Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : elevated temperature


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

Effect of Elevated Temperature on Punching Shear of Regular and Irregular Shaped Self-Compacted Concrete Slabs

Luma Fadhil H

Engineering and Technology Journal, 2010, Volume 28, Issue 19, Pages 5893-5906

The exposure of reinforced concrete slabs to high temperature causes changes
in their structural behavior.
This work aims to study the post-heating behavior of self compacted concrete
(SCC) regular (square) and irregular (trapezoidal) shaped flat plates and assessing
the residual punching shear strength of these slabs.
Twenty four reduced scale reinforced concrete slab specimens divided into
two main groups (square and trapezoidal slabs), each of which consists of twelve
slab identical in size and shape but different in concrete compressive strength
(30,50,70) MPa. These specimens are subjected to different temperature levels
(100, 300, 500) 0C and still heated in that temperature level for one hour using an
electric furnace and the results are compared with specimens tested at room
temperature 25 0C.
The effect of specimen shape, heating level, concrete compressive strength on
the punching shear resistance of slabs are discussed in details.
Results indicate that the reduction in punching shear strength is ranged between
(0 and 16) %, for square slab, at maximum temperature exposure (500) 0C, while
this rate is ranged between (6.3 and 40.4) % for trapezoidal slabs. This indicates
that the punching shear resistance of regular shaped slabs is higher than that of
irregular shaped slabs.