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Analysis and optimization of mechanical properties of recycled concrete based on aggregate characteristics

  • Jiangwei Bian , Wenbing Zhang EMAIL logo , Zhenzhong Shen EMAIL logo , Song Li and Zhanglan Chen
Published/Copyright: September 23, 2021
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Science and Engineering of Composite Materials
From the journal Science and Engineering of Composite Materials Volume 28 Issue 1

Abstract

The most significant difference between recycled and natural concretes lies in aggregates. The performance of recycled coarse aggregates directly affects the characteristics of recycled concrete. Therefore, an in-depth study of aggregate characteristics is of great significance for improving the quality of recycled concrete. Based on the coarse aggregate content, maximum aggregate size, and aggregate shape, this study uses experiments, theoretical analysis, and numerical simulation to reveal the impact of aggregate characteristics on the mechanical properties of recycled concrete. In this study, we selected the coarse aggregate content, maximum aggregate size, and the aggregate shape as design variables to establish the regression equations of the peak stress and elastic modulus of recycled concrete using the response surface methodology. The results showed that the peak stress and elastic modulus of recycled concrete reach the best when the coarse aggregate content is 45%, the maximum coarse aggregate size is 16 mm, and the regular round coarse aggregates occupy 75%. Such results provide a theoretical basis for the resource utilization and engineering design of recycled aggregates.

Keywords: recycled concrete; aggregate characteristics; response surface analysis; numerical simulation; mechanical properties

1 Introduction

Resource depletion is one of the major challenges the world is facing today. The construction industry, one of the largest industries in the world, consumes a lot of resources every year [1]. According to statistics, construction waste in European Union countries exceeds 800 million tons per year [2], accounting for 25–30% of all waste, and that in the United States has been on the rise in the past 20 years [3]. As early as 2017, China produced nearly 1.6 billion tons of construction waste. By 2020, China’s construction waste exceeded 3 billion tons. Construction waste causes long-term damage to the ecological environment, as well as air pollution and soil pollution. The key solution to such a problem is the resource utilization. Replacing natural aggregates with the recycled aggregates can reduce the impact on the environment and save resources. However, the current utilization rate of construction waste in China is less than 10%. To better understand the characteristics of recycled aggregates and increase their utilization rate, it is important to study the impact of recycled aggregate characteristics on the performance of recycled concrete.

In recent years, with the continuous in-depth study of recycled concrete, recycled coarse aggregates show a broad space for development. Related technologies have been improved, and valuable experience has been accumulated in long-term practice. Recycled concrete is a multiphase artificial composite consisting of recycled coarse aggregates and cement mortar. Recycled coarse aggregate is the framework material of recycled concrete. Aggregate type, content, maximum aggregate size, and shape have a decisive influence on the macroscopic strength and mechanical properties of recycled concrete. Regarding the impact of aggregate particles on the mechanical properties of concrete, many scholars have conducted a lot of research and achieved some fruitful results. Meddah et al. [4] held that aggregates generally account for about 75% of concrete in volume, including nearly 45% coarse aggregates. Cetin and Carrasquillo [5] obtained through experiments that 36–40% of coarse aggregates can ensure the best performance of concrete, and once the coarse aggregate content exceeds 40%, the compressive strength of concrete will be reduced. Li and Gao [6] found through experiments that when the water–cement ratio and coarse aggregate content are constant, the compressive strength of concrete will decrease with the increase of the coarse aggregate size. Woode et al. [7] also drew the same conclusion. Elices and Rocco [8,9] explored the impact of aggregate size and shape on the tensile strength and elastic modulus of concrete. Zhou [10] studied the influence of different types of coarse aggregates on the mechanical properties of recycled concrete, and the results showed that the relative strength and elastic modulus of recycled concrete containing rubble aggregates are lower than those of recycled concrete containing gravel aggregates.

The response surface methodology (RSM), as a method for optimization of processes and experimental conditions, is more suitable to solve the problem of nonlinear data processing. Given the advantages of the RSM and the advances in computer performance, the combination of the RSM and finite element has been highly recognized and widely used in the engineering sector, solving many practical engineering problems. Liang et al. [11] used the RSM and genetic algorithm to optimize the material parameters of the solder joints, reduce the maximum torsional stress in the solder joints, and improve the torsion resistance of the micro-scale solder joints of the chip-size package. Fu and Hu [12] used the RSM to establish a multiple regression model between process parameters and optimization goals, and verified the effectiveness of the prediction model through analysis of variance. Cao et al. [13] studied the effect of rainwater runoff head height, horizontal runoff velocity, and sample porosity on the blocking of pervious concrete using the RSM. Zhang and Zhai [14] optimized the alkali-activated cement–mortar ratio based on the RSM. Liu et al. [15] optimized the mix ratio of slag-based solid waste cementing materials using the RSM.

As mentioned above, aggregate particles affect the heterogeneity of recycled concrete materials, but there are fewer studies about the impact of recycled aggregate characteristics on recycled concrete. To this end, this study establishes a two-dimensional mesomechanical simulation method based on the aggregate characteristics, and designs a uniaxial compression model of recycled concrete based on the different coarse aggregate content, maximum sizes, and proportions of regular round coarse aggregates (i.e., “the coarse aggregate shape”). Besides, this study also explores the influence of aggregate characteristics on the mechanical properties of recycled concrete using the RSM.

2 Materials and methods

2.1 Characteristics of coarse aggregates in recycled concrete

Aggregates play an important role in recycled concrete and characterize the heterogeneity of recycled concrete. Recycled coarse aggregate is composed of raw coarse aggregate, old mortar, and the interfacial transition zone (ITZ) between the raw coarse aggregate and old mortar. Due to the rough surface with many edges and corners and irregularities of old cement mortar, the apparent density, porosity, water absorption, and crush index of recycled aggregates are significantly different from those of natural aggregates. Therefore, it is necessary to reinforce recycled aggregates to improve the performance of recycled aggregates and recycled aggregate concrete. Recycled aggregate reinforcing methods mainly include removal and reinforcement of old mortar [16]. Old mortar is generally removed with the physical grinding and chemical methods. The mechanical treatment method, especially the wear treatment method, has been proved to be the most environment-friendly method [17]. Pandurangan et al. [18] found that recycled coarse aggregates with a round shape can be obtained through this mechanical treatment method. In this study, we removed the excess mortar using the wear treatment method, and finally obtained recycled coarse aggregates with a round shape. However, only the edges and corners of the excess mortar were removed, so the mesoscopic composition on the surface of the recycled coarse aggregates after treatment remains unchanged.

2.2 Mesoscopic model of recycled concrete

In recent years, mesoscale numerical simulation has developed fast and been widely used by scholars as a highly effective method for studying the mechanical properties of concrete materials. On the mesoscale, recycled concrete is generally seen as a five-phase composite material consisting of raw aggregate, old mortar, new mortar, old interface, and new interface. Otsuki et al. [19] found through experiments that the new interface plays a leading role in the strength of recycled concrete, and it is weaker than the old interface. Thus, recycled concrete is regarded as a three-phase composite material composed of the recycled coarse aggregate, new mortar, and ITZ between the new mortar and recycled coarse aggregate. In the numerical simulation, the simply crushed recycled coarse aggregate without wear treatment was simplified into irregular polygonal particles, and the recycled coarse aggregate with wear treatment was simplified into regular round particles, as shown in Figure 1. With reference to the literature [20], we conducted an uniaxial compression test in the laboratory to obtain the experimental data, and then carried out inverse analysis based on these experimental data. The uniaxial compression test uses a 100 mm × 100 mm × 100 mm recycled concrete cube test block, and the aggregate is a standard secondary gradation. The mix ratio is shown in Table 1. The test adopts the universal testing machine displacement control method for loading. In the numerical simulation of uniaxial compression, we treated the constitutive model of each meso-component of recycled concrete as a linear elastic model, and used the maximum tensile stress criterion as the failure criterion. The numerical simulation test software adopts ANSYS, and the model size is consistent with the indoor test. As it is a two-dimensional model, the model size is 100 mm × 100 mm, and the unit type is PLANE82. Figure 2 is a comparison between the results of numerical simulation inversion and indoor compression test. The mesoscopic parameters of each component of recycled concrete are shown in Table 2.

Figure 1 Finite element model of the recycled concrete.
Figure 1

Finite element model of the recycled concrete.

Table 1

Mix proportions used in the uniaxial compression test

Water–cement ratio Unit volume consumption (kg m−3)
Cement Sand Recycled coarse aggregate Water
0.43 430 492 1,149 185
Figure 2 Comparison of the numerical simulation inversion results and the indoor test results.
Figure 2

Comparison of the numerical simulation inversion results and the indoor test results.

Table 2

Mesoscopic component parameters

Mesoscopic component Elastic modulus (MPa) Poisson’s ratio Tensile strength (MPa)
Recycled coarse aggregate 16,230 0.16 2.50
Cement mortar 12,880 0.22 1.90
Interface 9,500 0.20 1.73

3 Single factor analysis influencing the mechanical properties of recycled concrete

3.1 The impact of coarse aggregate content on the mechanical properties of recycled concrete

Based on the above finite element analysis model of recycled concrete, we constructed three finite element models with the coarse aggregate content of 30, 40, and 50% and other constant parameters (maximum aggregate size: 16 mm, 50% regular round aggregates + 50% irregular polygonal aggregates) to analyze the mechanical properties of recycled concrete, and obtained the peak stress and elastic modulus in the uniaxial compression test under different coarse aggregate contents (Table 3).

Table 3

Peak stress and elastic modulus of recycled concrete under uniaxial compression test with different coarse aggregate contents

Coarse aggregate content (%)
30 40 50
Experiment no. 1
  Peak stress ( MPa ) 30.07 31.69 31.29
  Elastic modulus ( MPa ) 14321.40 15091.61 14899.72
Experiment no. 2
  Peak stress ( MPa ) 31.16 32.92 30.52
  Elastic modulus ( MPa ) 14838.85 15676.66 14533.19
Experiment no. 3
  Peak stress ( MPa ) 30.43 31.63 30.74
  Elastic modulus ( MPa ) 14488.45 15061.43 14637.86

It can be seen in Table 3 that the peak stress and elastic modulus of recycled concrete vary with the coarse aggregate content. With the increase of coarse aggregate content, the peak stress and elastic modulus of recycled concrete first increase and then decrease. This result is similar to that in the literature [21], indicating the accuracy of simulation in this study. The reason for this phenomenon is that too much or too little aggregate content is not enough to make the whole test block in a relatively dense state, so that its mechanical properties are reduced. When the coarse aggregate content is 40%, the maximum peak stress and elastic modulus are 31.69 and 15091.61 MPa, respectively.

3.2 The impact of maximum aggregate size on the mechanical properties of recycled concrete

Three finite element models were constructed with the maximum aggregate size of 16, 20, and 31.5 mm and other constant parameters (coarse aggregate content: 40%, 50% regular round aggregates + 50% irregular polygonal aggregates) to analyze the mechanical properties of recycled concrete, and the peak stress and elastic modulus in the uniaxial compression test under different maximum aggregate sizes were obtained (Table 4).

Table 4

Peak stress and elastic modulus of recycled concrete under uniaxial compression test with different maximum aggregate sizes

Maximum coarse aggregate size (mm)
16 20 31.5
Experiment no. 1
  Peak stress (MPa) 31.69 29.94 28.51
  Elastic modulus (MPa) 15091.61 14258.18 13576.76
Experiment no. 2
  Peak stress (MPa) 32.92 29.92 29.41
  Elastic modulus (MPa) 15676.66 14246.30 14005.19
Experiment no. 3
  Peak stress (MPa) 31.63 29.74 29.22
  Elastic modulus (MPa) 15061.43 14060.73 13912.21

It can be seen in Table 4 that the peak stress and elastic modulus of recycled concrete vary with the maximum aggregate size. As the maximum aggregate size increases, the peak stress and elastic modulus of recycled concrete gradually decrease. This result is the same as that in the literature [6,22], indicating the accuracy of simulation in this study. When the maximum aggregate size is 16 mm, the peak stress and elastic modulus reach the highest, that is, 31.69 and 15091.61 MPa, respectively. When the maximum aggregate size is 31.5 mm, the peak stress and elastic modulus reach the lowest, that is, 28.51 and 13576.76 MPa, respectively.

3.3 The impact of aggregate shape on the mechanical properties of recycled concrete

Three finite element models were constructed: 25% regular round aggregates + 75% irregular polygonal aggregates; 50% regular round aggregates + 50% irregular polygonal aggregates; and 75% regular round aggregates + 25% irregular polygonal aggregates with other constant parameters (coarse aggregate content: 40%, and maximum aggregate size: 16 mm) to analyze the mechanical properties of recycled concrete, and the peak stress and elastic modulus in the uniaxial compression test under different aggregate shapes were obtained (Table 5).

Table 5

Peak stress and elastic modulus of recycled concrete under uniaxial compression test with different proportion of aggregate shape

Coarse aggregate shape
25 + 75% 50 + 50% 75 + 25%
Experiment no. 1
  Peak stress (MPa) 30.88 31.69 33.68
  Elastic modulus (MPa) 14706.69 15091.61 16039.98
Experiment no. 2
  Peak stress (MPa) 30.29 31.16 32.96
  Elastic modulus (MPa) 14423.76 14833.52 15697.60
Experiment no. 3
  Peak stress (MPa) 29.78 31.63 33.82
  Elastic modulus (MPa) 14181.85 15061.43 16104.81

It can be seen in Table 5 that the peak stress and elastic modulus of recycled concrete vary with the mix ratio of different aggregate shapes. As the proportion of regular round aggregates increases, the peak stress and elastic modulus of recycled concrete also increase. This result is similar to that in the literature [9,23,24], indicating the accuracy of simulation in this study. When 75% of regular round aggregates and 25% of irregular polygonal aggregates are mixed, the peak stress and elastic modulus of recycled concrete reach the maximum 33.68 and 16039.98 MPa, respectively.

4 Optimization and validation of characteristic parameters of recycled concrete aggregates based on the RSM

To improve the mechanical properties of recycled concrete, it is necessary to optimize and analyze the aggregate characteristic parameters and obtain the optimal combination of these parameters. To maximize the peak stress and elastic modulus of recycled concrete under uniaxial compression test, we used the RSM in this study to obtain the optimal combination of aggregate characteristic parameters.

4.1 Simulation test based on the RSM

In this study, we established the relationship between the mechanical properties of recycled concrete and the characteristic parameters of aggregates using the RSM. First, we chose the coarse aggregate content, the maximum aggregate size, and the aggregate shape as parameters, and selected three values for each parameter. The factors are shown in Table 6. Second, we designed aggregates’ characteristic factor levels in line with the RSM BOX-Behnken experimental design scheme [25,26]. The designed combinations are shown in Table 7. There were 17 combinations of different aggregate characteristic parameter levels. Based on this, we built 17 corresponding simulation models and obtained the mechanical properties of recycled concrete (see the last two columns of Table 7).

Table 6

Factor level table

Factor −1 0 1
Coarse aggregate content A (%) 30 40 50
Maximum coarse aggregate size B (mm) 16 20 31.5
Coarse aggregate shape C 25% + 75% 50% + 50% 75% + 25%
Table 7

Response surface combination and analysis results of peak stress and elastic modulus

Number Coarse aggregate content A Maximum coarse aggregate size B Coarse aggregate shape C Peak stress (MPa) Elastic modulus (MPa)
1 0 0 0 29.94 14582.18
2 0 −1 1 33.68 16039.98
3 0 1 1 29.63 14111.60
4 1 1 0 28.22 13438.14
5 0 0 0 29.94 14258.18
6 −1 0 −1 28.25 13451.63
7 1 0 −1 28.29 13470.67
8 0 1 −1 27.46 13075.53
9 0 0 0 29.94 14258.18
10 −1 −1 0 30.07 14321.40
11 −1 1 0 27.76 13216.97
12 0 −1 −1 30.88 14706.69
13 0 0 0 29.94 14258.18
14 0 0 0 29.94 14258.18
15 −1 0 1 30.46 14505.09
16 1 −1 0 31.29 14899.72
17 1 0 1 30.32 14437.72

4.2 Response surface analysis

Based on the Weierstress polynomial optimal approximation theorem, most functions can be solved by polynomial approximation, and the polynomial approximation model can deal with many nonlinear problems [27]. We performed multiple regression fitting analysis on the peak stress and elastic modulus of recycled concrete, and obtained the quadratic polynomial regression equations of the peak stress ( Y 1 ) and elastic modulus ( Y 2 ) with the coarse aggregate content ( A ), maximum aggregate size ( B ), and aggregate shape ( C ) (see Equations (1) and (2)):

(1) Y 1 = 28.85 + 0.20 ⁎ A − 1.61 ⁎ B + 1.15 ⁎ C − 0.84 ⁎ A 2 + 1.33 ⁎ B 2 + 0.23 ⁎ C 2 ,

(2) Y 2 = 13739.56 + 93.90 ⁎ A − 765.69 ⁎ B + 548.73 ⁎ C − 403.15 ⁎ A 2 + 632.64 ⁎ B 2 + 111.25 ⁎ C 2 .

Given that the P values of AB , AC , and BC are greater than 0.05, they have no significant influence on the model, and thus can be ignored in the model. To ensure the credibility of the regression equations, we made variance analysis and model significance test on the above formulas, and obtained the relevant evaluation indices [26] (Table 8).

Table 8

Response surface analysis results

Source of variance Prob > F Significance R-squared Adj R-squared Pred R-squared
Peak stress <0.0001 Significance 0.9651 0.9442 0.8605
Elastic modulus <0.0001 Significance 0.9654 0.9446 0.8615

As shown in the table, the models “ prob > F” of peak stress and elastic modulus obtained by RSM are both less than 0.0001 (generally, it is significant when the value is less than 0.05), indicating that the regression effect of these response surface models is particularly significant. The coefficients (R-squared) of the peak stress and elastic modulus regression equations are 0.9651 and 0.9654, respectively, indicating that these equations have a high degree of fitting; the adjustment coefficients (adj R-squared) are 0.9442 and 0.9446, respectively, indicating that these equations have a good fitting; and the predictive coefficients (Pred R-squared) are 0.8605 and 0.8615, respectively, indicating that these equations have high prediction accuracy. All the above coefficients exhibit that Equations (1) and (2) can highly fit the test results in the table, and this model can replace the true test values and analyze the test results.

It can be seen in Figures 3–8 that the normal probability distribution of residuals in the model of peak stress and elastic modulus lies on a straight line. The residuals and predicted values are distributed irregularly; the measured values and predicted values are distributed close to a straight line, indicating good fitness of the peak stress and elastic modulus model.

Figure 3 Peak stress-residual normal probability distribution diagram.
Figure 3

Peak stress-residual normal probability distribution diagram.

Figure 4 Peak stress-predicted value and residual distribution map.
Figure 4

Peak stress-predicted value and residual distribution map.

Figure 5 Distribution of peak stress – measured and predicted values.
Figure 5

Distribution of peak stress – measured and predicted values.

Figure 6 Elastic modulus – residual normal probability distribution diagram.
Figure 6

Elastic modulus – residual normal probability distribution diagram.

Figure 7 Elastic modulus – prediction and residual distribution.
Figure 7

Elastic modulus – prediction and residual distribution.

Figure 8 Elastic modulus-measured value and predicted value distribution map.
Figure 8

Elastic modulus-measured value and predicted value distribution map.

The RSM-based three-dimensional response surface and contour map can directly reflect the interaction between the aggregate characteristics of recycled concrete. Given that other factors were fixed, we analyzed the influence of any two factors on the peak stress and elastic modulus of recycled concrete. The resulting response surface and contour map are shown in Figures 9–14. The shape of the contour line reflects the intensity of the interaction: the ellipse indicates that the interaction between the two factors is significant, and the circle indicates that the interaction between the two factors is not significant.

Figure 9 Interaction of coarse aggregate content and maximum aggregate size on peak stress of recycled concrete. (a) Response surface cloud map. (b) Contour map.
Figure 9

Interaction of coarse aggregate content and maximum aggregate size on peak stress of recycled concrete. (a) Response surface cloud map. (b) Contour map.

Figure 10 Interaction of coarse aggregate content and aggregate shape on peak stress of recycled concrete. (a) Response surface cloud map. (b) Contour map.
Figure 10

Interaction of coarse aggregate content and aggregate shape on peak stress of recycled concrete. (a) Response surface cloud map. (b) Contour map.

Figure 11 Interaction of maximum aggregate size and aggregate shape on peak stress of recycled concrete: (a) Response surface cloud map. (b) Contour map.
Figure 11

Interaction of maximum aggregate size and aggregate shape on peak stress of recycled concrete: (a) Response surface cloud map. (b) Contour map.

Figure 12 Interaction of coarse aggregate content and maximum aggregate size on elastic modulus of recycled concrete: (a) Response surface cloud map. (b) Contour map.
Figure 12

Interaction of coarse aggregate content and maximum aggregate size on elastic modulus of recycled concrete: (a) Response surface cloud map. (b) Contour map.

Figure 13 Interaction of coarse aggregate content and aggregate shape on elastic modulus of recycled concrete: (a) Response surface cloud map. (b) Contour map.
Figure 13

Interaction of coarse aggregate content and aggregate shape on elastic modulus of recycled concrete: (a) Response surface cloud map. (b) Contour map.

Figure 14 Interaction of maximum aggregate size and aggregate shape on elastic modulus of recycled concrete: (a) Response surface cloud map. (b) Contour map.
Figure 14

Interaction of maximum aggregate size and aggregate shape on elastic modulus of recycled concrete: (a) Response surface cloud map. (b) Contour map.

Figures 9 and 12 show the response surface curves and contour lines of the peak stress and elastic modulus of recycled concrete under the interaction of the coarse aggregate content and the maximum aggregate size when the regular round aggregates account for 50%. As seen in Figures 9 and 12, with the increase of the coarse aggregate content, the peak stress of recycled concrete shows a trend of first increasing and then decreasing, so does the elastic modulus; with the increase of the maximum aggregate size, the peak stress and elastic modulus of recycled concrete decrease. The influence of the coarse aggregate content on the interaction is more significant than that of the maximum aggregate size.

Figures 10 and 13 show the response surface curves and contour lines of the peak stress and elastic modulus of recycled concrete under the interaction of the coarse aggregate content and the aggregate shape when the maximum aggregate size is 23.75 mm. As seen in Figures 10 and 13, the impact of the coarse aggregate content on the peak stress and elastic modulus of recycled concrete is the same as the above conclusions. As the proportion of regular round aggregates increases, the peak stress and elastic modulus of recycled concrete also increase. The influence of the coarse aggregate content on the interaction is more significant than that of the aggregate shape.

Figures 11 and 14 show the response surface curves and contour lines of the peak stress and elastic modulus of recycled concrete under the interaction of the maximum aggregate size and the aggregate shape when the coarse aggregate content is 40%. As seen in Figures 11 and 14, the impact of the maximum aggregate size on the peak stress and elastic modulus of recycled concrete is the same as the above conclusions. As the proportion of regular round aggregates increases, the peak stress and elastic modulus of recycled concrete also increase. The influence of the aggregate shape on the interaction is more significant than that of the maximum aggregate size.

4.3 Optimization and validation of characteristic parameters of recycled concrete aggregates

We optimized and solved the objective equation using the optimization module in the response surface software, and obtained the optimal parameter combination concerning the mechanical properties of recycled concrete [28] (Table 9). When the coarse aggregate content is 45%, the maximum aggregate size is 16 mm, and there are 75% regular round aggregates and 25% irregular polygonal aggregates, the theoretical peak stress of the optimization model is 33.06 MPa, and the elastic modulus is 15744.03 MPa.

Table 9

Response surface design optimization results

Factor Result Appropriateness
Coarse aggregate content (%) Maximum coarse aggregate size (mm) Coarse aggregate shape (%) Peak stress (MPa) Elastic modulus (MPa)
45 16 75 33.06 15744.03 0.932

The confirmatory experiment was done under the conditions presented in Table 8. The peak stress of recycled concrete is 33.41 MPa and the elastic modulus is 16385.53 MPa, which are in good agreement with the optimization results of the response surface design. With reference to the literature [5], when the coarse aggregate content is 45%, the mechanical properties of recycled concrete reach the best. Experiment [7] proved that the compressive strength of recycled concrete decreases with the increase of the maximum aggregate size, and the regular aggregates outperform irregular aggregates in terms of mechanical properties [29]. The absolute and relative errors of the peak stress of recycled concrete are calculated as 0.35 MPa and 1.05%, respectively, and those of the elastic modulus are 641.5 MPa and 3.92%, respectively. Through the error values, we found that the optimization results of the response surface design can accurately predict the mechanical properties of recycled concrete.

5 Conclusion

Using the finite element numerical simulation software and the response surface analysis software, we established the peak stress and elastic modulus models based on the coarse aggregate content, the maximum aggregate size, and the aggregate shape, and drew the following conclusions:

  1. When the maximum aggregate size and aggregate shape remain unchanged, the peak stress and elastic modulus of recycled concrete first increase and then decrease with the increase of the coarse aggregate content. When the coarse aggregate content and aggregate shape remain unchanged, the peak stress and elastic modulus of recycled concrete decrease with the increase of the maximum aggregate size. When the coarse aggregate content and maximum aggregate size remain unchanged, the peak stress and elastic modulus of recycled concrete increase with the increase of regular round aggregates.

  2. The aggregate characteristic parameters were optimized through numerical simulation and response surface analysis, and the results showed that the peak stress and elastic modulus of recycled concrete reach the best when the coarse aggregate content is 45%, the maximum aggregate size is 16 mm, and the regular round aggregates occupy 75% and irregular polygonal aggregates occupy 25%. Such results provide theoretical support for engineering design and construction.

  1. Funding information: This research was funded by Henan Provincial Natural Science Foundation Project: (202300410270) Research on Frost Resistance Durability Behavior and Deterioration Damage Mechanism of Cemented Sand and Gravel.

  2. Conflicts of interest: The authors declare no conflict of interest.

  3. Data availability statement: All data, models, and code generated or used during the study appear in the published article.

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Received: 2021-06-21
Revised: 2021-08-20
Accepted: 2021-09-02
Published Online: 2021-09-23

© 2021 Jiangwei Bian et al., published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

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https://doi.org/10.1515/secm-2021-0050
Keywords for this article
recycled concrete; aggregate characteristics; response surface analysis; numerical simulation; mechanical properties
Creative Commons
BY 4.0

Articles in the same Issue

  1. Effects of Material Constructions on Supersonic Flutter Characteristics for Composite Rectangular Plates Reinforced with Carbon Nano-structures
  2. Processing of Hollow Glass Microspheres (HGM) filled Epoxy Syntactic Foam Composites with improved Structural Characteristics
  3. Investigation on the anti-penetration performance of the steel/nylon sandwich plate
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  10. An investigation on the degradation behaviors of Mg wires/PLA composite for bone fixation implants: influence of wire content and load mode
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  12. Self-Fibers Compacting Concrete Properties Reinforced with Propylene Fibers
  13. Study on the fabrication of in-situ TiB2/Al composite by electroslag melting
  14. Characterization and Comparison Research on Composite of Alluvial Clayey Soil Modified with Fine Aggregates of Construction Waste and Fly Ash
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  17. Nano titanium oxide for modifying water physical property and acid-resistance of alluvial soil in Yangtze River estuary
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  22. Mechanical and fracture properties of steel fiber-reinforced geopolymer concrete
  23. Handcrafted digital light processing apparatus for additively manufacturing oral-prosthesis targeted nano-ceramic resin composites
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  26. The electrochemical performance and modification mechanism of the corrosion inhibitor on concrete
  27. Evaluation of the applicability of different viscoelasticity constitutive models in bamboo scrimber short-term tensile creep property research
  28. Experimental and microstructure analysis of the penetration resistance of composite structures
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  30. Active vibration suppression of wind turbine blades integrated with piezoelectric sensors
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  52. Investigation of the influence of recyclate content on Poisson number of composites
  53. A hard-core soft-shell model for vibration condition of fresh concrete based on low water-cement ratio concrete
  54. Retraction
  55. Thermal and mechanical characteristics of cement nanocomposites
  56. Influence of class F fly ash and silica nano-micro powder on water permeability and thermal properties of high performance cementitious composites
  57. Effects of fly ash and cement content on rheological, mechanical, and transport properties of high-performance self-compacting concrete
  58. Erratum
  59. Inverse analysis of concrete meso-constitutive model parameters considering aggregate size effect
  60. Special Issue: MDA 2020
  61. Comparison of the shear behavior in graphite-epoxy composites evaluated by means of biaxial test and off-axis tension test
  62. Photosynthetic textile biocomposites: Using laboratory testing and digital fabrication to develop flexible living building materials
  63. Study of gypsum composites with fine solid aggregates at elevated temperatures
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  65. Engineering of composite materials made of epoxy resins modified with recycled fine aggregate
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  70. Effect and mechanism of different excitation modes on the activities of the recycled brick micropowder
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