Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Silica fume


Mechanical Properties of High Performance Fiber Reinforced Concrete

Wasan Ismail Khalil; Ikbal Naeem Gorgis; Zeinab Raad Mahdi

Engineering and Technology Journal, 2013, Volume 31, Issue 7, Pages 1365-1387

An experimental work was carried out to produce high performance concrete (HPC) using superplasticizer and silica fume reinforced with fiber. The variables studied were fibers type (steel fibers and polypropylene fibers), aspect ratio of steel fibers (60 and 100) and fiber volume fraction (0.0%, 0.5%, and 0.75%). The effect of fibers on the mechanical properties (compressive strength, splitting tensile and flexural strength, static modulus of elasticity, toughness, and resilience) of normal strength and high performance concrete was also studied. The results show that the optimum dosage of silica fume is 5% as addition by weight of cement with superplasticizer dosage 2 liter/100kg of cement. This dosage of silica fume improves the compressive strength of concrete by about 25% relative to concrete mix without silica fume. The addition of steel fibers causes a slight increase in compressive strength of HPC as fiber volume fraction increases, while the compressive strength decreases as fiber aspect ratio increases. Both splitting tensile and flexural strengths show a significant increase as the fiber volume fraction and aspect ratio increases. The percentage increase in compressive, splitting tensile and flexural strengths for HPC with steel fiber volume fraction 0.75% and aspect ratio 100 at age 60 days is about 9%, 75%, 64%, while for HPC containing polypropylene fiber with volume fraction 0.5% is about 8.5%, 2%, 0% respectively relative to non fibrous HPC.

Mechanical Properties of Polymer-, Pozzolanic Cement- Based Repairing Materials

Qais J. Frayyeh; Maan S. Hassan; Tahseen D. Saadoon

Engineering and Technology Journal, 2012, Volume 30, Issue 7, Pages 1211-1221

In this study, the mechanical properties of five different cement based repairing materials were evaluated. These materials were classified into two groups: laboratory made materials with or without admixtures (3 types), and other two types of commercial proprietary pre-packaged with additives. Mechanical properties, such as compressive strength, modulus of rupture and drying shrinkage were studied. Results show that these mechanical properties were varying significantly from each other. The drying shrinkage of the commercial proprietary repair materials
was less than that of the conventional mortar. This will lead to a reduced cracking risk in the former repair materials compared to the latter. Through the regression analysis on the experimental data collected, power relation with coefficient of determination of 0.766 is obtained between compressive and modulus of rupture.

Mechanical Properties of High Performance Carbon Fiber Concrete

Wasan I. Khalil; Akar Abdulrazaq

Engineering and Technology Journal, 2011, Volume 29, Issue 5, Pages 906-924

In this research mechanical properties of high performance carbon fiber concrete
are studied. The experimental work includes, producing high performance concrete
using superplasticizer and condensed silica fume reinforced with different volume
fractions (0%, 0.2%, 0.3%, 0.4% and 0.5%) of carbon fibers. The effect of chopped
carbon fibers on the mechanical properties (compressive strength, splitting tensile and
flexural strengths, and modulus of elasticity) of high performance concrete was also
studied. Generally, the results show that the addition of carbon fibers improves the
mechanical properties of high performance concrete. Also the results show that Using
condensed silica fume as addition by weight of cement increases the compressive
strength more than that as replacement by weight of cement. The percentages increase
in compressive strength of concrete containing 15% silica fume as replacement and as
addition by weight of cement are about 14% and 26% respectively. The addition of
carbon fibers causes a slight increase in compressive strength and modulus of
elasticity of high performance concrete when the fiber volume fraction increases,
while the splitting tensile and flexural strengths shows a significant increase relative
to the reference high performance concrete (without fiber). The percentage increase in
splitting tensile and flexural strengths for high performance concrete with fiber
volume fraction 0.5% at 28 days is about 45% and 46% respectively.

Factors Affecting the Relationship Between Total Porosity and Electrical Resistivity for Concrete Repair Materials

Maan Salman Hassan

Engineering and Technology Journal, 2008, Volume 26, Issue 8, Pages 1016-1024

The paper examines the properties of five different types of repair and substrate
materials, including conventional mortar, fly ash mortar, silica fume mortar, conventional
concrete substrate, and high-performance concrete substrate materials. Assessment was
carried out on the basis of some physical properties (total porosity, and electrical resistivity).
These properties were measured at early age and later after 14 weeks of exposure conditions
to 6 % (by weight) of sodium chloride solution to simulate typical marine environment.
The results show that the electrical resistivity and total porosity measurements appear
to be related and the measurements obtained are affected by the pore structure of the
materials. It is also expresses that if a material has grater proportion of coarse aggregates (e.g.
the substrate concrete in this study) it will appear to have a lower porosity although the
porosity of mortar surrounding the aggregates could be higher. This makes comparisons
between materials containing different aggregates proportions and size difficult.