1 Introduction
2 Experimental Procedure
2.1 Materials
2.1.1 Aggregates
Aggregate | Packing density (kg/m3) | Apparent density (kg/m3) | Water content (%) |
---|---|---|---|
Coarse aggregate | 1479 | 2632 | 0.3 |
Fine aggregate | 1342 | 2381 | 0.1 |
2.1.2 Fly Ash
Chemical composition | SiO2 | Al2O3 | CaO | Fe2O3 | MgO | K2O | SO3 | TiO2 | Na2O | LOIa |
---|---|---|---|---|---|---|---|---|---|---|
Fly ash (%) | 50.76 | 27.32 | 5.4 | 4.64 | 3.72 | 4.85 | 2.0 | 1.16 | 0.8 | 2.83 |
2.1.3 Alkali-Activator Solution
2.2 Specimen Preparation
2.2.1 Mixture Design
Level | Variables | ||
---|---|---|---|
A (L/FA) | B (SHC) (mol) | C (SS/SH) | |
1 | 0.40 | 8 | 2.0 |
2 | 0.44 | 10 | 2.5 |
3 | 0.48 | 12 | 3.1 |
4 | 0.52 | 14 | 4.0 |
Mix no. | Mix designation | A (L/FA) | B (SHC) (mol) | C (SS/SH) |
---|---|---|---|---|
1 | A1B1C1 | 0.40 | 8 | 2.0 |
2 | A1B2C2 | 0.40 | 10 | 2.5 |
3 | A1B3C3 | 0.40 | 12 | 3.1 |
4 | A1B4C4 | 0.40 | 14 | 4.0 |
5 | A2B1C2 | 0.44 | 8 | 2.5 |
6 | A2B2C1 | 0.44 | 10 | 2.0 |
7 | A2B3C4 | 0.44 | 12 | 4.0 |
8 | A2B4C3 | 0.44 | 14 | 3.1 |
9 | A3B1C3 | 0.48 | 8 | 3.1 |
10 | A3B2C4 | 0.48 | 10 | 4.0 |
11 | A3B3C1 | 0.48 | 12 | 2.0 |
12 | A3B4C2 | 0.48 | 14 | 2.5 |
13 | A4B1C4 | 0.52 | 8 | 4.0 |
14 | A4B2C3 | 0.52 | 10 | 3.1 |
15 | A4B3C2 | 0.52 | 12 | 2.5 |
16 | A4B4C1 | 0.52 | 14 | 2.0 |
Mix no. | CAa | Sb | FAc | SSd | SHe | Na2O/SiO2 | Si/Al |
---|---|---|---|---|---|---|---|
1 | 1212 | 544 | 460 | 122.7 | 61.3 | 0.66 | 1.81 |
2 | 1212 | 544 | 460 | 131.4 | 52.6 | 0.65 | 1.82 |
3 | 1212 | 544 | 460 | 139.1 | 44.9 | 0.63 | 1.84 |
4 | 1212 | 544 | 460 | 147.2 | 36.8 | 0.58 | 1.85 |
5 | 1201 | 539 | 460 | 142.9 | 57.2 | 0.59 | 1.85 |
6 | 1201 | 539 | 460 | 133.4 | 66.7 | 0.74 | 1.83 |
7 | 1201 | 539 | 460 | 160.1 | 40.0 | 0.55 | 1.88 |
8 | 1201 | 539 | 460 | 151.3 | 48.8 | 0.66 | 1.86 |
9 | 1186 | 533 | 460 | 166.9 | 53.9 | 0.54 | 1.89 |
10 | 1186 | 533 | 460 | 176.6 | 44.2 | 0.52 | 1.91 |
11 | 1186 | 533 | 460 | 147.2 | 73.6 | 0.80 | 1.85 |
12 | 1186 | 533 | 460 | 157.7 | 63.1 | 0.75 | 1.87 |
13 | 1174 | 527 | 460 | 191.4 | 47.8 | 0.49 | 1.94 |
14 | 1174 | 527 | 460 | 180.9 | 58.3 | 0.58 | 1.92 |
15 | 1174 | 527 | 460 | 170.9 | 68.3 | 0.70 | 1.90 |
16 | 1174 | 527 | 460 | 159.5 | 79.7 | 0.86 | 1.88 |
2.2.2 Casting and Curing of Test Specimens
2.3 Test Procedure
2.3.1 Compressive Strength Test
2.3.2 Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) Test
2.3.3 Thermogravimetric Analysis (TGA) and Derivative Thermogravimetric Analysis (DTG)
3 Test Results and Discussions
3.1 Compressive Strength
Compressive strength of FAGCs (MPa) | |||
---|---|---|---|
Mix no. | 7-day | 28-day | 480-day |
1 | 37.6 ± 0.9 | 39.5 ± 4.6 | 45.8 ± 0.7 |
2 | 52.2 ± 2.7 | 54.3 ± 1.5 | 65.5 ± 4.0 |
3 | 57.1 ± 5.4 | 60.4 ± 1.8 | 72.1 ± 5.3 |
4 | 52.3 ± 6.6 | 56.5 ± 3.4 | 73.7 ± 2.3 |
5 | 38.1 ± 1.6 | 40.7 ± 2.9 | 50.7 ± 3.2 |
6 | 61.5 ± 4.6 | 61.9 ± 5.9 | 71.0 ± 6.6 |
7 | 47.3 ± 3.3 | 49.9 ± 1.5 | 62.8 ± 4.7 |
8 | 71.1 ± 0.8 | 72.3 ± 2.1 | 80.7 ± 2.5 |
9 | 34.8 ± 1.0 | 36.8 ± 1.2 | 47.8 ± 0.9 |
10 | 34.3 ± 0.8 | 41.4 ± 2.9 | 52.6 ± 3.1 |
11 | 65.9 ± 1.8 | 70.4 ± 7.7 | 83.3 ± 0.4 |
12 | 72.6 ± 0.5 | 73.2 ± 4.3 | 88.7 ± 3.2 |
13 | 24.1 ± 0.6 | 25.7 ± 0.6 | 34.3 ± 0.4 |
14 | 36.6 ± 1.2 | 39.6 ± 0.7 | 51.5 ± 2.7 |
15 | 58.4 ± 1.5 | 61.9 ± 1.1 | 75.5 ± 1.1 |
16 | 64.6 ± 3.3 | 66.6 ± 6.3 | 84.5 ± 2.5 |
3.2 The Failure Pattern of Concrete
3.3 Microstructures
Elements | M13 (spectrum 1) | M14 (spectrum 2) | M15 (spectrum 3) | M16 (spectrum 4) | ||||
---|---|---|---|---|---|---|---|---|
Weight, % | Atom, % | Weight, % | Atom, % | Weight, % | Atom, % | Weight, % | Atom, % | |
O | 47.24 | 57.96 | 51.15 | 60.55 | 45.7 | 58.73 | 42.43 | 56.92 |
Na | 38.31 | 32.71 | 43.42 | 35.78 | 8.28 | 7.41 | 1.45 | 1.36 |
Al | 1.39 | 1.01 | 0.73 | 0.51 | 11.06 | 8.43 | 20.45 | 16.27 |
Si | 8.97 | 6.27 | 4.64 | 3.13 | 34.19 | 25.03 | 27.24 | 20.82 |
K | 4.09 | 2.05 | 0.06 | 0.03 | 0.77 | 0.4 | 8.42 | 4.62 |
Total | 100.00 | 100.00 | 100.00 | 100.00 | 100.00 | 100.00 | 100.00 | 100.00 |
Si/Al Ratio | 6.45 | 6.21 | 6.36 | 6.14 | 3.09 | 2.97 | 1.33 | 1.28 |
3.4 Thermogravimetric Analysis
4 Property Development and Optimal Mixture Design of FAGC
4.1 Mechanism of Strength Development and Failure Analysis Under Compression
4.2 Optimal Mixture Design
4.2.1 Orthogonal Analysis Principle
4.2.2 Results of Orthogonal Analysis and Optimal Mixture Design
Factors | 7-day compressive strength | 28-day compressive strength | 480-day compressive strength | ||||||
---|---|---|---|---|---|---|---|---|---|
A (L/FA) | B (SHC) | C (SS/SH) | A (L/FA) | B (SHC) | C (SS/SH) | A (L/FA) | B (SHC) | C (SS/SH) | |
K1 | 199.3 | 134.7 | 227.1 | 211.5 | 142.8 | 238.4 | 260.5 | 178.7 | 284.6 |
K2 | 218.0 | 184.7 | 218.3 | 224.8 | 197.1 | 230.0 | 265.3 | 240.6 | 280.4 |
K3 | 207.6 | 228.7 | 192.9 | 221.7 | 243.3 | 210.1 | 272.4 | 297.1 | 255.6 |
K4 | 183.8 | 260.6 | 159.9 | 193.8 | 268.6 | 173.6 | 245.8 | 327.6 | 223.4 |
K | 808.7 | 808.7 | 808.7 | 851.8 | 851.8 | 851.8 | 1044.0 | 1044.0 | 1044.0 |
R | 34.2 | 125.8 | 71.7 | 31.1 | 125.8 | 64.8 | 26.6 | 149.0 | 61.2 |
Sources of variation | 7-day compressive strength | 28-day compressive strength | ||||||
---|---|---|---|---|---|---|---|---|
SS | DF | F | P | SS | DF | F | P | |
A(L/FA) | 193.1 | 3 | 0.257 | 0.855 | 160.8 | 3 | 0.218 | 0.882 |
B(SHC) | 2133.2 | 3 | 7.964 | 0.003 | 2239.3 | 3 | 10.135 | 0.001 |
C (SS/SH) | 731.3 | 3 | 1.183 | 0.357 | 616.6 | 3 | 0.986 | 0.432 |
Error | 3.654 | 3 | 1.0 | 0.5 | 3.604 | 3 | 1.0 | 0.5 |