research centers


Search results: Found 9

Listing 1 - 9 of 9
Sort by

Article
Resistance of High-Volume Fly Ash SelfCompacting Concrete to Internal Sulfate Attack

Authors: Tareq S. al-Attar --- Ahmed A. Taha
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2018 Volume: 36 Issue: 12 Part (A) Engineering Pages: 1260-1266
Publisher: University of Technology الجامعة التكنولوجية

Loading...
Loading...
Abstract

This paper investigates the durability of high-volume Fly ash selfcompactingconcrete, HVFASCC that exposed to internal sulfate attack. At thepresent work, HVFASCC was produced with two Fly ash replacements: 50 and60% by weight of Portland cement. The internal sulfate attack was simulated byadding natural gypsum (CaSO4) that contain ion (SO3-2) to fine aggregate bytwo weight percentages: 1 and 2%. Limestone dust was used as filler with acontent of 100 kg/m3. The cementitious materials, cement and Fly ash, contentwas 400 kg/m3 and the water to powder ratio for the studied mixes was 0.34 byweight. To ensure the self-compact ability of the mixes, slump flow, T500, Vfunneland L-box tests were done. The Compressive, Splitting and Flexuralstrength Tests were extended to the age of 240 days. The results showed thatthere is no significant difference between 1 and 2% of SO3 content on thebehavior of all mixes. The presence of limestone powder in the paste solutioncould have a role in stabilizing ettringite and reducing paste porosity at earlyages. At later age, 240 days, the harmful effect of SO3 is diminished and thatmay be caused by the depletion of gypsum and the dominant product will becalcium monosulfoluminate hydrates instead of calcium sulfoaluminatehydrates


Article
Direct Shear Behavior of Carbon Fiber Reinforced Self- Compacting Concrete
القص المباشر للخرسانة ذاتية الرص المدعمة بالياف الكاربون

Authors: Kaiss F. Sarsam --- Tareq S. Al-Attar --- Ghzwan Ghanim Jumah
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2014 Volume: 32 Issue: 10 Part (A) Engineering Pages: 2491-2513
Publisher: University of Technology الجامعة التكنولوجية

Loading...
Loading...
Abstract

This paperrepresents an experimental and statistical investigation for the behavior of connectionpoints produced by using self-compacting concrete and subjected to direct shear. The investigation also includes the effect of carbon fiber inclusion as reinforcement on self-compacting concrete (SCC) behavior in direct shear. This study gives results of sixteen push-off or direct shear specimens in four groups. Variations include volume fraction for carbon fiber (V_f= 0.00, 0.50, 0.75 and 1.00) % for every percentage change in the steel reinforcement. The steel reinforcement parameter ρ_vf f_y values are (0.00, 2.66, 5.33 and 7.99) MPa(where ρ_vf varies from 0.00 to 0.0173 and f_y=585.7MPa) . The main material properties studied include compressive strength, splitting tensile strength and modulus of rupture. Measurements of deformations were made throughout testing of shear specimens. The dimension of the shear plane in the push-off specimenswas 170x185 mm. The shear reinforcement was normal to the shear plane. Specimens were cast by using SCC which is a type of high performance concreteand reinforced with carbon fiber. This work aims to investigate the direct shear behavior of SCC with or without carbon fiber at constant water to cementitious materials ratio of 0.3 by weight. It is found that using carbon fiber increased the direct shear strength. However, carbon fiber alone (without reinforcement) leads to brittle failure. In contrast, adding rebars leads to higher strain and more ductile behavior-increased shear capacity is obtained when higher steel quantity is used. The aim of adding carbon fibers was the increase of the horizontal strain (displacement). It was found that the optimum percentage of volume fraction was 0.75 % for fresh and hardened concrete. In addition, the effects of carbon fiber on compressive strength of SCC lead to a drop in compressive strength (f_c^') compared with reference specimens. This drop in f_c^' was 2.39, 8.38 and 13.58% for V_f=0.50, 0.75 and 1.00%, respectively. In contrast, the splitting tensile strength increased by 3.34, 31.2 and 18.2 as compared with the cylinder strength without carbon fibers atV_f equal to0.50, 0.75 and 1.00% respectively. The modulus of rupture increased by [11.9, 21.99 and 13.83%] as compared with SCC without carbon fibers at〖 V〗_f equal to 0.50, 0.75 and 1.00% respectively.Based on push-off tests results for this work and those available in the literature, two statisticalmodels have been established using regression analysis. Four variables f_c^',f_ct,ρ_vf f_y and V_f, were included in these models. Both models showed good representation according to their coefficients of variation (COV)values. Verification of the models were done by using 273 observations from literature and the present work.

يقدم هذا العمل دراسة تجريبية و أحصائية لسلوك مناطق الاتصال باستخدام خرسانة ذاتية الرص, وايضا تم التحري تأثير ادخال الياف الكاربون لخرسانة ذاتية الرص على سلوك القص المباشر .تقدم هذه الدراسة نتائج الفحص لستة عشر نموذج للقص المباشر موزعة في اربعة مجاميع. تضمنت المتغيرات المدروسة النسبة الحجميةلالياف الكاربون والتي تراوحت من صفر الى 1 % مقابل تغير العامل ((ρ_vf f_y من صفر الى 7.99 ميكا باسكال. كانت الخواص المدروسة هي: مقاومة الانضغاط و مقاومة الشد بالانشطار مع قياس الانفعالات الافقية و الشاقولية للنموذج المفحوص. أن ابعاد مستوي القص للنموذج المفحوص كانتx170 185 ملم و تم توزيع حديد التسليح ليكون عموديا على مستوي القص.و استخدام خرسانة الذاتية الرص (عالية الاداء) في صب هذه النماذج مع تدعيمها بالياف الكاربون.من خلال نتائج البحث وجد ان استخدام الياف الكاربون قد ادت الى زيادة في مقاومة القص المباشر للخرسانة ولكنها لم تمنع حدوث الفشل الفجائي في حالة عدم وجود حديد التسليح الرئيسي. في حين ان وجود حديد التسليح الرئيسي بقي هو المسيطر على الانفعالات (التشوهات) القصحيث زادت مقاومة القص دائما بزيادة نسبة حديد التسليح. برز دور الياف الكاربون جليا في تقييد انفعالات (تشوهات) الافقية. كما وجد من خلال البحث بان النسبة الحجمية (0.75 %) لالياف الكاربون كانت هي المثالية في حالتي الخرسانة الطرية و المتصلبة. بالاضافة الى ذلك تمت دراسة تاثير الياف الكاربون على مقاومة الانضغاط للخرسانة ذاتية الرص حيث انخفضت مقاومة الانضغاطمقارنة الحالة V_fتساوي 0.00 %. ذلك النقصان في مقاومة الانضغاط كان 2.39, 8.38 و 13.58 %, على التوالي عندما كانت 0.50, 0.75, 1.00 %. بينما زادت مقاومة الشد بالانشطار بمقدار 3.34, 31.2 و 18.2 % لنسبة الياف الكاربون 0.50, 0.75, 1.00 %, على التوالي. ولقد زادت قيمة معامل الكسر بمقدار 11.9 , 21.9 و 13.8 % اذا ما قورنت بالعتبة ذات نسب الياف الكاربون 0.50, 0.75و 1.00 %, على التوالي. استند تحليل النتائج لهذه الدراسة و دراسات سابقة (لفحص القص المباشر)وقدم مقترحين للتصميم. باستخدام تحليل الانحدار. تعتمد على اربعة متغيرات هي f_c^' f_ct,,V_f وρ_vf f_y. عند مقارنة المقترحين مع الطرق الاخرى وجد بــانهما يعطيان افضل نتائج لـــ 273نتيجه اختبار لفحص القص المباشر.


Article
Workability of Hybrid Fiber Reinforced Self-Compacting Concrete

Authors: Anmar S. Dhaher --- Samer F. Daoud --- Tareq S. Al-Attar
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2018 Volume: 36 Issue: 2 Part (A) Engineering Pages: 111-116
Publisher: University of Technology الجامعة التكنولوجية

Loading...
Loading...
Abstract

The aim of this work is to evaluate the effect of adding different types of fibers on the fresh properties of the self-compacting concrete, SCC. The used types of fibers were steel (with volume ratios of 0.75, 1.0 and 1.25 %) and polypropylene fibers (0.10 and 0.15 %) and a hybrid system of these fibers (0.65 % steel and 0.10 % polypropylene). The conducted tests in the fresh state were slump flow, T500, V-funnel, and L-box. It was noticed that increasing the volume fraction of fibers would lead to decrease in the workability of SCC. According to EFNARC requirements for SCC, many test results were nonconforming. It was also concluded that polypropylene fibers have higher detrimental effect on fresh properties of SCC than steel fibers and that was attributed to the ability of polypropylene to absorb part of mixing water.


Article
Effect of Height to Diameter Ratio on The Behaviour of High Performance Concrete Specimen with Different Shapes under Compression Load
تاثير نسبة الارتفاع للقطرباختلاف الشكل للنموذج على سلوك الخرسانه عالية الاداء تحت احمال الانضغاط

Authors: Kaiss F. Sarsam --- Tareq S. AL-Attar --- Mohammed M. Al-Saqi
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2014 Volume: 32 Issue: 11 Part (A) Engineering Pages: 2734-2744
Publisher: University of Technology الجامعة التكنولوجية

Loading...
Loading...
Abstract

The strength of concrete is considered as the most basic and important material property in the design of reinforced concrete structures. The two standard methods (ASTMC39-03 and BS1881-part 116) for determining the compressive strength of concrete are the testing to failure of cylinder and cube specimens respectively. It has become a problem to use this value as the control specimen sizes and shapes are different from country to another. This study is made to comparison between propose hexagonal specimens with the standard cylindrical one in behaviour of specimens with different sizes under compression load. The new hexagonal specimen has a cross sectional area 4% greater than the cylindrical cross section. The volume of the hexagonal specimen is approximately equal to the cylindrical ones to give a greater uniformity of results. This proposed shape has height to average diameter ratio (H/D) = 1.95. The hexagonal mould has the ease of making a control specimen while avoiding the capping process which is necessary in cylinders and reducing the cost and time it takes to prepare. When the hexagonal specimen cast in horizontal plane so no need for end preparation because the top and bottom surface of the specimen who will be in contact with platen of testing machine, are 100 % levelled and orthogonal to the height of the specimen. Results show that the mean ratio of compressive strength for hexagonal to cylindrical specimen is 0.95.The results of testing specimens show that the compressive strength of the specimen obviously increases with decreasing the ratio of H/D. This behaviour is proving that the hexagonal specimen acts like the standard cylindrical in stress distribution. The using of hexagonal specimen to find the strength of concrete give better factor of safety in structural design that because strength determined from hexagonal specimens will be slightly smaller when compared with results determined from cylindrical and the behaviour of the hexagonal shape is similar to cylindrical one.

تعتبر مقاومة التحمل للخرسانه من اهم الخواص التي تعتمد في تصميم المنشاءات الخرسانية المسلحة. وهناك عدة طرق قياسية لتحديد مقاومة التحمل والتي تتفق بطريقة الفحص وهي تحميل النموذج حتى حدوث الفشل النهائي ولكنها تختلف في اعتماد شكل وابعاد العينات المستخدمة في الفحص. فبعضها يختبر عينات مكعبة ( مثل المواصفة البريطانية 1881-part 116BS) والاخر يفضل اختبار عينات اسطوانية (مثل المواصفة الامريكيةC39-03ASTM). تهدف هذه الدراسة للمقارنه بين النموذج المقترح ذو الشكل السداسي مع النموذج القياسي ذو الشكل الاسطواني في السلوك عند التعرض لاحمال الانضغاط مع تغير نسبة الارتفاع الى قطر النموذج. تم اختيار ابعاد العينات السداسية المقطع لتكون مقاربة الى درجة كبيرة لحجم ومساحة مقاطع النماذج الاسطوانة القياسية ليسهل مقارنة النتائج وبيان مدى اعتمادها. ان الشكل السداسي للنموذج المقترح يمتلك 1.95 كنسبة معدل القطر لارتفاع النموذج. تمتاز هذه القوالب الجديدة بخاصية سهولة تصنيع العينات والتي ولاتحتاج الى الجهد والوقت المبذولين في تهيئة النهايات. عند صب النموذج بشكل افقي لن تكون هنالك حاجة الى تهيئة النهايات للفحص وذلك بسبب كون السطح العلوي والسطح السفلي للنموذج واللذين سيكونان بتماس مع صفائح التحميل في جهاز الفحص مستويان بنسبة 100% ومتعامدان مع ارتفاعه. اظهرت نتائج الفحوصات المختبرية ان معدل نسبة مقاومة الانضغاط للنماذج هي 0.95 عند مقارنتها مع النماذج الاسطوانية. ومن الواضح في النتائج ان مقاومة الانضغاط تزداد مع نقصان نسبة الارتفاع للقطر. وهذا السلوك يتشابه مع النماذج الاسطوانية القياسية والذي يثبت كون النموذج السداسي القترح يعمل بشكل مشابه من ناحية توزيع الاجهادات داخل النموذج مع النموذج القياسي (الاسطواني). ان استعمال الشكل السداسي في ايجاد مقاومة الخرسانه يعطي المصمم الانشائي مقدارا اكبر من معامل الامان وذلك كون النتائج المستحصلة من فحص النماذج السداسية هي اقل بمقدار قليل من نتائج المستحصلة من فحص النماذج الاسطوانية.

Keywords


Article
Effect of Internal Curing on StrengthDevelopment of High Performance Concrete by Using Crushed Lightweight Porcelinite
تاثير الانضاج الداخلي على تطور المقاومة للخرسانة العالية الاداء وباستخدام البورسيلينايت المكسر الخفيف الوزن

Authors: Tareq S. Al-Attar --- Adil M. Abdullatif --- Ayman J. Al-Saad
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2014 Volume: 32 Issue: 11 Part (A) Engineering Pages: 2803-2814
Publisher: University of Technology الجامعة التكنولوجية

Loading...
Loading...
Abstract

High performance concrete, HPC, requires a low water-to-cementitious materials mass ratio w/cm and supplemental cementitious materials with silica fumes in the mixture, and use of a superplasticizer. Because of the low w/cm and rapid reaction at early ages, it becomes more difficult to provide curing water from the top surface and this water will be inadequate to satisfy the conventional curing. Therefore, there is a need to use internal curing that is supplied via internal materials, such as absorbent lightweight aggregate, which will be pre-saturated. The use of internal curing was investigated in this study by two ways. The first way was through the use of partial replacement of original coarse aggregate (gravel), meanwhile, the second was by replacing partiallythe original fine aggregate (sand)by crushed Porcelinite.The results showed that the fine Porcelinite replacement as internal curing material caused better enhancement instrengthof HPC than coarse Porcelinite. The replacement of original fine crushed Porcelinite caused an increase in compressive strength from 3.36 to 5.25percent, for splitting tensile strength from 5.48 to6.85 percent and for flexural strength from 11.76 to 12.74percent.

الخرسانة العالية الاداء تتطلب كمية مياه قليلة نسبة الى المواد الاسمنتية مع اضافة مواد اسمنتية مثل السليكا فيوم الى الخليط واضافة المواد الملدنة الفائقة . بسبب قلة الماء الى المواد الاسمنتية وسرعة التفاعل في الاوقات المبكرة يصبح من الصعوبة انضاج الخرسانه من السطح الخارجي بالطرق التقليدية . لذلك نستخدم الانضاج الداخلي الذي يتم تطبيقه عن طريق مواد داخلية مثل الركام الخفيف ذو الامتصاص العالي ويستعمل كركام مسبق التشبع بالماء عند الخلط .في هذا البحث جرى دراسة تأثير الانضاج الداخلي علىالخواص الميكانيكية مثل المقاومة .تم اعتماد اسلوبين في انجاز الانضاج الداخلي وهما : استبدال جزئي للركام الخشن وبأستخدام حجر البورسيلينايت المكسر. وتم في الاسلوب الثاني استبدال جزئي للركام الناعم وايضا بأستخدام حجرالبورسيلينايت المكسر.اظهر البحث ان استبدال الركام الناعم لحجر البورسيلينايت المكسر كمادة أنضاج داخلي كان الافضل في تعزيز الخواص الميكانيكية (المقاومة) من استبدال الركام الخشن لحجر البورسيلينايت المكسر. وكمثال على ذلك فقد كان استبدال الركام الناعم الاصلي بمواد الانضاج الداخلي سببا في زيادة مقاومة الانضغاط بعمر 28 يوم وبمقدار يتراوح ما بين 3.36 و 5.25 في المائة . بينما لمقاومة الشد كانت الزيادة من 5.48 الى 6.85في المائة ومقاومة الانحناء كانت الزيادة تتراوح بين 11.76 الى 12.74 في المائة .


Article
FFECT OF POZOOLANIC MATERIALS ON COMPRESSIVE STRENGTH OF GEOPOLYMER CONCRETE

Authors: Mohammed H. Shamsa --- Basil S. Al-Shathr --- Tareq S. Al-Attar
Journal: KUFA JOURNAL OF ENGINEERING مجلة الكوفة الهندسية ISSN: 25230018 Year: 2018 Volume: 9 Issue: 3 Pages: 26-36
Publisher: University of Kufa جامعة الكوفة

Loading...
Loading...
Abstract

The development that has occurred in industries and technologies after the Industrial Renaissance and beyond has led to consume a large amount of raw materials. The huge consumption of these materials is hard to be compensated. Therefore, it is necessary to find materials that can be recycled and environmentally friendly materials. Hence, the idea of sustainability, which states, the ability to meet our current needs without compromising the ability of future generation to meet theirs. It has become an urgent to produce materials that called environmentally friendly or sustainable materials. In the field of civil engineering, an important role has been played in producing of environmentally friendly concrete by using pozollanic materials. Using environmentally friendly concrete instead of traditional concrete can participate in reducing the effect of global warming. In this research, local materials like metakaolin and pozollanic materials such as, fly ash and grand granulated blast furnace slag GGBFS were used in the production of an environmentally friendly concrete which they are called Geopolymer concrete. The effect of pozzolanic material type and mixing ratios on compressive strength at 7, 28 and 60 days were studied.

Keywords

Sustainable --- Geopolymer --- Fly ash --- Metakaolin --- GGBFS.


Article
Flexural Behavior of RC Beams Strengthened by NSM-CFRP Laminates or Bars

Authors: Ikram A. Saeed --- Riadh. Al-Mahaidi --- Tareq. S. Al-Attar --- Basil. S. Al-Shathr
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2018 Volume: 36 Issue: 4 Part (A) Engineering Pages: 358-367
Publisher: University of Technology الجامعة التكنولوجية

Loading...
Loading...
Abstract

The strengthening and enhancing the structures represents an important aspect in the construction industry due to the growing need to increase the tolerability of origin to a specific level and within the required rehabilitation and maintenance work. This paper assessed the performance and effectiveness of the Near Surface Mounted (NSM) strengthening technique for the reinforced concrete beams. Three (140x260x2700 mm) reinforced concrete beams were strengthened in flexure with NSM strengthening systems using Carbon Fiber Reinforced Polymer (CFRP) strips, bars, and cement-based adhesive as a binding materials. The flexural behaviour of the beams was evaluated by testing the specimens under three-point loading to failure. The structural performance, deflection, ductility, stiffness, and modes of failure of the tested beams are presented and discussed in this paper. The test results indicate that using NSM-CFRP strips and bars is practical and significantly improves the stiffness and increases the flexural capacity of reinforced concrete beams. The strength increments were 48, 42, and 15 percent recorded with CFRP bars, rough strips, and smooth strips respectively. The deflection of the strengthened beams was reduced by about 66, 48, and 58 percent for CFRP smooth strips, rough strips, and CFRP bars respectively, compared with the control beam due to the increased stiffness of the strengthened beams.


Article
Prediction of Creep Strain for Self-Compacting Concrete by Artificial Neural Networks

Authors: Ammar S. Al-Rihimy --- Basil S. Al-Shathr --- Tareq S. Al-Attar
Journal: KUFA JOURNAL OF ENGINEERING مجلة الكوفة الهندسية ISSN: 25230018 Year: 2019 Volume: 10 Issue: 2 Pages: 90-100
Publisher: University of Kufa جامعة الكوفة

Loading...
Loading...
Abstract

Artificial Neural Networks, ANN, technique is a computerized system that is built to simulate the neural networks in the human brain. Throughout the recent couple decades, ANNs had solved with a good degree of success many problems. In the present work, ANN model was developed by SPSS software for estimating creep strain development of self-compacting concrete mixes produced with different types of Portland cement, Type I and Type IL. The independent variables in this model were: age, compressive strength, modulus of elasticity, applied stress, initial strain, water to powder ratio, water to binder ratio, filler to cement ratio, clinker to cement ratio, aggregate size, and slump flow. The used data for model building were local, extracted from the present work. The predictions of the model have been compared to those of an international well-known model, ACI 209 Committee. The comparison revealed the good reliability of the present models in predictions (r = 0.998).


Article
Performance of Geopolymer Concrete Exposed to Freezing and Thawing Cycles

Authors: Mohammed H. Shamsa --- Basil S. Al-Shathr --- Tareq S. al-Attar
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2019 Volume: 37 Issue: 3 Part (A) Engineering Pages: 78-84
Publisher: University of Technology الجامعة التكنولوجية

Loading...
Loading...
Abstract

In this study, the effect of rapid freezing and thawing (ASTM C666– procedure A) on three different types of Geopolymer concrete studiedusing three types of pozzolanic material: fly ash, metakaolin and groundgranulated blast furnace slag (GGBFS). The Geopolymer concrete wasprepared using 400 kg of the pozzolanic material with alkaline liquidprepared at 8 molar concentration with normal fine and coarse aggregates.The ratio of alkaline to fly ash and GGBFS was 1.5: 1 and for metakaolinwas 2: 1 for workability and compressive strength requirements. Specimens(100 × 100 × 400) mm were exposed to 100, 200 and 300 cycles of freezingand thawing. The decrease in measured compressive strength was (23, 43,and 26%) for Fly ash, metakaolin and GGBFS respectively. The investigatedtypes of concrete showed good resistance to freezing and thawing. Thedurability factor of these types was (77%, 68%, and 81%) for fly ash,metakaolin, and GGBFS respectively.Keywords- Freezing and thawing,

Listing 1 - 9 of 9
Sort by
Narrow your search

Resource type

article (9)


Language

English (9)


Year
From To Submit

2019 (2)

2018 (4)

2014 (3)