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Article
Effect of Adding some Additives and Drying Method on Compressive Strength of Gypsum Products

Authors: Wael Abdul Razak وائل عبد الرزاق --- Ihab N. Yassin ايهاب ياسين --- Firas Abd Kati فراس عبد كاطع
Journal: Tikrit Journal for Dental Sciences مجلة تكريت لعلوم طب الاسنان ISSN: 20731213 Year: 2017 Volume: 5 Issue: 2 Pages: 25-32
Publisher: Tikrit University جامعة تكريت

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Abstract

Gypsum products (dental plaster and stone) are widely used indentistry. However, the main problem with any gypsum productsis reproduction of fine details and dimensional stability. Thecurrent study was conducted to assess the effect of incorporatingvarious additives (i.e. cured resin, pulverised stone, pulverisedplaster, and glass fibers) and drying method on compressivestrength of gypsum products. A total of 160 specimens weredivided into 2 groups according to the method of drying (air andmicrowave). For each drying method, each group was subdivideddepending on the type of material used into 2 groups; dentalplaster and dental stone. Variuos additives were used forreinforcement; cured resin, pulverised plaster, pulverised stone,and glass fibers. The unmodified group was considered as control.The specimens were dried and the compressive strength test wasapplied on all specimens. All specimens' data were statisticallyanalysed via ANOVA, Tukey and independent T tests.Thecompressive strength of gypsum products was significantlyinfluenced by the type of additive used. The specimens reinforcedwith glass fibers, cured resin, pulverised plaster, and stone had agreater value of mean compressive strength compared withunmodified groups. Statistically, highly significant differenceswere observed among all dried groups (P≤0.001). As well, themicrowave specimens were more resistant to compressiveloadings than air dried specimens. No significant differences,however, were recorded between the two drying methods(P>0.05).The glass fibers have a significant effect on compressivestrength of gypsum products. The pulverised particles and curedresin can be added at 1 % by weight to enhance the mechanicalproperties of plaster and stone. Microwave drying for 5 minutescan fasten the drying time and permit early manipulation of plasterand stone models.


Article
The Effect of Formaldehyde Disinfectant on Compressive Strength of Dental Stone (Type IV)

Authors: Musab Mohamed Ibrahim --- Munther Najeeb Kazanji --- Salwa Hachim Mohammed
Journal: Al-Rafidain Dental Journal مجلة الرافدين لطب الأسنان ISSN: 18121217 Year: 2016 Volume: 16 Issue: 32 Pages: 1-9
Publisher: Mosul University جامعة الموصل

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Abstract

Aims: The purpose of this study is to evaluate the effect of 2% formaldehyde on compressive strength of dental stone (type IV), and to evaluate its antibacterial effect. Materials and methods: To study the effect of 2% formaldehyde on compressive strength of dental stone (type IV), ten samples of stone were prepared in cylindrical blocks and divided into two groups, each group contain of (5) samples. First group composed of stone and distilled water as (control group) and the second group composed of stone and (2%) formaldehyde solution. after (1h) the samples were tested for compressive strength using digital compression machine(ALFA Company, Turkey).To study the bacterial effect of formaldehyde 60 stone discs prepared and mixed with formaldehyde 2% divided into 12 group (each group consist of 5 discs) and stored for different intervals between 1-12 days, antibacterial effect against salivary sample for each interval day using disc diffusion test. Results: The statistical analysis of data by analysis of t-test reveals significant different in compressive strength between control group and stone-2% formaldehyde group at (P<0.05). The result showed that second group which contains 2%formaldehydehad higher values compared with control group. Also the results showed that the antibacterial effect of stone-formaldehyde discs continued till 12thday. Conclusions: Adding 2% formaldehyde as chemical disinfectant to dental stone increase the compressive strength in addition of the antibacterial activity of stone - formaldehyde disc continued till 12th day.


Article
Evaluation of compressive strength for refractory casts made from different investment materials

Author: Ahmed A Al–Ali
Journal: Al-Rafidain Dental Journal مجلة الرافدين لطب الأسنان ISSN: 18121217 Year: 2007 Volume: 7 Issue: 14 Pages: 166-172
Publisher: Mosul University جامعة الموصل

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Aims: To compare the compressive strength of refractory casts made from investments for cobalt–chromium and investment for titanium and to study the effect of mixing fluid on compressive strength.Materials and Methods: Three types of investments were used, one for titanium and two for cobalt–chromium, each one is mixed with three types of mixing fluids; tap water, distilled water and special liquid,to produce refractory casts. Compressive strength test was carried out using compression testing machine.Results: Showed significant differences in compressive strength between the types of investments, withtitanium investment mixed with special liquid showed the highest value. There were significant differencesbetween subgroups of the same type by changing mixing fluid type. Conclusions: Refractory casts madefrom titanium investment showed significantly higher compressive strength than refractory casts madefrom Co–Cr investments, and there was a difference between the two special liquids used, and tap water inwhich it produced casts with higher compressive strength than distilled water in two out of the threeinvestment materials tested.


Article
EFFECT OF MATERIALS THAT COMPONENT THE CONCRETE MIXTURES USED IN SALAH AL- DAIN PROJECTS ON THE COMPRESSIVE STRENGTH
تأثير المواد المكونة للخلطات الخرسانية المستخدمة في مشاريع محافظة صلاح الدين

Author: Dr. Jawdat Kadhim Abbas Yassen Ali Salh د.جودت كاظم عباس ياسين علي صالح
Journal: Tikrit Journal of Engineering Sciences مجلة تكريت للعلوم الهندسية ISSN: 1813162X 23127589 Year: 2006 Volume: 13 Issue: 2 Pages: 30-52
Publisher: Tikrit University جامعة تكريت

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Abstract

In this research, (192) concrete cubes were taken from different concrete mixtures incorporating coarse and fine aggregate from four different sources in Salah Al-Dain area with two types of cement; Iraqi cement & Turkish cement. The compressive strength of these cubes was examined to know the most suitable materials to product good concrete for use in the projects of Salah Al-Dain area. The results indicate that, the aggregate brings from Al-Tuz source gives compressive strength higher than the aggregate brings from other sources. The Turkish cement gives compressive strength higher that that gives by Iraqi cement.

في هذا البحث تم فحص مقاومة الانضغاط لـ(192) مكعب خرساني مأخوذ من خلطات خرسانية مختلفة تم إعدادها باستخدام ركام ناعم وخشن جلب من مقالع موزعة على أربعة مناطق مختلفة من محافظة صلاح الدين ولنوعين من السمنت البورتلاندي الاعتيادي (المتوفر في الأسواق المحلية خلال فترة إجراء الدراسة) هما السمنت التركي والعراقي، وذلك لمعرفة أفضل مواد يمكن استخدامها في إنتاج الخرسانة في مشاريع حملة الاعمار الجاري تنفيذها في محافظة صلاح الدين.تم فحص المكعبات بعمر 7 أيام و27 يوم ولنسبة خلط 4:2:1 نسبة ماء /سمنت مساوية لـ(0.45).اظهرت النتائج ان الركام بنوعيه الذي يتم جلبه من منطقة الطوز يعطي مقاومة انضغاط أعلى من الركام الذي يتم جلبه من مناطق اخرى.كما تبين ان السمنت التركي الاعتيادي نوع (أدنا) يعطي مقاومة انضغاط أعلى من السمنت العراقي الاعتيادي نوع (بادوش) .


Article
The effect of blood contamination on compressive strength of two materials used in treatment of furcation perforation (A comparative study)

Author: Linz A. Shalan لنز شالان
Journal: Journal of baghdad college of dentistry مجلة كلية طب الاسنان بغداد ISSN: 16800087 Year: 2012 Volume: 24 Issue: 4 Pages: 25-28
Publisher: Baghdad University جامعة بغداد

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Abstract

Background: blood contamination of the materials used for treatment of furcation perforation can affect on theirphysical properties (such as compressive strength). The aim of this study was to compare the effect of bloodcontamination on compressive strength for Mineral Trioxide Aggregate MTA and Resin Modified Glass IonomerCement RMGIC during furcation perforation management.Materials and methods: Forty plastic molds (4 mm diameter and 2mm thickness) were constructed to form samples.Ten samples were made for each group: MTA-without blood contamination GI, MTA- with blood contamination GII,RMGI- without blood contamination GIII and RMGI- with blood contamination GIV, and kept in plastic tubes withmoist cotton pellet at 37 oC for 4 days then all samples were subjected to compressive strength test by Instron testingmachine. Data were subjected to statistical analysis using descriptive analysis, ANOVA and t- test.Results: statistical analysis of the results showed that there was a highly significant differences in compressive strengthbetween GI and GII ( P< 0.01)and significant differences between GIII and GIV, GIII and GI, GIV and GII (P < 0.05),With lowest mean of compressive strength value was recorded to MTA- with blood contamination GII (31.32 ± 0.022Mpa) and highest mean for RMGI- without blood contamination GIII ( 168.725± 0.063Mpa).Conclusion: compressive strength value for both MTA and RMGI cement reduced when exposed to blood duringtreatment of furcation perforation, RMGI cement has higher value of compressive strength than MTA and it could besuitable choice in treatment of Furcal perforation in presence of bleeding and placing of coronal restoration after 4days.


Article
ESTIMATION OF COMPRESSIVE STRENGHT OF THE CONCRETE CONTAINING SUPERPLASTICIZERS
تخمين مقاومة الانضغاط للخرسانة الحاوية على ملدنات فائقة

Author: Aqeel Hatem Chkheiwer عقيل حاتم جخيور
Journal: KUFA JOURNAL OF ENGINEERING مجلة الكوفة الهندسية ISSN: 25230018 Year: 2017 Volume: 8 Issue: 1 Pages: 1-15
Publisher: University of Kufa جامعة الكوفة

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Abstract

The aim of this study is investigating of effect of superplasicizer (SP) type and dosage at different levels of compressive strength on the fresh concrete workability and compressive strength development with age. The experimental program included preparation of 18 concrete mixes; these mixes were divided to three groups depending on compressive strength level, in each group, three different types of superplasticizer with two different dosages (0.5 and 1.0%) for each type of SP. The results showed that the type and dosage of SP have pronounced an effect on the development in early age especially. The early compressive strength development of concrete containing PCP and AP types was almost similar and faster than that of NF type. The estimated compressive strength in the early ages by EC2 and ACI 209 equation was lower than the experimental results.

ان الهدف من هذه الدراسة هو التحري عن تأثير نوع وجرعة الملدن الفائق على مستوى مختلف من مقاومة الانضغاط على 18 قابلية التشغيل للخرسانة الطرية وتطور مقاومة الانضغاط للخرسانة مع تقدم العمر .وتضمن البرنامج العملي إعداد قسمت الخلطات لثلاث مجموعات تبعا لمستوى مقاومة الانضغاط. في كل مجموعة، استخدمت ثلاثة أنواع ،خلطة خرسانية من وزن الاسمنت لكل نوع من الملدن الفائق .تم اختبار مقاومة ٪1.0 و 0.5 مختلفة من الملدنان الفائقة,مع جرعتين يوما .وأظهرت النتائج ,أن لنوع وجرعة الملدن تأثير واضحا 180 و 120 ،90 ،56 ،28 ،14 ،7 ،3 الانضغاط في عمر على تطور مقاومة الانضغاط وخصوصا في الاعمار المبكرة .كانت بداية تطور مقاومة الانضغاط للخرسانة التي تحتوي على النوع المتعدد الكربوكسيل ونوع الاكريليك متماثلة تقريبا، وأسرع من نوع النفثالين الفورمالديهايد .و كانت مقاومة ACI 209 والمدونة الاميريكية EC2 الانضغاط المقدرة في سن مبكرة عن طريق معادلات الكود الاوربي , أقل من النتائج العملية.


Article
Compressive Strength of Lightweight Porcelanite Aggregate Concrete -New Formulas
مقاومة إنضغاط خرسانة البورسيلانايت خفيفة الوزن – معادلات جديدة

Authors: Nabeel A-M. Al-Bayati --- Kaiss F. Sarsam --- Ihsan A. S. Al-Shaarbaf
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2013 Volume: 31 Issue: 10 Part (A) Engineering Pages: 1897-1913
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

From the various kinds of concrete, lightweight concrete (LWC) is one of the most interesting subjects for researchers because of its advantages such as the savings in concrete member size, reinforcement, formwork and scaffolding , foundation costs as well as the savings derived from the reduced cost of transport and erection. The reduction of dead load due to a lower density of concrete allows for smaller and lighterweight structural members. Reductions in the dimensions of columns and beams result in more available space, and reductions in their selfweight can improve the seismic resistance capacity of building structures. Furthermore, better fire resistance, heat insulation, sound absorption, frost resistance, and increased damping are other advantages of lightweight concrete. Lightweight aggregate concrete (LWAC) is not new in concrete technology; it has been used since ancient times. The fact that some of these structures are still in good condition validates the durability of concrete. The paper presents the results of testing 30 specimens (15 cylinders and 15 cubes) according to ASTM for determining the mechanical properties of sand lightweight aggregate concrete (SLWAC)made from Porcelanite (as a natural local material). The paper further presents new empirical predicted formulas for cylinder compressive strength, cube compressive strength; and relationship between them.

من بين ألانواع المختلفه من الخرسانه تعتبرالخرسانه خفيفة الوزن(LWC) من أكثر المهمة المواضيع إثاره للاهتمام للباحثين بسبب مزاياها مثل التوفير في كمية خرسانة الصب، حديد التسليح, قالب الصب، وتكاليف الأساس، فضلا عن التوفير المستمد من انخفاض تكلفة النقل والإنشاء. التقليل من الحمل الميت نتيجة لانخفاض كثافة الخرسانه تسمح بتقليل أبعاد مقاطع الأعضاء الهيكليه. نتيجة إجراء هذه التخفيضات في أبعاد الأعمده والعتبات سوف يوفر المزيد من الحيز المتاح، وتحسين قدرة مقاومة الزلازل لهياكل المنشأ. وعلاوه على ذلك، تحسين مقاومة الحريق، العزل الحراري، وامتصاص الصوت، ومقاومة الصقيع، وكذلك زيادة التخميد التي تعتبر من المزايا الأخرى للخرسانة خفيفة الوزن. والخرسانة خفيفة الوزن (LWAC) ليست جديده في مجال تكنولوجيا الخرسانه، إلا أنها استخدمت منذ القدم. من المعلوم أن بعض هذه الهياكل الخرسانيه لا تزال في حاله جيده من سلامة وقوة التحمل مع مرور الزمن. يقدم البحث نتائج اختبار 30 عينه خرسانيه تتضمن (15 اسطوانه و 15 مكعب) وفقا للمواصفات الاميركيه لفحص المواد ASTM لتحديد الخواص الميكانيكية للخرسانه خفيفة الوزن (SLWAC) مصنوعه من البورسيلانايت (صخور طبيعية محلية). كذلك يعرض البحث الصيغ الجديده التجريبيه لتوقع مقاومة انضغاط, عينة الاسطوانة, مقاومة انضغاط عينة المكعب والعلاقة بينهما.


Article
The effect of 35% H2O2 and 22%carbamide peroxide on compressive strength of composite resin

Authors: Majida K.W. AL-Hashimi ماجدة الهاشمي --- Aliaa M. Jabbar علياء محمد جبار
Journal: Journal of baghdad college of dentistry مجلة كلية طب الاسنان بغداد ISSN: 16800087 Year: 2011 Volume: 23 Issue: 4 Pages: 16-19
Publisher: Baghdad University جامعة بغداد

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Abstract

Back ground: The compressive strength of composite resin may be affected by bleaching agent. This study wasconducted to evaluate the effect of two different bleaching agents; at home (22% carbamide peroxide) and inoffice; light activated (35% hydrogen peroxide) bleaching agent on the compressive strength of light curedcomposite resin; spectrum (submicron hybrid composite).Material and methods: A total number of 20 samples were prepared,10 samples for each type of bleaching agentwhich were divided in to 2 groups; first group was subjected to at-home bleaching for one day. The second groupwas subjected to at-home bleaching for one week, The third group was subjected to the in-office (35% H2O2) for oneday. The forth group was subjected to in-office bleaching for three days.Results: There were statistically significant differences between the tested groups (p=0.048). Highly significantreduction of the compressive strength of composite was observed subsequent to treatment with H2O2 for three times.Conclusion: Reduced compressive strength was detected in composite when it was subjected to bleaching processwith H2O2 carbamide peroxide.


Article
Effect of Wax Burn-Out Heating Temperature on The Compressive Strength of Casting Dental Alloy Investment

Author: Lamia T Rejab
Journal: Al-Rafidain Dental Journal مجلة الرافدين لطب الأسنان ISSN: 18121217 Year: 2008 Volume: 8 Issue: 16 Pages: 197-204
Publisher: Mosul University جامعة الموصل

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Aims: To evaluate the effect of the burn-out heating on the compressive strength of investment materials.Materials and Methods: Three commercial investment materials were used in this study. Seventy two cylindrical shape specimens were prepared to evaluate the compressive strength of the investment materials at room temperature (cold strength) and at two different burn-out heating temperatures : 700 oC and 1000 oC (hot strength). Three groups were prepared according to tested investment materials, The specimens were then subdivided into three subgroups according to burn-out heating temperatures,eight specimens for each subgroup. The compressive strength (kg /cm2) was evaluated by using Instron testing machine. Mean values were compared statistically with one way analysis of variance (ANOVA),Duncan , s multiple range test and t-test to determine the significant difference among the tested groups at (p<0.05) level of significance .Results: The results showed that there is a significant difference of the means value of the compressive strength among the three tested investment materials. The compressivestrength value significantly decreased with increasing burn-out heating temperature. Conclusion:The result of this study showed that the increase of burn-out heating had a significant decrease the compressive strength of the investment materials, and cold compressive strength gives an indicationof the hot strength .


Article
Effect of Liquids type on some Engineering Properties of Limestone Rock from Eski-Mosul
تأثيرنوعية السوائل على الخواص الهندسية لصخور الحجر الجيري من منطقة أسكي موصل

Authors: Thamer M. Nuri ثامر محمد نوري --- Ahmed M. Nejm Al-Deen أحمد محمد نجم الدين
Journal: AL Rafdain Engineering Journal مجلة هندسة الرافدين ISSN: 18130526 Year: 2010 Volume: 18 Issue: 3 Pages: 1-12
Publisher: Mosul University جامعة الموصل

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Abstract

This research studied the effect of liquids on the Engineering properties of the Limestone rocks. The liquids used were: crude oil from Ain Zala, crude oil from Kirkuk, natural ground Water. The Limestone used was brought from Eski Mosul situated at 45 Km north west of Mosul. Both the compressive and tensile tests were conducted on the Limestone rock specimens in the dry and saturated case using;Uniaxial, Triaxial Compression and Bending tests. The tests showed that saturation with any one of the liquids lead to a decrease of both compressive and tensile strength. The greatest decrease occurred when ground water was used to saturate the specimens, and it was also noted that the effect of saturation gave greater percentage of decrease on the compressive than the tensile strength. The study also showed that liquids lead to decrease in cohesion ( c ) and the Friction angle (Φ) obtained from triaxial test. The liquids used for saturation didn't have clear effect on the type and mode of failure on all specimens tested .Keyword: σc:Compressive strength σt: Tensile strength

الخلاصة يتضمن البحث دراسة تأثير السوائل (نفط خام عين زالة، نفط خام كركوك و المياه الجوفية) على الخواص الهندسية لصخور الحجر الجيري المأخوذة من منطقة أسكي موصل الواقعة شمال غرب مدينة الموصل، حيث تم إيجاد المقاومة الانضغاطية الأحادية والثلاثية المحاور ومقاومة الشد غير المباشر لنماذج الصخور وذلك للحالة الجافة والمشبعة بالسوائل. أظهرت نتائج هذه الدراسة أن السوائل المستخدمة تقلل كلا من المقاومة الانضغاطية والشدية، وإن أكبر نقصان في المقاومة يحصل في حالة تشبع الصخور بالمياه الجوفية، كما لوحظ أن تأثير السوائل على المقاومة الانضغاطية أكبر من تأثيرها على المقاومة الشدية، كما بينت الدراسة أن هذه السوائل تقلل من قيمة التماسك وزاوية الاحتكاك الداخلي للنماذج في فحص الانضغاط ثلاثي المحاور.كما لوحظ أن نوعية السوائل المستخدمة في عملية تشبيع النماذج ليس لها تأثير واضح على شكل الفشل.

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