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Volume 13, Number 4, April 2022

3D printing cement-based materials (3DPCBM) is an innovative rapid prototyping technology for construction materials. This study is tested on the rheological behavior, printability and buildability of steel slag (SS) content based on the extrusion system of 3D printing. 0, 8 wt%, 16 wt%, 24 wt%, 32 wt% and 40 wt% SS was replaced cement, The test results revealed that the addition of SS would increase the fluidity of the printed paste, prolong the open time and setting time, reduce the plastic viscosity, dynamic yield stress and thixotropy, and is beneficial to improve the pumping and extrudability of 3DPCBM. With the increase of SS content, the static yield stress developed slowly with time which indicated that SS is harmful to the buildability of printing paste. The content of SS in 3DPCBM can reach up to 40% at most under the condition of satisfying rheological property and buildability, it provides a reference for the subsequent introduction of SS and other industrial solid waste into 3DPCBM by explored the influence law of SS on the rheological properties of 3DPCBM.

Key Words
3D printing cement-based materials; buildability; printability; rheological behavior; steel slag

Lingli Zhu: School of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo 454000, China
Zhang Yang: School of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo 454000, China
Yu Zhao: School of Civil Engineering, Henan Polytechnic University, Jiaozuo 454000, China
Xikai Wu: School of Civil Engineering, Henan Polytechnic University, Jiaozuo 454000, China
Xuemao Guan: School of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo 454000, China

The present investigation deals with the production of the innovative lightweight fly ash angular aggregates (FAA) first time in India using local class 'F' fly ash, its characterization, and exploring the potential for its utilization as alternative coarse aggregates in structural concrete applications. Two types of aggregates are manufactured using two different kinds of binders. The manufacturing process involves mixing fly ash, binder, and water, followed by the briquetting process, sintering and crushing them into suitable size aggregates. Tests are conducted on fly ash angular aggregates to measure their physical properties such as crushing value, impact value, specific gravity, water absorption, bulk density, and percentage of voids. Study shows that the physical parameters are significantly enhanced as compared to commercially available fly ash pellets (FAP). The developed FAA are used in concrete vis-à-vis conventional granite aggregates and FAP to determine their compressive, split tensile and flexural strengths. Although being lightweight, the strength parameters for concrete containing FAA are well compared with conventional concrete. This might be due to the high pozzolanic reaction between fly ash angular aggregates and cement paste. Also, RCC beams are cast and the load-deflection behaviour and ultimate load carrying capacity signify that FAA can be suitably used for RCC construction. Hence, the utilization of fly ash as angular aggregates can reduce the dead load of the structure and at the same time serves as a solution for fly ash disposal and mineral depletion problem.

Key Words
Fly Ash Angular Aggregates (FAA); lightweight; sintering; specific strength; sustainable

Pritam K. Pati and Shishir K. Sahu: Department of Civil Engineering, National Institute of Technology, Rourkela, Odisha, 769008, India

This paper performs an experimental study on the flexural behavior of preloaded reinforced self-compacted concrete beams strengthened with carbon fiber reinforced polymers CFRP. A group of six preloaded strengthened beams was investigated along with one unstrengthened beam used as a reference beam RB. All beams have the same dimensions and reinforcement details: three beams are strengthened with CFRP laminates against flexural failure and three beams are strengthened with CFRP sheets. For simulating actual conditions, the beams are loaded before strengthening. Then, after strengthening, the beams are tested for flexural strength using 4-point loads where cracked and ultimate load and failure mode, along with load-deflection relation are recorded. To study the different configurations of strengthening, one layer, two layers, and U-wrap formation of laminates and sheets are considered. The results show that strengthing the RC beams using CFRP is an effective method to increase the beam's capacity by 47% up to 153% where deflection is reduced by 5%-80%. So, the beams strengthened with CFRP laminates have higher load capacity and lower ductility in comparison with the beams strengthened with CFRP sheets.

Key Words
CFRP laminated; CFRP sheets; flexural strengthening; preloading; RC beam; self-compacted concrete

Youssef Lattif: Department of Structural Engineering, Zagazig University, Zagazig, Egypt
Osman Hamdy: Department of Civil Engineering, Zagazig Higher Institute of Engineering and Technology, Zagazig, Egypt

Reinforced concrete structures are exposed throughout their lifetime to the phenomenon of carbonation, which considerably influences their durability by causing corrosion of the reinforcements. The fight against this phenomenon is usually ensured by anti-carbonation coatings which have the possibility of limiting the permeability to carbon dioxide or with coatings which absorb the CO2 present in the air. A coating with good crack-bridging (sealing) capacity will prevent water from entering through existing cracks in concrete. Despite the beneficial effect of these coatings, their durability decreases considerably over time with temperature and humidity. In order to use coatings made from local materials, not presenting any danger, available in abundance in our country, very economical and easy to operate is the main objective of this work. This paper aim is to contribute to the formulation of a corrected dune sand-based mortar as an anti-carbonation coating for concrete. The results obtained show that the cement mortar based on dune sand formulated has a very satisfactory compressive strength, a very low water porosity compared to ordinary cement mortar and that this mortar allows an improvement in the protection of the concrete against the carbonation of 60% compared to ordinary cement mortar based on alluvial sand. Moreover, the formulated cement mortars based on dune sand have good adhesion to the concrete support, their adhesion strengths are greater than 1.5MPa recommended by the standards.

Key Words
adhesion; alluvial sand; anti-carbonation coating; carbonation; concrete; corrosion; dune sand; mortar; sustainability

Youssef Korichi: Civil Engineering Research Laboratory, Ammar Thélidji University of Laghouat, Algeria
Ahmed Merah: Civil Engineering Research Laboratory, Ammar Thélidji University of Laghouat, Algeria
Med Mouldi Khenfer: Civil Engineering Research Laboratory, Ammar Thélidji University of Laghouat, Algeria
Benharzallah Krobba: Structure Rehabilitation and Materials Laboratory (SREML), Ammar Thélidji University of Laghouat, Algeria

This paper is concerned with the vibration analysis of middle layer cylindrical shell made of functionally graded material. The outer layers and inner layer are composed of functionally graded and isotropic material respectively. The Rayleigh Ritz method is applied to solve the presented shell dynamics equations. Two configurations are constructed with layers distributions. Fundamental natural frequencies of the three layered cylindrical shell is plotted against the circumferential wave number with different power law exponents. The frequency decreases with the increase of power law exponent. The fundamental natural frequencies first decreases and fall down to its minimum value, after frequencies increases with circumferential wave number. This is due to change in the magnitude of extensional and bending energies of the cylindrical shells. The computer software MATLAB has been employed for the computation of presented frequencies and tested the results obtained in order to assess the accuracy and validity of the cylindrical shell model for predicting the vibration frequencies of cylindrical shell.

Key Words
circumferential wave number, dynamics equations, functionally graded material; fundamental natural frequencies, MATLAB

Muzamal Hussain: Department of Mathematics, Govt. College University Faisalabad, 38000, Faisalabad, Pakistan
Mohamed A. Khadimallah: Civil Engineering Department, College of Engineering, Prince Sattam Bin Abdulaziz University, BP 655, Al-Kharj,16273, Saudi Arabia; Laboratory of Systems and Applied Mechanics, Polytechnic School of Tunisia, University of Carthage, Tunis, Tunisia
Hamdi Ayed: Department of Civil Engineering, College of Engineering, King Khalid University, Abha, Kingdom of Saudi Arabia; Higher Institute of Transport and Logistics of Sousse, University Sousse, Tunisia
Adil Alshoaibi: Department of Physics, College of Science, King Faisal University, Al-Hassa, P.O Box, Hofuf,31982, Saudi Arabia
Hassen Loukil: Department of Electrical Engineering, College of Engineering, King Khalid University, Abha-61421, Saudi Arabia
Ghazi Alsoruji: Mechanical Engineering Department, Faculty of Engineering, King Abdulaziz University, Jeddah, Saudi Arabia
Abdelouahed Tounsi: YFL (Yonsei Frontier Lab), Yonsei University, Seoul, Korea; Department of Civil and Environmental Engineering, King Fahd University of Petroleum and Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia

Retrofitting in reinforced concrete structures has been one of the most important research topics in recent years. There are several methods for retrofitting RC moment-resisting frames. the most important of which is the use of steel bracing systems with yielding dampers. With a proper design of yielding dampers, the stiffness of RC frame systems can be increased to the required extent so that the ductility of the structure is not significantly reduced. In the present study, two experimental samples of a one-third scale RC moment-resisting frame were loaded in the laboratory. In these experiments, the retrofitting effect of RC frames was investigated using Non-uniform Slit Dampers (NSDs). Based on the experimental results of the samples, seismic parameters, i.e., stiffness, ductility, ultimate strength, strength reduction coefficient, and energy dissipation capacity, were compared. The results demonstrated that the retrofitted frame had very significant growth in terms of stiffness, ultimate strength, and energy dissipation capacity. Although the strength reduction factor and ductility decreased in the retrofitted sample. In general, the behavior of the frame with NSDs was evaluated better than the bare frame.

Key Words
experimental assessment; Non-uniform Slit yielding Dampers (NSDs); RC moment-resisting frame; retrofitting; seismic parameters; yielding dampers

J. Esfandiari: Department of Civil Engineering, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran
E. Zangeneh: Department of Civil Engineering, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran
S. Esfandiari: Departments of Civil Engineering, RWTH Aachen University, Aachen, Germany

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