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Volume 16, Number 5, November 2023

The purpose of this study was to evaluate the practical application of high-flowing concrete for a steel–concrete panel (SCP) module for a liquefied natural gas (LNG) storage tank. We evaluated the physical properties and filling performance of the developed concrete for the SCP module. First, slump tests were performed to evaluate the performance of the proposed standards for the filling tests. All the concrete mixes showed satisfactory performance. Based on the results of the previous study, the reliability of the required time measured using the T500 test and the rheometer results measured before and after pumping was 0.94, indicating that segregation and blocking should not occur. L-box and U-box tests were conducted before and after pumping. All the recommended standards showed satisfactory performance. The SCP structural module for LNG storage tanks was fabricated to a full scale to evaluate its practical application at the final site. Satisfactory filling performance was confirmed for all the specimens.

Key Words
LNG storage tanks; rheology; standards; steel-concrete panel

(1) Dong Kyu Lee:
Department of Safety Engineering, Dongguk University-Gyeongju, 123 Dongdae-ro, Gyeongju 38066, Republic of Korea;
(2) Jae Seon Kim:
National Disaster Management Research Institute, Ulsan, 44538, Republic of Korea;
(3) Myoung Sung Choi:
Department of Civil and Environmental Engineering, Dankook University, Gyeonggido Jukjeon-ro 152, Republic of Korea.

Microtubules in the cell are influenced by internal and external stimulation and play an important part in conveying protein substances and in carrying out medications to the intended targets. Waves are produced during these functions and in order to control the biological cell functions, it is important to know the wave velocities of microtubules. Owing to cylindrical shell shaped and mechanically elastic and orthotropic, cylindrical shell model based on gradient elasticity theory has been used. Wave velocities of the protein microtubule are carried out by considering Love's thin shell theory and Navier solution. Also, the effect of size parameter and other variables on the results are investigated.

Key Words
Love's thin shell theory; microtubules; Navier solution; wave propagation

(1) Muhammad Taj, Muhammad Safeer:
Department of Mathematics, University of Azad Jammu and Kashmir, Muzaffarabad, 1300, Azad Kashmir, Pakistan;
(2) Mohammad Amien Khadimallah:
Department of Civil Engineering, College of Engineering in Al-Kharj, Prince Sattam Bin Abdulaziz University, Al-Kharj, 11942, Saudi Arabia;
(3) Shahzad Ali Chattah:
Department of Chemistry, Government College University Faisalabad, 38000, Pakistan;
(4) Ikram Ahmad:
Department of Chemistry, University of Sahiwal, Sahiwal, 57000, Faisalabad, Pakistan;
(5) Sami Alghamdi:
Electrical and Computer Engineering Department, King Abdulaziz University, Jeddah, Saudi Arabia;
(6) Muzamal Hussain:
Department of Mathematics, University of Sahiwal, Sahiwal, 57000, Faisalabad, Pakistan;
(7) Rana Muhammad Akram Muntazir:
Department of Mathematics, Lahore Leads University, 54792, Lahore, Pakistan;
(8) Faisal Al-Thobiani:
Marine Engineering Department, Faculty of Maritime Studies, King Abdulaziz University, Jeddah, Saudi Arabia;
(9) Muhammad Naeem Mohsin:
Institute for Islamic Theological Studies, University of Vienna, Schenkenstrabe 8-10,1010, Vienna, Austria;
(10) Faisal Mehmood Butt:
Department of Electrical Engineering, University of Azad Jammu and Kashmir, Pakistan;
(11) Zafer Iqbal:
Department of Mathematics, University of Sargodha, Sargodha, Punjab, Pakistan;
(12) Zafer Iqbal:
Department of Mathematics, University of Mianwali, Punjab, Pakistan.

The production of ultra-early-strength concrete (UESC) traditionally involves complexity or necessitates hightemperature curing conditions. However, this study aimed to achieve ultra-early-strength performance solely through roomtemperature curing. Experimental results demonstrate that under room-temperature (28°C) curing conditions, the concrete attained compressive strengths of 20 MPa at 4 hours and 69.6 MPa at 24 hours. Additionally, it exhibited a flexural strength of 7.5 MPa after 24 hours. In contrast, conventional concrete typically reaches around 20.6 MPa (3,000 psi) after approximately 28 days, highlighting the rapid strength development of the UESC. This swift attainment of compressive strength represents a significant advancement for engineering purposes. Small amounts of steel fibers (0.5% and 1% by volume, respectively) were added to address potential concrete cracking due to early hydration heat and enhance mechanical properties. This allowed observation of the effects of different volume contents on ultra-early-strength fiber-reinforced concrete (UESFRC). Furthermore, the compressive strength of 0.5% and 1% UESFRC increased by 16.3% and 31.3%, respectively, while the flexural strength increased by 37.1% and 47.9%. Moreover, toughness increased by 58.2 and 69.7 times, respectively. These findings offer an effective solution for future emergency applications in public works.

Key Words
flexural strength growth rate; steel fibers; toughness growth value; ultra-early-strength fibers reinforced concrete

(1) Yi-Chun Lai:
Department of Civil Engineering, Military Academy, Kaohsiung, 83059, Taiwan, Republic of China;
(2) Ming-Hui Lee:
Department of Civil Engineering, National Pingtung University of Science and Technology, Pingtung, 912301, Taiwan, Republic of China;
(3) Yuh-Shiou Tai:
HiPer Fiber LLC, 25920 Northline Commerce Dr., STE 404, Taylor, Michigan, 48180, USA.

In order to study the effect of rubber particle size and admixture on the frost resistance of self-compacting concrete, three self-compacting concrete specimens with equal volume replacement of fine aggregate by rubber particles of different particle sizes were prepared, while conventional self-compacting concrete was made as a comparison specimen. The degradation law of rubber aggregate self-compacted concrete under freeze-thaw cycles was investigated by fast-freezing method test. The results show that the rubber aggregate has some influence on the mechanical properties and freeze-thaw durability of the selfcompacting concrete. With the increase of rubber aggregate, the compressive strength of self-compacting concrete gradually decreases, and the smaller the rubber aggregate particle size is, the smaller the effect on the compressive strength of the matrix; rubber aggregate can improve the frost resistance of self-compacting concrete, and the smaller the rubber particle size is, the more obvious the effect on the improvement of the frost resistance of the matrix under the same dosage. Through the research of this paper, it is recommended to use 60~80 purpose rubber aggregate and the substitution rate of 10% is chosen as the best effect.

Key Words
freeze-thaw damage; relative dynamic modulus of elasticity; rubber aggregate; self-compacting concrete

(1) Miao Liu, Jianhua Xiao, Lijuan Su:
Liaoning Technical University, Xihe District, Fuxin City, Liaoning 123000, China;
(2) En Yang:
Pengshui Miao and Tujia Autonomous County Housing and Urban-Rural Development Committee, Chongqing 409614, China.

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