Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : compressive strength


Thermal Properties of Recycle Aggregate Concrete with Different Densities

Amer M. Ibrahim; Shakir A. Al-Mishhadani; Noor Al Huda H. Ahmed

Engineering and Technology Journal, 2015, Volume 33, Issue 9, Pages 2027-2038

The present research intended to determine thermal properties (thermal
conductivity, thermal diffusivity and specific heat) of concrete manufactured by recycle waste of clay brick and thermostone for using it as aggregate after crushing process. For this purpose, three concrete mixes were prepared one of them using crushed clay brick as aggregate and two others were used crushed thermostone as aggregate too, these three mixes compared with reference normal concrete mix.
Specific heat was measured by using semi-adiabatic calorimeter method whereas thermal diffusivity was measured by using heating-cooling system. Thermal conductivity was obtained by multiplying the thermal diffusivity, specific heat and density. From experimental laboratory work, it was concluded that the thermal diffusivity increase with concrete density increment, but the specific heat was decreased with concrete density increment. Thermal conductivity had a linear relationship with thermal diffusivity. Mixing ratio also had an influence on thermal properties of concrete.

New Technique for Producing Vacuum Concrete

Haitham Hazim Saeed; Anas Amjed Ezzulddin

Engineering and Technology Journal, 2015, Volume 33, Issue 3, Pages 659-667

In this work a new technique is used to produce vacuum dewatered concrete. In this technique perforated PVC pipes encased in cotton cloth are used to dewater concrete from inside of concrete volume, rather than from the surface, as is the case in the conventional vacuum dewatering method. These pipes are laid in position inside concrete forms, and a vacuum pump is connected to the dewatering pipes, which is operated after casting of fresh concrete to remove the excessive water from internal portion. Properties of vacuum dewatered concrete using the new technique are investigated by a series of tests such as compressiveand flexural strength tests. Based on test results, the new technique improves concrete strength and other mechanical properties particularly at early ages. The new dewatering technique is a good alternative to the conventional vacuum dewatering technique and can have a wider range of practical applications than the conventional method.

Effect of Practical Curing Methods on the Properties of Roller Compacted Concrete

Hisham K. Ahmed; Intesar Kadhim Gata

Engineering and Technology Journal, 2015, Volume 33, Issue 2 engineering, Pages 500-511
DOI: 10.30684/etj.2015.101919

Roller Compacted Concrete (RCC) is a technology characterized mainly by the use of rollers for compaction. This construction method permits considerable reduction in costs and construction time of dams and roads. It is necessary to study the curing of RCC especially in hot weather because RCC has no slump and has low W/C ratio. Therefore the primary scope of this research is to study the effect of various curing methods (continuous watering, wet burlap, nylon, sprinkling, curing cycles, and curing compound) after 24 hrs from casting on the physical properties of roller compacted concrete.
The mix proportion which was used in this investigation, was designed and laboratory tried on the basis of using 250 kg/m³ of Ordinary Portland Cement. This work involves preparing cylindrical specimens with (diameter of 150 mm and height of 300 mm) for measuring the compressive strength, splitting-tensile strength, and static modulus of elasticity. And it also includes prism specimens with (100×100×400 mm) for measuring the modulus of rupture (flexural strength).
Results show that the curing of RCC with continuous watering clearly improved the RCC properties. The results also indicate that the RCC specimens without curing (left in air) suffered from permanent loss of strengths ranging between 20 to 25 % when compared with continuous watering at age of 28 days.

Effect of Compaction Methods on the Properties of Roller Compacted Concrete

Hisham Khalid Ahmed; Azal Thair Abdulrazzak

Engineering and Technology Journal, 2014, Volume 32, Issue 10, Pages 2454-2464
DOI: 10.30684/etj.32.10A.10

Roller compacted concrete (RCC) is a technology characterized mainly use of roller for compaction. This construction method permits considerable reduction in costs and construction time of dams and roads. The main aim of this work is to investigate the influence of compaction methods on the properties of RCC. the experimental program included preparing cylindrical specimens with (diameter of 150 mm by height of 300 mm) for measuring the compressive strength, splitting tensile strength and absorption. And it also includes prism specimens with (100*100*400) mm for measuring the modulus of rupture. These specimens were compacted by using different compaction methods, dynamicly (modified proctor hammer compaction (CBR test), vibrator table, and vibrator table with CBR test) and statically (compacting pressure (compacting pressure 10 MPa, 15 MPa and 20 MPa).
Results show that the compaction methods have a noticeable effect on the properties of RCC. The results also indicated that using vibrator table with CBR show an increase in the compressive strength, splitting tensile strength and modulus of rupture by 23%, 14% and 13%, respectively as compared with compacted by vibrator table only. The results also show that using compacting pressure 20 MPa show an increase in the compressive strength, splitting tensile strength and modulus of rupture by 31%, 27%, and 39%, respectively as compared with that made by compacting pressure 10 MPa.

Effect of Concrete Compressive Strength and Compression Reinforcement in Compression Zone on the Ductility of Reinforced Concrete Beams

Sawsan Akram Hassan; Awadh Ewayed Ajeel

Engineering and Technology Journal, 2014, Volume 32, Issue 5, Pages 1106-1116
DOI: 10.30684/etj.32.5A.2

Ductility is a mechanical property used to describe the extent to which materials can be deformed plastically without fracture giving warning of impending failure. In this paper the effect of increasing the strength in the compression zone of reinforced concrete beams on ductility was investigated. Seven reinforced concrete beams were tested for this purpose. The tested beams were divided into two groups depending on the manner at which the strength of the compression zone was increased. In the first group, the increase was done by increasing the amount of compression reinforcement. Four ratios of compression reinforcement were adopted. In the second group, the increase in the strength of the compression zone was done by increasing the concrete compressive strength in the upper third of the cross section which was subjected to compression stresses. Four compressive strengths were adopted .One beam was used as reference for the two groups. It was found that, the compression zone strengthening, by the two manners, increases both strength and ductility of the beams; but the increases due to increase the ratio of compressive reinforcement is higher and more safety than that attained due to increasing concrete compressive strength.

Behavior of Plain and High Performance Polypropylene Fiber Concrete Subjected to Elevated Temperatures

Luma Abdul Ghani Zghair

Engineering and Technology Journal, 2011, Volume 29, Issue 8, Pages 1517-1535

The aim of this work is to determine the residual compressive strength and splitting tensile strength after exposure to an elevated temperature (between100 to 500 C ◌ْ ) of plain and polypropylene fiber reinforced concrete (PPFRC) in comparison with specimens exposed to ordinary temperature 25C ◌ْ . High – performance concrete mixes were produced by using high rang reducing agent superplasticizer (SP) and 10% high reactivity metakaoline (HRM) as a partial replacement by weight of cement (350)Kg/m3 . A single concrete mix with HRM,
SP and four PPF contents of (0.25, o.5, o.75 and 1%) by volume were adopted. The workability of the concrete was kept constant ( slump 100 ± 5mm ).Each group of specimens ( plain and PPFRC ) was heated to a specified temperature and kept at the temperature for one hour before being gradually cooled to room temperature and then they were tested .
The results show at ordinary temperatures 25 C ◌ْ, the addition of fiber volume fraction (VF%) of (0.25%) increases the compressive ( 20.6% ) comparable to HPC without fiber . While the addition of ( 0.5 , 0.75 and 1% ) of polymer fibers , the compressive strength decreased (12.6 , 19 and 33%) respectively comparable to HPC without fiber . On the other hand the addition of (VF%) of (0.25) increased splitting tensile strength ( 15%) comparable to HPC without fiber . while the
addition of fiber volume fraction (VF%) of (0.5 ) increased splitting tensile strength by a percentage which is lower than that in specimens with VF% of 0.25 , the increase in splitting tensile strength was ( 6%) comparable to HPC without fiber at ordinary temperatures
The results also shows that , when (1% ) fibers was used , the splitting tensile strength decreased ( 10.8%) in comparable to HPC without fiber At elevated temperature the results show an appreciable decrease in compressive strength and splitting tensile strength after exposure to temperature higher than 300 C ◌ْ of both plain and PPFRC
Specimens containing PPF ( 0.25 , 0.5 , and 0.75 %) the percentage of
reduction in splitting tensile strength is lower than that in HPC specimens ( without fibers ) after exposure to a temperature ( 500 ,300 and 100 C ◌ْ ) comparable to normal temperature 25C ◌ْ .While specimen containing PPF ( 1% ) the percentage of reduction in splitting tensile strength was higher than specimen without PPF after exposure to a similar temperature .On the other hand , specimens containing PPF ( 0.25 , 0.5 , 0.75 and 1 %) the percentage of reduction in compressive strength is higher than that in HPC specimens ( without fibers ) after exposure to a temperature (500 ,300 and 100 C ◌ْ). comparable to normal temperature 25C ◌ْ

One Parameter Composite Semigroups of Linear Bounded Operators in Strong Operator Topology of Schatten Class Cp

Samir Kasim Hassan; Al-Taie M; Al-Malki Anam; Al-Attar Abeer; Mustafa Khaleel Ismael; Fatema Ahmed Sadeq; Radhi A .Zboon; Jehad R.Kider; Samir K .Hassan; Hussain J. M. Alalkawi; Raad H. Majid; Rawaa A. Alomairy; Luma Abdul Ghani Zghair; Hadia Kadhim J.Al-Ogili; Assifa M. Mohamad; Abbas Sheyaa Alwan; Haider L. Aneed; Assim H Yousif; Salema Sultan Salman; Abbas Hussien Miry; Abduladhem A.Ali; Mohammed Zeki Al-Faiz; Sabah N. mahmood; Khansaa Dawood Selman; Shaymaa Tareq Kadhim

Engineering and Technology Journal, 2011, Volume 29, Issue 8, Pages 1463-1470

For semigroups of linear bounded operators on Hilbert spaces, the problem of
being in Cp , 0 Keywords

Mechanical Strength of Silicon Carbide Bonded with Iraqi Clays

Abdul Mutalb Al Sheikh; Shihab Ahmed Zaidan Al- Juboori; Kassim S. Kassim

Engineering and Technology Journal, 2011, Volume 29, Issue 4, Pages 665-676

Two types of Iraqi clays (Kaolin and Bentonite) were used in bonding process
with different weight percentage (5%, 10%, 15%, 20%, and 25%) and with
different particle size from clays and silicon carbide.
The specimens were formed by using low biaxial pressing and two types of
internal lubricants (sodium silicate and the carbon paste) to increase the
specimen's cohesion. These specimens were sintered at various temperatures of
(1100°C, 1200°C, 1300°C, and 1400°C).
Increasing of clay percentage leads to decreasing the porosity. But it leads to
increase mechanical properties (compressive strength, diametrical strength and
bending strength ). Also, the effect of particle size on all properties is studied
together with sintering temperature. All mechanical properties (when bonded SiC
with bentonite) are higher than kaolin bonded SiC.

Mechanical Properties of High-Strength Fiber Reinforced Concrete

Zaid Muhammad Kani Al-Azzawi; Kaiss Sarsam

Engineering and Technology Journal, 2010, Volume 28, Issue 12, Pages 2442-2453

Experimental results of this work in addition to a wide range of data from previous work
were analyzed to study the mechanical properties and strength of high-strength concrete with and
without fibers. Different types of steel fibers (straight, hooked, duoform, crimped) with a volume
fraction ranging from 0 to 2 percent were studied. The concrete compressive strength ranged from 41
to 115 MPa. The influence of fiber on the compressive strength, axial strain, modulus of elasticity,
Poisson's ratio, modulus of rupture, and splitting tensile strength, were studied. In addition to that,
size effect of control specimens on high-strength fiber reinforced concrete materials, was observed.
The main conclusion indicates that high-strength concrete (HSC) properties, especially with fibers
are significantly different from normal-strength concrete (NSC).

The Production of Self-Compacting Concrete with Normal Cement Content

Luma A. G. Al- Rawi; Tariq S. Al-Attar; Shakir A. Al-Mishhadani

Engineering and Technology Journal, 2009, Volume 27, Issue 2, Pages 310-320

The main object of this work is to evaluate the possibility for using reasonable cement
content and fine materials to reduce costs of expensive chemical admixtures needed for the
manufacturing of self-compacting concrete (SCC). In this work, three values of cement content
are used (rich, medium and lean mixes) with cement content of 400, 300 and 250 kg/m3
respectively . Two maximum aggregate sizes of (10 and 20mm) for each cement content are
used. The powder content material is (cementations + filler ) is maintained constant (500kg/m3)
while the W/cm ratio ranges from 0.43 to 0.68. 10% Reactive Metakaolin Class N is used as a
partial replacement by weight of cement. On the other hand, limestone dust was used as a
partial replacement by weight of the powder content Tests were carried out on all mixes to
obtain the properties of fresh concrete in terms of viscosity and stability. The results showed that
increasing the percentage of filler (limestone dust) from 20% in rich mixes to50% in lean mixes
of the total weight of the powder content reduces the amount of cement in SCC without
significant effect on the fresh properties of the SCC mixes. This conclusion is significant from
the economical point of view. The mechanical properties of hardened SCC mixes are also
assessed. (compressive strength, modulus of elasticity ). The results obtained from this work
show that it is possible to produce SCC with different levels of cement content (250 to400kg/m3)
using local available materials which satisfy the requirements of this type of concrete .The test
data collected indicate that these materials can be used in the manufacturing of economical SCC.