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Test matrix
| Group | Concrete mixture | Specimens ID | RAP aggregate | Exposure to temperature | Strengthening | No. of specimens |
|---|---|---|---|---|---|---|
| Group “1” | A0 | A0-R | 0% | 26°C | – | 3 |
| A0-300 | 300° C | 3 | ||||
| A0-S-R | 26°C | CFRP | 3 | |||
| A0-S-300 | 300°C | 3 | ||||
| Group “2” | A25 | A25-R | 25% | 26°C | – | 3 |
| A25-300 | 300°C | 3 | ||||
| A25-S-R | 26°C | CFRP | 3 | |||
| A25-S-300 | 300°C | 3 | ||||
| Group “3” | A50 | A50-R | 50% | 26°C | – | 3 |
| A50-300 | 300°C | 3 | ||||
| A50-S-R | 26°C | CFRP | 3 | |||
| A50-S-300 | 300°C | 3 | ||||
| Total no. of specimens | 36 | |||||
Properties of the CFRP sheet and epoxy adhesive
| Material | A0 mixture | A25 mixture | A50 mixture | |
|---|---|---|---|---|
| MK | 350 | 350 | 350 | |
| Alkaline solutions | NaOH | 110.04 | 110.04 | 110.04 |
| Na2SiO3 | 196.98 | 196.98 | 196.98 | |
| Water | 5.74 | 5.74 | 5.74 | |
| Fine aggregate | White sand | 419 | 419 | 419 |
| Crushed limestone | 180 | 180 | 180 | |
| Coarse aggregate | Limestone | 1,272 | 954 | 636 |
| RAP | 0 | 334.9 | 669.7 | |
Summary of the test results
| Specimen ID | Average compressive strength | COV | Initial stiffness | Toughness index | |||
|---|---|---|---|---|---|---|---|
| (MPa) | Relative variation * | (N/mm) | Relative variation * | % | Relative variation * | ||
| A0-R | 58.20 | – | 9.69 | 19562.6 | – | 1.55 | – |
| A0-300 | 28.46 | -51.1% | 12.98 | 3265.6 | -83.3% | 1.51 | -2.5% |
| A0-S-R | 109.24 | +87.7% | 4.29 | 26563.4 | +35.8% | 1.06 | -31.9% |
| A0-S-300 | 92.43 | +58.8% | 1.65 | 3409.2 | -82.6% | 1.01 | -34.8% |
| A25-R | 35.46 | – | 7.16 | 17900.7 | – | 1.73 | – |
| A25-300 | 22.61 | -36.2% | 13.62 | 2540.9 | -85.8% | 1.52 | -11.7% |
| A25-S-R | 88.50 | +149.6% | 3.43 | 16389.2 | -8.4% | 1.04 | -39.9% |
| A25-S-300 | 65.79 | +85.5% | 2.66 | 2501.5 | -86.0% | 1.01 | -41.3% |
| A50-R | 19.31 | – | 15.39 | 13431.9 | – | 2.00 | – |
| A50-300 | 18.73 | -3.0% | 15.27 | 2019.7 | -85.0% | 1.86 | -7.1% |
| A50-S-R | 90.51 | +368.8% | 5.90 | 9028.6 | -32.8% | 1.03 | -48.2% |
| A50-S-300 | 49.02 | +153.9% | 3.06 | 2152.2 | -84.0% | 1.02 | -49.0% |
Chemical analysis of MK (% weight)
| Composition | SiO2 | Fe2O3 | Al2O3 | Na2O | CaO | SO3 | TiO2 | K2O | MgO | P2O5 | Others |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Value (%) | 50.995 | 2.114 | 42.631 | 0.284 | 1.287 | 0.439 | 1.713 | 0.337 | 0.127 | 0.051 | 0.022 |