Recently worldwide researches have been devoted to the use of steel fibers recovered from used tires in concrete. In Syria the amount of recovered steel from used tires is estimated about 6000 tons/year.
For this purpose a bead wire having a diamete
r of 0.8 mm from burnt tires was extracted and used. Three mixes with cement content 300- 350 -400kg/m3 were produced incorporating three different volumes of fiber 0.5%, 1.0%, and 1.5% and three different length 30-40-60 mm. The concrete obtained by adding these fibers evidenced a satisfactory improvement of the fragile matrix mostly in terms of toughness and post cracking behavior On the other hand it was improvements in compressive strength by steel fiber inclusion the interesting results confirm the promising application of concrete reinforced with steel fibers extracted from used tires in aircraft pavement hydraulic structures and ground slab in fabrics.
Recently, the importance of high Strength concrete has appeared due to its
application in manufacturing most of the concrete structures and members, as well as to its
importance in the implementation of civilian facilities like bridge bases, skyscr
apers and in
implementing the columns and platforms which carry oil installations carried out in the
oceans and seas. The research aims to design concrete mixtures with cylindrical resistors
( 55- 65- 75 Mpa) according to the American code AcI-211-4R-93 by using local and
appropriate additions as well as explaining the method used in designing. Then, studying
the transformation in stress strain curve – deformation
(σ- ζ ) undergoing a simple pressure on the previous samples throughout the
available devices. Then, it was compared to the charts obtained mathematically .Law
behaviour of stress strain and deformation curve was rated, in addition to modulus of
elasticity taken from the chart.
Couple of results and recommendations related to the issue were concluded, those
which were applied in praxis.
This research presents an experimental study behaviour of high strength concrete, for
evaluation of stress - strain curve and derivation of factors of equivalent compressive
stress block, we depend it in design of high strength concrete elements.
For this purpose, number of cylinders specimens with strength 60 MPa were prepared
and tested in compression, then curve was obtained.
The results showed the possibility of producing high strength concrete from local
materials and with strengths are highest than those were obtained, the resulting diagrams of
curve are shown to be essentially linearly elastic up to failure with a steeper declining
portion of the stress - strain diagram, which agree with the results of global researches, the
failure was almost sudden and rapid with increasing strength which shows that the highstrength
concrete less ductile than normal concrete at the failure. Curve of high strength
concrete differs from that normal concrete, this affects on the properties of rectangular
equivalent stress block which requires modifications on the factors led to optimum represent
for it and with evaluation of curve of the tested specimens, the diagram takes a
trapezoidal shape ( ), its value at the top is and the depth of the compressive
block is and we found and ( is average compression/cylinder
compressive strength of concrete, is ratio of the active depth that defined location of
compression force center), when concrete strength increases up , the diagram
shape will be closer to triangular than trapezoidal and then curve takes the shape of triangle its
value at the top is and the depth is and with replacing triangular diagram to rectangle.
This study presents definition of the types of lightweight concrete and
some studies, which use the volcanic scoria aggregates to produce
structural lightweight concrete.
Several concrete mixes were designed, and different tests were
performed to
determine its properties.
This study aimed to evaluate the fracture resistance of the E
glass Fiber Reinforced Composite when used to repair two different
kinds of dental porcelain.
The study of the effect of the common addition of Syrian Clay
and magnesium oxides on the specifications of the resulting
cement stone and specifically its effect on the elasticity of the
resulting stone.
This research presents an empirical relationship between modulus
of elasticity with compressive strength concrete that is prepeard
from localized materials and containing several perecentages of
natural pozzolan (0 ,10 ,15, 20)% , also for tow cem
ent quantity
(350 ,400 ) Kg/m3 and for tow ages(28 ,90 ) day .Then comparing
the experimentally obtained result with the mechanical properties
calculated using the recommend relationship from the various
design codes. A new empirical relationship between elastic
modulus, and compressive strength for concrete containing natural
pozzolan is proposed.
