors describe the role of non-destructive deflection tests in Airport Pavement Management System (APMS) presenting the experience developed at an Italian Airport. An original approach to APMS implementation is illustrated, based on the PDCA cycle for quality control and continuous improvement of processes. An example application for the management of the runway pavement is described. Deflection test results obtained in four tests campaign carried out over a ten years period were globally analyzed to obtain pavement bearing capacity evolution and demonstrate the effectiveness of cyclic approach to pavement management. It is showed that structural evaluation can be an invaluable tool in pavement management and assist planning activities in the medium and long term

Early age evolution of rheological properties of over-stabilized bitumen emulsion-cement pastes

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

Instrumented test section for analyzing the curing process of cold-recycled mixtures

An instrumented pavement section was realized during the widening of an Italian motor- way in order to evaluate the curing process and performance of two types of cold-recycled mixtures: a cement treated material (3% of cement) and a cement-bitumen treated material (2% of cement and 3% of bitumen emulsion). The mixtures were fabricated in place by full-depth reclamation and, before the construction of the upper courses, the recycled layer was instrumented with pressure cells, asphalt strain gauges, time domain reflectometer probes and ther mistors. After construction, part of the recycled layer was sealed with bitumen emulsion in order to evaluate the effect of free or prevented water evaporation on the curing process. This paper describes the site preparation, the pavement construction phases, sen- sor installation and the setup of the data acquisition system. The moisture data recorded by the time domain reflectometer probes during 90 days are presented. Results show that moisture loss was higher for the cement treated material that was characterized by higher cement content. In addition, covering the layer with a bitumen emulsion membrane (i.e. preventing water evaporation) induced a marked reduction (around 50%) of the initial curing rat

Cold in-place recycling for a base layer of an Italian high-traffic highway

Cold in-place recycling (CIR) has increasing interest worldwide due to the large economic and environmental benefits deriving from reduction of atmospheric emissions, preservation of natural resources, no hauling of the material to the recycling plant and back to the jobsite. However, a unique protocol for the structural rehabilitation of highly trafficked highways based on CIR has not been still developed, discouraging their application in the upper layers of the pavement (base layer). This paper describes a case study where a cold recycled asphalt base (CRAB), containing 100% of reclaimed asphalt treated with polymer-modified bitumen emulsion and cement, has been applied in the reconstruction of the SS268 divided highway in southern Italy. The technical approach followed in this project included the preliminary execution of falling weight deflectometer tests to estimate the subgrade stiffness, the design of the pavement structure through a mechanistic-empirical procedure, the mix design of the CRAB and the validation of the construction procedure and mix properties in a trial section. This paper aims to provide a protocol for the design and construction of CIR mixtures, allowing their use as base layer for the highways interested by a high traffic

Research and Engineering for Resilient Infrastructures and Environment Protection

We discuss the contribution of the research groups that work at UNIVPM in the field of infrastructure engineering to the design of resilient hydraulic and transportation infrastructures and related solutions for the protection of the environment. After recalling the long history of research and engineering intervention of the groups of Hydraulics and Transportation Infrastructures of UNIVPM, we show how the activities of such groups are becoming of increasing importance in response to the growing request of innovative solutions for resilient infrastructures (e.g. coastal protection and maritime structures, road and airport pavements) and environment protection (e.g. coastal and river flood, air pollution, waste recycling and materials reuse). Such activities have been recently boosted by the resources made available to the two groups through the “Dipartimenti di Eccellenza” award, which largely focuses on the issue of engineering for resilient built and natural environments. A projection in the future of the activities of above is also proposed