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CONTENTS
Volume 12, Number 6, December 2021
 


Abstract
The mechanical behaviors and chloride resistance performance of fiber reinforced cementitious composites (FRCC) with hybrid polyethylene (PE) and steel fiber (in total 2% by volume) were investigated. Based on micro-mechanics and fracture mechanics, the reason why the tensile strain capacity of FRCC changed obviously was obtained. Besides, the effects of the total surface area of fiber in FRCC on compressive strength and chloride content were clarified. It is found that the improvement of the tensile strain capacity of FRCC with hybrid fiber is attributed to the growth of strain-hardening performance index (the ratio of complementary energy to crack tip toughness). As the total surface area of fiber related with the interfacial transition zone (ITZ) between fiber and matrix increases, compressive strength decreases obviously. Since the total surface area of fiber is small, the chloride resistance performance of FRCC with hybrid PE and steel fiber is better than that of FRCC containing only PE fiber.

Key Words
chloride resistance performance; fiber reinforced cementitious composites (FRCC); hybrid fiber; mechanical properties

Address
Qiao Liao: College of Civil Engineering, Tongji University, Shanghai 200092, China
Zhen-wen Guo: Shanghai Municipal Planning and Design Institute Co., Ltd., Shanghai 200031, China; Shanghai Engineering Research Center of Urban Road Ecological Technology, Shanghai 200031, China
Xin-zhi Duan: Shanghai Municipal Planning and Design Institute Co., Ltd., Shanghai 200031, China; Shanghai Engineering Research Center of Urban Road Ecological Technology, Shanghai 200031, China
Jiang-tao Yu: College of Civil Engineering, Tongji University, Shanghai 200092, China
Ke-ke Liu: Shanghai Municipal Planning and Design Institute Co., Ltd., Shanghai 200031, China
Fang-yuan Dong: Shanghai Municipal Planning and Design Institute Co., Ltd., Shanghai 200031, China

Abstract
Polyethylene-terephthalate (PET) from bottle waste and linear low-density polyethylene (LLDPE) from barrels and tanks waste are widely available and need to be recycled. Recycling them in concrete and mortar is an alternative solution for their disposal. In this study various quantities of sand (5%, 10%, 15% and 20%) were substituted by powder from LLDPE waste. In addition, PET waste fibers (corrugated, straight) were added to the mortar with different percentages (0.5%, 1%, 1.5% and 2%) of cement mass. This paper evaluate the mechanical and physical properties of the composites in fresh (workability, air content and density) and hardened state (compressive and flexural strength, water absorption and total shrinkage). From the experimental results, it can be concluded that the strengthening in tensile of the mortar with plastic waste corrugated fibers is improved. Other important results are that the water absorption and the density rate are less than that of the ordinary mortar.

Key Words
cement mortar; LLDPE powder waste; mechanical properties; PET fibers waste; physical properties

Address
Samir Benimam: LME Laboratory, University of Medea, Medea, 26000, Algeria
Mohamed Bentchikou:LMP2M Laboratory, University of Medea, Medea, 26000, Algeria
Farid Debieb:LME Laboratory, University of Medea, Medea, 26000, Algeria
Said Kenai:Geomaterials Laboratory, University of Blida, Blida 9000, Algeria
Mohamed Guendouz: LME Laboratory, University of Medea, Medea, 26000, Algeria


Abstract
Keratin fibres are waste products of the poultry industry. Natural materials made from chicken feather fibres (CFFs) are used in concrete-reinforced composites in this study. Brittleness is a major problem of high-strength concrete (HSC) that leads to sudden failure at the ultimate capacity of concrete. Hence, this work aims to investigate effects of using CFFs on improving the brittle behaviour of HSC. Two scenarios are performed to analyse the effectiveness of using CFFs. HSC containing different ratios of CFF (0% as the control, 0.5%, 1%, 1.5%, 2%, and 3%) by volume are tested in the first scenario. Glass fibres (GF) are used to replace CFFs in the other scenario. Tests of fresh, hardened and morphological properties for concrete are performed. Results showed the enhanced brittle behaviour of HSC when using both types of fibres. The preferable ratio of both types of fibres is 1% by volume. Flexural and splitting tensile strengths increased by about 44.9 % and 42.65 % for mixes containing 0.1% GF, respectively. While they were increased by about 21.6 % and 21.16 % for mixes containing 0.1% CFF, respectively.

Key Words
chicken feather fibre; fresh and hardened properties; glass fibre; high-strength concrete; microstructure

Address
Khaled Abdelsamie: Faculty of Engineering, Sohag University, Sohag, Egypt
Ibrahim Saad Agwa: 2=Civil and Architectural Constructions Department, Faculty of Technology and Education, Suez University, Egypt; Department of Civil Engineering, El-Arish High Institute for Engineering and Technology, El-Arish, North Sinai, Egypt
Bassam A. Tayeh: Civil Engineering Department, Faculty of Engineering, Islamic University of Gaza, Palestine
Radwa Defalla Abdel Hafez: Civil and Architectural Constructions Department, Faculty of Technology and education, Sohag University, Egypt

Abstract
Present research is mainly focused on, microstructural and durability analysis of Graphene Oxide (GO) in Wollastonite (WO) induced cement mortar with silica fume. The study was conducted by evaluating the mechanical properties (compressive and flexural strength), durability properties (water absorption, sorptivity and sulphate resistance) and microstructural analysis by SEM. Cement mortar mix prepared by replacing 10% ordinary portland cement with SF was considered as the control mix. Wollastonite replacement level varied from 0 to 20% by weight of cement. The optimum replacement of wollastonite was found to be 15% and this was followed by four sets of mortar specimens with varying substitution levels of cementitious material with GO at dosage rates of 0.1%, 0.2%, 0.3% and 0.4% by weight. The results indicated that the addition of up to 15%WO and 0.3% GO improves the hydration process and increase the compressive strength and flexural strength of the mortar due to the pore volume reduction, thereby strengthening the mortar mix. The resistance to water penetration and sulphate attack of mortar mixes were generally improved with the dosage of GO in presence of 15% Wollastonite and 10% silica fume content in the mortar mix. Furthermore, FE-SEM test results showed that the WO influences the lattice framework of the cement hydration products increasing the bonding between silica fume particles and cement. The optimum mix containing 0.3% GO with 15% WO replacement exhibited extensive C-S-H formation along with a uniform densified structure indicating that calcium meta-silicate has filled the pores.

Key Words
graphene oxide dispersion; mechanical properties; microstructural characteristics; silica fume; wollastonite

Address
V. Sairam, T. Shanmugapriya, Chetan Jain, Himanshu Kumar Agrahari and Tanmay Malpani: School of Civil Engineering, Vellore Institute of Technology, Vellore, India

Abstract
Cell components play vital role within the cell when the cell under goes deformation. These components are microtubules, microfilaments and intermediate filaments. Intermediate filaments are like thread and are of different types. Like microtubules and microfilaments these components also undergo the deformation and their dynamics affected when change occurs within cell. In the present study, bending of intermediate filaments are studied keeping the nonlocal effects under consideration. It is observed that the nonlocal parameter has a great impact on the dynamics of intermediate filaments. This study is made by the application of Euler beam theory.

Key Words
bending; Euler-Bernoulli beam theory; intermediate filaments; non-local parameters

Address
Muhammad Taj: Department of Mathematics, University of Azad Jammu and Kashmir, Muzaffarabad, 1300, Azad Kashmir, Pakistan
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, 11942, Saudi Arabia; Laboratory of Systems and Applied Mechanics, Polytechnic School of Tunisia, University of Carthage, Tunis, Tunisia
Jamel Baili: Department of Computer Engineering, College of Computer Science, King Khalid University, Abha 61413, Saudi Arabia; Higher Institute of Applied Science and Technology of Sousse (ISSATS), Cité Taffala (Ibn Khaldoun) 4003 Sousse, University of Souse, Tunisia
Khaled Mohamed Khedher: Department of Civil Engineering, College of Engineering, King Khalid University, Abha 61421, Saudi Arabia; Department of Civil Engineering, High Institute of Technological Studies, Mrezgua University Campus, Nabeul 8000, Tunisia
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

Abstract
Geopolymer binders fascinate the attention of researchers as a replacement to cement binder in conventional concrete. One-ton production of cement releases one ton of carbon-dioxide in the atmosphere. In the replacement of cement by geopolymer material, there are two advantages: one is the reduction of CO2 in the atmosphere, second is the utilization of Fly ash and Ground granulated blast furnace slag (GGBFS) are by-products from coal and steel industries. This paper focuses on the mechanical properties of steel fiber reinforced geopolymer concrete. The framework considered in this research work is geopolymer source (Fly ash, GGBFS and crimped steel fibre) and alkaline activator which consists of NaOH and Na2SiO3 of molarity 8M. Here the Na2SiO3 / NaOH ratio was taken as 2.5. The variables considered in this experimental work include Binder content (360,420 and 450 kg/m3), the proportion of Fly ash and GGBS (70-30, 60-40 and 50-50) for three different grades of Geopolymer concrete (GPC) GPC 20, GPC 40 and GPC 60. The percentage of crimped steel fibres was varied as 0.1%, 0.2%, 0.3%, 0.4% and 0.5%. Generally, the inclusion of steel fibres increases the flexural and split tensile strength of Geopolymer concrete. The optimum dosage of steel fibres was found to be 0.4% (by volume fraction).

Key Words
crimped steel fiber; fly ash; GGBFS

Address
Kallempudi Muralia and T. Meena: School of Civil Engineering, Vellore Institute of Technology, Vellore, Tamilnadu, India

Abstract
To evaluate the influence of slag on the alkalinity of pore solution and microstructure of concrete, this paper performs a leaching experiment on hardened cement-slag pastes (HCSP) slice specimens with different slag content in purified water. The pH value of pore solution, average porosity, morphology, phase composition and Ca/Si of HCSP specimens in the leaching process are measured by solid-liquid extraction, saturated-dried weighing, scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) and X-ray diffraction (XRD). Results shows that the addition of slag can mitigate an increase in porosity and a decrease in Ca/Si of HCSP in the leaching process. Besides, an appropriate slag content can improve the microstructure so as to obtain the optimum leaching resistance of HCSP, which can guarantee the suitable alkalinity of pore solution to prevent a premature corrosion of reinforced bar. The optimum slag content is 40% in HCSP with a water-binder ratio of 0.45, and an excessive slag causes a significant decrease in the alkalinity of pore solution, resulting in a loss of protection on reinforced bar in HCSP.

Key Words
alkalinity of pore solution; calcium leaching; hardened cement-slag paste (HCSP); microstructure, SEM-EDS; XRD

Address
Ya-Ru Hu, Xiao-Bao Zuo, Xiang-Nan Li and Dong-Qi Jiang: Department of Civil Engineering, Nanjing University of Science and Technology, No.200 Xiao Lingwei Street, Xuan Wu District, Nanjing, Jiangsu, China

Abstract
More underground structures are increasingly being constructed such as box culverts for electric power transmission, and the life extension of these structures is very important. It is well known that the steel embedded in concrete is usually invulnerable to corrosion because the high alkalinity of the pore solution in concrete generates a thin protective oxide layer on the surface of the steel. Recent observations in the field and experimental evidence have shown that even steel in concrete can be corroded through the carbonation reaction of cover concrete. Carbonation-induced corrosion in concrete may often occur in a high carbon dioxide environment. In this study, the risk of carbonation of underground box culverts in Korea was evaluated by measuring the car¬bonation rate and concrete cover depth in the field. Then, the carbonation-free service life for the cover depth of the steel was calcu¬lated with in situ information and Monte Carlo simulation. Additionally, an accelerated carbonation test for a cracked beam specimen was performed, and the effect of a crack on the service life of a box culvert was numerically investigated with Monte Carlo simulation based on experimental results.

Key Words
box culvert; carbonation; cover depth; durability; Monte Carlo simulation; service life

Address
Sang-Kyun Woo: Transmission Laboratory, KEPCO Research Institute, 105 Munji-Ro, Yuseong-Gu, Daejeon, 34056, Republic of Korea
In-Yeop Chu: Transmission Laboratory, KEPCO Research Institute, 105 Munji-Ro, Yuseong-Gu, Daejeon, 34056, Republic of Korea
Yun Lee: Department of Civil Engineering, Daejeon University, 62, Daehak-ro, Dong-gu, Daejeon, 34520, Republic of Korea
Byung-Jae Lee: Department of Civil Engineering, Daejeon University, 62, Daehak-ro, Dong-gu, Daejeon, 34520, Republic of Korea


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