Giulio Dondi

Construction and demolition waste recycling: an application for road construction

One of the applications of recycled aggregates from construction and demolition processes is the construction of embankments, subbases and foundations for roads where unbound materials are used in replacement for natural aggregates. This work focuses on studying the development of the stiffness of recycled materials during construction, as well as how it modifies over time. The study assessed also the correlation between testing systems. A purpose-built experimental embankment with four sections of different recycled materials was built and tested. Fields were made from two structural layers, forming a homogenous thickness of about 80 cm. The compaction and testing took place using the Continuous Compaction Control technique, obtaining bearing capacity records during the embankment construction phases. The structural performance of the embankment was also determined using different types of light-weight deflectometers. The results show that recycled aggregates perform well when properly compacted and may show some positive self-cementing properties.

Discrete particle element analysis of aggregate interaction in granular mixes for asphalt: combined DEM and experimental study

The conventional approach to modeling asphaltic materials is to treat them at macro-scale using continuum-based methods. Numerous research works, however, show that for these mixtures it’s very important to take into account their micromechanical behaviour, at the scale of aggregate particles, because it is a primary factor in terms of overall system performance. In this way the Distinct Particle Element Method (DEM) represents a very useful tool.

Rheological Characterization of Bituminous Mastics Containing Waste Bleaching Clays

Bleaching clays are mostly used in food industries to clarify vegetal oils. After use they are generally dumped as waste (stage 1) or used in green innovative plants to feed biogas reactors (stage 2). In latter stage the initial residual oil content (approx. 25 % by mass) is reduced to less than 1 % by the biological process. In this study the bleaching clays effects on bituminous mastics of a traditional binder course Hot Mix Asphalt have been investigated. The physical characteristics of the two bleaching clays and of a traditional limestone filler were also studied. DSR rheological tests at high and low temperatures were performed on mastics samples containing different amounts of fillers (limestone, stage 1 or stage 2). The addition of the different waste bleaching clays significantly affects the rheological behavior of the mastics: the filler from stage 2 increases the mastic stiffness improving the resistance to permanent deformations as shown by repeated creep tests, while the filler from stage 1 strongly interacts with the bitumen reducing the mechanical characteristics of the mastics at all temperatures.

Incorporation of Rubber Powder as Filler in a New Dry-Hybrid Technology: Rheological and 3D DEM Mastic Performances Evaluation

In recent years, the use of crumb rubber as modifier or additive within asphalt concretes has allowed obtaining mixtures able to bind high performances to recovery and reuse of discarded tires. To date, the common technologies that permit the reuse of rubber powder are the wet and dry ones. In this paper, a dry-hybrid technology for the production of Stone Mastic Asphalt mixtures is proposed. It allows the use of the rubber powder as filler, replacing part of the limestone one. Fillers are added and mixed with a high workability bitumen, modified with SBS (styrene-butadiene-styrene) polymer and paraffinic wax. The role of rubber powder and limestone filler within the bituminous mastic has been investigated through two different approaches. The first one is a rheological approach, which comprises a macro-scale laboratory analysis and a micro-scale DEM simulation. The second, instead, is a performance approach at high temperatures, which includes Multiple Stress Creep Recovery tests. The obtained results show that the rubber works as filler and it improves rheological characteristics of the polymer modified bitumen. In particular, it increases stiffness and elasticity at high temperatures and it reduces complex modulus at low temperatures.

The Use of Cryogenic Crumb Rubber in the Cold Recycling Technique

In the recent years, recycling has become one of the most attractive pavements rehabilitation alternatives and different recycling methods are now available to address specific pavement distresses and structural needs. Cold recycling is an economically efficient and environmental-friendly method for producing bituminous layers of adequate strength. This technique has been successfully used in Italy during the past 15 years to rehabilitate or upgrade many thousands of kilometers of highways and motorways’ pavements. Currently a wide range of materials can be used and consequently large is the number of variables to be considered in the mixdesign process. Being this a relatively new technique, new products are continually introduced or developed for recycling purposes. The main objective of this study is to investigate and evaluate the effects of crumb rubber, cement and bitumen proportions on the engineering properties of fully recycled cold mixes. In fact, the experimental plan includes the use of various quantities of Cryogenic Crumb Rubber (CCR) in mixtures containing 100% of Reclaimed Asphalt Pavement, bituminous emulsion and Portland cement. Thanks to the new European and national regulations, the use of recycled rubber in road construction applications has been growing so far and this application could represent a valid alternative to the classical use of rubber in HMAs.

Applying Geostatistics to Continuous Compaction Control of Construction and Demolition Materials for Road Embankments

AbstractContinuous compaction control (CCC) with constant roller settings provides useful data on the stiffness of the layers involved. By carefully analyzing the data, it is possible to estimate how compaction will evolve during the construction process. Applying geostatistics to CCC data means that spatial variability can be quantified, something that is difficult using simple statistical analysis. Univariate statistics of CCC measurements alone do not describe spatial variability, and neither do they address the issue of uniformity from a spatial standpoint. Furthermore, it is important to choose the variogram model wisely, so that the factors distinguishing the areas being investigated can be fully appreciated. This article was prepared using statistics and geostatistics on experimental data obtained from an embankment made of recycled materials.

Modular model building for vehicular traffic systems with macroscopic dynamics

Abstract Vehicular traffic modeling, analysis and supervision has became in the last year very attractive both for engineers and mathematicians with the aim of understanding, controlling and forecasting traffic phenomena. In this framework, the use of simulation tools has spread rapidly both to adequately perform the design of a road infrastructure, and as a support to simulate and verify the road infrastructure. Currently available simulators are in general closed systems where designers have no access to the implemented models, do not permit the integration of macroscopic and microscopic models together and are usually separated from design and verification tools. This paper presents a preliminary study on how to fill these gaps by using a modular model building approach. The developed elementary traffic models have been implemented into Matlab/Simulink environment and collected into a sort of library. The approach has been tested and validated using a real scenario and the available traffic measurements. Copyright ©2011 IFAC.

Experimental application of waste glass powder filler in recycled dense-graded asphalt mixtures

This paper presents laboratory study results, including both bituminous mastics and mixtures tests, to assess the use of glass powder (GP) as possible surrogate to limestone filler in recycled dense-graded asphalt mixtures. To achieve a comprehensive approach, the analysis has been divided into three parts including filler, mastics and mixture characterisation. The GP has been completely studied with chemical and physical tests to compare the fundamental characteristics to the commonly used limestone filler. In the second part, rheological tests using the Dynamic Shear Rheometer has been implemented to evaluate fillers interaction with not modified and modified bitumen. Finally, the mechanical properties of the asphalt mixtures containing GP filler were investigated in terms of indirect tensile strength, indirect tensile stiffness modulus and creep characteristics. According to the obtained results, GP filler provided comparable values to limestone filler within both mastic and mixture study. It is noteworthy that from the permanent deformation analysis, both MSCR and RLAT tests confirmed the improvement of rutting resistance with using GP filler.

Effects on Bonding of Anti-reflective Cracking Solutions at the Top Bituminous Interface of a Small Airport Pavement: A Laboratory and Modeling Study

The maintenance of bituminous airport pavements is of high concern when the limited available time for interventions and the performance effectiveness of the adopted materials are considered. In many cases, due to their former military vocation, small airport pavements have robust, sound and durable foundations that seldom require deep interventions of maintenance. Thus, it is more often needed to rehabilitate the pavement bituminous surface layers to restore the functional characteristics of the runaway and to protect the bottom layers from water leaching through the surface damages (e.g. cracks). This paper shows an example of airport pavement maintenance that was designed to rehabilitate the wearing course of a cracked bituminous structure that was proven to have sufficient bearing capacity. In order to prevent the reflection of cracks on the new layer, the effects of using both a geosynthetic net and a Stress Absorbing Membrane Interlayer (SAMI) were investigated at the old-new materials interface. The effects of debonding and the potential risk of slippage or delamination of the new wearing course were assessed by means of laboratory direct shear tests and multilayer elastic pavement system modeling.