# Behavior of Confined Self-Compacting Concrete under Compression at Elevated Temperatures

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## Abstract

**:**

## 1. Introduction

## 2. Research Significance

## 3. Methodology

#### 3.1. Equations and Procedure

#### 3.1.1. Load-Carrying Capacity

_{0}) of a CFST column is as follows [18]:

_{s}and A

_{c}are the cross-sectional areas of steel tube and concrete core, respectively. The compressive stress of an unconfined concrete cylinder is given by f

_{c}. The equivalent confinement coefficients for the two materials are 1 and 2.25. P

_{0}of the columns was estimated using the identical methods published by the Australian Standards (AS) and American Specifications (ACI), although neither specification takes the confinement on concrete into consideration (Equation (2)):

_{0}of concrete is calculated by deducting the amount of friction between the concrete core and steel tube from the axial load of the column, and the concrete compressive strength is derived by dividing the concrete compressive load by the concrete area of the section (Equation (3)):

_{cz}is the concrete compressive strength, and σ

_{z}is the axial strength of steel tube. Equation (3) can be rewritten in the form of Equation (4):

#### 3.1.2. Unconfined and Confined Concrete Stress and Strain

_{cu}). Unconfined strain was found to be approximately 0.003 [21], 0.0035 [26], and 0.0038 [27]

_{,}while the confined compressive strength (f

_{cc}) and related confined strain (ε

_{cc}) can be calculated using Equations (5) and (6), which were developed by Mander et al. [21]:

_{l}denotes the lateral confining pressure that a circular steel tube applies; this is dependent on the D/t ratio, along with the yield strength of the material. Hu et al. [28] developed a formula to calculate the predicted f

_{l}for the D/t values ranging from 21.7 to 150. They concluded that tubes with low D/t ratios are significantly influenced by f

_{l}, whereas tubes with high ratios are hardly influenced. Equations (5) and (6) can be utilized to calculate the equivalent uniaxial confined concrete compressive strength (f

_{cc}) and constrained strain (ε

_{cc}) with k

_{1}and k

_{2}as 4.1 and 20.5, respectively [29].

_{cc}). Researchers have reported Poisson’s ratio of confined concrete (ν

_{cc}) being constant at 0.2, while the modulus of elasticity of confined concrete (E

_{cc}) can be calculated using ACI (Equation (7)) [21]:

_{cc}/E

_{cc}) must be ascertained straddling proportional and restricted strains, whereas the stress values can be readily computed using Equation (8), presuming the values of strain:

_{E}and R values are based on Equations (9) and (10), respectively:

_{σ}and R

_{ε}were determined to be equal to 4. The third section of the stress–strain diagram for restricted concrete is the area where the curve steadily tapers from the concrete confined compressive strength (f

_{cc}) to a subsequent value comparable to rk

_{3}f

_{cc}at a strain of 11ε

_{cc}. The deduction factor (k

_{3}) determines the D/t ratio and steel tube’s yield strength (f

_{y}).

_{σ}and R

_{ε}were set as equal to 4. The third segment of the stress–strain diagram for confined concrete is the section where the curve reduces from f

_{cc}to a lower value equivalent to rk

_{3}f

_{cc}accompanied with a strain of 11ε

_{cc}. The value for the reduction factor (k

_{3}) is reliant on the D/t ratio and steel tube’s yield strength (f

_{y}). The k

_{3}value is obtained using empirical equations of Hu et al. [32]. These equations have an effect on D/t ratios and demonstrated a good confinement effect for a range from 21.7 to 150. Also, Hu et al. [32] considered the concrete grade (maximum at a set of 31.2 MPa) to improve the confinement effect. Later, Giakoumelis and Lam [32] mentioned that this value is suitable for cube strengths having a compressive strength lower than 30 MPa. In addition to this, it was found that in the case of the compressive strength higher than 30 MPa for the same values of D/t ratio, the yield stress effectively decreased. Due to this reason, Giakoumelis and Lam [32] designed a factor (r) to make a more precisely confined concrete model based on their experimental results. It is good to calculate the value of r and to start with one for concrete having a compressive strength of 30 MPa. Tomii [33] and Mursi [34] suggested to take a starting of r value equal to 0.5 for concrete having a compressive strength of higher than or equal to 100 MPa. Finally, Giakoumelis and Lam [32] decided to carry out linear interpolations of concrete having a compressive strength between 30 MPa and 100 MPa.

#### 3.2. Multiple Regression

_{c}and A

_{s}), the strength of concrete core (f

_{c}), and the yield strength of steel tube (f

_{y}), and one dependent variable (outcome: load-carrying capacity (P

_{0}))). (ii) Prepare data: Clean the dataset, handle missing values, and normalize variables if necessary. (iii) Choose variables: Select the relevant predictors that may impact the outcome. (iv) Build the model: Use statistical software to fit the data into a multiple linear regression model (y = a + bx + cz + …), where a designates the intersection, b represents the co-efficient of the variable x, c denotes the co-efficient of the variable z, and so on. (v) Evaluate model: Assess the model’s goodness-of-fit, check for multicollinearity, and analyze the significance of variables. (vi) Interpret results: Examine the coefficients and their significance to understand the relationship between the predictors and outcome. (vii) Validate and refine [35,36].

## 4. Results and Discussion

#### 4.1. Load–Axial Shortening Variation

#### 4.2. Compressive Strength at Elevated Temperatures

#### 4.3. Modulus of Elasticity at Elevated Temperatures

#### 4.4. Effect of Poisson’s Ratio

#### 4.5. Multiple Regression Fit

#### 4.5.1. Peak Load of Confined SCCFSTs

_{0}) of confined SCCFSTs in the temperature range from 30 °C to 400 °C can be approximated using Equation (11). The peak load is influenced by the temperature (T), with a positive coefficient of 0.0957. As the temperature increased within this range, the peak load tended to decrease, as depicted in Figure 7a. Furthermore, the peak load was affected by the area of steel tube (A

_{s}) and the yield strength of steel tube (f

_{y}), with a coefficient of 0.0011, as illustrated in Figure 7b. Additionally, the peak load was influenced by the area of concrete (A

_{c}) and the compressive strength of concrete (f

_{c}), with a coefficient of 0.00078, as displayed in Figure 7c. These factors collectively contributed to the peak load behavior within this temperature range. Temperature effect (from 500 °C to 800 °C): For elevated temperatures between 500 °C and 800 °C, the peak load of confined SCCFSTs can be estimated using Equation (12). The temperature (T) still plays a role in determining the peak load, but its influence is reduced compared to the previous temperature range. The temperature coefficient for this range was 0.0376, as demonstrated in Figure 7d, indicating a smaller impact on the peak load. Moreover, the area of steel tube (A

_{s}) and the yield strength of steel tube (f

_{y}) combined with the area of concrete (A

_{c}) and the compressive strength of concrete (f

_{c}) affected the peak load, with a coefficient of 0.0012, as shown in Figure 7e,f.

#### 4.5.2. Confinement Factor of Confined SCCFSTs

_{s}and A

_{c}designate the cross-sectional areas of steel tube and concrete core, respectively, and f

_{y}and f

_{c}represent the yield strength of steel tube and the strength of concrete core, respectively [43]. The graph of the multiple linear regression fit for λ of confined SCCFSTs demonstrates two Equations (13) and (14). The relationship between λ and T was described utilizing these equations for two distinct temperature ranges. For the temperature ranging from 30 °C to 400 °C, Equation (13) was used. On the other hand, for temperatures between 500 °C and 800 °C, Equation (14) was employed.

_{l}) was influenced by different temperature conditions. From Figure 8b,d, it can be observed that the relationship between λ and f

_{l}was linear for both temperature ranges. As the temperature increased within the specified ranges, the behavior of λ became apparent in the variations of f

_{l}. The coefficients of λ in Equations (13) and (14) gave insights into how changes in λ affected the response (f

_{l}) for each temperature range.

## 5. Conclusions

- The tested specimens had varying behaviors under elevated temperatures; at 30 °C one specimen showed hardening, while the others exhibited softening tendencies, and at 500 °C, one specimen presented the steepest strength reduction, indicating that elevated temperature played a dominant role in determining the peak behavior.
- The circular SCCFST specimens revealed comparable maximum normalized strength values ranging from 0.91 to 1.65, with remarkable effects from the surrounding temperatures, particularly when exposed to temperatures of 400 °C and above 500 °C.
- The compressive stress–strain curve of the circular SCCFSTs experienced a sudden drop of 14.77 MPa (22.65%) at 500 °C, followed by a gradual decrease in the mechanical strength beyond 400 °C up to 800 °C, which was attributed to the steel tube maintaining its strength up to 400 °C with only minimal reduction. But recrystallization above 400 °C resulted in a significant reduction in the mechanical strength of the confined SCCFSTs, and the most substantial drop in the reduction ratio occurred between 400 °C and 800 °C.
- The confined concrete displayed a relatively smaller reduction in the overall modulus of elasticity compared to its unconfined counterpart under elevated temperatures, with an average percentage of reduction ranging between 5.05% and 12.68%.
- A close relationship was found between the lateral strain and longitudinal strain within elastic limits under compression for temperatures ranging from 30 °C to 400 °C, but a sudden increase in strain was seen beyond 400 °C.
- The multiple regression analysis demonstrated a close alignment between the predicted and experimental P
_{0}values at elevated temperatures. The temperature was set between 30 °C and 400 °C, and the average variation was 2.23%, while above 400 °C, the average variation increased to 11.88%.

## Author Contributions

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

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**Figure 1.**(

**a**) Materials for preparing SCCFSTs, (

**b**) cutting steel tubes, and (

**c**) curing (with specimens under water; surface layer appears blurry due to presence of water).

**Figure 2.**Stress–strain curves for unconfined concrete and confined concrete under a uniaxial load [21].

**Figure 6.**Lateral strain and longitudinal strain versus stress curves of circular SCCFSTs at 30 °C, 400 °C, and 500 °C.

**Figure 7.**Predicted values of P

_{0}: (

**a**) Temperature line fit plot from 30 °C to 400 °C, (

**b**) A

_{s}f

_{y}line fit plot from 30 °C to 400 °C, (

**c**) A

_{c}f

_{c}line fit plot from 30 °C to 400 °C, (

**d**) Temperature line fit plot from 500 °C to 800 °C, (

**e**) A

_{s}f

_{y}line fit plot from 500 °C to 800 °C, and (

**f**) A

_{c}f

_{c}line fit plot from 500 °C to 800 °C.

**Figure 8.**Predicted values of lateral stress in steel with respect to confinement factor and temperature: (

**a**) Temperature line fit plot from 30 °C to 400 °C, (

**b**) λ = A

_{s}f

_{y}/A

_{c}f

_{c}fit plot from 30 °C to 400 °C, (

**c**) Temperature line fit plot from 500 °C to 800 °C, and (

**d**) λ = A

_{s}f

_{y}/A

_{c}f

_{c}line fit plot from 500 °C to 800 °C.

**Table 1.**Chemical compositions and various properties of OPC, aggregates, silica fume, and Fosroc Conplast.

Chemical Composition | OPC | Fine Aggregate (M-Sand) | Coarse Aggregate | Silica Fume (Admixture) | Fosroc Conplast SP430 (Superplasticizer) | |
---|---|---|---|---|---|---|

SiO_{2} | 22% | 67% | 67% | 91% | — | |

Al_{2}O_{3} | 5% | 15% | 15% | 0.3% | — | |

Fe_{2}O_{3} | 1.5% | 5% | 5% | 1% | — | |

CaO | 62% | 3% | 3% | 0.7% | — | |

MgO | 2% | — | — | 0.2% | — | |

CaSO_{4} | 0.3% | — | — | — | — | |

SO_{3} | 1% | — | — | — | — | |

Na_{2}O | 0.5% | 3% | 3% | 0.4% | 72 g per liter | |

H_{2}O | — | 2% | 0.5% | — | — | |

Properties | ||||||

Density (kg/m^{3}) | 1438 | 1690 | 1463 | 525 | 1200 | |

Specific gravity | 3.1 | 2.68 | 2.74 | 2.2 | 1.2 | |

Setting time (min) | Initial | 43 | — | — | — | — |

Final | 250 | — | — | — | — | |

Days | Compressive strength (MPa) | |||||

M25 | M30 | M40 | ||||

3 | 10.2 | 13.8 | 18.1 | |||

7 | 15.5 | 19.0 | 25.2 | |||

14 | 23.5 | 26.7 | 36.5 | |||

28 | 26.5 | 32.0 | 43.1 |

Element (%) | ||||||
---|---|---|---|---|---|---|

C | Mn | S | P | Si | Al | |

0.064 | 0.330 | 0.010 | 0.015 | 0.011 | 0.042 | |

Properties | Value (MPa) | |||||

Yield strength | 348.80 | |||||

Ultimate strength | 457.90 |

**Table 3.**SCC mix designs in accordance with IS 10262-2009 and Nan Su technique, selection of dimension, and temperature.

Grade | Cement (C) in kg/m^{3} | Fine Aggregate (FA) in kg/m^{3} | Coarse Aggregate (CA) in kg/m^{3} | Mix Proportion (C:FA:CA) | Silica Fume (Admixture) | Fosroc Conplast SP430 (Superplasticizer) | W/B |
---|---|---|---|---|---|---|---|

M25 | 363.54 | 895.19 | 604.69 | 1:2.46:1.66 | 5% | 1.5% | 0.55 |

M30 | 524.31 | 778.57 | 773.06 | 1:1.48:1.47 | 7.5% | 2% | 0.45 |

M40 | 494.4 | 932.04 | 688.867 | 1:1.88:1.39 | 10% | 2.5% | 0.40 |

Dimension | d in mm | L in mm | L/d ratio | Temperature (°C) | |||

M25 M30 M40 | 50 | 400 and 500 | 8 and 10 | 30 and 100 to 800 | |||

60 | 480 and 600 | 8 and 10 |

Notations Based on Temperature | Length-to-Diameter Ratio | Diameter-to-Thickness Ratio (t = 2 mm) | Area of Cross-Section (mm^{2}) | |||||
---|---|---|---|---|---|---|---|---|

Concrete | Steel | |||||||

L | d | L/d | d/t | A_{c} | A_{s} | |||

T = 30 °C | T = 400 °C | T = 500 °C | (mm) | (mm) | ||||

A1 | A13 | A25 | 400 | 50 | 8 | 25 | 1661.9 | 301.59 |

A2 | A14 | A26 | 400 | 50 | 8 | 25 | 1661.9 | 301.59 |

A3 | A15 | A27 | 400 | 50 | 8 | 25 | 1661.9 | 301.59 |

A4 | A16 | A28 | 480 | 60 | 8 | 30 | 2463 | 364.42 |

A5 | A17 | A29 | 480 | 60 | 8 | 30 | 2463 | 364.42 |

A6 | A18 | A30 | 480 | 60 | 8 | 30 | 2463 | 364.42 |

A7 | A19 | A31 | 500 | 50 | 10 | 25 | 1661.9 | 301.59 |

A8 | A20 | A32 | 500 | 50 | 10 | 25 | 1661.9 | 301.59 |

A9 | A21 | A33 | 500 | 50 | 10 | 25 | 1661.9 | 301.59 |

A10 | A22 | A34 | 600 | 60 | 10 | 30 | 2463 | 364.42 |

A11 | A23 | A35 | 600 | 60 | 10 | 30 | 2463 | 364.42 |

A12 | A24 | A36 | 600 | 60 | 10 | 30 | 2463 | 364.42 |

Designation | Compressive Strength (MPa) | Confinement Factor | Load-Carrying Capacity (kN) | Comparison of Load-Carrying Capacity | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|

Concrete Mix | Steel | P_{u} | P_{0} | P_{u}/P_{0} | |||||||||

f_{ck} | f_{c} | f_{y} | λ | Tested | EC4 [18,19] | ACI [20] | Zhao et al. [22] | Mander et al. [21] | EC4 [18,19] | ACI [20] | Zhao et al. [22] | Mander et al. [21] | |

At ambient temperature | |||||||||||||

A1 | 26.5 | 21.2 | 347.13 | 2.97 | 128 | 130.23 | 135.5 | 111.29 | 105.75 | 0.98 | 0.94 | 1.15 | 1.21 |

A2 | 32 | 25.6 | 347.13 | 2.46 | 135 | 137.55 | 141.72 | 112.90 | 114.45 | 0.98 | 0.95 | 1.20 | 1.18 |

A3 | 43.1 | 34.48 | 347.13 | 1.83 | 148 | 152.3 | 154.26 | 120.41 | 132.01 | 0.97 | 0.96 | 1.23 | 1.12 |

A4 | 26.5 | 21.2 | 347.13 | 2.42 | 167 | 167.01 | 171.93 | 143.96 | 135.55 | 1.00 | 0.97 | 1.16 | 1.23 |

A5 | 32 | 25.6 | 347.13 | 2.01 | 178 | 177.85 | 181.14 | 147.73 | 148.07 | 1.00 | 0.98 | 1.20 | 1.20 |

A6 | 43.1 | 34.48 | 347.13 | 1.49 | 193 | 199.72 | 199.73 | 160.56 | 173.35 | 0.97 | 0.97 | 1.20 | 1.11 |

A7 | 26.5 | 21.2 | 347.13 | 2.97 | 125 | 130.23 | 135.5 | 111.29 | 105.75 | 0.96 | 0.92 | 1.12 | 1.18 |

A8 | 32 | 25.6 | 347.13 | 2.46 | 133 | 137.55 | 141.72 | 112.90 | 114.45 | 0.97 | 0.94 | 1.18 | 1.16 |

A9 | 43.1 | 34.48 | 347.13 | 1.83 | 145 | 152.3 | 154.26 | 120.41 | 132.01 | 0.95 | 0.94 | 1.20 | 1.10 |

A10 | 26.5 | 21.2 | 347.13 | 2.42 | 164 | 167.01 | 171.93 | 143.96 | 135.55 | 0.98 | 0.95 | 1.14 | 1.21 |

A11 | 32 | 25.6 | 347.13 | 2.01 | 175 | 177.85 | 181.14 | 147.73 | 148.07 | 0.98 | 0.97 | 1.18 | 1.18 |

A12 | 43.1 | 34.48 | 347.13 | 1.49 | 190 | 199.72 | 199.73 | 160.56 | 173.35 | 0.95 | 0.95 | 1.18 | 1.10 |

At 400 °C temperature | |||||||||||||

A13 | 26.5 | 21.2 | 244.6 | 2.09 | 119 | 121.43 | 128.02 | 109.13 | 75.27 | 0.98 | 0.93 | 1.09 | 1.58 |

A14 | 32 | 25.6 | 244.6 | 1.73 | 121 | 126.91 | 132.68 | 107.56 | 81.56 | 0.95 | 0.91 | 1.12 | 1.48 |

A15 | 43.1 | 34.48 | 244.6 | 1.29 | 130 | 137.98 | 142.09 | 109.16 | 94.25 | 0.94 | 0.91 | 1.19 | 1.38 |

A16 | 26.5 | 21.2 | 244.6 | 1.71 | 151 | 153.96 | 160.84 | 138.92 | 96.6 | 0.98 | 0.94 | 1.09 | 1.56 |

A17 | 32 | 25.6 | 244.6 | 1.41 | 162 | 162.08 | 167.74 | 138.3 | 105.65 | 1.00 | 0.97 | 1.17 | 1.53 |

A18 | 43.1 | 34.48 | 244.6 | 1.05 | 173 | 178.49 | 181.69 | 142.87 | 123.92 | 0.97 | 0.95 | 1.21 | 1.40 |

A19 | 26.5 | 21.2 | 244.6 | 2.09 | 117 | 121.43 | 128.02 | 109.13 | 75.27 | 0.96 | 0.91 | 1.07 | 1.55 |

A20 | 32 | 25.6 | 244.6 | 1.73 | 119 | 126.91 | 132.68 | 107.56 | 81.56 | 0.94 | 0.90 | 1.11 | 1.46 |

A21 | 43.1 | 34.48 | 244.6 | 1.29 | 125 | 137.98 | 142.09 | 109.16 | 94.25 | 0.91 | 0.88 | 1.15 | 1.33 |

A22 | 26.5 | 21.2 | 244.6 | 1.71 | 142 | 153.96 | 160.84 | 138.92 | 96.6 | 0.92 | 0.88 | 1.02 | 1.47 |

A23 | 32 | 25.6 | 244.6 | 1.41 | 154 | 162.08 | 167.74 | 138.3 | 105.65 | 0.95 | 0.92 | 1.11 | 1.46 |

A24 | 43.1 | 34.48 | 244.6 | 1.05 | 165 | 178.49 | 181.69 | 142.87 | 123.92 | 0.92 | 0.91 | 1.15 | 1.33 |

At 500 °C temperature | |||||||||||||

A25 | 26.5 | 21.2 | 194.79 | 1.67 | 99 | 95.24 | 100.3 | 96.08 | 60.1 | 1.04 | 0.99 | 1.03 | 1.65 |

A26 | 32 | 25.6 | 194.79 | 1.38 | 105 | 99.63 | 104.03 | 93.95 | 65.14 | 1.05 | 1.01 | 1.12 | 1.61 |

A27 | 43.1 | 34.48 | 194.79 | 1.03 | 109 | 108.48 | 111.56 | 93.98 | 75.31 | 1.00 | 0.98 | 1.16 | 1.45 |

A28 | 26.5 | 21.2 | 194.79 | 1.36 | 125 | 120.87 | 126.12 | 121.73 | 77.16 | 1.03 | 0.99 | 1.03 | 1.62 |

A29 | 32 | 25.6 | 194.79 | 1.13 | 130 | 127.37 | 131.64 | 120.15 | 84.41 | 1.02 | 0.99 | 1.08 | 1.54 |

A30 | 43.1 | 34.48 | 194.79 | 0.84 | 145 | 140.49 | 142.8 | 122.27 | 99.06 | 1.03 | 1.02 | 1.19 | 1.46 |

A31 | 26.5 | 21.2 | 194.79 | 1.67 | 95 | 95.24 | 100.3 | 96.08 | 60.1 | 1.00 | 0.95 | 0.99 | 1.58 |

A32 | 32 | 25.6 | 194.79 | 1.38 | 100 | 99.63 | 104.03 | 93.95 | 65.14 | 1.00 | 0.96 | 1.06 | 1.54 |

A33 | 43.1 | 34.48 | 194.79 | 1.03 | 105 | 108.48 | 111.56 | 93.98 | 75.31 | 0.97 | 0.94 | 1.12 | 1.39 |

A34 | 26.5 | 21.2 | 194.79 | 1.36 | 120 | 120.87 | 126.12 | 121.73 | 77.16 | 0.99 | 0.95 | 0.99 | 1.56 |

A35 | 32 | 25.6 | 194.79 | 1.13 | 124 | 127.37 | 131.64 | 120.15 | 84.41 | 0.97 | 0.94 | 1.03 | 1.47 |

A36 | 43.1 | 34.48 | 194.79 | 0.84 | 135 | 140.49 | 142.8 | 122.27 | 99.06 | 0.96 | 0.95 | 1.10 | 1.36 |

Length-to-Diameter Ratio | Diameter-to-Thickness Ratio (t = 2 mm) | Compressive Strength (MPa) | Confined Compressive Strength (MPa) (f _{cc}) for Various Temperatures (°C) | |||||||
---|---|---|---|---|---|---|---|---|---|---|

Concrete Mix | ||||||||||

L/d | d/t | f_{ck} | f_{c} | 30 | 100 | 200 | 300 | 400 | 500 | 600 |

8 | 25 | 26.5 | 21.2 | 65.19 | 64.68 | 64.17 | 61.62 | 60.61 | 50.42 | 34.63 |

32 | 25.6 | 68.75 | 67.23 | 66.21 | 63.66 | 61.62 | 53.48 | 36.67 | ||

43.1 | 34.48 | 75.38 | 73.85 | 72.32 | 69.26 | 66.21 | 55.51 | 40.74 | ||

30 | 26.5 | 21.2 | 59.06 | 58.36 | 56.94 | 54.82 | 53.41 | 44.21 | 33.25 | |

32 | 25.6 | 62.95 | 62.25 | 60.83 | 59.42 | 57.30 | 45.98 | 33.95 | ||

43.1 | 34.48 | 68.26 | 67.20 | 65.78 | 63.31 | 61.19 | 51.28 | 37.14 | ||

10 | 25 | 26.5 | 21.2 | 63.66 | 63.15 | 62.64 | 60.61 | 59.59 | 48.38 | 33.10 |

32 | 25.6 | 67.74 | 66.21 | 65.19 | 62.64 | 60.61 | 50.93 | 34.63 | ||

43.1 | 34.48 | 73.85 | 72.83 | 70.28 | 65.19 | 63.66 | 53.48 | 38.20 | ||

30 | 26.5 | 21.2 | 58.00 | 57.30 | 55.88 | 53.05 | 50.22 | 42.44 | 30.06 | |

32 | 25.6 | 61.89 | 60.83 | 59.06 | 56.94 | 54.47 | 43.86 | 31.83 | ||

43.1 | 34.48 | 67.20 | 65.78 | 63.66 | 60.83 | 58.36 | 47.75 | 33.60 |

Temperature (°C) | Reduction Ratio | |||
---|---|---|---|---|

EC4 [18,19] | Tested (Confined Concrete) | |||

Unconfined Concrete | M25 | M30 | M40 | |

30 | 1.00 | 1.000 | 1.000 | 1.000 |

100 | 1.00 | 0.992 | 0.978 | 0.980 |

200 | 0.95 | 0.984 | 0.963 | 0.959 |

300 | 0.85 | 0.945 | 0.926 | 0.919 |

400 | 0.75 | 0.930 | 0.896 | 0.878 |

500 | 0.60 | 0.773 | 0.778 | 0.736 |

600 | 0.45 | 0.531 | 0.533 | 0.541 |

700 | 0.30 | 0.281 | 0.304 | 0.304 |

800 | 0.15 | 0.156 | 0.185 | 0.189 |

Mix | Grade of Concrete (MPa) | Compressive Strength (f_{c}) in MPa | Unconfined Modulus of Elasticity (E_{cu}) in GPa | Confined Modulus of Elasticity (E_{cc}) in GPa | ||
---|---|---|---|---|---|---|

30 °C | 400 °C | 500 °C | ||||

M25 | 25 | 27.5 | 28.51 | 37.95 | 36.59 | 33.37 |

M25 | 25 | 25.5 | 27.36 | 36.12 | 34.35 | 31.25 |

M25 | 25 | 26.5 | 26.47 | 37.5 | 36.28 | 32.69 |

M30 | 30 | 29 | 29.01 | 38.97 | 36.90 | 34.37 |

M30 | 30 | 34 | 29.13 | 37.29 | 35.58 | 31.87 |

M30 | 30 | 33 | 28.24 | 38.68 | 36.59 | 33.54 |

M40 | 40 | 44.5 | 31.63 | 40.81 | 38.24 | 35.02 |

M40 | 40 | 43.4 | 32.06 | 38.83 | 36.76 | 33.66 |

M40 | 40 | 41.4 | 30.54 | 40.39 | 37.50 | 34.37 |

Mix | Grade of Concrete (MPa) | Compressive Strength (f_{c}) in MPa | Poisson’s Ratio of Unconfined Concrete | Poisson’s Ratio of Confined Concrete | ||
---|---|---|---|---|---|---|

30 °C | 400 °C | 500 °C | ||||

M25 | 25 | 27.5 | 0.185 | 0.282 | 0.283 | 0.396 |

M25 | 25 | 25.5 | 0.180 | 0.258 | 0.240 | 0.317 |

M25 | 25 | 26.5 | 0.178 | 0.258 | 0.265 | 0.384 |

M30 | 30 | 29.0 | 0.165 | 0.280 | 0.275 | 0.360 |

M30 | 30 | 34.0 | 0.158 | 0.280 | 0.278 | 0.391 |

M30 | 30 | 33.0 | 0.161 | 0.245 | 0.253 | 0.350 |

M40 | 40 | 44.5 | 0.140 | 0.320 | 0.338 | 0.470 |

M40 | 40 | 43.4 | 0.135 | 0.279 | 0.378 | 0.351 |

M40 | 40 | 41.4 | 0.138 | 0.337 | 0.344 | 0.480 |

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## Share and Cite

**MDPI and ACS Style**

Ulla Khan, A.; Sateesh Kumar, N.; Bahrami, A.; Özkılıç, Y.O.; Imran, M.; Althaqafi, E.; Islam, S.
Behavior of Confined Self-Compacting Concrete under Compression at Elevated Temperatures. *Buildings* **2023**, *13*, 3115.
https://doi.org/10.3390/buildings13123115

**AMA Style**

Ulla Khan A, Sateesh Kumar N, Bahrami A, Özkılıç YO, Imran M, Althaqafi E, Islam S.
Behavior of Confined Self-Compacting Concrete under Compression at Elevated Temperatures. *Buildings*. 2023; 13(12):3115.
https://doi.org/10.3390/buildings13123115

**Chicago/Turabian Style**

Ulla Khan, Athiq, Nanjundaswamy Sateesh Kumar, Alireza Bahrami, Yasin Onuralp Özkılıç, Mohammed Imran, Essam Althaqafi, and Saiful Islam.
2023. "Behavior of Confined Self-Compacting Concrete under Compression at Elevated Temperatures" *Buildings* 13, no. 12: 3115.
https://doi.org/10.3390/buildings13123115