RICE PARTNERS
RICE SUMMARY
The main theme of research is the modeling of disordered materials, like e.g., cohesive (concrete) or loose (soil) materials. In the context of structural concrete, scientific activity will cover the study and development of fiber reinforced cementitious material for high performances, characterized not only by high strength, but also by ductility, durability and resistance to aggressive agents. These innovative materials, which Japan and United States began to use for the construction of structures, must be designed with a bottom-up multiscale approach, namely defining the properties of constituents and their mutual interactions and the proportions from nano- to micro- and meso-scales. In particular, the nanometric material design covers the cement mixture and the fiber/matrix interface.
At the micro-and meso-scopico level, the proper mix-design of aggregates, the definition of the percentage in volume and of the type of fiber, are crucial and the inclusion of free-flowing additives to maintain the appropriate characteristics of workability and cohesion is very important too. The joint research with Japanese and American partners will allow researchers from UTIU and Politecnico to develop new skills, expendable not only on scientific grounds, but also in technological innovation of construction products like concrete. Interest in this respect was expressed by Italian (Italcementi, Buzzi Unicem) and European (Bekaert) Companies.
RICE DETAILED DESCRIPTION
The work group investigates, from a theoretical and experimental point of view, the mechanism of adhesion in fiber reinforced composites, ordinary (FRC) and with high ductility (HPFRCC). This mechanism regulates the onset and the development of cracking, and is therefore crucial in modeling the mechanical behavior of concrete structures armed with steel bars. In the case of reinforced FRC, the study of the stick-slip mechanism, will involve the interaction fiber-cement matrix and the composite cement with rebars. The ultimate aim is to promote a wider use of the FRC in engineering structures, particularly in combination with traditional reinforcement bars. More specifically in geotechnics, the research aims to study the peculiarities of the behavior of soil materials in the mining process, in order to highlight the mechanisms that lead to phenomena of instability. In particolar, with reference to the phenomena of liquefaction of granular materials, the study will be finalized to the definition of assessment procedures that take into account explicit information about the tensional state of the porous material, overcoming the limitations inherent to the traditional semi-empiric calculations. Furthermore, the study will be focused on assessing of the evolutionary dynamics of the deformative processes that lead to the liquefaction phenomenon.
RICE OBJECTIVES
The principal aim of the research is to introduce methods of calculation and analysis that can allow a larger use of the innovative materials in construction. Based on the experimental information, a mathematical model able to justify the initiation of the phenomenon under the influence of static and dynamic loads, is desirable. This model will be used for the backward analysis in cases of rupture occurred in the past and well documented in the scientific literature, and for the assessment of stability conditions in existing or new manufacts.
In addition, experimental information about the mechanical behavior of loose granular materials, constitutes an element of fundamental importance for the study of soil liquefaction phenomena induced by earthquakes. Therefore, the results of the experimental campaign conducted on these materials, will be further supplemented by other experimental results for the study of phenomena in soil liquefaction.
RICE RESULTS
The proposed theme, characterized by a synergistic theoretical and experimental approach, will be immediately transfered to technology. There is a common opinion that a correct and comprehensive mechanical characterization of fiber reinforced composite still has not been reached. Consequently, there is no safe modeling that allows the definition of the cohesive law in a sufficient and reliable way for the current design procedures. The definition of this law can be a useful contribution for Building Codes.
Regarding geotechnics, it is expected that the laboratory tests will provide useful guidance in interpreting the mechanical behavior of loose granular materials. As already stated, the results of the experiments, will be used for the definition of a mathematical model able to interpret the phenomena of instability for the assessment of safety conditions.
The study may provide important elements for verification of the liquefaction susceptibility in the granular deposits under seismic effects, which is another aspect of particular importance, whose tremendous effects have been also documented in occasion of recent earthquakes in Japan and Turkey. Safety calculations are usually conducted on the basis of semi-empiric procedures, based on experimental correlations between the evidence of the liquefaction phenomenon and the characterization tests. There is therefore, within the technical-scientific community, a considerable interest in this topic at international level (notably Japan).
RICE ROLE OF UNINETTUNO
The UTIU provides the coordination of research, provides personnel and informatic equipment.
RICE WORK PROGRAM
Innovative high performance materials, modeling of disordered materials, mechanisms of adhesion in fiber reinforced composites.
RICE PARTNERS DESCRIPTION
The theoretical and numerical modeling for the theoretical definition of micro and meso mechanical behavior in the reinforced fiber cement composite, will be mainly developed in collaboration with MIT, where non-destructive procedures for characterization of disordered materials are adopted since several years. The experimental investigation, aimed at observing the different structural response depending on the mix design of the composite, will be conducted in collaboration with the Japanese partner. The European partners, including UTIU, will provide valuable experience on engineering achievements made by this innovative materials, especially in the field of maritime construction (Delft University, Netherlands).