scholarly journals Influence of Fiber Volume Fraction and Fiber Orientation on the Uniaxial Tensile Behavior of Rebar-Reinforced Ultra-High Performance Concrete

Fibers ◽  
2019 ◽  
Vol 7 (7) ◽  
pp. 67 ◽  
Author(s):  
Manish Roy ◽  
Corey Hollmann ◽  
Kay Wille
Keyword(s):  
Fiber Orientation ◽  
High Performance ◽  
Fiber Volume Fraction ◽  
High Performance Concrete ◽  
Volume Fraction ◽  
Tensile Behavior ◽  
Uniaxial Tensile ◽  
Ultra High Performance Concrete ◽  
Load Direction ◽  
Fiber Volume

This paper studied the influence of fiber volume fraction ( V f ), fiber orientation, and type of reinforcement bar (rebar) on the uniaxial tensile behavior of rebar-reinforced strain-hardening ultra-high performance concrete (UHPC). It was observed that the tensile strength increased with the increase in V f . When V f was kept constant at 1%, rebar-reinforced UHPC with fibers aligned with the load direction registered the highest strength and that with fibers oriented perpendicular to the load direction recorded the lowest strength. The strength of the composite with random fibers laid in between. Moreover, the strength, as well as the ductility, increased when the normal strength grade 60 rebars embedded in UHPC were replaced with high strength grade 100 rebars with all other conditions remaining unchanged. In addition, this paper discusses the potential of sudden failure of rebar-reinforced strain hardening UHPC and it is suggested that the composite attains a minimum strain of 1% at the peak stress to enable the members to have sufficient ductility.

scholarly journals Experimental Study on Shear Performance of Cast-In-Place Ultra-High Performance Concrete Structures

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3254 ◽  
Author(s):  
Li ◽  
Feng ◽  
Ke ◽  
Pan ◽  
Nie
Keyword(s):  
Shear Strength ◽  
High Performance ◽  
Fiber Volume Fraction ◽  
Steel Fiber ◽  
High Performance Concrete ◽  
Volume Fraction ◽  
Steel Fibers ◽  
Direct Shear ◽  
Ultra High Performance Concrete ◽  
Fiber Volume

In order to study the direct shear properties of ultra-high performance concrete (UHPC) structures, 15 Z-shaped monolithic placement specimens (MPSs) and 12 Z-shaped waterjet treated specimens (WJTSs) were tested to study the shear behavior and failure modes. The effects of steel fiber shape, steel fiber volume fraction and interface treatment on the direct shear properties of UHPC were investigated. The test results demonstrate that the MPSs were reinforced with steel fibers and underwent ductile failure. The ultimate load of the MPS is about 166.9% of the initial cracking load. However, the WJTSs failed in a typical brittle mode. Increasing the fiber volume fraction significantly improves the shear strength, which can reach 24.72 MPa. The steel fiber type has little effect on the shear strength and ductility, while increasing the length of steel fibers improves its ductility and slightly reduces the shear strength. The direct shear strength of the WJTSs made from 16 mm hooked-type steel fibers can reach 9.15 MPa, which is 2.47 times the direct shear strength of the specimens without fibers. Finally, an interaction formula for the shear and compressive strength was proposed on the basis of the experimental results, to predict the shear load-carrying capacity of the cast-in-place UHPC structures.

Ductility of Ultra-High Performance Concrete and its Correlation with Tensile Strength Increase

2015 ◽  
Vol 665 ◽  
pp. 21-24
Author(s):  
B.I. Bae ◽  
Hyun Ki Choi ◽  
Chang Sik Choi
Keyword(s):  
Tensile Strength ◽  
High Performance ◽  
High Performance Concrete ◽  
Volume Fraction ◽  
High Strength ◽  
Reinforcement Ratio ◽  
Fiber Reinforced Concrete ◽  
Strength Increase ◽  
Ultra High Performance Concrete ◽  
Fiber Volume

In this study, ductility of members with ultra-high performance concrete was investigated using moment-curvature analysis for the verification of safety under large deformation of ultra-high performance concrete structural members. For the analysis of members with ultra-high performance concrete, mathematical stress-strain model was selected among the results conducted by other researchers on the compressive and tensile behavior of high strength concrete and fiber reinforced concrete. According to the investigation on ductility of members with ultra-high performance concrete, decrease of ductility was observed with increase of tensile strength of concrete under the same reinforcement ratio. Members with 2~3% of reinforcement ratio, which usually be used in the field engineering, show the decrease of ductility with increase of fiber volume fraction. As a results of parametric study, limitation of maximum reinforcement ratio ( or limitation of net tensile strain ) suggested by current design code is not safe when using ultra-high performance concrete.

scholarly journals Effects of Pumice-Based Porous Material on Hydration Characteristics and Persistent Shrinkage of Ultra-High Performance Concrete (UHPC)

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 11 ◽  
Author(s):  
Kaizhi Liu ◽  
Rui Yu ◽  
Zhonghe Shui ◽  
Xiaosheng Li ◽  
Xuan Ling ◽  
...  
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Volume Fraction ◽  
Energy Dispersive Spectrometer ◽  
Effective Area ◽  
Mineral Admixtures ◽  
Ultra High Performance Concrete ◽  
Composition And Structure ◽  
Different Diameters ◽  
Hydration Characteristics

In this paper, two kinds of pumice particles with different diameters and water absorption rates are employed to substitute the corresponding size of river sands by volume fraction, and their effects on the hydration characteristics and persistent shrinkage of Ultra-High Performance Concrete (UHPC) are investigated. The obtained experimental results show that adopting a low dosage of 0.6–1.25 mm saturated pumice as the internal curing agent in UHPC can effectively retract the persistent shrinkage deformation of concrete without a decrease of strength. Heat flow calorimetry results demonstrate that the additional water has a retarding effect and promotes the hydration process. X-ray Diffraction (XRD) and Differential Thermal Gravimetry (DTG) are utilized to quantify the Ca(OH)2 content in the hardened paste, which can confirm that the external moisture could accelerate the early cement hydration and secondary hydration of active mineral admixtures. The Ca/Si ratio of C–S–H calculated by the Energy Dispersive Spectrometer (EDS) reveals that the incorporation of wet pumice can transform the composition and structure of hydration products in its effective area.

Influence of Short Polypropylene Fibers on the Toughness of High Performance Cement Slurries

2014 ◽  
Author(s):  
Thayane Martins Barghigiani ◽  
Romildo Dias Toledo Filho ◽  
Vivian K. C. B. L. M. Balthar ◽  
Cristiane R. Miranda ◽  
Reila V. Velasco
Keyword(s):  
High Performance ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Peak Load ◽  
Strain Curve ◽  
Free Fluid ◽  
Polypropylene Fibers ◽  
Fluid Density ◽  
Fiber Volume ◽  
Cracking Behavior

In oil wells, one of the goals of the cement sheath is the hydraulic seal. Generally, cement pastes, which are adopted in cementing operations, exhibit brittle fracture when subjected to tensile stresses. This behavior can compromise the hydraulic seal promoted through the sheath. One way to mitigate this problem is the use of slurries with more deformability. In this context, this work aims the determination of the toughness of high performance cement slurries reinforced by different volume fractions (0.50% and 0.75%) of short polypropylene fibers (6mm long). The influence of fiber addition in the rheological behavior, free fluid, density, stability and unconfined compression of the slurries was also determined. The obtained results indicated an increase in the yield strength and a reduction in the spreading of the reference mix with the increase of the fiber volume fraction. The free fluid, density and stability behavior of the reinforced slurries were similar to that of the control mix. An expressive change in the fracture behavior of the brittle matrix was observed in both mechanical tests carried out. Under uniaxial compression loads, although the ascending branch of the stress-strain curve did not show expressive differences with the fiber reinforcement (only minor modifications in the peak load), the descending branches were significantly modified with the reinforced mixes presenting a smooth post-cracking behavior. The greatest benefit provided by the fibers was observed, however, in the bending tests. Both, the maximum post-cracking strength and bending toughness, were significantly augmented with the increase of the fiber volume fraction.

scholarly journals Damage evaluation of ultra-high performance concrete columns after blast loads

2018 ◽  
Vol 9 (1) ◽  
pp. 44-64 ◽  
Author(s):  
Jun Li ◽  
Chengqing Wu
Keyword(s):  
High Performance ◽  
Dynamic Behaviour ◽  
High Performance Concrete ◽  
Concrete Columns ◽  
Constitutive Law ◽  
Column Height ◽  
Uniaxial Tensile ◽  
Blast Loads ◽  
Ultra High Performance Concrete ◽  
Pressure Impulse

As emerging advanced construction material, ultra-high performance concretes have seen increasing field applications over the past two decades to take advantages of their ultra-high mechanical strength and durability; yet the systematic study on its dynamic behaviour under impact and blast loads is not commonly seen. This article presents an experimental and numerical study on the static and dynamic behaviour of an existing ultra-high performance concrete material. Experimental study on its flexural behaviour under static loads is conducted and an inverse study is carried out to derive its uniaxial tensile constitutive law. The derived relationship is used in the material model in hydro-code LS-DYNA together with dynamic material properties to study ultra-high performance concrete columns under blast loads. The residual loading capacity of the column is studied and pressure–impulse diagrams for assessing the ultra-high performance concrete column damage under blast loads are proposed. Parametric study on effects of ultra-high performance concrete strength, column height, cross-section size and reinforcement ratio is performed and analytical equations are proposed for generating pressure–impulse diagrams for generic ultra-high performance concrete columns.

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