Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Superplasticizer


Strengthening of Ferrocement Beams in Torsion by CFRP Strips

Aseel Sami Al-Obaidy; Kaiss F.Sarsam; Alaa K. Abdul Karim

Engineering and Technology Journal, 2014, Volume 32, Issue 3, Pages 702-719

Torsion is resisted well by closed form reinforcement, due to the circulatory nature of the torsion inducing shear flow stresses in a beam. Therefore, it will be more efficient to have strengthening schemes, which are wrapped in closed form around the cross section. An experimental work was carried out and used superplasticizer with mix 1:1.5 to improve the mechanical properties of mortar. 12 rectangular beams (50x120)mm and 1m length are cast, strengthened and tested under pure torsion. The Variables considered in the test program include: effect number of wire mesh layers ( unit ), this unit consists of two layers of wire mesh with skeletal steel, (2, 3, 4) units and effect spacing of CFRP strips, (100,160,200) mm c/c. Test results are discussed based on torque – rotation behavior and influence of parameters on ultimate torque and failure modes. Generally, using optimum dosage of super plasticizer (1.4 % of weight of cement) gave compressive strength 65.65 MPa. Increasing the number of units from 2 to 4(reinforcement near the surface of beam section) led to increased ultimate torque by (13.44 %) and from 2 to 3(uniformly distributed reinforcement) led to increases the ultimate torque by only (3.24 %). When the beams are strengthened with CFRP strips, the lowest and highest increase in torque is at 112 % (4-units,@200 spacing) and 312 % (4-units,@100 spacing), respectively. The ultimate torque of beams with CFRP strips @ 100 mm and 160 mm spacing is greater than beams with CFRP strips @ 200 mm spacing by ( 94.34,45.28) %, respectively for the group having 4-units.

Some Properties of Concrete Containing High Fraction Volume of Metakaolin

Kais J. Frieh; Waleed A.Abbas; Marawan Mohammed Hamid

Engineering and Technology Journal, 2014, Volume 32, Issue 1, Pages 230-248

In this research, a study has been made on the effect of high fractional volume of replacement Metakaolin that results from grinding and burning the local kaolin from (Doeakhla zone / west of Baghdad / Iraq) with fineness of 18000 cm2/gm., and with temperature 700°C for one hour, on some properties of concrete (compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, density,
absorption and drying shrinkage). Also, non-destructive tests have been made (Schmidt rebound hummer and Ultrasonic pulse velocity). In this study, ten concrete mixes have been used in two Groups to get a compressive strength 40 N/mm2 at 28 days. In Group A, the percentage replace of Metakaolin have been changed from (0-70) % by weight of cement with percent increment equal to 10% for each mix, and
change the maximum size of aggregates to determine the effect of changing the surface area of aggregate as variable on the properties of concrete-containing Metakaolin, The tests for all mixes were made at ages ranged from 1 day to 90 days after mixing and replacement a dosage of superplasticizer by water content of the mix to make a constant workability with slump 50±5mm. The aim of this research is to
find a type of concrete that can be used in dams as one of the types of mass concrete, concluded from this research that replacing 70% Metakaolin instead of cement mixing the compressive strength aged 90 days less than the 63%, splitting strength at 28 days less than 27%, flexural strength at 28 days less than about 27%, the modulus
of elasticity at 28 days less than 54%, density of less than about 8% at 28 days, the absorption rate increases about 27% and drying shrinkage 1.65 * 10-4 at 60 days when compared all these tests with the reference concrete.

Mechanical Properties of Reactive Powder Concrete (RPC) with Various Steel Fiber and Silica Fume Contents

Lubna S. Danha; Wasan Ismail Khalil; Hisham M. Al-Hassani

Engineering and Technology Journal, 2013, Volume 31, Issue 16, Pages 3090-3108

An experimental work was carried out to investigate some mechanical properties
of Reactive Powder Concrete (RPC) which are particularly required as input data for
structural design. These properties include compressive strength, tensile strength
(direct, splitting and flexural), flexural toughness, load-deflection capacity and static
modulus of elasticity. The effects of three variable parameters on these properties were
carefully studied which are, the silica fume content SF (0%, 10%, 15%, 20%, 25%, and
30%) as a partial replacement by weight of cement, hooked macro steel fibers volume
fraction Vf (0%, 1%, 2% and 3%) and superplasticizertype(Sikament®-163N and
PC200).The diameter of the steel fiber is 0.5mm and its length is 30mm with aspect
ratio 60.The experimental results showed that as the silica fume content (SF) increases
from 0% to 30% the compressive strength significantly increases, while the increase in
tensile strength is relatively lower. The inclusion of steel fibers leads to a considerable
increase intensile strength, while the addition of steel fibers causes a slight increase in
compressive strength of RPC as fiber volume fraction increases from 0% to 3%.The
increase in the steel fibers volume fraction and silica fume content improved the loaddeflection
behavior and consequently gave higher ductility and fracture toughness of
RPC.

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 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.

Predicting Mechanical Properties of High Performance Concrete by Using Non-destructive Tests

Sura F. Al-Khafaji; Waleed A. Al-Qaisi; Shakir A. Al-Mishhadani

Engineering and Technology Journal, 2009, Volume 27, Issue 3, Pages 425-444

In this study, high performance concrete mixes were produced by using high
range water reducing agent and also by using 10% silica fume or 10% high
reactivity metakaolin as a partial replacement by weight of cement. Three cement
contents (350, 450, and 550) kg/m3 were used through this study. A total of 330
(100 mm) cubes, 132 (100×200 mm) cylinders, 132 (100×100×400 mm) prisms,
and 66 (150×300 mm) cylinders were casted and cured to the required age of test .
All specimens were cured in tap water except 165 cubes, which were submerged in
Cl ˉ + SO4ˉ ˉ solution at concentration identical to those present in severe
aggressive environment to study the effect of this solution on the compressive
strength of high performance concrete mixes. Compressive strength, splitting
tensile strength, modulus of rupture, static modulus, rebound number, ultrasonic
pulse velocity, dynamic modulus, initial surface absorption, density ,and total
absorption tests were investigated for all mixes at 7, 28, 90, and 120 days age.
Results of the destructive tests (compressive tensile strength, strength, splitting
modulus of rupture, and static modulus) and non–destructive tests (hammer,
ultrasonic pulse velocity, and dynamic modulus) are statistically analyzed by using
SPSS Ver.15 software to study the possibility of predicting the mechanical
properties of high performance concrete by using non–destructive tests. Simple and
multiple linear regression analysis of the obtained results leads to the proposed
statistical models for evaluating the compressive strength, splitting tensile
strength, modulus of rupture, and static modulus by using one or two or three of
the above mentioned non–destructive tests. Analysis of variance (ANOVA)
and t–test was also used to investigate the adequacy of the statistical models.