Techno Press
Tp_Editing System.E (TES.E)
Login Search
You logged in as

acc
 
CONTENTS
Volume 17, Number 5, May 2024
 

Abstract
The problem of carbonation-induced corrosion has become a concern in recent times, especially in the 21st century, due to the increase in global temperatures and carbon dioxide (CO2) concentration in the atmosphere possessing a significant threat to the durability of reinforced concrete (RC) structures worldwide, especially in inland tropical regions where carbonation is the most significant concrete degradation mechanism. Therefore, a study was conducted to predict the impact of global warming on the carbonation of RC structures in Lusaka, Zambia, and Tokyo, Japan. The Impact was estimated based on a carbonation meta-model that applies the analytic solution of Fick's 1st law using literature-based concrete mix design data and forecasted local temperature and CO2 concentration data over a 100-year period with relative humidity assumed constant. The results showed that CO2 diffusion increased between 17-31%, effecting a 40-45% rise in carbonation coefficient and a significant reduction in corrosion initiation time of 50-52% in the two cities. Moreover, for the same water-cement ratio, Lusaka showed almost twice higher carbonation coefficient values and one third shorter corrosion initiation time compared to Tokyo, mainly due to its higher temperature and low relative humidity. Additionally, the carbonation propagation depth at the end of 100 years was between 12-22 mm in Tokyo and 18-40 mm in Lusaka. These findings indicate that RC structures in these cities are at risk of rapid deterioration, especially in Lusaka, where they are more vulnerable.

Key Words
carbonation coefficient; corrosion initiation time; global warming; Japan; reinforced concrete structures; Zambia

Address
Department of Civil and Environmental Engineering, Kanazawa Institute of Technology, Nonoichi City 921-8501, Japan.


Abstract
During any construction involving mass concrete, it is crucial to control cracking during the placement and curing process. This study develops an intelligent cooling control system that regulates water temperature and flow based on concrete hydration heat, effectively preventing cracking in bridge construction. The system consists of hardware, a neural network-based control algorithm, and an information management system. An optimal cooling control strategy is proposed to dynamically regulate water flow and temperature, preventing cracking by utilizing real-time temperature data, target control curves, neural network algorithms, and cloud-based computing. The intelligent cooling control system has been successfully implemented in controlling cracking risks during bridge construction. It not only mitigates the risk but also provides a convenient management strategy for bridge construction projects. The optimal cooling control strategy ensures high accuracy and stability under unsupervised learning conditions. This intelligent cooling control system can be applied to similar constructions such as bridge, dam, and building that involve the use of mass concrete.

Key Words
bridge construction; cracking control; intelligent cooling system; machine learning; mass concrete

Address
(1) Ruinan An, Peng Lin, Daoxiang Chen, Jianshu Ouyang
Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, China;
(2) Peng Lin, Zichang Li:
Sichuan Energy Internet Research Institute, Tsinghua University, Chengdu 610213, China;
(3) Zheng Zhang:
China Highway Engineering Consulting Corporation, Beijing 100089, China;
(4) Jianshu Ouyang:
China Three Gorges Corporation, Beijing 100038, China;
(5) Yuanguang Liu:
Snohydro Bureau 11 Co. LTD., Sanmenxia 472001, China;
(6) Ruinan An:
Rocket Force Academy, Beijing 100011, China.

Abstract
The steel-concrete composite system has been playing a vital role in the construction sector for the past two decades. By using steel and concrete together, we achieve strong load resistance with minimal deflection and bending stress. The study focuses on the numerical and analytical behaviour of concrete encased steel castellated beams and compared them with previous experiments. The study used five composite beams, including one control reinforced concrete beam (CC), one fully concrete encased steel beam (FCES), and three fully concrete encased castellated beams. The major variable is the opening configuration of the castellated beam, such as openings along the longitudinal axis, above the longitudinal axis, and below the longitudinal axis. The 150 mm × 250 mm cross section and 2000 mm in length of beams were used. Using the finite element software ANSYS, we conduct nonlinear finite element analysis for the entire beam and compare it with test data. The numerical load carrying capacity of concrete encased steel castellated beam with a hexagonal opening above the longitudinal axis (FCESCB H2) is 160 kN is closer to the experimental observation. Von Mises strain of FCESB is 0.004232, which is lower than CB and composite castellated beam. The ductility factor and energy absorption capacity of FCESB are 5.090 and 1688.47 kNm. It was observed that the configuration of the opening will influence the strength of the composite beam. Plastic moment methods were employed to estimate the ultimate load carrying capacity of the beam. In the analytical study the beams were assumed as perfectly plastic. The ultimate analytical load carrying capacity of FCESCB H2 is 21.87% higher than FCESB. It found that performing FCESCB H2 is superior to the entire specimen.

Key Words
castellated beam; encased beam; FEM; flexural behavior; plastic moment

Address
(1) G. Velrajkumar:
Department of Civil Engineering, Easwari Engineering College, Chennai, Tamilnadu, 600 089, India;
(2) M.P. Muthuraj:
Department of Civil Engineering, Coimbatore Institute of Technology, Coimbatore, Tamilnadu, 641 014, India.

Abstract
In order to improve the mixing effect of slurry-foam during the preparation of foam concrete, this study takes an SK static mixer as the mixing device, establishes a three-dimensional physical model and a theoretical calculation model, and numerically simulates the effects of different parameters such as foam inlet angle and pipe inner diameter on the mixing of cement slurry and foam under the given boundary conditions, so as to optimize the structure of this mixing device. The results show that when the pipe diameter of the mixer is larger than 60 mm, the phenomenon of backflow occurs in the pipe, which affects the mixing effect. The smaller the pipe diameter, the shorter the distance required to stabilize the cross-sectional average density and density uniformity index. When the foam inlet angle is different, the average density and density uniformity index of the radial cross-section have the same rule of change along the length of the pipeline, and all of them tend to stabilize gradually. At Y = 0.5 m, the average density basically stabilizes at 964 kg/m3 and remains stable until the outlet. At Y = 0.6 m, the density uniformity index basically stabilizes above 0.995 and remains stable until the outlet. Except for the foam inlet position (Y = 0.04 m), the foam inlet angle has little effect on the cross-sectional average density and density uniformity index. Under the boundary conditions given in this study, a pipe diameter of 40 mm, a foam inlet angle of 90°, and a pipe length of 700 mm are the optimal geometries for the preparation of homogeneous foam concrete with a density of 964 kg/m3 in this static mixer.

Key Words
density uniformity index; foam concrete; numerical simulation; SK mixer

Address
Department of Building Engineering, Zibo Vocational Institute, No. 506, Liantong Road, Zhoucun District, Zibo City, Shandong Province, P.R. China.


Abstract
Ultra-high-performance fiber-reinforced concrete (UHPFRC) is a form of cement-based material that has a compressive strength above 150 MPa, excellent ductility, and superior durability. This composite material demonstrates innovation and has the potential to serve as a viable substitute for concrete constructions that are subjected to harsh environmental conditions. Over many decades, extensive research and progressive efforts have introduced several commercial UHPFRC compositions globally. These compositions have been specifically designed to cater to an increasing variety of applications and meet the rising need for building materials of superior quality. However, the effective manufacturing of UHPFRC relies on the composition of its materials, especially the inclusion of fiber content and the proportions in the mixture, resulting in a more compact and comparatively uniform packing of particles. UHPFRC has notable benefits in comparison to conventional concrete, yet its use is constrained by the dearth of design codes and the prohibitive expenses associated with its implementation. The study demonstrates that UHPFRC presents a viable, long-lasting option for improving sustainable construction. This is attributed to its outstanding strength properties and superior durability in resisting water and chloride ion permeability, freeze-thaw cycles, and carbonation. The analysis found that a rheology-based mixture design technique may be employed in the production of UHPFRC to provide enough flowability. The study also revealed that the use of deformed steel fibers has shown enhanced mechanical qualities in comparison to straight steel fibers. However, obstacles such as higher initial costs, the requirement for highly specialized personnel, and the absence of comprehensive literature on global UHPFRC standards that establish minimum strength criteria and testing requirements can hinder the widespread implication of UHPFRC. Finally, this review attempts to deepen our foundational conception of UHPFRC, encourages additional study and applications, and recommends an in-depth investigation of the mechanical and durability properties of UHPFRC to maximize its practicality.

Key Words
long-term integrity; manufacturing; mechanical properties; sustainability; ultra-high-performance fiberreinforced concrete

Address
(1) Dongmei Chen, Lu Ma:
Wuhan Railway Vocational College of Technology, School of Railway Engineering, Wuhan, Hubei Province, China, 430205;
(2) Yueshun Chen:
Hubei University of Technology, School of Civil Engineering Architecture & the Environment, Wuhan, Hubei Province, China, 430068;
(3) Md. Habibur Rahman Sobuz, Md. Kawsarul Islam Kabbo:
Department of Building Engineering and Construction Management, Khulna University of Engineering & Technology, Khulna, Bangladesh;
(4) Md. Munir Hayet Khan:
Faculty of Engineering & Quantity Surveying, INTI International University (INTI-IU), Persiaran Perdana BBN, Putra Nilai, Nilai 71800, Negeri Sembilan, Malaysia.

Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2024 Techno-Press ALL RIGHTS RESERVED.
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Email: admin@techno-press.com