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Valeria Corinaldesi - One of the best experts on this subject based on the ideXlab platform.

  • Uniaxial Tensile Behavior of Ultra-High Performance Fiber-Reinforced Concrete (Uhpfrc): Experiments and Modeling
    Composite Structures, 2021
    Co-Authors: Jacopo Donnini, Giovanni Lancioni, Gianluca Chiappini, Valeria Corinaldesi
    Abstract:

    Abstract Ultra-High Performance Fiber-Reinforced Concrete (UHPFRC) is considered a promising material for many structural applications where high strength and high energy absorption capacity are required. The purpose of this work is to study the uniaxial tensile behavior of soft cast (flowable at Casting Time) UHPFRC by varying the amount of hooked steel fibers (30-mm long) from 0% up to 2.55% by volume. Direct tensile tests have been performed on dog-bone shaped specimens and Digital Image Correlation (DIC) has been used to measure displacements and deformations and to monitor the evolution of cracks. Then, a phase-field model has been implemented in a FE code and numerical simulations have been performed to better understand the effects of different fiber dosages on the mechanical behavior of UHPFRC composites and on their post-elastic evolution. Concrete matrix and fiber reinforcement have been modeled as brittle and elasto-plastic phases of a mixture, whose internal energies are enriched by non-local damage and plasticity contributions. The different failure mechanisms observed in experiments have been reproduced, including the ductile failure experienced by specimens with sufficiently high fiber dosage, which distinguishes for a strain-hardening phase of matrix multi- micro-cracking that anticipates material failure.

  • mechanical and thermal evaluation of ultra high performance fiber reinforced concretes for engineering applications
    Construction and Building Materials, 2012
    Co-Authors: Valeria Corinaldesi, Giacomo Moriconi
    Abstract:

    Ultra High Performance Fiber Reinforced Concrete (UHPFRC) is a cement-based material, which behaves like a low-porosity ceramic material with excellent mechanical performance. This work was aimed to study soft cast (flowable at Casting Time) UHPFRC s and, in particular, the Time development of compressive strength, flexural strength and elastic modulus was monitored for UHPFRC prepared by varying the water to cement ratio from 0.20 to 0.32. Silica fume, steel fibers and acrylic-based superplasticizer were employed to prepare the UHPFRC mixtures. Optimum workability and mechanical performance were obtained with a water to cement ratio of 0.24. Thermal conductivity was determined for the same UHPFRC, in the presence and in the absence of steel fibers. The scope was to evaluate the effect of steel fibers on the thermal conductivity coefficient, in order to predict the UHPFRC capacity for heat loss. This information as well as its drilling characteristics, in order to test its suitability to be machined, could be essential for possible fields of application such as in mechanical engineering, where UHPFRC materials can be employed as high abrasion-resistant dies in the molding process of metal and polymer products.

  • The Study of Using Fly Ash to Produce Ultra High Performance Fibre Reinforced Concrete
    Advanced Materials Research, 2012
    Co-Authors: Valeria Corinaldesi
    Abstract:

    Ultra High Performance Fibre Reinforced Concrete (UHPFRC) is a cement-based material, which behaves like a low-porosity ceramic material with excellent mechanical performance. This work was aimed to study soft cast (flowable at Casting Time) UHPFRCs and, in particular, UHPFRC mechanical performance was monitored by means of compression, bending and splitting tension tests. Two different kinds of mineral addition were compared: silica fume and fly ash. In the case of fly ash, several water to cement ratios were tested ranging from 0.20 to 0.25. Moreover, steel fibers and acrylic-based superplasticizer were employed to prepare the UHPFRC mixtures.

Koji Watari - One of the best experts on this subject based on the ideXlab platform.

  • Slip Casting using wet-jet milled slurry
    Journal of The European Ceramic Society, 2006
    Co-Authors: Yuji Hotta, Naoki Omura, Kimiyasu Sato, Koji Watari
    Abstract:

    Green bodies fabricated by slip Casting using wet-jet milled slurries at different solid contents (10, 30, and 50 vol.%), which had low viscosity, had very high relative density and showed very small shrinkage during sintering, as comparing to the ball-milled slurries. The square of the thickness of green bodies was proportional to Casting Time indicating slip Casting was implemented well. The relative density of the green body prepared by the wet-jet milled slurries was 67%, indicating much higher than that of the ball-milled slurries. After sintering, the linear shrinkage of the sintered bodies prepared by wet-jet slurries at different solid contents was constant at 11%. On the other hand, the linear shrinkage of the sintered bodies prepared by the ball-milled slurries was dependent on the solid contents in slurries. Thus, it was possible to produce not only green bodies with high density but also sintered bodies with low shrinkage by using the wet-jet milled slurries.

  • Slip Casting of Al2O3 slurries prepared by wet jet milling
    Journal of the Ceramic Society of Japan, 2005
    Co-Authors: Naoki Omura, Shoichi Kume, Kimiyasu Sato, Yoshiaki Kinemuchi, Yuji Hotta, Koji Watari
    Abstract:

    Green body fabricated by slip Casting using wet jet milled slurry, which had low viscosity and low re-flocculation property, had very high relative density and showed very small shrinkage during sintering. The square of the thickness of green bodies was proportional to Casting Time indicating slip Casting was implemented well. The relative density of the green body prepared by wet jet milled slurry was 67%, markedly higher than that of ball milled slurry (58%). After sintering, the compacts prepared by wet jet milled and ball milled slurry had a similar relative density of 99%. The linear shrinkages of the sintered bodies prepared by wet jet milled and ball milled slurry were 11.5 and 16.8%, respectively.

Giacomo Moriconi - One of the best experts on this subject based on the ideXlab platform.

  • mechanical and thermal evaluation of ultra high performance fiber reinforced concretes for engineering applications
    Construction and Building Materials, 2012
    Co-Authors: Valeria Corinaldesi, Giacomo Moriconi
    Abstract:

    Ultra High Performance Fiber Reinforced Concrete (UHPFRC) is a cement-based material, which behaves like a low-porosity ceramic material with excellent mechanical performance. This work was aimed to study soft cast (flowable at Casting Time) UHPFRC s and, in particular, the Time development of compressive strength, flexural strength and elastic modulus was monitored for UHPFRC prepared by varying the water to cement ratio from 0.20 to 0.32. Silica fume, steel fibers and acrylic-based superplasticizer were employed to prepare the UHPFRC mixtures. Optimum workability and mechanical performance were obtained with a water to cement ratio of 0.24. Thermal conductivity was determined for the same UHPFRC, in the presence and in the absence of steel fibers. The scope was to evaluate the effect of steel fibers on the thermal conductivity coefficient, in order to predict the UHPFRC capacity for heat loss. This information as well as its drilling characteristics, in order to test its suitability to be machined, could be essential for possible fields of application such as in mechanical engineering, where UHPFRC materials can be employed as high abrasion-resistant dies in the molding process of metal and polymer products.

Arnaud Deraemaeker - One of the best experts on this subject based on the ideXlab platform.

  • Damage detection monitoring applications in self-healing concrete structures using embedded piezoelectric transducers and recovery
    Journal of Physics: Conference Series, 2015
    Co-Authors: G Karaiskos, Eleni Tsangouri, Arnaud Deraemaeker, Dimitrios G Aggelis, Danny Van Hemelrijck
    Abstract:

    The ageing, operational and ambient loadings have a great impact in the operational and maintenance cost of concrete structures. Their service life prolongation is of utmost importance and this can be efficiently achieved by using reliable and low-cost monitoring and self-healing techniques. In the present study, the ultrasonic pulse velocity (UPV) method using embedded small-size and low-cost piezoelectric PZT (lead zirconate titanate) ceramic transducers in concrete with self-healing properties is implemented for monitoring not only the setting and hardening phases of concrete since Casting Time, but also for the detection of damage initiation, propagation and recovery of integrity after healing. A couple of small-scale notched unreinforced concrete beams are subjected to mode-I fracture through three-point bending tests. After a 24-hour healing agent curing period, the beams are reloaded using the same loading scenario. The results demonstrate the excellent performance of the proposed monitoring technique during the hydration, damage generation and recovery periods.

  • Monitoring of the ultrasonic P-wave velocity in early-age concrete using Smart Aggregates
    MATEC Web of Conferences, 2012
    Co-Authors: Cédric Dumoulin, G Karaiskos, Jerome Carette, Stéphanie Staquet, Arnaud Deraemaeker
    Abstract:

    This paper deals with the use of embedded piezoelectric transducers to monitor the ultrasonic P- wave velocity evolution during the setting and hardening phases of concrete since Casting Time. The main ad- vantage of the technique is the ability to overcome the limitations of traditional methods which do not allow to apply specific mechanical boundary conditions during the measurement. The embedded transducers are based on the "Smart Aggregates" concept previously developed at the University of Houston, Texas. Two piezoelectric transducers are embedded in a prismatic mold and the evolution of the P-wave velocity is recorded for the first 24 hours in concrete after Casting Time. The results are very promising and show a good agreement with classical ultrasonic tests using external transducers.

  • monitoring of the ultrasonic p wave velocity in early age concrete with embedded piezoelectric transducers
    Smart Materials and Structures, 2012
    Co-Authors: Cédric Dumoulin, G Karaiskos, Jerome Carette, Stéphanie Staquet, Arnaud Deraemaeker
    Abstract:

    This note deals with the use of embedded piezoelectric transducers to monitor the ultrasonic P-wave velocity evolution during the setting and hardening phases of concrete subsequent to Casting Time. The main advantage of the technique is the possibility of overcoming the limitations of traditional methods which prevent the application of specific mechanical boundary conditions during the measurement. The embedded transducers are based on the ‘smart aggregates’ concept previously developed at the University of Houston, Texas. Two piezoelectric transducers are embedded in a prismatic mold and the evolution of the P-wave velocity is recorded for the first 24 h in concrete after the Casting Time. The results are very promising and show a good agreement with classical ultrasonic tests using external transducers. (Some figures may appear in colour only in the online journal)

Yuji Hotta - One of the best experts on this subject based on the ideXlab platform.

  • Slip Casting using wet-jet milled slurry
    Journal of The European Ceramic Society, 2006
    Co-Authors: Yuji Hotta, Naoki Omura, Kimiyasu Sato, Koji Watari
    Abstract:

    Green bodies fabricated by slip Casting using wet-jet milled slurries at different solid contents (10, 30, and 50 vol.%), which had low viscosity, had very high relative density and showed very small shrinkage during sintering, as comparing to the ball-milled slurries. The square of the thickness of green bodies was proportional to Casting Time indicating slip Casting was implemented well. The relative density of the green body prepared by the wet-jet milled slurries was 67%, indicating much higher than that of the ball-milled slurries. After sintering, the linear shrinkage of the sintered bodies prepared by wet-jet slurries at different solid contents was constant at 11%. On the other hand, the linear shrinkage of the sintered bodies prepared by the ball-milled slurries was dependent on the solid contents in slurries. Thus, it was possible to produce not only green bodies with high density but also sintered bodies with low shrinkage by using the wet-jet milled slurries.

  • Slip Casting of Al2O3 slurries prepared by wet jet milling
    Journal of the Ceramic Society of Japan, 2005
    Co-Authors: Naoki Omura, Shoichi Kume, Kimiyasu Sato, Yoshiaki Kinemuchi, Yuji Hotta, Koji Watari
    Abstract:

    Green body fabricated by slip Casting using wet jet milled slurry, which had low viscosity and low re-flocculation property, had very high relative density and showed very small shrinkage during sintering. The square of the thickness of green bodies was proportional to Casting Time indicating slip Casting was implemented well. The relative density of the green body prepared by wet jet milled slurry was 67%, markedly higher than that of ball milled slurry (58%). After sintering, the compacts prepared by wet jet milled and ball milled slurry had a similar relative density of 99%. The linear shrinkages of the sintered bodies prepared by wet jet milled and ball milled slurry were 11.5 and 16.8%, respectively.