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CONTENTS
Volume 12, Number 1, July 2021
 


Abstract
The sound-absorption and NOx-removal performances of TiO2-incorporated porous concrete made with bottom ash aggregates were investigated. Concrete samples made with bottom ash aggregates having different paste-to-aggregate volume ratios (i.e., 0.2, 0.3 and 0.4) and TiO2 contents (i.e., 0%, 1% and 3%) were fabricated. The correlation between the voids and the mechanical strength values of concretes made with bottom ash aggregates was investigated through void ratio measurement and compressive strength tests to derive a proper aggregate size. The influence of target void and TiO2 content on the void ratio, compressive strength, sound-absorption, and NOx-removal performances of the samples was explored through compressive strength, void ratio, sound-absorption, and NOx-removal performance tests. The test results indicated that the sound-absorption and NOx-removal performances of the concrete samples were greatly influenced by the total void ratio, and the NOx-removal efficiency of the concrete samples was further promoted with an increase in the TiO2 content. These coupled effects were possibly attributed to the fact that the photocatalytic reaction is surface-oriented and can be affected by an increase in the total void ratio, increasing the available number of TiO2 particles on the surface that can facilitate the photocatalytic reaction when exposed to light.

Key Words
bottom ash; NOx-removal performance; photocatalyst; porous concrete; sound absorption

Address
H.N. Yoon, Joonho Seo, Seonhyeok Kim, Taegeon Kil, Daeik Jang, Jin-Ho Bae and H.K. Lee: Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea

Abstract
This study presents the experimental performance of a high ductility and energy dissipation capacity connector named notched-slab fastener, which is developed for timber-concrete composite floor structures. Notched-slab fastener is unique because the notch was left in the concrete slab instead of a timber beam for the first time. In this way, cross-section loss in the timber beam is prevented. This is one of the most important benefits of the proposed connector. Experimental performance of the purposed connector was investigated with two test methods: push-out test and bending test. For comparison purposes, a notched fastener was also produced and tested as reference sample. Test results showed that notched-slab fastener has stable load carrying behavior under push-out loading with high-energy dissipation and no sudden strength degradation. In addition, notched slab design provided moment arm to the fastener and the damage is concentrated in the connector instead of concrete.

Key Words
bending test; glued solid timber; push-out test; shear connection; timber-concrete

Address
Semih Yilmaz: Department of Architecture, Karadeniz Technical University, 61080, Trabzon, Turkey
Serhat Demir: Department of Civil Engineering, Karadeniz Technical University, 61080, Trabzon, Turkey
Nilhan Vural: Department of Architecture, Karadeniz Technical University, 61080, Trabzon, Turkey

Abstract
In this study, pozzolanic reactivity and strength activity of zeolitic tuffs containing similar amount of zeolitic phase (clinoptilolite) and different types and amounts of impurities were examined in order to understand the role of mineralogical composition in the efficiency of zeolitic natural pozzolans. Mineralogical and chemical compositions as well as the physical properties of the zeolitic tuffs were determined. Their pozzolanic reactivity were measured as depletion of calcium hydroxide in the pastes containing lime and zeolitic tuff, which is determined by thermogravimetric analysis. Furthermore, compressive strength of blended cement mortars prepared with 20% replacement of Portland cement by finely ground tuffs were determined at 7, 28 and 56 days of age. It was demonstrated that the type and amount of impurities in mineralogical composition of zeolitic tuffs are significantly effective on their early pozzolanic reactivity. Zeolite mineral content, however, is more determinative on long term reactivity. For a strength activity, mineralogical composition was clearly effective on the preparation of mortar samples, which depends on water requirement of zeolitic tuffs.

Key Words
characterization; lime fixation; natural zeolite; pozzolan; strength activity

Address
Sevgi Özen: Geological Engineering Department, Recep Tayyip Erdogan University, Fener-Rize 53100, Turkey
Burak Uzal: Civil Engineering Department, Abdullah Gul University, Erkilet Blv. Kayseri 38080, Turkey

Abstract
This research aims to study factors affecting the strength of adhesion between old concrete and new concrete. Among the factors that have been studied in this research are the type of bonding material and the roughness of the surface adhesion, four types of bonding materials (EPICHOR-1768, C-Latex, SikaBond-T21, EPICHOR-500) have been selected because they are available in local markets. A wire brush is used in order to increase the roughness of sample surfaces. The pulloff and slant shear tests have been adopted to assess the bonding strength between the test the old and new concrete. 30 cylindrical samples (7 cm diameter) have been examined by pull-off test, also slant shear test was conducted on 40 samples (10 cmx10 cmx30 cm). The obtained results showed that there is an active role for the bonding material as well as the surface roughness to increase the strength of adhesion between the old and new concrete. Also, it showed that the best of these bonding materials is EPICHOR-1768 because of its significant impact in increasing the strength of the adhesion between the old and new concrete where the percentage of increase 124% in the pull-off test and 48% in slant shear test, compared to the reference sample for each test. As well, as a result of roughening the surface by brush, the strength of adhesion reaches 4% increase in the pull-off test and 23% in the slant shear test compared with the reference sample for each test, which demonstrates the importance of surface roughness to increase the bonding strength between the old and new concrete.

Key Words
bond strength; bonding agents; old and new concrete; pull-off test; slant shear test; substrate roughness

Address
Hassan M. Magbool: Civil Engineering Department, College of Engineering, Jazan University, Jazan, Saudi Arabia
Bassam A. Tayeh: Civil Engineering Department, The Islamic University of Gaza, Gaza, Palestine

Abstract
The main goal of this research is to investigate the effect of polyvinyl alcohol (PVA) fiber and steel fiber on lightweight concrete, in which lightweight aggregate was used as the coarse aggregate. The lightweight aggregate was a kind of expanded clay aggregate made using bottom ash from a thermal power plant located in South Korea. Three types of specimens, lightweight concrete without fibers (LC), lightweight concrete containing polyvinyl alcohol fiber (LCPVA), and lightweight concrete with steel fiber (LCSF) were cast with two different fiber-volume fractions (0.5 and 1.0%). Tests of their compressive strength and splitting tensile strength were performed to evaluate the effectiveness of fiber type and fiber-volume fraction in lightweight concrete at 28 days and after 90 days. The results indicated that using fibers in lightweight concrete improved both the compressive strength and splitting tensile strength. The addition of fibers in lightweight concrete showed a positive effect, and the effectiveness of PVA fiber at 28 and 90 days (regarding compressive strength and splitting tensile strength) was more pronounced than steel fiber. Overall, it can be concluded that the 1.0% PVA fiber-volume fraction showed good performance in the lightweight concrete.

Key Words
fiber-reinforced lightweight concrete; lightweight aggregate; PVA fiber; steel fiber; strength

Address
Sardorbek Rustamov, Sangwoo Kim, Minho Kwon and Jinsup Kim: Department of Civil Engineering, Gyeongsang National University, 501 Jinju Daero, Jinju-si, Gyeongsangnam-do 52828, Republic of Korea

Abstract
In the present work the author incorporated the surrounding medium with Hodgkin Huxley model to account the effect of surroundings on the flow of current in cardiac muscles fibers. The Hodgkin Huxley Kelvin like model is developed here and then the governing equations are solved by appropriate mathematical methods and the obtained results are compared with the previous experimental findings. Through obtained solutions, we check the mechanical properties in actual environment of cardiac muscles fibres and compare our findings with experimental results. Previous Hodgkin Huxley model did not give any idea about the medium, in which the cardiac muscles are immersed. The new developed model accounts the effect of medium efficiently on the current flow along with fiber's stimulation in cardiac muscles.

Key Words
anisotropic cardiac muscles; cardiac muscles; current; Hodgkin Huxley model; viscoelastic medium

Address
Muhammad Taj: Department of Mathematics, University of Azad Jammu and Kashmir, Muzaffarabad, 1300, Azad Kashmir, Pakistan
Mohamed Amine Khadimallah: Civil Engineering Department, College of Engineering, Prince Sattam Bin Abdulaziz University, Al-Kharj, 16273, Saudi Arabia; Laboratory of Systems and Applied Mechanics, Polytechnic School of Tunisia, University of Carthage, Tunis, Tunisia
Muzamal Hussain: Department of Mathematics, Govt. College University Faisalabad, 38000, Faisalabad, Pakistan
E. Ghandourah: Department of Nuclear Engineering, Faculty of Engineering, King Abdulaziz University, Jeddah, Saudi Arabia
Muhammad Safeer: Department of Mathematics, University of Azad Jammu and Kashmir, Muzaffarabad, 1300, Azad Kashmir, Pakistan
Mohamed Elbahar: Civil Engineering Department, College of Engineering, Prince Sattam Bin Abdulaziz University, Al-Kharj, 16273, Saudi Arabia
Manzoor Khan: Department of Mathematics, University of Azad Jammu and Kashmir, Muzaffarabad, 1300, Azad Kashmir, Pakistan
Elaloui Elimame: Laboratory of Materials Applications in Environment, Water and Energy LR21ES15, Faculty of Sciences, University of Gafsa, Tunisia

Abstract
This paper presents the experimental results of research into the behavior of shear-enhanced reinforced concrete R.C beams using steel stirrups, Fiber Reinforced Polymers FRP rods, and Fiber Reinforced Polymers FRP strips. This enhancement was accomplished by the Near Surface Mounted technique NSM. The NSM technique contains a groove on the outside surface of the concrete member to adjust the depth to be less than the cover of the member. After cleaning, the epoxy paste was used to fill half of the groove's depth. In the groove, the particular FRP element is then installed. Finally, the groove is filled with epoxy and the outside surface of the concrete is levelled with so much epoxy. This method enables the fiber reinforcement polymer FRP materials is covered completely by epoxy. The objective of this research is to study the effect of NSM technique on shear resistance for stressed beam. 13 experimental studies of half-scale R.C beams were involved in this paper. The experimental program included two specimens strengthened with steel stirrups, eight specimens strengthened with stirrups of Glass Fiber Reinforced Polymer GFRP rods with the shape of deferent end anchorage and angle, two specimens strengthened with externally bonded GFRP strips. The remaining un-strengthened specimen was allocated for comparison as a control one. The test results included ultimate load of capacity, deflection, cracking, and failure mode. All beams enhanced with GFRP rods showed a capacity improvement ranging from 14% to 85% compared to the reference beam, and compared to the reference beam, beams enhanced with GFRP strips showed a capacity improvement ranging from 7% to 22%.

Key Words
fiber reinforced polymer FRP; near surface mounted NSM; reinforced concrete RC; shear; strengthening

Address
Ahmed H. Abdel-kareem, Ahmed S. Debaiky, Mohamed H. Makhlouf and M. Abdel-baset: Department of Civil Engineering, Benha Faculty of Engineering, Benha University, Egypt

Abstract
Heavyweight concrete having unit weight above 2600 kg/m3 has wide applications that include radiation shielding, offshore, and ballasting of pipelines, etc. In this study, high-performance heavyweight concrete mixtures were developed utilizing industrial byproducts as high-density coarse aggregates. These heavyweight coarse aggregates included steel slag, steel shots, and iron ore. Normal-weight limestone aggregate was also used in the control mixture and for partially replacing the heavyweight aggregates in some of the mixtures. Considering different combinations of coarse aggregates, a total of nineteen concrete mixtures with same water/cement ratio and cement content were prepared and tested for evaluating their performance in terms of different engineering properties. Except the control mixture containing normal-weight limestone aggregate, all eighteen heavyweight concrete mixtures considered in the present work, achieved unit weight (dry density) in the acceptable range of 2600 to 3563 kg/m3. Most of the heavyweight concrete mixtures attained compressive strength either close to or more than 40 MPa, splitting tensile strength and modulus of elasticity above the minimum acceptable limits, drying shrinkage below permissible value, and high resistance against reinforcement corrosion as indicated by their high electrical resistivity and low chloride diffusion coefficient. The experimental data generated under the present work can be utilized to select optimum mixtures of heavyweight concrete satisfying the service conditions.

Key Words
chloride diffusion; compressive and splitting tensile strength; density; heavyweight concrete; modulus of elasticity; resistivity; shrinkage

Address
Salah U. Al-Dulaijan, Mukhtar Oluwaseun Azeez, Shamsad Ahmad: Civil & Environmental Engineering Department, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia
Mohammed Maslehuddin: Research Institute, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia


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