1 Introduction
2 Research methodology
2.1 Materials
2.2 Sample preparation
2.3 Methods
Abbreviation for sample | Sample-description | Solid layer | Foamed layer | |||
---|---|---|---|---|---|---|
MKF | Foamed GP based on metakaolin | 50% MK | 1% flax | 75% MK | 1% flax | 2% H\(_{2}\)O\(_{2}\) |
50% sand | fibers | 25% sand | fibers | |||
FAF | Foamed GP based on fly ash | 50% FA | 1% flax | 85% FA | 1% flax | 2% H\(_{2}\)O\(_{2}\) |
50% sand | fibers | 15% sand | fibers | |||
MKS | Foamed GP based on metakaolin | 50% MK | 1% flax | NA | NA | NA |
50% sand | fibers | |||||
FAS | Solid GP based on fly ash | 50% FA | 1% flax | NA | NA | NA |
50% sand | fibers |
3 Results and discussion
3.1 Mechanical properties
Sample | Compressive strength | Flexural strength | ||
---|---|---|---|---|
MKS | 42.9 MPa | ± 9.4 | 7.2 MPa | ± 0.2 |
FAS | 75.4 MPa | ± 15.4 | 8.2 MPa | ± 0.8 |
MKF | 6.8 MPa | ± 1.5 | 0.9 MPa | ± 0.2 |
FAF | 5.9 MPa | ± 1.5 | 1.6 MPa | ± 0.2 |
3.2 Porosity measurements
Sample (type of measurements) | Total interparticle porosity [%] | Total intraparticle porosity [%] | Total porosity [%] | Theoretical porosity [%] |
---|---|---|---|---|
FAF (high pressure) | 0.3189 | 8.7024 | 9.0213 | 75.0700 |
FAF (low pressure) | 22.8754 | 0.000 | 22.8754 | 75.0700 |
MKF (high pressure) | 1.0453 | 17.1929 | 18.2382 | 82.3450 |
MKF (low pressure) | 10.3950 | 0.000 | 10.3950 | 82.3450 |
FAS (high pressure) | 0.0214 | 4.9191 | 4.9405 | 52.8500 |
FAS (low pressure) | 0.5168 | 0.000 | 0.5168 | 52.8500 |
MKS (high pressure) | 0.0282 | 4.9011 | 4.9293 | 67.2000 |
MKS (low pressure) | 0.7358 | 0.000 | 0.7358 | 67.2000 |
3.3 Water absorption
Initial weight | Weight after 12 weeks | % of initial weight | Weight after drying | % of initial weight | Water |
---|---|---|---|---|---|
0.085 | 0.129 | 152 | 0.082 | 96 | Fresh |
0.087 | 0.124 | 143 | 0.080 | 92 | Fresh |
0.089 | 0.130 | 146 | 0.087 | 98 | Fresh |
0.087 | 0.107 | 123 | 0.068 | 78 | Salt |
0.083 | 0.130 | 157 | 0.081 | 98 | Salt |
0.077 | 0.123 | 160 | 0.074 | 96 | Salt |
Initial weight | Weight after 12 weeks | % of initial weight | Weight after drying | % of initial weight | Water |
---|---|---|---|---|---|
0.088 | 0.118 | 134 | 0.085 | 97 | Fresh |
0.103 | 0.145 | 141 | 0.098 | 95 | Fresh |
0.094 | 0.134 | 143 | 0.090 | 96 | Fresh |
0.086 | 0.124 | 144 | 0.083 | 97 | Salt |
0.117 | 0.158 | 135 | 0.112 | 96 | Salt |
0.088 | 0.105 | 119 | 0.073 | 83 | Salt |
Initial Weight | Weight after 12 weeks | % of initial weight | Weight after drying | % of initial weight | Water |
---|---|---|---|---|---|
0.226 | 0.258 | 114 | 0.228 | 101 | Fresh |
0.228 | 0.258 | 113 | 0.224 | 98 | Fresh |
0.224 | 0.252 | 113 | 0.220 | 98 | Fresh |
0.212 | 0.242 | 114 | 0.208 | 98 | Salt |
0.238 | 0.268 | 113 | 0.236 | 99 | Salt |
0.220 | 0.246 | 112 | 0.214 | 97 | Salt |
Initial weight | Weight after 12 weeks | % of initial weight | Weight after drying | % of initial weight | Water |
---|---|---|---|---|---|
0.264 | 0.280 | 106 | 0.258 | 98 | Fresh |
0.262 | 0.278 | 106 | 0.256 | 98 | Fresh |
0.250 | 0.260 | 104 | 0.236 | 94 | Fresh |
0.264 | 0.286 | 108 | 0.258 | 98 | Salt |
0.268 | 0.286 | 107 | 0.256 | 96 | Salt |
0.240 | 0.258 | 108 | 0.232 | 97 | Salt |
4 Conclusions
-
Geopolymer composites can be successfully produced with the addition of natural fibers and have good strength parameters even after long-term use (materials were tested after 360 days).
-
The composites were exposed to large amplitudes of temperature and humidity, and after 90 days showed no signs of degradation or decrease (visual observation).
-
The porosity measurements confirmed the high porosity of foamed materials and they show also significant micro-porosity of solid materials that potentially could have an influence on environmental degradation.
-
The water absorption in fresh and salt water is comparable for solid and foamed samples.
-
The water absorption for the foamed samples is significantly higher than that of the solid samples.
-
The compressive strength tests after water absorption for the foamed sample based on fly ash do not show any significant differences compared to the compressive strength provided by the control samples.