Mesoscopic numerical analysis of dynamic tensile fracture of recycled concrete

2020 ◽  
Vol 37 (6) ◽  
pp. 1899-1922 ◽  
Author(s):  
Liping Ying ◽  
Yijiang Peng ◽  
Mahmoud M.A. Kamel
Keyword(s):  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Failure Pattern ◽  
Recycled Aggregate ◽  
Tensile Fracture ◽  
Aggregate Model ◽  
Element Mesh ◽  
Content Type ◽  
Random Aggregate ◽  
Force Element

Purpose Based on the random aggregate model of recycled aggregate concrete (RAC), this paper aims to focus on the effect of loading rate on the failure pattern and the macroscopic mechanical properties. Design/methodology/approach RAC is regarded as a five-phase inhomogeneous composite material at the mesoscopic level. The number and position of the aggregates are modeled by the Walraven formula and Monte–Carlo stochastic method, respectively. The RAC specimen is divided by the finite-element mesh to establish the dynamic base force element model. In this model, the element mechanical parameters of each material phase satisfy Weibull distribution. To simulate and analyze the dynamic mechanical behavior of RAC under axial tension, flexural tension and shear tension, the dynamic tensile modes of the double-notched specimens, the simply supported beam and the L specimens are modeled, respectively. In addition, the different concrete samples are numerically investigated under different loading rates. Findings The failure strength and failure pattern of RAC have strong rate-dependent characteristics because of the inhomogeneity and the inertial effect of the material. Originality/value The dynamic base force element method has been successfully applied to the study of recycled concrete.

scholarly journals Numerical Simulation of Recycled Concrete Using Convex Aggregate Model and Base Force Element Method

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Yijiang Peng ◽  
Hao Chu ◽  
Jiwei Pu
Keyword(s):  
Damage Model ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Aggregate Model ◽  
Energy Principle ◽  
Force Element ◽  
Damage Processes ◽  
Random Convex ◽  
Element Method

By using the Base Force Element Method (BFEM) on potential energy principle, a new numerical concrete model, random convex aggregate model, is presented in this paper to simulate the experiment under uniaxial compression for recycled aggregate concrete (RAC) which can also be referred to as recycled concrete. This model is considered as a heterogeneous composite which is composed of five mediums, including natural coarse aggregate, old mortar, new mortar, new interfacial transition zone (ITZ), and old ITZ. In order to simulate the damage processes of RAC, a curve damage model was adopted as the damage constitutive model and the strength theory of maximum tensile strain was used as the failure criterion in the BFEM on mesomechanics. The numerical results obtained in this paper which contained the uniaxial compressive strengths, size effects on strength, and damage processes of RAC are in agreement with experimental observations. The research works show that the random convex aggregate model and the BFEM with the curve damage model can be used for simulating the relationship between microstructure and mechanical properties of RAC.

scholarly journals Application of Base Force Element Method to Mesomechanics Analysis for Recycled Aggregate Concrete

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Yijiang Peng ◽  
Yinghua Liu ◽  
Jiwei Pu ◽  
Lijuan Zhang
Keyword(s):  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Triangular Element ◽  
Aggregate Model ◽  
Energy Principle ◽  
Aggregate Concrete ◽  
Tension Tests ◽  
Random Aggregate ◽  
Force Element ◽  
Element Method

The base force element method (BFEM) on potential energy principle is used to analyze recycled aggregate concrete (RAC) on mesolevel. The model of BFEM with triangular element is derived. The recycled aggregate concrete is taken as five-phase composites consisting of natural coarse aggregate, new mortar, new interfacial transition zone (ITZ), old mortar, and old ITZ on meso-level. The random aggregate model is used to simulate the mesostructure of recycled aggregate concrete. The mechanics properties of uniaxial compression and tension tests for RAC are simulated using the BFEM, respectively. The simulation results agree with the test results. This research method is a new way for investigating fracture mechanism and numerical simulation of mechanics properties for recycled aggregate concrete.

scholarly journals Discrete Element Simulation Analysis of Biaxial Mechanical Properties of Concrete with Large-Size Recycled Aggregate

2021 ◽  
Vol 13 (13) ◽  
pp. 7498
Author(s):  
Tan Li ◽  
Jianzhuang Xiao
Keyword(s):  
Mechanical Properties ◽  
Stress State ◽  
Strain Curve ◽  
Confining Pressure ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Aggregate Model ◽  
Large Size

Concrete made with large-size recycled aggregates is a new kind of recycled concrete, where the size of the recycled aggregate used is 25–80 mm, which is generally three times that of conventional aggregate. Thus, its composition and mechanical properties are different from that of conventional recycled concrete and can be applied in large-volume structures. In this study, recycled aggregate generated in two stages with randomly distributed gravels and mortar was used to replace the conventional recycled aggregate model, to observe the internal stress state and cracking of the large-size recycled aggregate. This paper also investigated the mechanical properties, such as the compressive strength, crack morphology, and stress–strain curve, of concrete with large-size recycled aggregates under different confining pressures and recycled aggregate incorporation ratios. Through this research, it was found that when compared with conventional concrete, under the confining pressure, the strength of large-size recycled aggregate concrete did not decrease significantly at the same stress state, moreover, the stiffness was increased. Confining pressure has a significant influence on the strength of large-size recycled aggregate cocrete.

Numerical Simulation on Damage and Failure of Recycled Aggregate Concrete with a Lattice Model

2009 ◽  
Vol 417-418 ◽  
pp. 689-692 ◽  
Author(s):  
Jian Zhuang Xiao ◽  
Qiong Liu ◽  
Vivian W.Y. Tam
Keyword(s):  
Lattice Model ◽  
Structural Damage ◽  
Fortran Program ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Aggregate Model ◽  
Mixture Ratio ◽  
Aggregate Concrete ◽  
Damage And Failure ◽  
Random Aggregate

A random aggregate model of recycled aggregate concrete is developed in this paper on the base of a mixture ratio. Combining a lattice model with random aggregate of recycled aggregate concrete, lattice elements in the lattice model of recycled aggregate concrete can be classified into five types: (1) nature aggregate, (2) old hardened mortar, (3) new hardened mortar, (4) old interface transition zone (ITZ), and (5) new ITZ. The fundamental mechanical parameters of the lattice elements are chosen from the authors’ test as well as other references. A FORTRAN program of the lattice model is then written with basic theories of finite element method (FEM) for simulating the meso-structural damage of recycled aggregate concrete under uniaxial compression.

Effects of Recycled Aggregate Replacement Rate on Compression Mechanical Behavior of Concrete Based on Base Force Element Method

2021 ◽  
Vol 894 ◽  
pp. 121-126
Author(s):  
Li Ping Ying ◽  
Yi Jiang Peng
Keyword(s):  
Failure Process ◽  
Strain Curve ◽  
Simple Algorithm ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Concrete Aggregate ◽  
Test Results ◽  
Force Element ◽  
Element Method

A meso-analysis method which is derived from the base force element method (BFEM) was proposed for recycled aggregate concrete (RAC). A simple algorithm was used to generate the convex recycled concrete aggregate (RCA) model. Uniaxial compression numerical simulations were carried out on the numerical specimens with different replacement rates of RCA. The model predictions were in a good agreement with the test results. The proposed method is very promising. It can totally predict the full stress-strain curve of RAC, as well as the failure process and failure mode, including strain softening and strain localization.

scholarly journals Experimental Study on the Mechanical Properties and Compression Size Effect of Recycled Aggregate Concrete

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2323
Author(s):  
Yubing Du ◽  
Zhiqing Zhao ◽  
Qiang Xiao ◽  
Feiting Shi ◽  
Jianming Yang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Size Effect ◽  
Compressive Stress ◽  
Failure Modes ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Aggregate Concrete ◽  
Substitution Ratio ◽  
The Impact

To explore the basic mechanical properties and size effects of recycled aggregate concrete (RAC) with different substitution ratios of coarse recycled concrete aggregates (CRCAs) to replace natural coarse aggregates (NCA), the failure modes and mechanical parameters of RAC under different loading conditions including compression, splitting tensile resistance and direct shear were compared and analyzed. The conclusions drawn are as follows: the failure mechanisms of concrete with different substitution ratios of CRCAs are similar; with the increase in substitution ratio, the peak compressive stress and peak tensile stress of RAC decrease gradually, the splitting limit displacement decreases, and the splitting tensile modulus slightly increases; with the increase in the concrete cube’s side length, the peak compressive stress of RAC declines gradually, but the integrity after compression is gradually improved; and the increase in the substitution ratio of the recycled aggregate reduces the impact of the size effect on the peak compressive stress of RAC. Furthermore, an influence equation of the coupling effect of the substitution ratio and size effect on the peak compressive stress of RAC was quantitatively established. The research results are of great significance for the engineering application of RAC and the strength selection of RAC structure design.

Study on the Basic Mechanical Properties of Recycled Concrete Hollow Block Masonry

2013 ◽  
Vol 438-439 ◽  
pp. 749-755 ◽  
Author(s):  
Tong Hao ◽  
Dong Li
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Shear Behavior ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Test Results ◽  
Aggregate Concrete ◽  
Mortar Strength ◽  
Hollow Block

By the experimental studying on the basic mechanical properties of recycled concrete hollow block masonry, the compressive and shear behavior of recycled aggregate concrete hollow block masonry under different mortar strength were analyzed. Research indicated that the compressive and shear behavior of recycled aggregate concrete hollow block masonry was similar to that of ordinary concrete hollow block masonry. The normal formula was recommended to calculate the compressive strength of the masonry. The shear strength of the masonry was affected by the mortar strength. The shear strength calculation formula of recycled concrete hollow block masonry was proposed according to the formula of masonry design code. The calculating results were in good agreement with the test results.

Recycling of Waste Concrete and Fly Ash for Recycled Aggregate Concrete: Fundamental Characteristics Evaluation

2009 ◽  
Vol 620-622 ◽  
pp. 255-258 ◽  
Author(s):  
Cheol Woo Park
Keyword(s):  
Fly Ash ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Experimental Program ◽  
Concrete Aggregate ◽  
Fine Aggregate ◽  
Recycled Concrete Aggregate ◽  
Aggregate Concrete ◽  
Waste Concrete

As the amount of waste concrete has been increased and recycling technique advances, this study investigates the applicability of recycled concrete aggregate for concrete structures. In addition fly ash, the industrial by-product, was considered in the concrete mix. Experimental program performed compressive strength and chloride penetration resistance tests with various replacement levels of fine recycled concrete aggregate and fly ash. In most case, the design strength, 40MPa, was obtained. It was known that the replacement of the fine aggregate with fine RCA may have greater influence on the strength development rather than the addition of fly ash. It is recommended that when complete coarse aggregate is replaced with RCA the fine RCA replacement should be less than 60%. The recycled aggregate concrete can achieve sufficient resistance to the chloride ion penetration and the resistance can be more effectively controlled by adding fly ash. It I finally conclude that the recycled concrete aggregate can be successfully used in the construction field and the recycling rate of waste concrete and flay ash should be increased without causing significant engineering problems.

scholarly journals Shear Behavior of Steel-Fiber-Reinforced Recycled Aggregate Concrete Deep Beams

Buildings ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 423
Author(s):  
Nancy Kachouh ◽  
Tamer El-Maaddawy ◽  
Hilal El-Hassan ◽  
Bilal El-Ariss
Keyword(s):  
Shear Behavior ◽  
Shear Capacity ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Steel Fibers ◽  
Recycled Aggregate ◽  
Shear Reinforcement ◽  
Deep Beams ◽  
Control Beam ◽  
Shear Response

Results of an experimental investigation aimed at studying the effect of steel fibers on the shear behavior of concrete deep beams made with a 100% recycled concrete aggregate (RCA) are presented in this paper. The study comprised testing of seven concrete deep beam specimens with a shear span-to-depth ratio (a/h) of 1.6. Two beams were made of natural aggregates (NAs) without steel fibers, two beams were made of a 100% RCA without steel fibers, and three beams were made of RCA-based concrete with steel fibers at volume fractions (vf) of 1, 2, and 3%. Two of the beams without steel fibers included a minimum shear reinforcement. Test results showed that the beam with a 100% RCA without steel fibers exhibited a lower post-cracking stiffness, reduced shear cracking load, and lower shear capacity than those of the NA-based control beam. The detrimental effect of the RCA on the shear response was less pronounced in the presence of the minimum shear reinforcement. The addition of steel fibers significantly improved the shear response of the RCA-based beams. The post-cracking stiffness of the RCA-based concrete beams with steel fibers coincided with that of a similar beam without fibers containing the minimum shear reinforcement. The use of steel fibers in RCA beams at vf of 1 and 2% restored 80 and 90% of the shear capacity, respectively, of a similar beam with the minimum shear reinforcement. The response of the RCA specimen with vf of 3% outperformed that of the NA-based control beam with the minimum shear reinforcement, indicating that steel fibers can be used in RCA deep beams as a substitution to the minimum shear reinforcement. The shear capacities obtained from the tests were compared with predictions of published analytical models.

scholarly journals Studies on Hemp and Recycled Aggregate Concrete

2020 ◽  
Vol 14 (1) ◽  
Author(s):  
Samer Ghosn ◽  
Nour Cherkawi ◽  
Bilal Hamad
Keyword(s):  
Mechanical Properties ◽  
Fiber Length ◽  
Plain Concrete ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Silane Treatment ◽  
Hemp Fiber ◽  
Fiber Treatment

Abstract This paper reports on the first phase of a multi-phase research program conducted at the American University of Beirut (AUB) on “Hemp and Recycled Aggregates Concrete” (HRAC). HRAC is a new sustainable concrete material where hemp fibers are incorporated in the mix, the coarse aggregate content is reduced by 20% of the concrete volume, and 50% of the natural coarse aggregates (NCA) are replaced by recycled concrete aggregates (RCA), thus saving on natural resources and addressing the problem of waste material disposal. The effect of the new material on concrete consistency and hardened mechanical properties was studied. Also, few durability tests were conducted. Variables included percentage replacement of NCA by RCA (0 or 50%), maximum size aggregate (10 or 20 mm), hemp fiber length (20 or 30 mm), and hemp fiber treatment (alkali or silane or acetyl). Fiber characterization tests were conducted including morphology, crystallinity, and thermal analysis. The tests indicated that alkali and acetyl fiber treatments were better than the silane treatment in removing impurities on the fiber surface. Also, alkali and acetyl treatments have increased the crystallinity of the fibers while silane treatment decreased it. Results of mechanical properties tests showed that while HRAC has considerable lower compressive strength and modulus of elasticity than plain concrete, the flexural strength and splitting tensile strength are not significantly affected. The flexural stress–strain behavior of HRAC is ductile as compared to the brittle behavior of the plain concrete beams indicating positive impact on toughness and energy dissipation. The durability tests indicated that whereas HRAC mixes have higher absorption than plain concrete, they have better thermal properties and their resistance to freeze–thaw cycles is comparable to plain concrete. All test results were not significantly affected by fiber length or fiber treatment.

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