السنة | 2023-12-19 |
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التخصص | ماجستير هندسة الإنشاءات |
العنوان | Repairing and strengthening of reinforced concrete columns containing construction defects using ultra-high performance concrete jacketing |
اسم المشرف الرئيسي | محمد سلمان عباس الامي | Mohammed Salman AL-lami |
اسم المشرف المشارك | | |
اسم الطالب | محمد وليد حسني الاحمد | Mohammad Waleed Alahmad |
Abstract | "Ultra-High-Performance Concrete" (UHPC), is a modern concrete technology that has gained popularity recently. It has very high compressive strength, ranging from 120 MPa to over 180 MPa. Many researchers tried to use this type of concrete to strengthen the structural elements, where the result shows that UHPC might be a good alternative to strengthening techniques. But many of these UHPC mixtures have a commercial name, which indicates that to use these mixtures, it is required to order them from the manufactory as ready mixes, which are delivered and sold packaged. In this research, an experimental program was conducted to test 14 trial mixtures by using materials that were available in the local market to select the highest possible compressive strength mixture for UHPC, aiming to achieve results comparable to ready-mix. The materials used in this study were: cement, micro silica, crushed quartz, silica sand, calcium carbonate, crushed basalt, steel fiber, and three different types of superplasticizer additives. Five reinforced concrete (RC) columns were cast using normal concrete (NC), and four of them were cast without concrete cover as defects, resulting in their inability to bear the intended loads due to weakening. The columns were repaired and strengthened using a UHPC jacket in order to study the feasibility of using UHPC to increase the maximum capacity load of defective reinforced concrete columns. The UHPC jackets were cast with maximum compressive strength obtained from trial mixtures reaching 123.6 MPa at 28 age days and different thicknesses (20 mm, 30 mm, and 40 mm). The results obtained from this study showed the following: 1.Using the UHPC as a jacketing showed an efficiency increase in maximum capacity load, reaching up to 253.3% in comparison with defective RC column, and more than 17% in comparison with normal RC column that have the same dimensions. 2.All the jacket specimens had a failure in the way of spalling, where the jacket's failure method was predictable prior to its occurrence, as the failure occurred gradually, from a hairline crack to a complete failure, due to the use of steel fiber, which helped prevent the expansion of cracks. 3.The results showed that the jacket thicknesses had a clear effect on the behavior of the columns. Whereas the 20 mm thickness gave a slight improvement, while the 30mm thickness resulted in better column improvement, but neither of these thicknesses were able to restore the defective RC column to its original condition. On the other hand, a column with a jacket thickness of 40 mm was able to restore the defective RC column to better than its original condition. |
الأبحاث المستلة |