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Volume 15, Number 1, January 2023

Concrete is one of the most widely used structure materials. Concrete is like the motor of the construction industry. The remarkable feature of this Concrete is its cheapness and low energy consumption. Concrete alone does not show resistance against any force but only against compressive forces. Therefore, steel rebar product is used as a reinforcement and increase the strength of Concrete. It can be done by putting rebar in Concrete in different ways. Rebar rusting is one of the crucial symptoms that cause swift destruction in reinforced structures–factors such as moisture in concrete increase the steel corrosion rate. In most cases, it is difficult to compensate for the damage caused by the corrosion of base metals, so preventing corrosion will be much more cost-effective. Coatings made with nanotechnology can protect Concrete against external degradation factors to prevent water and humidity from penetrating the Concrete and prevent rusting and corrosion of the rebar inside. It prevents water penetration and contamination into the Concrete and increases the Concrete's quality and structural efficiency. In this research, silica and titanium dioxide nanoparticle coatings have been used due to their suitable electrical and thermal properties, resistance to oxidation, corrosion, and wear to prevent the corrosion of rebars in Concrete. The results of this method show that these nanoparticles significantly improve the corrosion resistance of rebars.

Key Words
concrete; nanoparticles; quality; rebar; silica; titanium oxide

(1) Jundong Wu:
China Airport Planning & Design Institute Co., Ltd. Northwest Branch, Xi'an 710000, Shaanxi, China;
(2) Yan Cui:
School of Civil Engineering, Hebei Polytechnic Institute, Shijiazhuang 050091, Hebei, China.

Autogenous healing of concrete can be helpful in structural maintenance by healing cracks using a healing material created by the precipitation of calcite and by the hydration of unhydrated binder around the cracks. Against this backdrop, this study investigated the physicochemical properties and autogenous healing performance of ternary blended binder composed of ordinary Portland cement (OPC), blast furnace slag (BFS), and calcium sulfoaluminate (CSA) clinker. Ternary blended binders with various contents of OPC-BFS-CSA clinker were prepared, and their physicochemical properties and autogenous healing performances were examined using various analytical techniques and visually observed using a microscope. The obtained results indicated that increase in the BFS content accompanied the increased the amount of unreacted BFS even after 28 days of curing and had a positive effect on the autogenous healing performance due to its latent hydration. However, replacing the CSA clinker did not increase the autogenous healing performance owing to an insufficient sulfate source for the formation of ettringite. The main precipitates around the cracks were calcite, C-S-H. Other hydration products such as portlandite, monosulfate, and ettringite, which were not found in the Raman and scanning electron microscope analyses.

Key Words
autogenous healing; blast-furnace slag; blended cement calcium sulfoaluminate cement; hydration products; ordinary Portland cement

(1) H.N. Yoon, Joonho Seo, Naru Kim, 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;
(2) H.M. Son:
Device Solutions, Samsung Electronics, Samsungjeonja-ro 1, Hwaseong-si, Gyeonggi-do, 18448, South Korea.

One of the important problems of concrete placing is the concrete compaction, which can affect the strength, durability and apparent quality of the hardened concrete. Therefore, vibrating operations might be accompanied by much noise and the need for training the involved workers, while inappropriate functioning can result in many problems. One of the most important methods to solve these problems is to utilize self-compacting cementitious composites instead of the normal concrete. Due to their benefits of these new materials, such as high tensile, compressive, and flexural strength, have drawn the researchers' attention to this type of cementitious composite more than ever. In this experimental investigation, six mixing designs were selected as a base to acquire the best mechanical properties. Moreover, forty-eight rectangular composite panels with dimensions of 300 mm × 400 mm and two thickness values of 30 mm and 50 mm were cast and tested to compare the flexural and impact energy absorption. Steel fibers with volume fractions of 0%, 0.5% and 1% and with lengths of 25 mm and 50 mm were imposed in order to prepare the required cement composites. In this research, the composite panels with two thicknesses of 30 mm and 50 mm, classified into 12 different groups, were cast and tested under three-point flexural bending and repeated drop weight impact test, respectively. Also, the examination and comparison of flexural energy absorption with impact energy absorption were one of the other aims of this research. The obtained results showed that the addition of fibers of longer length improved the mechanical properties of specimens. On the other hand, the findings of the flexural and impact test on the self-compacting composite panels indicated a stronger influence of the long-length fibers.

Key Words
cementitious composites; flexural strength; impact strength; self-compacting; steel fibers; tensile strength

(1) Denise-Penelope N. Kontoni:
Department of Civil Engineering, School of Engineering, University of the Peloponnese, GR-26334 Patras, Greece;
(2) Denise-Penelope N. Kontoni:
School of Science and Technology, Hellenic Open University, GR-26335 Patras, Greece;
(3) Behnaz Jahangiri, Ahmad Dalvand, Mozafar Shokri-Rad:
Faculty of Engineering, Lorestan University, Khorramabad, Iran;
(4) Ahmad Dalvand:
Centre for Infrastructure Engineering, Western Sydney University, Penrith NSW 2751, Australia.

Sport has no age limit and can be done anywhere and in any condition with minimal equipment. The existence of sports spaces in all parts of the world is considered a citizen's right. One of the activities carried out in this field is installing sports equipment and structures in parks and encouraging citizens to use this equipment for physical health with the least cost and facilities. Installing sports structures in open spaces such as parks is a practical step for developing citizens' sports. Although using devices in parks is acceptable, it is more critical to meet scientific and technical standards. The components of these structures must have high strength and endurance against changes in environmental conditions such as humidity, temperature difference, and corrosion. Among the various causes of material degradation, corrosion has always been one of several fundamental causes of metal equipment failure. Sports structures in open spaces are not safe from corrosion. Uniform corrosion is the most common type of corrosion. This corrosion usually occurs uniformly through a chemical or electrochemical reaction across the surface exposed to the corrosive environment. Rust and corrosion of outdoor sports structures are examples of this corrosion. For this reason, in this research, with the green synthesis of silica nanoparticles and its application in outdoor sports structures, the life span of these structures can be increased for the use of physical exercises as well as their quality.

Key Words
corrosion; green synthesis; physical exercise; silica nanoparticles; sports structures

(1) Zhixin Zhang, Zhiqiang Cai:
College of Physical Education, Langfang Normal University, Langfang 065000, Hebei, China;
(2) Khidhair Jasim Mohammed:
Air conditioning and Refrigeration Techniques Engineering Department, Al-Mustaqbal University College, Babylon 51001, Iraq;
(3) H. Elhosiny Ali:
Research Center for Advanced Materials Science (RCAMS), King Khalid University, P.O. Box 9004, Abha 61413, Saudi Arabia;
(4) H. Elhosiny Ali:
Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha 61413, Saudi Arabia;
(5) H. Elhosiny Ali:
Physics Department, Faculty of Science, Zagazig University, Zagazig 44519, Egypt.

This paper examines the dynamic response of rotating nanodevices under the external harmonic load. The spinning nanosystem is made of nanoscale tubes that rotate around the central nanomotor and is mathematically modeled via high-order beam theory as well as nonclassical nonlocal theory for the size impact. According to the Hamilton principle, the dynamic motion equations are derived, then the time-dependent results are obtained using the Newmark Beta technique along with the generalized differential quadratic method. The presented results are discussed dynamic deflection, resonant frequency, and natural frequency in response to the different applicable parameters, which help develop and produce nanoelectromechanical systems (NEMS) for various applications.

Key Words
computational modelling; dynamic analysis; NEMS; resonant frequency; spinning structures

(1) Jun Xiang:
Faculty of Architecture and Civil Engineering, Huaiyin Institute of Technology, Huaian, Jiangsu 223001, China;
(2) Mengran Xu:
College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310000, Zhejiang, China;
(3) Mengran Xu:
The Fourth Engineering Company, Zhejiang Construction Investment Transportation Infrastructure Group Co., Ltd, Hangzhou 310000, Zhejiang, China.

All production and consumption activities produce wastes, which often cause damage to our environment and multiple risks to the human health. The valorization of these wastes in concrete technology is a future solution that will allow finding other construction materials sources, optimizing energy consumption and protecting the environment. Among these wastes, there is the marble waste. Every year, huge amount of marble waste is discarded as dust or aggregates form, in open-air storage areas causing serious problems for the environment and public health. In this context, the incorporation of marble waste as a replacement of ordinary aggregates or cement in concrete composition is actively investigated by researchers. This paper presents a comprehensive review of published studies over the last 20 years, dealing the effect of marble waste on fresh and hardened properties of concrete. Most of the studies carried out have used marble waste as dust with substitution rates between 5 and 20%. Besides the economic and ecological benefits, this review showed that marble waste can improve the physical, mechanical and durability properties of concrete. This improvement depends on the form (dust, fine aggregate or coarse aggregate), substitution method (as cement or aggregates replacement) and substitution rate of marble waste. Additionally, the review results showed that the use of 10-15% of marble waste dust as cement substitution can lead to increase the compressive strength.

Key Words
cement; concrete; marble; properties; valorization; waste

(1) Rachid Djebien, Amel Bouabaz, Yassine Abbas:
LMGHU laboratory, Department of Civil Engineering, University 20 August 1955 – Skikda, Algeria;
(2) Yasser N. Ziada:
Department of Civil Engineering, University of Souk Ahras, Algeria.

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