Properties of hydroxyapatite based geopolymer synthesized from bituminous fly ash

This research studied the engineering properties of hydroxyapatite based on fly ashgeopolymer
as a biomaterial. The ratio of Na2O/SiO2 and K2O/SiO2 at 0.15 0.20 0.25 0.30 by
mole, 2.5 5.0 7.5, 10 wt.% of calcium phosphate and heat treatment at 500°C, 600°C and 700°C
for 2 hours were used to studied changed of compressive strength and crystalline phase in
samples. The results observed highest 28-days compressive strength of 21.99 and 19.14 MPa for
0.20 by mole of Na2O/SiO2 and 0.15 by mole of K2O/SiO2, respectively. When calcium
phosphate (CP) was added in fly ash-geopolymer, the optimum ratio of CP was found in 2.5
wt.% that have unconfined compressive strength (UCS) of 19.03 and 13.60 MPa for NaOH and
KOH activator. After heat treatment of geopolymer at 500°C, the maximum compressive
strength at 9.09 MPa and 22.76 MPa for each activator was obtained. Finally, the XRD resulted
show hydroxyapatite, mullite quartz and sodium aluminum silicate peaks in both fly ashgeopolymer
with NaOH and KOH and 2.5% CP.