Table 1.
Composition of RSF-SCC mix
| Cement CEM I 42.5R (kg/m3) | 485 | |
| Natural sand (0–2 mm) (kg/m3) | 749 | |
| Coarse aggregate (2–8 mm) (kg/m3) | 936 | |
| Superplasticizer (kg/m3) | 17 | |
| Stabilizer (kg/m3) | 1.6 | |
| Silica fume (kg/m3) | 48.5 | |
| Water (kg/m3) | 203 | |
| Steel fibres | by volume (%) | 1.0; 1.5 |
| dosage (kg/m3) | 80; 120 | |
| W/B | 0.38 | |
Table 2.
Properties of fibers from end-of-life tires
| Length [mm] | 2÷30 |
| Diameter [mm] | 0.15 ± 5% |
| Tensile strength [MPa] | ≥ 2850 |
| Aspect ratio (length/diameter) | 13 ÷ 200 |
| Longitudinal shape | irregular (curved, twisted) |
Figure 1.
Fibers from end-of-life tires – recycled steel fibers (RSF)
Figure 2.
Four-point flexural test set-up
Table 3.
Rheological tests results and compressive strength of RSF-SCC
| Vf | Slump flow test | L-box (H2/H1) | Compressive strength [MPa] | |
|---|---|---|---|---|
| SFD [mm] | T500 [s] | |||
| 0 | 740 | 1 | 1.0 | 59.62 (10%) |
| 1% | 700 | 13 | 0.85 | 58.73 (19%) |
| 1.5% | 550 | 18 | 0.69 | 63.30 (13%) |
Figure 3.
The results from the slump flow tests of SCC containing: a) Vf = 0%; b) Vf = 1.0%; c) Vf = 1.5% of RSF
Figure 4.
The RSF-SCC specimens before (a) and after (b) the flexural tests
Figure 5.
Load-deflection curves obtained in flexural tests of self-compacting concrete reinforced with the amount of RSF equal to: (a) 1.0%; (b) 1.5%
Figure 6.
Comparison of average load-deflection curves of RSF-SCC
Figure 7.
Determination of the residual and maximum flexural tensile strength from the load – deflection curve according to [26]
Figure 8.
Variation of residual strength according to the amount of RSF
Table 4.
Flexural properties of RSF-SCC
| Mix | Peak load PP (kN) | Net deflection δP (mm) | Flexural tensile strength fp (MPa) | Toughness T100,2 (Nm) | Residual flexural tensile strength at L/600 f100,0.5 (MPa | Residual flexural tensile strength at L/150 f100,2 (MPa) | Equivalent flexural tensile strength feq [MPa] |
|---|---|---|---|---|---|---|---|
| 0 | 16.87 (8%) | 0.02 (70%) | 5.06 (8) | - | - | - | - |
| 1% | 19.61 (1%) | 0.07 (84%) | 5.88 (1.4%) | 23.78 (6.4%) | 4.13 (9.9%) | 1.95 (9.6%) | 3.57 (6.45%) |
| 1.5% | 21.71 (5%) | 0.17 (85%) | 6.51 (4.9%) | 29.58 (10.1%) | 5.57 (10.6%) | 3.24 (17%) | 4.44 (10.6%) |