الفهرس 
American standardOnly 14 pages are availabe for public view
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Abstract
Structural Behavior of Concrete Beams Cast with Blended Cement
An experimental study has been carried out in the present work to study the
structural behavior of reinforced concrete beams cast using blended cement
concrete. Each beam of the twenty two tested beams was 160 cm long × 20 cm
depth × 12 cm thick, and was simply supported.
As a first phase of this study; a limited investigation of the influence of the
dolomite powder on the mechanical properties of concrete was performed in an
earlier stage of the research to select the mixes used in the preparation of the
spliced beams. The mixes were proportioned to consider the influence of both
adding and replacing the dolomite powder at different percentages on the
compressive strength and the fracture modulus. This phase was developed to
examine 20 different normal strength concrete mixes and select the appropriate
mixes yielding the required strength and workability. Ten mixes were cast using
crushed Dolomite (D) as Coarse Aggregate (CA), and the other ten mixes were
cast using gravel (G) as coarse aggregate. The other ten mixes were
proportioned for a constant cement content of 350 kg/m3 and the Dolomite
Powder (DP) used as an addition. The other ten mixes were proportioned by
replacing the cement content (400 kg/m3) using the dolomite powder. The
addition/replacement ratios were 5, 10, 15 and 20 percent by weight of cement.
The second phase was developed to prepare and test a total of 22 RC beams.
The beams were divided into five groups A, B, C, D and E. The beams were
reinforced with two different steel reinforcement ratios of 0.70% and 1.0%.
Four beams were control beams cast using Portland cement and the other
eighteen beams were cast using blended cement incorporating 5%, 10% and
15% dolomite powder as cement replacement.
Eight beams were reinforced with unspliced steel bars as control beams,
another eight beams were provided with 200 and 240 mm splice length for the
10 and 12 mm steel bars, respectively. The remaining six beams were prepared
using a concrete mix with 15% dolomite powder and variable splice lengths
corresponding to 15, 30 and 40 times the steel bar diameter.
The aim of the research is to study the structural behavior of RC beams cast
using blended cement concrete. To achieve this aim; all beams were tested
under 4-point loading until failure and the following measurements have been
recorded during testing the beams:
1. The compressive and tensile strains in concrete and steel for each load
increment.
2. Mid-Span deflection was measured for each load increment.
3. The propagation of cracks was marked on the side and soffit of the beam.
Thesis content
The present thesis contains five chapters:
Chapter (1) Introduction
This chapter provides an introduction to the present work. It
contains the objectives of the research and the thesis outline.
Chapter (2) Literature Review
This chapter presents a summary of the previous works related
to the current research. It also presents the specifications and the
technical information about blended cement.
Chapter (3) Experimental Work
This chapter presents the detailed experimental work by
showing the configurations of test specimens, their manufacturing
and testing. It also gives all the necessary information about the
properties of the materials used in casting the test specimens.
Chapter (4) Analysis of Test Results
This chapter presents the experimental results of testing the
twenty two beams. It also explains the effect of the different
parameters. The comparisons necessary to explain the effect of
each parameter are also included.
Chapter (5) Conclusions and Further studies
This chapter reports the basic conclusions and ends with
recommendations for future research.
Research Conclusions
Based on the present research, it has been found that:
1. The compressive strength of concrete tends to decrease as the dolomite
powder replacement ratio increased. The compressive strength decreased at
a reduced rate as the replacement ratio increased.
2. Most of the reduction in the 28-day compressive strength was due to the 5
percent replacement ratio when crushed dolomite was used as coarse
aggregate. On the other hand, this ratio has almost no effect on the 28-day
compressive strength when gravel was used.
3. Concrete mixes incorporating dolomite powder showed higher rates for
gaining compressive strength between 28 and 90 days compared to control
mixes without dolomite powder.
4. Better consistency in terms of slump was obtained due to the incorporation
of dolomite powder in the concrete mixes.
5. The structural performance of unspliced beams was not significantly
influenced by the 5% dolomite powder replacement in terms of stiffness,
flexure capacity, cracking characteristics and failure mode. Higher dolomite
powder ratios of 10 and 15 percent resulted in reduced stiffness and
relatively larger tensile and compressive strain, while the cracking
characteristics and failure mode were not changed.
6. The bond strength was significantly reduced as dolomite powder
replacement ratio increased to 10 and 15 percent. Only marginal reduction
was observed at a dolomite powder replacement ratio of 5 percent.
7. The steel rebars with 10 mm diameter provided higher normalized bond
strength compared to the 12 mm rebars independent of the dolomite powder
replacement ratio.
8. The ACI 318-08 code equation for calculating the development length can
be safely applied for concrete mixes incorporating up to 15% dolomite
powder replacement.