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20 pages, 8592 KiB

Open AccessArticle

Combined Effects of Steel and Glass Fibres on the Fracture Performance of Recycled Rubber Concrete

by Xiaohui Li, Zezhou Pan, Hao Zhen, Wenhua Luo, Zhuangwei Chen, Hongming Li, Zhichao Wu, Feng Liu and Lijuan Li

Buildings 2024, 14(4), 864; https://doi.org/10.3390/buildings14040864 - 22 Mar 2024

Cited by 1 | Viewed by 1454

Abstract

As an environmentally friendly construction material, recycled rubber concrete (RRC) is commonly used as a road material owing to its excellent flexural strength and crack resistance. Previous studies have shown that the addition of fibres is an effective method for improving the crack resistance of concrete. The purpose of this study is to investigate the fracture performance of RRC reinforced with steel fibres (SFs) and glass fibres (GFs). A total of 28 RRC mixtures were prepared. The results of the fracture test showed that the addition of SFs and GFs significantly enhanced the RRC fracture performance. The maximum increases or decreases in flexural strength, brittleness coefficient, fracture energy, initial fracture toughness, and unstable fracture toughness were 64.9, −34.6, 775.6, 92.0, and 118.4%, respectively. The ideal GF content is usually in the range of 0.4–0.6% and decreases with increasing SF content. In addition, scanning electron microscope (SEM) tests were conducted to explore the mechanism of the effect of hybrid fibres on RRC at a microscopic level. The results show that SFs were always pulled out, while GFs were pulled apart at the initial defects. At the same time, excessive GFs caused more initial defects. These results are expected to provide theoretical direction and experimental support for the practical application of hybrid fibre-reinforced recycled rubber concrete (HFRRRC). Full article

(This article belongs to the Special Issue New Concrete Materials: Performance Analysis and Research)

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20 pages, 10567 KiB

Open AccessArticle

Mesoscopic Analysis of Rounded and Hybrid Aggregates in Recycled Rubber Concrete

by Mahmoud M. A. Kamel, Yu Fu, Xiaowei Feng and Yijiang Peng

Materials 2023, 16(19), 6600; https://doi.org/10.3390/ma16196600 - 8 Oct 2023

Cited by 3 | Viewed by 1702

Abstract

Recycled rubber concrete (RRC), a sustainable building material, provides a solution to the environmental issues posed by rubber waste. This research introduces a sophisticated hybrid random aggregate model for RRC. The model is established by combining convex polygon aggregates and rounded rubber co-casting schemes with supplemental tools developed in MATLAB and Fortran for processing. Numerical analyses, based on the base force element method (BFEM) of the complementary energy principle, are performed on RRC’s uniaxial tensile and compressive behaviors using the proposed aggregate models. This study identified the interfacial transition zone (ITZ) around the rubber as RRC’s weakest area. Here, cracks originate and progress to the aggregate, leading to widespread cracking. Primary cracks form perpendicular to the load under tension, whereas bifurcated cracks result from compression, echoing conventional concrete’s failure mechanisms. Additionally, the hybrid aggregate model outperformed the rounded aggregate model, exhibiting closer peak strengths and more accurate aggregate shapes. The method’s validity is supported by experimental findings, resulting In detailed stress–strain curves and damage contour diagrams. Full article

(This article belongs to the Special Issue Mechanical Behavior of Concrete Materials and Structures: Experimental Evidence and Analytical Models (Volume II))

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25 pages, 15652 KiB

Open AccessArticle

A Study of the Compressive Behavior of Recycled Rubber Concrete Reinforced with Hybrid Fibers

by Xiaohui Li, Lijuan Li, Yingming Zheng, Yanlong Li, Zijiang Chen, Jie Xiao, Min Yuan, Jian Zhang, Zezhou Pan and Zhe Xiong

Materials 2023, 16(13), 4731; https://doi.org/10.3390/ma16134731 - 30 Jun 2023

Cited by 5 | Viewed by 1943

Abstract

With the development of the automotive industry, a large amount of waste rubber is produced every year. The application and development of recycled rubber concrete (RRC) can effectively reduce ‘black pollution’ caused by waste rubber. However, the addition of recycled rubber particles can lead to a decrease in the compressive behavior of concrete. Previous research has demonstrated that by preventing crack growth, fiber addition can increase the strength and ductility of concrete. In this work, a total of 28 RRC mixes are designed, and the compressive behavior of RRC reinforced by steel fibers (SFs) and glass fibers (GFs) is investigated. The workability of fresh RRC can be negatively impacted by an increase in both fiber contents, with the GF content having a more notable effect. With the addition of fibers, the maximum increase rates for the compressive strength, elastic modulus, strain at peak stress, and compressive toughness were 27%, 8%, 45%, and 152%, respectively. A constitutive model is concurrently put forward to forecast the stress–strain curves of RRC with various fiber contents. These findings indicate that the maximum improvement in compressive behavior is achieved when the GF content was 0.4% and the SF content was 1.2%. The proposed constitutive model can be used to predict the stress–strain curve of hybrid fiber-reinforced recycled rubber concrete (HFRRRC). Full article

(This article belongs to the Special Issue Durability and Mechanical Properties of Sustainable, High-Performance and Multi-Functional Concrete Materials)

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