Bone ash reinforced geopolymer composites

Potassium-based, geopolymer composites were made with BASF(R) metakaolin and Mymensingh clay-derived metakaolin from Bangladesh. Since the natural Mymensingh clay contained 40 wt.% quartz, this same amount of quartz particulates was added to the BASF(R) metakaolin to make a synthetic analog of the natural calcined clay. By analogy with bone china, bone ash or calcined hydroxyapatite (5CaO center dot 3P(2)O(5) or HA) particles, having a Ca: P ratio of 3.3:1, were added to make the three types of geopolymer-based composites described above. For less refractory particulate additions, dicalcium phosphate (DCP) (2CaO center dot P2O5 or DCP) particles, having a Ca: P ratio of 2:1, were also added to another set of geopolymers. The ambient temperature compressive and flexural strengths were measured for all of the geopolymer composites. The HA or DCP reinforced geopolymer composites were fabricated and heat-treated to 1150 degrees C/1 h, after which they were converted to their mineralogical analogs. Their mechanical properties of compressive and 3-point flexural strengths were again measured. Flexural strengths of 22.42 +/- 11.0 MPa and 31.97 +/- 8.3 MPa were measured in 1 x 1 x 10 cm(3) heat-treated geopolymer bars reinforced with 10 wt.% of DCP and in geopolymer reinforced with 10 wt.% DCP +40 wt.% quartz additions, respectively. Significant improvements to ambient temperature properties were observed due to the self-healing effect of the flowing amorphous DCP, whose presence was verified by SEM. The geopolymer samples exhibited reduced water absorption (WA) (on a percentage dry weight basis) of within 0.03-0.5% after being heated at 1100celcius/1 h and 1125celcius/1 h, as compared with those at room temperature, which varied between 2.56% and 7.89%.

Automated summary

Potassium-based geopolymer composites were fabricated using different materials and improvements were made to their mechanical properties and high-temperature resistance by adding various particles. Results showed that the addition of bone ash or DCP significantly enhanced the strength of the composites, with DCP exhibiting a self-healing effect and reducing water absorption rate.