1 Introduction
2 Experimental Program
2.1 Materials
2.1.1 Cement
Item | CaO | SiO2 | Al2O3 | CaSO4 | Fe2O3 | MgO | Sulphur | Alcalies | Total (%) |
---|---|---|---|---|---|---|---|---|---|
Percentage (%) | 62 | 22 | 5 | 4 | 3 | 2 | 1 | 1 | 100 |
2.1.2 Sawdust and Wooden Plates
Properties | SD | Fine aggregate (sand) |
---|---|---|
Average particle size | 500 μm | 4.95 mm |
Fineness Modulus | 5.01 | 7.26 |
Specific gravity | 2.12 | 2.50 |
Bulk density | 421.5 kg/m3 | 1302 kg/m3 |
Water absorption | 19.5% | 0.8% |
2.1.3 Aggregate
2.1.4 Reinforcing Steel Rebars
Properties | Diameter of rebar | |
---|---|---|
Ø8 mm | Ø10 mm | |
Yield stress (σy) | 240 MPa | 520 MPa |
Strain at yield stress (εy) | 1.2‰ | 2.25‰ |
Ultimate stress (σu) | 380 MPa | 620 MPa |
Strain at ultimate stress (εu) | 22‰ | 20‰ |
2.2 Specimen Preparation and Instrumentation
Specimen ID | Unit | Water | Cement | Aggregate | SD | |
---|---|---|---|---|---|---|
Coarse | Fine | |||||
NC | Weight (kg) | 240 | 400 | 1300 | 650 | 0 |
SDC | Weight (kg) | 240 | 400 | 1300 | 552.5 | 10.9 |
2.3 Testing Methodology
Specimen ID | Concrete mix | Strengthening | Strengthening type |
---|---|---|---|
NC-1 | NC | None | None |
SDC-1 | SDC | None | None |
SDC-E | SDC | Yes | Wooden plate fixed by epoxy resin (see Fig. 4b) |
SDC-2A | SDC | Yes | Wooden plate fixed by epoxy resin and two steel angles (see Fig. 4c) |
SDC-11A | SDC | Yes | Wooden plate fixed by epoxy resin and eleven steel angles (see Fig. 4d) |
2.4 Strengthening Schemes
Material | Manufacturer | Color | Preparation method |
---|---|---|---|
Sikadur 330 | Sika | Grey | Mixing a two-component (an epoxy-based resin) and putting it on the RC beam and the wood strengthening plate surfaces |
3 Results and Discussion
3.1 Workability
Mechanical properties | NC | Average | STDV | SDC | Average | STDV | ||||
---|---|---|---|---|---|---|---|---|---|---|
Sample (1) | Sample (2) | Sample (3) | Sample (1) | Sample (2) | Sample (3) | |||||
Slump value (mm) | 21 | 19 | 20 | 20 | 1 | 10 | 11 | 10 | 10 | 0.58 |
Compressive stress (MPa) | 29 | 32 | 31 | 31 | 1.5 | 17 | 20 | 20 | 19 | 1.7 |
Splitting tensile stress (MPa) | 5 | 4 | 4 | 4 | 0.6 | 2 | 2 | 3 | 2 | 0.6 |
3.2 Compressive Strength
3.3 Splitting Tensile Strength
3.4 Failure Modes and Crack Pattern
Specimen ID | Shear cracks | Flexural cracks | Concrete crushing |
---|---|---|---|
NC-1 | Fewer, narrow, short | Numerous flexural crack | None |
SDC-1 | Fewer, narrow, short | Major and narrow flexural cracks | Crushing at the compression zone between load points |
SDC-E | Fewer, narrow, short | Fewer, narrow, short | Close to the left support, separation occurred with a layer of concrete on the wooden plate |
SDC-2A | Significant diagonal cracks close to the left/right support | Fewer, narrow, short | Separation of the concrete surrounding the steel angle and debonding of the wooden plate edge on the left/right support |
SDC-11A |
3.5 Load–Displacement/Strains Characteristics
3.6 Ultimate Load Capacity
Specimen ID | NC-1 | SDC-1 | SDC-E | SDC-2A | SDC-11A |
---|---|---|---|---|---|
Max. deflection Δu (mm) | 26.89 | 24.19 | 16.51 | 26.92 | 16.01 |
DF = Δu/Δu (NC-1 control) | – | 0.90 | 0.61 | 1.00 | 0.60 |
Ultimate load Pu (kN) | 64.62 | 62.12 | 64.26 | 77.47 | 69.62 |
SF = Pu/Pu (NC-1 control) | – | 0.96 | 0.99 | 1.20 | 1.08 |
PF = DF*SF | – | 0.86 | 0.60 | 1.20 | 0.65 |
3.7 Effectiveness of Strengthening Scheme
4 Comparison of Current Research Findings with Previous Studies
References | ID | Cement (kg/m3) | Aggregate | SD | Water | Compressive strength, C (MPa) | Tensile strength, T (MPa) | C/T | ||
---|---|---|---|---|---|---|---|---|---|---|
Coarse (kg/m3) | Fine (kg/m3) | Weight (kg/m3) | Ratio by volume | |||||||
Siddique et al. (2020) | CA | 394 | 970 | 818 | 0 | 0 | 197 | 28 | 2.9 | 9.7 |
AW5 | 777 | 41 | 5 | 26 | 2.8 | 9.3 | ||||
AW10 | 736 | 82 | 10 | 20 | 2.0 | 10 | ||||
AW15 | 695 | 123 | 15 | 14 | 1.7 | 8.2 | ||||
AW20 | 654 | 164 | 20 | 10 | 1.3 | 7.7 | ||||
Ahmed et al. (2018) | NWC | 416 | 1041 | 625 | 0 | 0 | 208 | 38.8 | Not provided | Not provided |
05SD | 594 | 5.25 | 5 | 37.8 | ||||||
10SD | 562 | 10.50 | 10 | 36 | ||||||
15SD | 531 | 15.75 | 15 | 34.2 | ||||||
Dias et al. (2022) | REF | 400 | 1141 | 690 | 0 | 0 | 162 | 64 | Not provided | Not provided |
SD5 | 598 | 60 | 5 | 63 | ||||||
SD10 | 507 | 121 | 10 | 59 | ||||||
SD15 | 415 | 181 | 15 | 58 | ||||||
Batool et al. (2021) | SD0 | 420 | 1260 | 840 | 0 | 0 | 189 | 27 | 2.5 | 10.8 |
SD10 | 756 | 84 | 10 | 23 | 2.4 | 9.6 | ||||
SD20 | 672 | 168 | 20 | 18 | 1.7 | 10.6 | ||||
SD30 | 588 | 252 | 30 | 7 | 0.8 | 8.8 | ||||
SD40 | 504 | 336 | 40 | 5.5 | 0.5 | 11 | ||||
SD50 | 420 | 420 | 50 | 3.5 | 0.4 | 8.8 | ||||
SD60 | 336 | 504 | 60 | 1.9 | 0.3 | 6.3 | ||||
Current study | NC | 400 | 1300 | 650 | 0 | 0 | 240 | 31 | 4 | 7.8 |
SDC | 400 | 1300 | 552.5 | 10.9 | 15 | 240 | 19 | 2 | 9.5 |