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CONTENTS
Volume 6, Number 5, October 2018
 

Abstract
This paper investigates the behavior of normal and self-compacted steel fiber reinforced concrete (SCC-SFRC) corbels rehabilitated by Basalt Fiber Mesh (BFM) and Basalt Fiber Fabric (BFF) for the first time in literature. The research objective is to study the effectiveness of BFM and BFF in the rehabilitation of damaged reinforced concrete corbels with and without epoxy injection. The experimental program includes two types of concrete: normal concrete, and self-compacted concrete. For normal concrete, 12 corbels were rehabilitated by BFM without injection epoxy in cracks, with two values of compressive strength, three ratios of steel fiber (SF), and two values of shear span. For self-compacted concrete, 48 corbels were rehabilitated with different parameters where 12 corbels were rehabilitated by BFM with and without epoxy injection, 18 heated corbels with three different high-temperature level were rehabilitated by repairing cracks only by epoxy injection, and 18 heated corbels with three different high-temperature level were rehabilitated by repairing cracks by epoxy and wrapping by BFF. All 48 corbels have two values of compressive strength, three values volumetric ratios of SF, and two values of the shear span. Test results indicate that RC corbels rehabilitated by BFM only without injection did not show any increase in the ultimate load capacity. Moreover, For RC corbels that were repaired by epoxy without basalt wrapping, the ultimate load capacities showed an increase depending on the mode of failure of corbels before the rehabilitation. However, the rehabilitation with only crack repairing by epoxy injection is more effective on medium strength corbels as compared to high strength ones. Finally, it can be concluded that use of BFF is an effective and powerful technique for the strengthening of damaged RC corbels.

Key Words
corbels; Self-Compacted Concrete (SCC); Steel Fiber(SF); rehabilitation; Basalt Fiber Mesh (BFM); Basalt Fiber Fabric (BFF)

Address
Mehmet Eren Gulsan: Civil Engineering Department, Gaziantep University, Gaziantep, Turkey
Mohammed S. Al Jawahery: Duhok Polytechnic University, Duhok, Iraq
Adnan H. Alshawaf: Civil Engineering Department, Gaziantep University, Gaziantep, Turkey
Twana A. Hussein: Civil Engineering Department, Gaziantep University, Gaziantep, Turkey
Khamees N. Abdulhaleem: Civil Engineering Department, Kirkuk, Iraq
Abdulkadir Cevik: Civil Engineering Department, Gaziantep University, Gaziantep, Turkey

Abstract
The most crucial factor determining the pumping performance of concrete is the characteristics of the lubricating layer formed between the pipe wall and the inner concrete. Thus, it is important to accurately identify the rheological properties of the lubricating layer to predict the pumping of concrete. In this study, a new method is proposed for measuring the rheological properties of the lubricating layer with improved convenience. To verify the new method, a pumping test was conducted with 337 m-long horizontal piping. The rheological properties of the lubricating layer were assessed by a previously verified method and the new method proposed in this study for a total of four concrete mixtures with design strength ranging from 27 MPa to 60 MPa. The correlation between the existing method and the new method in relation to the viscosity of the lubricating layer was determined, and it was possible to predict the pumping performance with an accuracy of about 88.5% using the viscosity of the lubricating layer obtained from this correlation.

Key Words
lubricating layer; pumping; rheological property; prediction; pumpability

Address
Kyong Pil Jang: Department of Civil and Environmental Engineering, Myongji University, Republic of Korea
Woo Jae Kim: Engineering Center, POSCO Engineering and Construction, Republic of Korea
Myoung Sung Choi: Department of Safety Engineering, Dongguk University, Republic of Korea
Seung Hee Kwon: Department of Civil and Environmental Engineering, Myongji University, Republic of Korea

Abstract
Concrete-Filled Steel Tube (CFST) columns are an increasingly popular means to support great compressive loads in buildings. The residual strength capacity of CFST stub columns may be utilized to assess the potential damage caused by fire and calculate the structural fire protection for least post-fire repair. Ten specimens under room conditions and 10 specimens under fire exposure to the Eurocode smouldering slow-growth fire were tested to examine the effects of diameter to thickness D/t ratio and reinforcing bars on residual strength capacity, ductility and stiffness of CFST stub columns. On the other hand, in sixteen among the twenty specimens, three or six reinforcing bars were welded inside the steel tube. The longitudinal strains in the steel tube and load-displacement relationships were recorded throughout the subsequent compressive tests. Corresponding values of residual strength capacity calculated using AISC 360-10 and EC4 standards are presented for comparison purposes with the experimental results of this study. The test results showed that after exposure to 750oC, the residual strength capacity increased for all specimens, while the ductility and stiffness were slightly decreased. The comparison results showed that the predicted residual strength using EC4 were close to those obtained experimentally in this research.

Key Words
circular CFST stub columns; post-fire residual strength; welded reinforcing bars; design specifications

Address
Ihssan A. Alhatmey, Talha Ekmekyapar and Salih K. Alrebeh: Department of Civil Engineering, University of Gaziantep, 27310 Gaziantep, Turkey

Abstract
In this paper the application of forging process as benefit technique in Reinforced Concrete (RC) beam bars and comparison to lap splices was experimentally investigated with four concrete beam specimens with same dimensions and reinforcement details. The reference specimen was with no splices and the other three beams were with different splices (100% forging in the middle, 50% forging, and 100% lap splices in the middle). Beams were tested with the four points load system. Experimental test results indicated that using forging process as new bar splicing method can have high effects on increasing ductility and energy dissipation of concrete structures. It also proved that this method increased the flexural rigidity, energy absorption, and ductility of the RC beams. And also this research results showed that the flexural capacity and ductility of the beam with 50% forging were respectively increased up to 10% and 75% comparing to that of reference specimen, but the energy absorption of this beams was decreased up to 27%. The ductility of beam with 50% forging was increased up to 25% comparing the ductility of beam with 100% forging.

Key Words
forging welding; GPW; flexural capacity; ductility; energy absorption; lap splice

Address
Mohammad K. Sharbatdar, Omid Mohammadi Jafari and Mohammad S. Karimi: Civil Engineering Faculty, Semnan University, Semnan, Iran

Abstract
Crack control of precast members is crucial for durability. However, there is no clear provision to check the crack width of precast joints. This study presents an experimental investigation of loop joint details for use in a precast bridge deck system. High strength concrete of 130 MPa was chosen for durability and closer joint spacing. Static tests were conducted to investigate the cracking and ultimate behavior of test specimens. The experimental results indicate that current design codes provide reasonable estimation of the flexural strength and cracking load of precast elements with loop joint of high strength concrete. However, the crack width control of the loop joints with high strength concrete by the current design practices was not appropriate. Some recommendations to improve crack control of the loop joint were derived.

Key Words
loop joint; cracking; precast deck; high strength concrete; static test

Address
Changsu Shim, Chi dong Lee and Sung-woong Ji: Department of Civil Engineering, College of Engineering, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul 156-756, Republic of Korea

Abstract
The ever-increasing cost of natural sand and the environmental impacts of extracting manufactured sand (quarry sand) calls for exploring the potential to use alternative materials as fine aggregates in concrete. Copper slag and ferrous slag are industrial by products obtained from the smelting process of copper and iron respectively. A large quantity of copper slag and ferrous slag end up being disposed as waste in landfills and this poses a serious threat to the environment. Copper slag and ferrous slag have similar physical and chemical properties as natural sand and also exhibit pozzolanic activity. This paper studies the technical feasibility of industrial by-products such as copper slag and ferrous slag to replace the fine aggregate in concrete by evaluating the workability, strength and durability characteristics of concrete. The test results indicate that the strength properties are not affected by 40% or 100% replacement of quarry sand with iron slag or copper slag. However, 40% replacement of quarry sand with iron slag or copper slag in concrete is recommended considering the durability aspects of concrete.

Key Words
slag; concrete; replacement; strength; durability; fine aggregate

Address
Job Thomas, Nassif N. Thaickavil and Mathews P. Abraham: Department of Civil Engineering, Cochin University of Science and Technology, Kochi, Kerala, India

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