FRCC is a relatively new technology receiving a grea t deal of attention because of huge potential of application in the fiel d of civil engineering, but not limited to. The main advantage of such technol ogy with respect to the traditional concrete reinforced with steel bars ( RC) is related to increased durability, due to reduced cracking (especi ally crack width), reduced shrinkage, reduced vulnerability to corrosio n phenomena. However, in terms of mechanical performance the addition of fibers generally is not able to enhance flexural peak streng th but only to improve the post-cracking behaviour (with benefits in terms of ductility, toughness, impact resistance as well as fatigue strength). Neverthel ess, the enhancement of the flexural peak strength (as well as of residual stresses) would be a precious achievement for FRCC, allowing either to reduce longitudinal steel bar reinforcement (or even completely eliminate it in certain cases), with savings in terms of reduced manpower or to reduce se ction of structural elements (with improved lightening and energy efficiency). In particular, the purpose of this study was to evalua te the influence of different dosages of CaO-based expansive agent on the pr operties of FRCCs prepared with different types of fibers: metalli c, polymeric and glass fibers. The attention was focussed on FRCC drying shrinkage and flexural strength, since some authors detected a synergic effect between expansive agent and steel fibers in terms of increased peak flexura l/tensile strength. The final goal of this study is to proportion FRCC mix tures able to achieve very high performance in bending, both in ter ms of peak strength and post-cracking behavior, close to that obtained by the expensive UHPCs. In these FRCC mixtures, typical ingredients of UHPC such silica fume or micro silica were not used at all, and the cemen t dosage is quite low by improving the ir environmental im pact with respect to UHPCs.
calcestruzzi fibrorinforzati a matrice cementizia ( FRCC) sono materiali da costruzione relativamente recenti, che stanno desta ndo molto interesse per via delle loro grandi potenzialità applicative in ambito di ingegneria civile e non solo. Il principale vantaggio di tale t ecnologia rispetto al tradizionale calcestruzzo armato è la maggiore durabilit à del materiale, grazie alla possibilità di ridurre l ’ insorgenza di fessurazioni (e soprattutto di limitarne l ’ ampiezza), di ridurre i fenomeni di ritiro, di ridurr e la vulnerabilità ai fenomeni di corrosione. In termini di prestazioni meccaniche, l ’ aggiunta di fibre generalmente non comporta un aumento della resistenza di picco a flessione ma semplicemente un miglioramento del comportamento post-fessur ativo (con benefici in termini di duttilità, tenacità, resistenza all ’ impatto e alla fatica). Tuttavia se si riuscisse ad aumentare il valore della resi stenza massima a flessione (così come della resistenza residua), si raggiun gerebbe un prezios o traguardo per i FRCC, che permetterebbe di ridurre l a quantità di armature longitudinali (o anche di eliminarle completame nte in alcuni casi), con un risparmio in termini di manodopera, o di ri durre le sezioni degli elementi strutturali con un miglioramento in termi ni di leggerezza (con notevoli vantaggi in zona sismica) ed efficienza energetica. In particolare, lo scopo di questo studio è stato quello di valutare l ’ influenza di differenti dosaggi di un ’ agente espansivo a base di ossido di calcio sulle pr oprietà di calcestruzzi fibrorinforzati a matrice cemen tizia (FRCC) realizzati con differenti tipi di fibre: meta lliche, polimeriche e vetro. Si è posta attenzione al ritiro da essiccamento ed alla resistenza a flessione dei FRCC, poiché alcuni autori hanno evidenziato un a possibile sinergia tra agente espansivo e fibre metalliche in termini di a umento di resistenza di picco a flessione/trazione del FRCC. Obiettivo finale dello studio è stato il proporzioname nto di miscele cementizie fibrorinforzate capaci di raggiungere alt e prestazioni a flessione, sia in termini di resistenza di picco che in f ase post-fessurativa, simili a quelle ottenibili con i più costosi UHPC. In q ueste nuove miscele messe a punto non sono stati impiegati ingredienti costosi come il fumo di silice o la microsilice, e il dosaggio di cemento è stato contenuto permettendo così di migliorare l ’ impatto ambientale di questo materiale rispetto agli UHPC.
ADVANCED CEMENT-BASED COMPOSITES: STUDY OF THE SINERGIC EFFECT BETWEEN FIBER-REINFORCEMENT AND EXPANSIVE AGENT / Nardinocchi, Alessandro. - (2016 Mar 04).
ADVANCED CEMENT-BASED COMPOSITES: STUDY OF THE SINERGIC EFFECT BETWEEN FIBER-REINFORCEMENT AND EXPANSIVE AGENT
Nardinocchi, Alessandro
2016-03-04
Abstract
FRCC is a relatively new technology receiving a grea t deal of attention because of huge potential of application in the fiel d of civil engineering, but not limited to. The main advantage of such technol ogy with respect to the traditional concrete reinforced with steel bars ( RC) is related to increased durability, due to reduced cracking (especi ally crack width), reduced shrinkage, reduced vulnerability to corrosio n phenomena. However, in terms of mechanical performance the addition of fibers generally is not able to enhance flexural peak streng th but only to improve the post-cracking behaviour (with benefits in terms of ductility, toughness, impact resistance as well as fatigue strength). Neverthel ess, the enhancement of the flexural peak strength (as well as of residual stresses) would be a precious achievement for FRCC, allowing either to reduce longitudinal steel bar reinforcement (or even completely eliminate it in certain cases), with savings in terms of reduced manpower or to reduce se ction of structural elements (with improved lightening and energy efficiency). In particular, the purpose of this study was to evalua te the influence of different dosages of CaO-based expansive agent on the pr operties of FRCCs prepared with different types of fibers: metalli c, polymeric and glass fibers. The attention was focussed on FRCC drying shrinkage and flexural strength, since some authors detected a synergic effect between expansive agent and steel fibers in terms of increased peak flexura l/tensile strength. The final goal of this study is to proportion FRCC mix tures able to achieve very high performance in bending, both in ter ms of peak strength and post-cracking behavior, close to that obtained by the expensive UHPCs. In these FRCC mixtures, typical ingredients of UHPC such silica fume or micro silica were not used at all, and the cemen t dosage is quite low by improving the ir environmental im pact with respect to UHPCs.File | Dimensione | Formato | |
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