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Volume 15, Number 3, March 2023

Water glass (WG) and sodium sulfate (SS) were used to prepare polymeric aluminum chloride residue cement mortar (PACRM) by single and compound blending with polymeric aluminum chloride waste residue, respectively. The structural strength and textural characteristics examinations showed that PACRM consistency increased by incorporating WG, but decreased by incorporating SS. When WG and SS were compounded, the mortar consistency initially rose before falling. The compressive strength of PACRM increased and then decreased as WG was increased. The mechanical properties of PACRM were better enhanced by SS than WG, showing no strength deterioration. The main reason for the improved mechanical properties of polymeric aluminum chloride waste residue in the presence of activators is the increased precipitation of reactive substances, such as C-S-H gels, calcium silica, and Ca(OH)2. The density of the specimens with PACRM and the degree of aggregation of hydration products were significantly enhanced by generating more hydration products in the mortar. Further, the cracks and pores were significantly reduced, and the matrix structure was continuous and dense at 5% SS doping and 3% compound doping.

Key Words
alkali-activated reagents; compressive strength; microstructure; polymeric aluminum chloride residue

(1) Ping Xu, Yuhao Cui, Minxia Zhang, Yahong Ding:
College of Civil Engineering, Henan Polytechnic Univ., Jiaozuo, Henan 454003, China;
(2) Dong Han:
Citic Heavy Industry Engineering Technology Co. LTD, Luoyang City, Henan 471000, China.

Ultra-high-performance concrete (UHPC) is produced using high amount of cementitious materials, very low water/cementitious materials ratio, fine-sized fillers, and steel fibers. Due to the dense microstructure of UHPC, it possesses very high strength, elasticity, and durability. Besides that, the UHPC exhibits high ductility and fracture toughness due to presence of fibers in its matrix. While the high ductility of UHPC allows it to undergo high strain/deflection before failure, the high fracture toughness of UHPC greatly enhances its capacity to absorb impact energy without allowing the formation of severe cracking or penetration by the impactor. These advantages with UHPC make it a suitable material for construction of the structural members subjected to special loading conditions. In this research work, the UHPC mixtures having three different dosages of steel fibers (2%, 4% and 6% by weight corresponding to 0.67%, 1.33% and 2% by volume) were characterized in terms of their mechanical properties including facture toughness, before using these concrete mixtures for casting the slab specimens, which were tested under high-energy impact loading with the help of a drop-weight impact test setup. The effect of fiber content on the impact energy absorption capacity and central deflection of the slab specimens were investigated and the equations correlating fiber content with the energy absorption capacity and central deflection were obtained with high degrees of fit. Finite element modeling (FEM) was performed to simulate the behavior of the slabs under impact loading. The FEM results were found to be in good agreement with their corresponding experimentally generated results.

Key Words
concrete damage plasticity model; fiber content; finite element modeling (FEM); fracture toughness; impact; UHPC

(1) Muhammad Umar Khan, Shamsad Ahmad, Mohammed A. Al-Osta, Ali Husain Algadhib, Husain Jubran Al-Gahtani:
Department of Civil & Env. Eng., KFUPM, Dhahran 31261, Saudi Arabia;
(2) Muhammad Umar Khan:
Department of Civil Engineering & Technology, Qurtuba University of Science and Information Technology, D.I. Khan 29150, Pakistan;
(3) Shamsad Ahmad, Mohammed A. Al-Osta, Ali Husain Algadhib, Husain Jubran Al-Gahtani:
Interdisciplinary Research Center for Construction and Building Materials, KFUPM, Dhahran 31261, Saudi Arabia.

Cytoskeleton components play key role in maintaining cell structure and in giving shape to the cell. These components include microtubules, microfilaments and intermediate filaments. Among these filaments intermediate filaments are the most rigid and bear large compressive force. Actually, these filaments are surrounded by other filaments like microtubules and microfilaments. This network of filaments makes a layer as a surface on intermediate filaments that have great impact on buckling behavior of intermediate filaments. In the present article, buckling behavior of intermediate filaments is studied by taking into account the effects of surface by using Euler Bernoulli and Timoshenko beam theories. It is found that effects of surface greatly affect the critical buckling force of intermediate filaments. Further, it is observed that the critical buckling force is inversely proportional to the length of filament. Such types of observations are helpful for further analysis of nanofibrous in their actual environments within the cell.

Key Words
buckling behavior; intermediate filaments; residual stress; young's Laplace equation

(1) Muhammad Taj, Manzoor Ahmad:
Department of Mathematics, University of Azad Jammu and Kashmir, Muzaffarabad, 1300, Azad Kashmir, Pakistan;
(2) Muzamal Hussain:
Department of Mathematics, Govt. College University Faisalabad, 38000, Faisalabad, Pakistan;
(3) Mohamed A. Khadimallah:
Department of Civil Engineering, College of Engineering in Al-Kharj, Prince Sattam Bin Abdulaziz University, Al-Kharj, 11942, Saudi Arabia;
(4) Mohamed A. Khadimallah:
Laboratory of Systems and Applied Mechanics, Polytechnic School of Tunisia, University of Carthage, Tunis, Tunisia;
(5) Muhammad Safeer:
Department of Mathematics University of Poonch Rawalwkot 12350 Azad Kashmir, Pakistan;
(6) S.R. Mahmoud:
GRC Department, Faculty of Applied Studies, King Abdulaziz University, Jeddah, Saudi Arabia;
(7) Zafer Iqbal:
Department of Mathematics, University of Sargodha, Sargodha, Punjab, Pakistan;
(8) Zafer Iqbal:
Department of Mathematics, University of Mianwali, Mianwali, Pakistan;
(9) Mohamed R. Ali:
Faculty of Engineering and Technology, Future University in Egypt New Cairo 11835, Egypt;
(10) Mohamed R. Ali:
Basic Engineering Science Department, Benha Faculty of Engineering, Benha University, Benha, Egypt;
(11) Aqib Majeed:
Department of Mathematics, The University of Faisalabad, Sargodha Road, University Town Faisalabad, 38000, Pakistan;
(12) Abdelouahed Tounsi:
YFL (Yonsei Frontier Lab), Yonsei University, Seoul, Korea;
(13) Abdelouahed Tounsi:
Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia.

The effect of glass fibres (GF) and polypropylene fibres (PPF) on the fresh properties and mechanical properties of lightweight concrete (LWC) exposed to high temperatures is investigated in this study. In this study, fifteen LWC mixtures were carried out in three different groups reinforced with PPF or GF fibers by 0%, 0.2%, and 0.4% by volume of concrete. The first group included aluminum powder (AP) as an air agent at 0.03% with the normal weight coarse aggregate (NWCA) by 100% of the weight of coarse aggregate. In the second group, 33% of the NWCA weight was replaced by lightweight coarse aggregate (LWCA). In the third group, 67% of the NWCA weight was replaced by LWCA. The slump, unit weight, Compressive strength (CS), tensile strength (TS), and flexural strength (FS) were examined. For two hours, the CS and FS were subjected to elevated temperatures of 200°C, 400°C, and 600°C, in addition to microstructure analysis of concrete. In comparison to the reference mixture, the fresh properties and bulk density of LWC decreased with the use of the air agent or the replacement of 67% of the NWCA with LWCA. As a result of the fiber addition, both the slump test and the bulk density decreased. The addition of fibers increased the CS; the highest CS was 38.5 MPa when 0.4% GF was added, compared to 28.9 MPa for the reference mixture at the test age of 28 days. In addition, flexural and TS increased by 53% and 38%, respectively, for 0.4% GF mixes. As well as, adding 0.4% GF to LWC maintained a higher CS than other mixtures.

Key Words
elevated temperatures; glass fibre; mechanical characteristics; microstructure; lightweight concrete; polypropylene fibre

(1) Abdulnour Ali Jazem Ghanim:
Department of Civil Engineering, College of Engineering, Najran University, Najran, Saudi Arabia;
(2) Mohamed Amin, Ibrahim Saad Agwa:
Civil and Architectural Constructions Department, Faculty of Technology and Education, Suez University, Egypt;
(3) Abdullah M. Zeyad:
Civil Engineering Department, College of Engineering, Jazan University, Jazan, Saudi Arabia;
(4) Bassam A. Tayeh:
Civil Engineering Department, Faculty of Engineering, Islamic University of Gaza, P.O. Box 108, Gaza Strip, Palestine;
(5) Ibrahim Saad Agwa:
Department of Civil Engineering, El-Arish High Institute for Engineering and Technology, El-Arish, North Sinai, Egypt;
(6) Yara Elsakhawy:
Civil Engineering Dept., Faculty of Engineering, Delta University for science and Technology, Gamasa, Egypt.

Palm oil fuel ash (POFA) is a newly emerging pozzolanic material having high amount of silica content. Various forms of POFA were used in cement-based materials (CBMs) in replacement of cement in different dosages of low and high volume. Although, there are many researches on POFA to be used in concrete and mortar, however, this material was not practically used in the construction industry. Engineers and designers need to be confident to use any new developed materials by knowing all engineering properties at short and long terms. As durability concern, concrete pH value is one of the most important properties. Portland cement produces are alkaline initially, however, it may be reduced due to aging and its components. It is believed that by incorporation of supplementary cementitious materials in CBMs the pH value reduces due to utilization of Ca(OH)2 in pozzolanic reaction. This study is the first attempts to understand the pH value of mortars containing up to 30% POFA under different curing conditions and its changes with time. The results were also compared with the pH of ground granulated ballast furnace slag (GGBFS) and fly ash (FA) content mortars. In addition, the compressive strength of different mortars under different curing conditions were also studied. The results showed that the pH value of control mix (without cementitious materials) was more than all the blended cement mortars indifferent curing conditions at the same ages. However, there was a reducing trend in the pH value of all mortar mixes containing POFA.

Key Words
cementitious materials; compressive strength; curing; durability; palm oil fuel ash; pH value

(1) Payam Shafigh:
Center for Building, Construction & Tropical Architecture (BuCTA), Faculty of Built Environment, University of Malaya, 50603 Kuala Lumpur, Malaysia;
(2) Sumra Yousuf:
Department of Building and Architectural Engineering, Faculty of Engineering & Technology, Bahauddin Zakariya University Multan 60000, Pakistan;
(3) Belal Alsubari:
Department of Civil Engineering, Faculty of Engineering, Miami College of Henan University, Kaifeng, Henan, China;
(4) Zainah Ibrahim:
Department of Civil Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia.

New techniques, technologies, and materials should be used to design and build sports stadiums. Since this century, much progress has been made in covering the roofs of sports stadiums, and the possibility of accurate computer calculatio has been provided for stadiums, so by choosing a new structure, we can double the beauty and resistance of these stadiums. A stadium has an excellent and valuable design when its structure, shell, building, materials, and joinery follow a high architectural idea at all levels and scales. This article examines the mechanical performance of polymer cement strength in the construction of football stadiums, along with their structural knowledge in the form of the best examples in the world. Portland cement is one of the most used materials for constructing football stadiums. However, its production requires spending a lot of money, wasting energy, and damaging the environment. Considering the disadvantages in the production and consumption of concrete in different environments, it is necessary to find alternative materials. It should be used with cheaper, simpler technology, abundant primary resources, energy saving, less environmental damage, and better chemical and physical properties in concrete. Highstrength concrete technology is considered a new development in the construction industry of concrete structures. In hardened concrete, strength and durability are two main factors, and as the compressive strength of concrete increases, concrete becomes more brittle. As a result, its tensile strength does not increase in proportion to the increase in compressive strength and has less strain tolerance. For this reason, the need to use is evident from the fibers in high-strength concrete. Fibers are used in concrete to increase tensile strength, prevent crack propagation, and significantly increase softness. The increase with the change of these resistances depends on the strength of concrete without fibers, the shape of fibers, and the percentage of fibers. This cement is obtained from the wastes of chemical and petrochemical industries and the wastes from coal combustion, which have the properties mentioned as substitutes for Portland cement.

Key Words
coal combustion; football; polymer cement; Portland; stadium

(1) Zhuhai University of Science and Technology, Zhuhai 519000, Guangdong, China;
(2) St.Paul University Philippines, Tuguegarao, Philippines.

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