Table 1.
Composition of OPC and RHA
| Chemical composition (%) | OPC | RHA |
|---|---|---|
| Silicon dioxide (SiO2) | 22.0 | 77.34 |
| Aluminum oxide (Al2O3) | 5.50 | 6.92 |
| Ferric oxide (Fe2O3) | 3.50 | 4.89 |
| Calcium oxide (CaO) | 64.25 | 3.56 |
| Magnesium oxide (MgO) | 2.50 | 1.59 |
| Sulfur trioxide (SO3) | 2.90 | 0.34 |
| Sodium oxide (Na2O) | 0.20 | 1.27 |
| Potassium Oxide (K2O) | 1.00 | 2.69 |
| Loss on ignition | 0.64 | 4.81 |
| Physical properties | ||
| Specific gravity | 3.04 | 2.13 |
| Specific surface (m2/kg) | 308 | 600 |
| Compressive strength 3 days (MPa) | 20.76 | |
| 7 days | 31.89 | |
| 28 days | 39.41 | |
| 56 days | 42.52 | |
| Consistency (%) | 29.25 | |
| Initial Setting Time (min) | 110 | |
| Final Setting Time (min) | 228 |
Table 2.
Casting schedule and details of test specimens
| Test details | Specimen details | Age (days) | Total for (1 mix) | Total (5 mixes) | |||
|---|---|---|---|---|---|---|---|
| 3 | 7 | 28 | 56 | ||||
| Compressive strength | Cubes (150 × 150 x 150 mm) | 3 | 3 | 3 | 3 | 12 | 60 |
| Split cylinder test | Cylinders (150 mm high × 300 mm dia.) | 3 | 3 | 3 | 3 | 12 | 60 |
| Flexural strength test | Beams (100 × 100 × 500 mm) | - | - | 3 | - | 3 | 15 |
| Water permeability test | Cube (96.8 mm × 96.8 mm × 150 mm) | - | - | 3 | 3 | 6 | 240 (48 for each mix) |
| Cube (146.9 mm × 146.9 mm × 150 mm) | - | - | 3 | 3 | 6 | ||
| Cylinder (96.8 mm high × 150 mm diameter) | - | - | 3 | 3 | 6 | ||
| Cylinder (146.9 mm high × 150 mm diameter) | - | - | 3 | 3 | 6 | ||
Figure 1.
Gradation curve of fine aggregates
Figure 2.
Gradation curve of coarse aggregates
Figure 3.
XRD report of RHA sample
Figure 4.
SEM images of RHA sample
Table 3.
Weights of the material mix
| Mixture No: | Mixture Type | Water (kg) | OPC (kg) | Rice Husk Ash (kg) | Sand (kg) | Coarse Aggregates (kg) | Slump flow (mm) |
|---|---|---|---|---|---|---|---|
| SM1 | OPC | 33.10 | 55.17 | 0 | 111.42 | 222.86 | 95 |
| SM2 | 6% Replacement | 33.10 | 51.84 | 3.31 | 111.42 | 222.86 | 105 |
| SM3 | 12% Replacement | 33.10 | 48.55 | 6.62 | 111.42 | 222.86 | 112 |
| SM4 | 18% Replacement | 33.10 | 45.24 | 9.93 | 111.42 | 222.86 | 123 |
| SM5 | 24% Replacement | 33.10 | 41.93 | 13.24 | 111.42 | 222.86 | 135 |
| Total | 139.25 | 242.75 | 33.1 | 557.1 | 1114.3 |
Figure 5.
Replacement level versus slump of concrete
Figure 6.
Replacement level versus compressive strength at different ages
Figure 7.
Box Whisker plot for compressive strength at all ages
Table 4.
Strength Activity Index of concrete samples
| Strength Activity Index | ||||||||
|---|---|---|---|---|---|---|---|---|
| Ratio | 3 Days | 7 Days | 28 Days | 56 Days | ||||
| Compressive Strength (MPa) | S.A.I | Compressive strength (MPa) | S.A.I | Compressive strength (MPa) | S.A.I | Compressive strength (MPa) | S.A.I | |
| 0% | 3.229 | 100.0 | 6.932 | 100.0 | 13.563 | 100.0 | 23.251 | 100.0 |
| 6% | 3.380 | 104.7 | 7.535 | 108.7 | 14.640 | 107.9 | 25.404 | 109.3 |
| 12% | 3.294 | 102.0 | 6.050 | 87.3 | 13.090 | 96.5 | 21.744 | 93.5 |
| 18% | 2.885 | 89.3 | 5.813 | 83.9 | 12.056 | 88.9 | 20.022 | 86.1 |
| 24% | 2.583 | 80.0 | 5.425 | 78.3 | 11.303 | 83.3 | 17.438 | 75.0 |
Figure 8.
Rate of gain of compressive strength of concrete with age
Table 5.
Split cylinder strength activity index of concrete
| Split cylinder strength activity index | ||||||||
|---|---|---|---|---|---|---|---|---|
| Ratio | 3 Days | 7 Days | 28 Days | 56 Days | ||||
| Split cylinder strength (MPa) | S.A.I | Split cylinder strength (MPa) | S.A.I | Split cylinder strength (MPa) | S.A.I | Split cylinder strength (MPa) | S.A.I | |
| 0% | 0.953 | 100.0 | 1.179 | 100.0 | 1.891 | 100.0 | 3.358 | 100.0 |
| 6% | 1.000 | 105.0 | 1.281 | 108.7 | 2.124 | 112.3 | 3.563 | 106.1 |
| 12% | 0.863 | 90.6 | 1.014 | 86.0 | 1.275 | 67.4 | 3.049 | 90.8 |
| 18% | 0.884 | 92.8 | 0.932 | 79.1 | 1.597 | 84.4 | 2.844 | 84.7 |
| 24% | 0.836 | 87.8 | 0.891 | 75.6 | 1.329 | 70.3 | 2.570 | 76.5 |
Figure 9.
Replacement level versus split cylinder strength of concrete
Figure 10.
Box Whisker plot for Tensile strength at all ages
Figure 11.
Rate of gain of split cylinder strength of concrete with age
Figure 12.
Replacement level versus modulus of rupture of concrete
Figure 13.
Replacement level versus water permeability through concrete
Table 6.
Cost comparison between normal and blended concretes
| Items | Quantity of concrete | Quantity of cement | Quantity of RHA (6%) | Quantity of fine aggregates | Quantity of coarse aggregates | |
|---|---|---|---|---|---|---|
| Weight of materials | Raw concrete | 1 m3 (35.31 cft) 2415 kg | 8.62 cft 345 kg | --- | 15.73 cft 690 kg | 31.47 cft 1380 kg |
| Blended concrete | 1 m3 (35.31 cft) 2415 kg | 8.10 cft 324.3 kg | 1.38 cft 20.7 kg | 15.73 cft 690 kg | 31.47 cft 1380 kg | |
| Cost of materials | Raw concrete | USD 21.57/- | USD 13.80/- | --- | USD 2.0/- | USD 5.77/- |
| Blended concrete | USD 21.09/- | USD 12.97/- | USD 0.35/- | USD 2.0/- | USD 5.77/- | |
| Difference in cost | USD 0.47/- (2.2% of normal concrete) | USD 0.82/- (6% of pure cement) | --- | --- | --- |