Ductilityof fiber-reinforcedself-consolidatingconcreteundermulti-axial compression

The results of 12 multi-axial compression tests performed on cylinders made of self-consolidating concrete, plain (SCC) and reinforced with steel fibers (FR-SCC), are presented. In the experimental campaign, four ‘‘reference'' confining pressures (0, 1, 3 and 10 MPa) were applied on the lateral surface of the specimens. After the first stage of loading, when a hydraulic stress was applied to the cylinders, and progressively increased up to the value of a pre-established confining pressure, a longitudinal compressive load was used to generate crushing of concrete. During this failure, the post-peak behavior of SCC and FR-SCC can be defined by a non-dimensional function that relates the inelastic displacement and the relative stress during softening. Such a function also reveals the ductility of SCC, which increases with the confinement stress and with the fiber volume fraction. In particular, by adding 0.9% in volume of steel fibers, FR-SCC can show practically the same ductility measured in unreinforced SCC with 1MPa of confining pressure. Thus, the presence of an adequate amount of fibers in SCC columns is sufficient to create a sort of distributed confinement

Comparing the environmental performances of new and renovated school buildings

Evaluating which is the best choice between renovating an existing construction or building a new structure in countries like Italy, where a huge post-war un-listed building heritage does not satisfy the current standards and the economic resources are limited, is not trivial. Several parameters come into play, such as such the extent of the construction work, the environmental cost of disposing old materials, the carbon footprint and volume of new materials. This paper is devoted to the analysis of two projects. The first consists of a renovation of a multi-storey existing school built in 1960s having total area of about 9900 m2. The second is a new construction of a three-story school having a total area of about 14000 m2 and made with timber. The results show that the existing school building, although having a lower embodied carbon related to materials, has a higher overall carbon footprint due to the CO2 emissions related to operational energy

Mechanical and Environmental Proprieties of {UHP}-{FRCC} Panels Bonded to Existing Concrete Beams

Among the techniques used to retrofit existing reinforced concrete structures, methods involving Ultra High Performance Fiber Reinforced Cementitious Composites (UHP-FRCC) are widely regarded. However, current practices make the use of this material for in-situ application expensive and complicated to perform. Accordingly, a new method to strengthen existing concrete beams by applying a precast UHP-FRCC layer on the bottom side are introduced and described herein. Two test campaigns are performed with the aim of defining the best conditions at the interface between the reinforcing layer and the existing beam and to reducing the environmental impact of UHP-FRCC mixtures. As a result, the eco-mechanical analysis reveals that the best performances are attained when the adhesion at interface is enhanced by means of steel nails on the upper surface of the UHP-FRCC layer, in which 20% of the cement is replaced by fly ash

ADVANTEX: Research of innovative tools to support the logistics of the use of excavation materials produced by the Lyon-Turin railway line for the best sustainability and circular economy of the process

The Mont-Cenis Base Tunnel is the key work of the new Lyon-Turin railway line. The project envisages a total volume of 37.2 million tons of excavated material over a period of 10 years: a considerable part of the excavated material will be used for the tunnel lining (con-crete or railway embankments) and for the embankments of the open-air sectors, while the remaining part will be transported by rail, conveyor belts, and heavy vehicles to the temporary and permanent storage sites. To maximize the circular economy and the efficiency of the materials logistic, TELT is working with the Politecnico di Torino (Department of Environment, Land, and Infrastructure Engineering, Department of Structural, Geotechnical and Building Engineering, and Department of Applied Science and Technology) and the Interdepartmental Laboratory SISCON - Safety of Infrastructures and Constructions, to study innovative solutions for the char-acterization and reuse of the excavated materials. Given that the materials are substantially undif-ferentiated during the excavation and that the geological classification requires long and complex additional verification activities, which can negatively affect the process, a significant sample of materials excavated at the survey tunnel of La Maddalena (place where the base tunnel will be excavated) were analyzed. The objective of this first phase is the search for new technologies and new processes for the early characterization of the excavated material in order to determine its intended use, designing green concretes (defining its sustainability and mechanical characteristics for structural use, through synthetic parameters, including durability analysis) and backfilling, seeking innovative tools for optimal logistics, in order to “industrialize” the identification process and optimal technologies for automatic process control and traceability, in order to give strength and speed to all activities. The subject of this work is the results of the early characterization experimentation process with the application of artificial intelligence and possible innovative circu-lar solutions

A new strategy to reduce the environmental impact of FRC

Concrete cylinders are subjected to uniaxial compression tests in order to define the whole mechanical response of different mixtures, including the strength and the post-peak ductility. With respect to traditional concretes, the deleterious effects produced by the reduction of cement content (and thus of dioxide carbon emission) can be mitigated by adding mineral admixtures and/or fibers. For instance, fly ashes and silica fumes can increase the compressive strength, even in the presence of a high water/cement ratio. Similarly, low amounts of steel fibers (less than 1% in volume) can drastically enhance the post-peak toughness. Starting from these experimental observations, a new eco-mechanical index is here introduced with the aim of defining an effective strategy to reduce the environmental impact of concrete, without any mechanical detriment. The theoretical and the experimental analyses here developed seem to confirm that the idea of tailoring a new generation of fiber-reinforced concrete, capable of maintaining high mechanical properties with a reduced amount of cement, is not a chimera

Eco-mechanical performances of reinforced concrete

A new eco-mechanical index (EMI) has been introduced with the aim of quantifying the environmental impact of concrete structures. From a general point of view, this indicator represents the amount of carbon dioxide released to produce certain mixtures of pre-established strength and ductility. Both for normal strength and high strength concrete, with and without steel fibers, these mechanical properties are summarized by the work of fracture under tensile actions. If also structural durability has to be taken into account, the maximum crack width of reinforced concrete structures must be computed. This is possible by using a tension-stiffening model, here applied to reinforced concrete elements in tension. However, with or without the evaluation of crack width, the concrete with the best EMI releases the highest fracture energy. For this reason, the work of fracture represents also a durability parameter, and therefore it can be used to tailor cement-based composites with the highest strength, ductility, and durability, and the lowest environmental impact