Researcher Mohammed Farhan Ajami's doctoral dissertation was discussed at the College of Engineering, Department of Civil Engineering, University of Basra, entitled "The Structural Behavior of Reinforced Concrete Beams Strengthened with Slurry Infiltrated Fiber Concrete includes:
Slurry-infiltrated fiber concrete (SIFCON) can be considered a specialized
type of fiber-reinforced concrete, offering superior mechanical and durability
properties. Several factors affect the mechanical properties of SIFCON. In this
experimental study, an attempt was made to investigate the effect of five essential
factors on the mechanical properties of the SIFCON in its fresh and hardened
states. These five factors are the mixing procedure of the raw materials, the sand-
to-binder ratio, the replacement ratio of cement with mineral additives, the casting
strategy of SIFCON, and the geometry and characteristics of the steel fiber. The
study determined the best ratios of slurry components and explained how these
ratios affect the properties of SIFCON. It also identified the most effective mixing
method for the raw materials and the best pouring technique for SIFCON. The
results demonstrate that the geometry and characteristics of the fiber have a
significant influence on the mechanical properties of hardened SIFCON. Among
the studied fibers, the hook-ended steel fiber with a length of 30 mm and a
diameter of 0.5 mm yielded the best results.
Also, This study examined the influence of various factors on the bonding
performance between the SIFCON overlay and the Normal Strength Concrete
NSC substrate. The research investigated the effects of surface preparation
methods, types of bonding agents, steel fiber geometry, bonding conditions (fresh
overlay on hardened substrate and hardened overlay on hardened substrate),
dowel placement, the geometry of the SIFCON jackets, and the bonding
mechanism. Four tests were conducted to evaluate bond strength: the Slant Shear
Test (SST), Tensile Bond Test (TBT), Flexural Bond Test (FBT), and Direct
Shear Test (DST) using a reinforced NSC cube externally bonded with SIFCON
jackets subjected to direct shear. In all tests, using epoxy as a bonding agent
resulted in superior bond performance compared to samples without a binder or
those that used latex. The results show that using chipping instead of diamond
cutting increased the bonding strength by 8.91% to 13.84%. Additionally, using
dowels in the bonding systems contributed to improvements in bond performance
ranging from 10.89% to 16.97%. The bond performance of the specimens with a
cast-in-situ jacket is superior to that of the specimens with a precast jacket layer.
This study examined the structural behavior of sixteen shear-deficient and
fourteen flexural-deficient RC beams strengthened or repaired with SIFCON
jacketing. It highlighted the most important factors influencing the effectiveness
of the strengthening and repair methods. These factors include jacket
configurations, jacket thickness, jacket length, the type of steel fibers in SIFCON,
whether the main reinforcement is within the jacket, bonding strategy, and shear-
span-to-depth ratio. The study concluded that using SIFCON jacketing has a
significant impact on the structural behavior of the strengthened beams. Although
all the strengthened samples showed notable improvements in load-bearing
capacity, this may potentially lead to the deterioration of some structural
properties, such as ductility and toughness. there is no single best strengthening
configuration, as its effect on structural properties varies. Therefore, the optimal
strengthening configuration depends on the specific property that needs to be
improved when strengthening the beam. If the goal is to increase the ultimate load,
stiffness, or serviceability, then the U-shaped strengthening approach is preferred.
To improve ductility, using SIFCON jackets on the beam webs may be the best
choice. Also, it can be concluded that the efficiency of strengthening and repairing
an existing shear-deficient beam with SIFCON jacketing increases as the shear-
span-to-depth ratio rises.
