ThesisPDF Available

Fracture Behavior of Hybrid Fiber Reinforced Self-compacting Concrete.

Authors:
Fracture Behavior of Reinforced Self-
Compacting Concrete with Hybrid
Fibers
A Thesis
Submitted to the Department of Building and Construction Engineering of
the University of Technology
In Partial Fulfillment of the Requirements for the Degree of Master of Science
in Structural Engineering
By
Anmar Saddi Dhaher
(B. Sc. University of Technology, 2013)
Supervised by
Prof. Dr. Tareq Salih Al-Attar
Dr. Samer Fawzy
Republic of Iraq
Ministry of Higher Education
And Scientific Research
University of Technology
Building and Construction
Engineering Department
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Acknowledgements
First, great praise be to God who gave me the strength, faith and health
to undertake this work.
I would like to express my gratitude and thanks to my supervisors,
Prof. Dr. Tareq Salih Al Attar and Dr. Samer Fawzy, for their invaluable
advice, guidance, help and supervision throughout the performance of
this work.
I also could not forget the staff of Building and Construction Department
for their appreciable assistance and advice.
Forever, great thank are due to my family, especially my Father and my
mother for their support to finish this work.
Finally, I would like to express my extreme love and appreciation to
everyone who has supported this work especially to my friend Ahmed
Saad for his help throughout the performance of this work.
ABSTRCT
This work represents an experimental investigation and finite element modeling of
the fracture behavior of hybrid fiber reinforced self-compacting concrete,
HFRSCC. In the experimental part, two types of fiber, steel and polypropylene,
were used separately and in combination for this purpose. The adopted fiber
volumetric ratios: for steel were 0.75, 1.0 and 1.25 percent, for polypropylene were
0.10, 0.15 and 0.25 percent. In addition to that, a hybrid mixture of the
aforementioned types was used with a volumetric ratio of 0.75 percent (0.65
percent steel and 0.10 percent polypropylene fibers). This ratio was the only
possible one that succeeded in achieving the fresh requirements of self-compacting
concrete. The conducted tests were: slump flow, V-funnel, L-box, compressive
strength, splitting tensile strength and modulus of elasticity. Flexure test was done
on un-notched and notched specimens to determine fracture parameters i.e. flexural
toughness, critical stress intensity factor, KIC, fracture energy, GF, and characteristic
length, lch for the studied HFRSCC mixes. Load-deflection, P - δ and load- crack
mouth opening displacement, P - CMOD curves were plotted for both un-notched
and notched specimens. Size effect law was also investigated for the current mixes.
Four lengths of notched specimens have been adopted: 200, 400, 800 and 1200
mm. The specimen length to depth ratio, L/d, was 2.67, meanwhile the notch
depth, a0, was 0.2d.
The experimental results show that adding fibers to SCC mixes would cause a
significant reduction in the fresh state properties. Therefore, only mixes with
volumetric ratios of 0.75 and 1.0 percent steel and 0.10 and 0.15 percent
polypropylene fibers have achieved the requirements of SCC. The usage of steel
fibers always shows better results in all strength types than polypropylene fibers.
For any tested mix, the improvement in splitting strength was much higher than
that in compressive strength. Mix MSF75, containing 0.75 percent steel fibers, and
the hybrid mix MHF75, containing 0.65 percent steel and 0.10 percent
polypropylene fibers, showed almost similar improvements in post-peak strains,
splitting and flexural strengths. This observation emphasizes the advantage of
using hybrid systems of fiber from an economical point of view.
Dealing with the load deflection curves, for both un-notched and notched
specimens, a post-cracking area was developed due to the inclusion of fibers
irrespective of their type and content. The present results also prove that there is
almost linear positive relationship between deflections and CMODs of all tested
beams.
Analyzing the results of fracture parameters, KIC, GF and lch revealed that the
inclusion of fibers, irrespective of their type and content, has largely improved the
fracture behavior. These improvements were higher in value than those recorded
for compressive, tensile and flexural strengths. In addition to what stated above,
adopting the hybrid system of fiber reinforcement was effective in increasing the
fracture resistance of the studied SCC mixes. This effectiveness encourages the
usage of such system for its economic advantage.
Finite element software, ANSYS Multiphysics FLEX1m version14, was used to
simulate the behavior of fibrous reinforced SCC. The finite element model used
the smeared cracking approach. The fibers were assumed as smeared
reinforcement layers embedded in solid 65 elements. The layers were assumed to
be uniformly distributed in three directions.
A parametric study was carried out to investigate the effect of fiber content, notch
depth and size of the beam.
... Reactive powder concrete (RPC) is one of the modern and most important developments in concrete technology, it has established great attention in recent years in the world due to its superior mechanical properties such as; high strength, high ductility, high durability, limited shrinkage, high resistance to corrosion and abrasion [4,5] . Many research studied the hybrid structural element [6][7][8][9][10][11][12][13]. However, through the literature review of this study, cannot find any investigation on hybrid beam with LWC at its tension layer. ...
Article
Full-text available
The main objective of this research was studied the flexure behavior of hybrid reinforced concrete beams combining reactive powder concrete (RPC) and lightweight concrete (LWC). The experimental work consists of casting and testing in flexure seven simply supported reinforced concrete beams. The dimensions of (7) beams were geometrically similar, having rectangular cross-section, of dimensions (125×200×1600) mm. Lightweight concrete was used in tension layer and reactive powder concrete was used in compression layer for all hybrid concrete beams. The main variables were; type of concrete (LWC and RPC), thicknesses of RPC layer (hR =0, 50, 100 and 200) mm and longitudinal reinforcement ratios (ρ= 0.0033 and 0.0227). The type of LWC used in the experimental work was porecilenite aggregate. The results showed that the characteristic strength (first and ultimate loads) was increased when the thickness of RPC layer was increased. In addition to that, these parameters were decreased the values of deflection. All beams failed by flexure mode without any shear cracks which achieved by yielding of tensile steel in the tension zone. Also, for all hybrid beams, the slip was absent between the concrete layers. Finally, the reinforcement ratio (ρ) had more effective factor of all parameter used to increase the stiffness value of the beams which increased the characteristic strength and reduced the deflection values.
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