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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: 28 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: 10 Pages: 166-172
Publisher: Mosul University جامعة الموصل

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Abstract

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
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: 12 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
THE EFFECT OF CURING CONDITION ON COMPRESSIVE STRENGTH IN HIGH STRENGTH CONCRETE
تأثير طريقة ألإنضاج على مقاومة الانضغاط في الخرسانة عالية المقاومة

Author: Ali H. Hameed علي حسين حميد
Journal: DIYALA JOURNAL OF ENGINEERING SCIENCES مجلة ديالى للعلوم الهندسية ISSN: 19998716/26166909 Year: 2009 Volume: 2 Issue: 1 Pages: 35-48
Publisher: Diyala University جامعة ديالى

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Abstract

The paper shows the effect of curing condition on compressive strength in high strength concrete in three cases (Group A(moist curing in water for 7 days followed by air curing ) ,Group B(curing until the age test in water) and Group C(curing at high temperature 60ºC±2ºC for six days ) and two types of specimen of cubes (150 x150 and 100 x 100) used in the test age (7,28and 90 day) respectively in four mix proportion (Mix No.1(40 Mpa ,Mix No. 2(fcu 60 Mpa) ,Mix No. 3 (fcu 70 Mpa) and Mix No. 4 (fcu 80 Mpa) ). Results demonstrate that, in general, concrete specimens moist cured until testing ages (Group B) give compressive strength greater than specimens moist cured for 7 days in water then followed by air – drying (Group A). The percentage of increase in strength is (5 and12%) for mix No.3 and 6% for mix No.4, as compared with 3% for mix No.1 and (2 and4%) for mix No.2. When the curing temperature (group C ) increases, the compressive strength increases at different ratios ,the percentage of increase in compressive strength at 7,28 and 90 days for mix No.1 , mixes No.2 and 3 are (20,15 and 14% ), ( 7,11 and 5% ) and (13,12 and 5% ) respectively, while mix No4. shows an increase of 4 and 10% in compressive strength at 7 and 28 days where there is a reduction in the strength at 90 days by about 2%. Generally, as the size of specimen decreases, the effect of temperature curing (group C)on the compressive strength increases.

أن البحث المقدم يبين تأثير ثلاثة طرق للإنضاج (مجموعة A, مجموعة B , مجموعة C ) على مقاومة الانضغاط في لخرسانة ذات مقاومة عالية باستخدام نوعين من نماذج الفحوصات للمكعب (150 *150 ملم و 100*100 ملم ) فحصت بأعمار (7 ,28 و 90 يوم )بالتتابع لأربع خلطات (خلطة رقم 1 , خلطة رقم 2 , خلطة رقم 3 وخلطة رقم 4 ). النتائج المقدمة بشكل عام لنماذج (المجموعة B ) المرطبة لغاية الفحص أعطت أعلى مقاومة مقارنتا (بالمجموعة ِA ) المرطبة لعمر 7 أيام وإتمام الإنضاج بالهواء . معدل الزيادة (5-12%)للخلطة رقم 3 و6%للخلطة رقم 4 مقارنتا مع 3%للخلطة رقم 1 و(2-4) للخلطة رقم 2 . بزيادة الإنضاج الحراري (المجموعة C) مقاومة الانضغاط تزداد لمختلف النسب ومعدل الزيادات في مقاومة الانضغاط للأعمار(7 ,28 و90 يوم )للخلطة رقم1 والخلطة رقم 2 والخلطة رقم 3 هي (20 ,15 و 14 %)(7 ,11 و5 %)(13 ,12 و5 %) بالتتابع. بينما معدل الزيادة في مقاومة الانضغاط للخلطة رقم 4 (4و10 %) لعمر 7 و28 يوم وأعطت تقصان في المقاومة بعمر 90 يوم مقداره 2%.بشكل عام عندما يقل حجم النموذج تأثير الإنضاج بزيادة درجات الحرارة (المجموعة C)يزيد مقاومة الانضغاط .


Article
Effects of Chrome Lignosulfonate Concentration and Temperature on Compressive
المستخدم G ودرجة الحرارة على قوة تصلب الأسمنت صنف Chrome Lignosulfonate تأثیرات تركیز

Author: Jamal Harbi Al-Seedi جمال حربي حسین السعیدي
Journal: JOURNAL OF THI-QAR SCIENCE مجلة علوم ذي قار ISSN: 19918690 Year: 2012 Volume: 3 Issue: 2 Pages: 76-84
Publisher: Thi-Qar University جامعة ذي قار

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Abstract

Abstract:The primary function of Retarders in cement slurry design is to increase the thickening time to allow timefor placement of the liquid slurry, The current study to observe the effects of temperature and differentconcentrations of the substance chrome lignosulfonate used as retarder (one on the additives)to cement classG used in cementing operation wells in oil fields southern Iraq on the compressive strength of the cement.The compressive strength of the samples concrete was measured by UCA equipment with differenttemperature depending on the depth and internal conditions of the well ( 40Cº ,60Cº and 80Cº), andpressuring affixed amount of 3000 psi .The experiments showed that the highest compressive strength was1308 psi ,3130psi,3200psi of cement slurry where the concentration of chrome lignosulfonate 0.1% attemperature 40 Cº,60Cº,80Cº respectively after a period of curing time24 hours ,while the less compressivestrength within the study was 326 psi , 412 psi , 477 psi of cement slurry where concentration of chromelignosulfonate 0.5% after curing time 24 hours. The concrete increased as the temperature during the curingtime increased within the range studied and decreasing compressive strength with addition a higher level ofchrome lignosulfonate.

الخلاصة:الوظیفة الأساسیة للمبطئات في تصمیم الخلیط الأسمنتي هو لزیادة زمن تخثر الأسمنت للوصول إلى الزمن المسموح لضخوٕا ا زحة سائل الأسمنت داخل البئر ضمن الشروط الداخلیة من درجة ح ا ررة وضغط.لذلك تخصصت الد ا رسة الحالیة لملاحظة تأثی ا رتالمتغی ا رت درجة الح ا ررة و الت ا ركیز المختلفة لمادة كروم- لكنو سلفونیت المستخدمة كمبطئ (أحد المضافات) على قوة التصلبالمستخدم في تسمیت الآبار النفطیة في حقول جنوب الع ا رق. حیث تم قیاس قوة التصلب مختبریا" لجمیع G للسمنت صنفوبدرجات ح ا ررة مختلفة (UCA) الخلطات الأسمنتیة المحضرة بإضافة ت ا ركیز مختلفة من مادة كروم لكنوسلفونیت بواسطة جهاز3000 . وأوضحت التجارب أن PSI 80 درجة مئویة وضغط ثابت مقداره , 60 , اعتمادا" على عمق وظروف البئر الداخلیة , 403200 للخلطة الأسمنتیة التي تركیز كروم لكنوسلفونیت % 0.1 وبدرجات psi 3130 و psi, 1308 psi أعلى قوة تصلب كانت412 PSI ,326 PSi 80 على التوالي خلال 24 ساعة بینما كانت أقل قوة تصلب ضمن الد ا رسة الحالیة Cº, 60Cº , 40Cº الح ا رریة80 على التوالي Cº, 60Cº , 40Cº 477 للخلطة الأسمنتیة التي یكون فیها تركیز كروم لكنوسلفونیت % 0.5 بدرجات الح ا ررة PSI ,بعد فترة زمنیة مقد ا رها 24 ساعة كما وجدت الد ا رسة أن قوة التصلب تزداد بزیادة درجة الح ا ررة وزمن الأنتظار ضمن معدل درجاتالح ا ررة والزمن في هذة الد ا رسة . كما أوضحت الد ا رسة نقصان قوة التصلب بصورة ملحوظة عند إضافة ت ا ركیز عالیة من مادة كروملكنوسلفونیت.

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