This paper describes an experimental study on the mechanical properties of highstrength fiberreinforced concrete (HSFRC). The experimental parameters included the content and length of the steel fiber as well as the use of either a singletype fiber or hybrid steel fibers. The steel fiber contents were 1.0, 1.5, and 2.0% based on the volume of HSFRC, and the steel fiber lengths were 13, 16.5, and 19.5 mm. In addition, hybrid steel fibers incorporating steel fibers of different lengths were used. Compression tests and crack mouth opening displacement tests were performed for each HSFRC mixture with different experimental parameters. The mechanical properties of the HSFRC, such as compressive strength, elastic modulus, and tensile strength, increased with the steel fiber content. The mechanical property results of the HSFRC mixture using a single fiber length of 13 mm were greater than the results of the other mixtures. The compressive strength, elastic modulus, and tensile strength of the HSFRC mixture with hybrid steel fibers were similar to those of the mixtures with a single length of steel fiber. Additionally, based on the test results of the material properties, equations for predicting the elastic modulus and tensile strength of the HSFRC were suggested; the predictions using the proposed formula closely agreed with the experimental results.
Highstrength fiberreinforced concrete (HSFRC) has an improved particle size distribution due to the constituent materials, and the microstructural porosity of HSFRC is minimized by using fillers with fine aggregates. In addition, steel fibers are contained within the HSFRC. Therefore, the HSFRC characteristics, including compressive behavior, tensile behavior, and durability, are superior to those of conventional concrete [
The results of previous studies have shown that the compressive strength of HSFRC is between 130 and 200 MPa. The amount and type of steel fiber used in the HSFRC affect its mechanical properties, with an elastic modulus between 45 and 55 GPa and a tensile strength between 10 and 20 MPa [
Most of the studies on HSFRC have been carried out with a single type of fiber. However, in recent years, the mechanical characteristics of steel fiberreinforced concrete with hybrid steel fibers, which incorporate two different types of fiber or different lengths of steel fiber, were investigated [
In addition, Akcay and Tasdemir [
Here, an experimental study on the mechanical properties of HSFRC was carried out using steel fibers with lengths of 13, 16.5, and 19.5 mm. Additionally, the effects of different fiber types including single and hybrid steel fibers as well as the contents on the HSFRC were evaluated.
Table
Mix proportions of the HSFRC.
Mixture  W/B  W  OPC  Zr  SF  BFS  FA  F  Steel fiber  

Fiber content by volume 
Diameter 

F10SL130  0.16  157  770  —  193  —  848  231  1.0 = 1.0 (13.0 mm)  0.2 
F10SL195  0.22  209  770  58  —  135  847  231  1.0 = 1.0 (19.5 mm)  0.2 
F10H  0.16  157  770  —  193  —  848  231  1.0 = 0.5 (16.5 mm) + 0.5 (19.5 mm)  0.2 
F15SL130  0.16  157  770  —  193  —  848  231  1.5 = 1.5 (13 mm)  0.2 
F15H(BFS)  0.18  180  788  99  —  99  867  236  1.5 = 0.5 (16.5 mm) + 1.0 (19.5 mm)  0.2 
F15H  0.18  178  783  196  —  —  862  235  1.5 = 0.5 (16.5 mm) + 1.0 (19.5 mm)  0.2 
F20SL130  0.16  157  770  —  193  —  848  232  2.0 = 2.0 (13 mm)  0.2 
F20H  0.16  157  770  —  193  —  848  232  2.0 = 1.0 (16.5 mm) + 1.0 (19.5 mm)  0.2 
HSFRC also includes steel fiber. The contents, type, and lengths of the fiber are different in each mixture. The steel fibers were 1.0, 1.5, and 2.0% based on the volume of the mixture; in Table
Steel fiber used in this study. (a)
A cylindrical specimen with a diameter of 100 mm and a height of 200 mm was fabricated from each mixture. The specimens were wet cured for the first day after casting, and then, steam curing was carried out at 90 ± 5°C for 72 hours. After the samples were steam cured, wet curing was carried out for 28 days after specimen fabrication.
Three linear displacement transducers (LVDTs) were installed around the cylindrical specimen, with a distance of 100 mm between the attachment points. The displacement was measured during loading, as shown in Figure
Compressive strength test.
The mean compressive strength and elastic modulus of the F10SL130, F10SL195, and F10H mixtures are shown in Table
Test results of the compressive strength and elastic modulus
Mixture  Batch  Number of specimens  Fiber content 
Compressive strength 
Elastic modulus 

F10SL130  1  4  1.0  174.6  43,551 
2  3  1.0  181.3  45,561  
3  2  1.0  168.9  43,396  
4  4  1.0  167.2  44,051  
Mean  173.0  44,145  


F10SL195  1  5  1.0  121.6  41,469 
2  5  1.0  138.5  39,936  
3  4  1.0  137.1  39,192  
4  4  1.0  134.6  39,081  
5  5  1.0  137.4  40,652  
Mean  133.7  40,147  


F10H  1  5  1.0  174.0  43,550 
Mean  174.0  43,550 
In contrast, the mean compressive strength of the F10SL130 and F10H mixtures was 173.0 and 174.0 MPa, respectively, and the mean elastic modulus of each mixture was 44,145 and 43,550 MPa, respectively. The compressive strength and the elastic modulus of the two mixtures did not show any significant differences. The two mixtures had the same waterbinder ratio of 0.16, meaning that they had the same concrete mixing proportions but different fiber lengths with the same fiber content of 1.0%. This indicates that the use of hybrid steel fibers (16.5 and 19.5 mm) and short fibers (13 mm) in the HSFRC had approximately the same effect on the compressive strength and elastic modulus of the HSFRC.
The mean compressive strength and elastic modulus of the F15SL130, F15H(BFS), and F15H mixtures are shown in Table
Test results of the compressive strength and elastic modulus
Mixture  Batch  Number of specimens  Fiber content 
Compressive strength 
Elastic modulus 

F15SL130  1  4  1.5  188.2  45,930 
2  4  1.5  183.6  45,849  
3  4  1.5  193.0  46,924  
4  4  1.5  189.2  45,281  
Mean  188.5  45,996  


F15H(BFS)  1  4  1.5  169.2  48,334 
2  5  1.5  132.5  39,123  
Mean  148.8  43,217  


F15H  1  3  1.5  182.9  — 
2  3  1.5  179.9  —  
3  3  1.5  181.9  —  
4  3  1.5  177.8  —  
5  3  1.5  178.6  —  
6  3  1.5  186.1  —  
Mean  181.2  — 
The F15SL130 mixture contained 1.5% of steel fibers with a length of only 13 mm, and the F15H mixture contained hybrid steel fibers with lengths of 16.5 and 19.5 mm. The compressive strength of the F15SL130 mixture with short fibers was not significantly different from that of the F15H mixture with hybrid steel fibers, indicating that the compressive strength of the HSFRC including hybrid steel fibers with lengths of 16.5 and 19.5 mm and the HSFRC containing a single type of steel fiber with a length of only 13 mm was approximately equal. These characteristics are also similar to the compressive strength characteristics of the F10 series mixtures containing 1.0% of steel fibers, as previously explained.
The F15H(BFS) mixture contained 1.5% hybrid steel fibers with lengths of 16.5 and 19.5 mm and the blastfurnace slag. The compressive strength of the F15H(BFS) mixture was less than that of the F15H mixture, indicating that the incorporation of blastfurnace slag adversely affected the strength of the HSFRC.
The mean compressive strength and elastic modulus of the F20SL130 and F20H mixtures are shown in Table
Test results of the compressive strength and elastic modulus
Mixture  Batch  Number of specimens  Fiber content 
Compressive strength 
Elastic modulus 

F20SL130  1  3  2.0  158.2  46,880 
2  3  2.0  188.4  45,894  
3  6  2.0  177.9  47,650  
4  6  2.0  175.5  49,212  
5  5  2.0  180.1  46,883  
6  4  2.0  185.5  47,781  
7  4  2.0  189.8  45,509  
8  4  2.0  188.5  46,294  
9  4  2.0  182.3  45,348  
Mean  180.7  47,016  


F20H  1  3  2.0  192.0  49,465 
2  3  2.0  192.0  43,883  
3  4  2.0  177.5  40,806  
4  4  2.0  183.5  45,009  
5  4  2.0  166.5  43,537  
6  3  2.0  185.7  44,267  
Mean  181.9  44,267 
Therefore, the mean compressive strength of the HSFRC with the hybrid steel fibers with lengths of 16.5 and 19.5 mm was not overall significantly different from that of the HSFRC with a single type of steel fiber with a length of 13 mm.
The results of the compressive strength tests on specimens with various steel fiber contents indicated that the incorporation of steel fiber content based on the concrete volume of less than 1.5% had a significant influence on the compressive strength of the HSFRC.
For the mixture with a single type of steel fiber, the F10SL130, F15SL130, and F20SL130 mixtures contained 1.0, 1.5, and 2.0% steel fibers based on the volume of concrete with a length of 13 mm, respectively. The compressive strength of each mixture was 173.0, 188.5, and 180.7 MPa, respectively. The compressive strength of the F15SL130 and F20SL130 specimens was 9.0 and 4.5% greater, respectively, than that of the F10SL130 specimen. The elastic modulus value of the F10SL130, F15SL130, and F20SL130 specimens was 44,145, 45,996, and 47,016 MPa, respectively. The elastic modulus of the F15SL130 and F20SL130 specimens was 4.2 and 6.5% greater, respectively, than that of the F10SL130 specimen.
For the mixture with hybrid steel fibers, the F10H, F15H, and F20H mixtures contained 1.0, 1.5, and 2.0% hybrid steel fibers based on the concrete volume, respectively. The compressive strength of each mixture was 174.0, 181.2, and 181.9 MPa, respectively. The compressive strength of the F15H and F20H specimens increased by 4.1% and 4.5%, respectively, compared with the F10H mixture. However, the compressive strength of the F20H mixture was similar to that of the F15H mixture. The elastic modulus of the F20H specimen was 1.6% greater than that of the F10H specimen.
The elastic modulus was estimated by using a predictive equation from a design code and other equations that were suggested by researchers. The American Concrete Institute (ACI) 31811 equation [
The experimental results were compared with the predicted results of the elastic modulus by using the equations proposed in an earlier work and in this study. The elastic modulus predictions
Prediction of the elastic modulus at various compressive strengths.
Comparison of the test results and prediction of the elastic modulus.
Source  Equation  Range of compressive strengths 
 

Mean 
S.D. 
C.O.V 

ACI 31811 

—  1.38  1.16  0.84 
ACI 363 


1.13  0.82  0.73 
Graybeal 


1.13  0.95  0.84 
Kakizaki 


1.07  0.90  0.84 
This study 


0.99  0.83  0.84 
The mean
The tensile strength of concrete can be determined by either a direct tensile test or a crack mouth opening displacement (CMOD) measurement method for a notched specimen. In the direct tensile test method, eccentricity at both ends of a specimen can cause variability in the experimental tensile strength results. Fracture mechanics factors such as toughness, energy release rate, and tensile strength of a steel fiberreinforced concrete can be obtained by using CMOD measurement results of notched specimens.
RILEM [
LoadCMOD test setup.
The comparison of the loadCMOD measurement of the F10SL130 and F10H mixtures is shown in Figure
Comparison of the loadCMOD curves of the F10 series mixtures. (a) F20SL130 mixture. (b) F20H mixture.
Comparison of the loadCMOD curves of the F15 series mixtures. (a) F10SL130 mixture. (b) F10H mixture.
Comparison of the loadCMOD curves of the F20 series mixtures. (a) F15SL130 mixture. (b) F15H mixture.
The variation of the maximum loads in each loadCMOD curve for the F10SL130, F15SL130, and F20SL130 mixtures with a single type of steel fiber was small. The variation of the maximum loads in each loadCMOD curve for the F10H mixture with 1.0% hybrid steel fibers based on volume was also small. However, the variation of the maximum loads in each loadCMOD curve for the F15H and F20H mixtures with 1.5 and 2.0% hybrid steel fibers based on volume was greater than that of the maximum loads in each loadCMOD curve for the F10H mixture. This result indicates that the combination of two types of steel fibers with more than 1.5% steel fiber content by volume might cause variations in the maximum loads during the CMOD test, which would accordingly influence the tensile strength of the UHFRC.
After the maximum load was reached, the load tended to decrease. The curves of the F15SL130 specimens decreased more sharply than those of the F15H specimens, indicating that the longer hybrid fibers in the F15H specimens became more active in crack bridging after the maximum load was reached. The short fibers in the F15SL130 specimens were pulled out earlier as the crack width increased.
The mean value of the maximum load in the CMOD test for the F10SL130, F10SL195, and F10H mixtures was 45.1, 34.0, and 47.8 kN, respectively, as shown in Table
Comparison of the test results and estimation from the regression analysis of the tensile strength
Mixture  Batch  Number of specimens  Number of specimens successfully evaluated in the inverse analysis  Maximum load 
Test result of the tensile strength 
Prediction of the tensile strength 

F10SL130  1  5  4  48.8  10.07  10.31 
2  3  1  47.3  10.13  10.00  
3  5  2  43.8  8.86  9.25  
4  6  2  42.0  9.21  8.87  
Mean  45.1  9.61  9.53  


F10SL195  1  4  3  46.6  9.65  9.84 
2  4  3  31.7  6.12  6.69  
3  4  2  30.2  6.22  6.39  
4  4  2  28.7  6.31  6.05  
5  3  2  32.6  7.07  6.88  
Mean  34.0  7.21  7.18  


F10H  1  5  2  47.8  9.85  10.09 
Mean  47.8  9.85  10.09 
Comparison of the test results and estimation from the regression analysis of the tensile strength
Mixture  Batch  Number of specimens  Number of specimens successfully evaluated in the inverse analysis  Maximum load 
Test result of the tensile strength 
Prediction of the tensile strength 

F15SL130  1  5  3  63.6  14.24  13.43 
2  5  4  64.8  13.86  13.69  
3  6  4  64.3  14.22  13.59  
4  5  3  66.6  14.49  14.07  
Mean  64.8  14.18  13.69  


F15H(BFS)  1  4  2  36.3  8.65  7.66 
2  4  2  34.7  9.48  7.32  
Mean  35.5  9.07  7.49  


F15H  1  6  3  55.7  11.65  11.76 
2  2  1  44.5  6.42  9.39  
3  6  2  40.9  7.35  8.65  
4  6  2  26.7  5.44  5.63  
5  5  1  25.1  5.94  5.29  
6  5  2  33.5  6.22  7.06  
Mean  37.4  7.76  7.89 
Comparison of the test results and estimation from the regression analysis of the tensile strength
Mixture  Batch  Number of specimens  Number of specimens successfully evaluated in the inverse analysis  Maximum load 
Test result of the tensile strength 
Prediction of the tensile strength 

F20SL130  1  3  —  69.7  —  14.71 
2  4  3  60.0  12.73  12.67  
3  4  1  62.5  12.90  13.2  
4  4  3  63.3  13.10  13.36  
5  4  1  61.3  8.90  12.94  
6  4  2  72.0  15.00  15.21  
7  6  3  74.7  17.29  15.77  
8  6  4  79.7  17.15  16.83  
9  5  2  73.4  16.86  15.5  
Mean  67.2  14.92  14.18  


F20H  1  6  2  89.0  18.80  18.8 
2  3  1  70.1  14.69  14.8  
3  5  4  71.9  15.36  15.18  
4  6  2  62.6  13.38  13.21  
5  6  1  61.5  13.79  12.98  
6  6  4  62.3  13.58  13.16  
Mean  69.4  14.90  14.66 
In this study, an inverse analysis was performed using the loadCMOD curve obtained in the experiment to determine the tensile stressCMOD relationship. A virtual crack model from Hillerborg et al. [
The tensile strength of the HSFRC was evaluated from the tensile stressCMOD relationship. The tensile strength of each mixture group is shown in Tables
The number of specimens that were successfully evaluated in the inverse analysis of the F10SL130, F10SL195, and F10H mixtures was 9, 12, and 2, respectively, and the mean tensile strength was 9.61, 7.21, and 9.85 MPa, respectively. The tensile strength of the F10SL195 mixture containing steel fibers with a length of 19.5 mm was less than that of the F10SL130 mixture containing steel fibers with a length of 13.0 mm. The tensile strength of the F10H specimens was almost the same as that of the F10SL130 specimens but 36.6% greater than that of the F10SL195 specimens. The experimental results showed that the use of 16.5 and 19.5 mm hybrid steel fibers affected the tensile strength of the HSFRC as much as the use of a single type of steel fiber with a length of only 13 mm. However, the orientation and dispersion of using the 19.5 mm singletype steel fibers in the HSFRC were less advantageous than those of using the 13.0 mm singletype steel fiber, resulting in a decrease in the tensile strength of the HSFRC.
The numbers of specimens that were successfully evaluated in the inverse analysis of the F15SL130, F15H(BFS), and F15H mixtures with a steel fiber content of 1.5% were 14, 4, and 11, respectively, and these mixtures had mean tensile strength of 14.18, 9.07, and 7.76 MPa, respectively. The tensile strength of the F15H specimens was reduced by 45.3% compared to that of the F15SL130 specimens.
In addition, the numbers of specimens that were successfully evaluated in the inverse analysis of the F20SL130 and F20H mixtures with a 2.0% steel fiber content were 19 and 14, respectively, and these mixtures had mean tensile strength of 14.92 and 14.90 MPa, respectively. The experimental results showed that the tensile strength of the HSFRC with 16.5 and 19.5 mm hybrid steel fibers was similar to that of the HSFRC using only 13.0 mm steel fibers. As discussed in the comparison of the F10SL130 and F10H mixtures, the experimental results showed that in the case of the HSFRC containing a 2% steel fiber content based on the volume of concrete, the use of hybrid steel fibers with lengths of 16.5 and 19.5 mm affected the tensile strength of the HSFRC as much as the use of a single type of steel fiber with a length of only 13 mm.
Overall, the tensile strength obtained from the maximum load of the CMOD test and the inverse analysis of the CMOD test results of the F10SL195 and F15H(BFS) mixtures was low because the blastfurnace slag binder decreased the tensile strength of the concrete, as mentioned previously.
The tensile strength of HSFRC was affected by the steel fiber content. The tensile strength of the F10SL130, F15SL130, and F20SL130 mixtures was 9.61, 14.18, and 14.92 MPa, respectively. The tensile strength of the F15SL130 and F20SL130 specimens was 47.6% and 55.3% greater, respectively, than that of the F10SL130 specimen. The tensile strength of the specimens using the hybrid steel fibers was also affected by the steel fiber content. The tensile strength of the F20H specimen was 51.3% higher than that of the F10H specimen.
Since the tensile strength could not be obtained when the iterative calculation did not converge to a solution during the inverse analysis, determination of the tensile strength of each specimen with the inverse analysis using the loadCMOD relationship curve was limited. A regression analysis was performed with the maximum load from the loadCMOD test results, and the tensile strength obtained through the inverse analysis. The regression analysis was used to predict the tensile strength of the HSFRC. The predicted tensile strength from the regression analysis is as follows:
The relationship between the maximum load in the loadCMOD curve and the tensile strength of the specimens that were successfully determined in the inverse analysis using the CMOD experiment measurements is shown in Figure
Comparison of the maximum loads in the loadCMOD curve with the tensile strength.
The tensile strength predicted using (
The tensile strength could not be directly obtained from the CMOD test results when the inverse analysis failed to obtain a solution. When tensile strength cannot be directly obtained through an inverse analysis, the tensile strength can be accurately predicted by using the formula proposed in this study without inverse analysis.
Several equations have been proposed for predicting the tensile strength using the compressive strength of concrete [
Graybeal [
The tensile strength of HSFRC is affected by the steel fiber content. Therefore, in this study, a prediction equation of the tensile strength is proposed by considering the compressive strength of the concrete as well as the steel fiber content as dependent variables. The proposed equation is as follows:
The tensile strength predicted from Graybeal’s equation and the tensile strength predicted from the proposed equation in this study are shown in Figure
Prediction of the tensile strength by using the compressive strength and steel fiber content of the HSFRC.
A comparison of the test results of tensile strength and the predicted tensile strength from the proposed equation in this study is shown in Figure
Comparison of the test results and prediction of the tensile strength.
The effect of steel fiber content on the compressive strength, elastic modulus, and tensile strength of HSFRC was investigated, and a correlation equation was proposed. Figure
Mechanical properties according to the fiber contents. (a) Compressive strength. (b) Elastic modulus. (c) Tensile strength.
The compressive strength of the F10SL130, F10SL195, and F10H mixtures with a steel fiber content of 1.0% is between 121.6 and 181.2 MPa, the elastic moduli are between 39,081 and 45,561 MPa, and the tensile strength is between 6.12 and 10.13 MPa. The compressive strength of the F15SL130, F15H(BFS), and F15H mixtures containing 1.5% steel fiber is between 132.5 and 188.5 MPa, the elastic moduli are between 39,123 and 48,334 MPa, and the tensile strength is between 5.44 and 14.49 MPa. The compressive strength of the F20SL130 and F20H mixtures with a steel fiber content of 2.0% is between 158.2 and 192.5 MPa, the elastic moduli are between 40,806 and 49,465 MPa, and the tensile strength is between 12.67 and 18.80 MPa.
In addition, the maximum values of the compressive strength, elastic modulus, and tensile strength of the F20SL130 and F20H mixtures with a steel fiber content of 2.0% are 192.0 MPa, 49,465 MPa, and 18.80 MPa, respectively. The minimum values of compressive strength, elastic modulus, and tensile strength are 158.2 MPa, 40,806 MPa, and 12.67 MPa, respectively.
The compressive strength, elastic modulus, and tensile strength of the F10SL195 and F15H(BFS) mixtures that include blastfurnace slag as the binder are smaller than those of the other mixtures. Regression analysis was performed to evaluate the compressive strength, elastic modulus, and tensile strength prediction formulas according to the steel fiber content based on the volume of concrete as follows:
In this study, the compressive strength, elastic modulus, CMOD, and tensile strength of the HSFRC fabricated with a single type of steel fiber and the HSFRC fabricated with hybrid steel fibers were investigated. The main experimental results are as follows:
In this study, steel fiber contents of 1.0, 1.5, and 2.0% were used to fabricate HSFRC. The compressive strength, tensile strength, and elastic modulus of the HSFRC increased with the steel fiber content. The compressive strength of the F15SL130 and F20SL130 specimens was 9.0 and 4.5% greater, respectively, than that of the F10SL130 specimen. The elastic modulus of the F15SL130 and F20SL130 specimens was 4.2 and 6.5% greater, respectively, than that of the F10SL130 specimen. The tensile strength of the F15SL130 and F20SL130 specimens was 47.6 and 55.3% greater, respectively, than that of the F10SL130 specimen. The tensile strength of the HSFRC was most affected by the steel fiber content.
The compressive strength, elastic modulus and tensile strength of the HSFRC containing steel fibers with a length of only 19 mm were measured and were found to be smaller than those of the mixtures containing steel fibers with a length of only 13.5 mm. The compressive strength of the F10SL130 and F10SL195 mixtures was 173.0 and 133.7 MPa, respectively, and the elastic modulus of the two mixtures was 44145 and 40147 MPa, respectively. In addition, the tensile strength of the two mixtures was 9.61 and 7.21 MPa, respectively. The different waterbinder ratios of the two mixtures might be an important influential factor in the reduction of the compressive strength, elastic modulus, and tensile strength. In addition, the dispersion of steel fibers might affect these HSFRC mechanical properties. The decrease in compressive strength, elastic modulus, and tensile strength could result from the decrease in the dispersion of the steel fibers in the HSFRC due to the use of longer steel fibers.
The experimental results of the compressive and tensile strengths of the HSFRC with hybrid steel fibers with lengths of 16.5 and 19.5 mm were similar to those of the HSFRC containing a single type of steel fiber with a length of only 13 mm. The mean compressive strength of the F10SL130, F15SL130, and F20SL130 mixtures containing a single type of steel fiber with a length of only 13 mm was 173.0, 188.5, and 180.7 MPa, respectively, and that of the F10H, F15H, and F20H mixtures containing hybrid steel fibers was 174.0, 181.2, and 181.9 MPa, respectively. In addition, the mean tensile strength of the F10SL130 and F20SL130 mixtures was 9.61 and 14.92 MPa, respectively, and that of the F10H and F20H mixtures was 9.85 and 14.90 MPa, respectively. Therefore, in this study, the use of hybrid steel fibers was advantageous for ensuring the strength of HSFRC.
A prediction equation that considers the compressive strength of HSFRC was proposed to predict the HSFRC elastic modulus. The equation suggested in this study accurately predicted the experimental results of the elastic modulus.
An equation to predict the tensile strength of HSFRC was suggested using the maximum load obtained from the loadCMOD relationship. The prediction of tensile strength by using the proposed equation and the test results were approximately equal.
An extensive experimental investigation of the mechanical properties of highstrength fiberreinforced concrete (HSFRC) was carried out in this study.
The test parameters included a single type of steel fiber and hybrid steel fibers with lengths of 13, 16.5, and 19.5 mm and steel fiber contents of 1.0, 1.5, and 2.0% based on the volume of HSFRC.
The mechanical properties of the HSFRC with hybrid steel fibers were similar to those of the HSFRC with a single length of steel fiber.
Equations for predicting the elastic modulus and tensile strength of HSFRC were proposed based on the test results, and the predictions closely agreed with the experimental results.
The authors declare that they have no conflicts of interest.
This research was supported by a grant (13SCIPA02) from the Smart Civil Infrastructure Research Program funded by the Ministry of Land, Infrastructure and Transport (MOLIT) of the Korean government and the Korea Agency for Infrastructure Technology Advancement (KAIA).