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IndexTerms-Atterberg's limit, compaction test, permeability, unconfined compressive strength, water treatment residue.

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This research synthesized the geopolymer from calcined kaolin (600°C for 2 h in a muffle furnace) using sodium hydroxide (NaOH) and potassium hydroxide (KOH) as alkali activators. Calcium phosphate (CP) and heat treatment were introduced to study their effects on the unconfined compressive strength (USC) and crystalline phases formation of kaolin-based geopolymer. Results showed that the highest USC strength at 28 days of geopolymer was obtained from 0.4 moles of Na2O/SiO2 and K2O/SiO2 and gave strength of 12.95 and 11.56 MPa, respectively. The USC of geopolymer was observed to decrease with the addition of CP. The amounts of 5 wt.% of CP gave a 28-day strength of kaolin-based geopolymer containing NaOH and KOH activators at 9.95 and 8.88 MPa, respectively. The CP-doped geopolymers were then heated at temperatures of 500, 600, and 700°C for 2 h Results indicated that heat treatment at 600°C gave the highest USC of CP-doped geopolymer containing NaOH and KOH equal to 7.61 and 4.61 MPa, respectively with the appearance of hydroxyapatite, muscovite, and quartz in the XRD diffractograms.

This research studied the engineering properties of hydroxyapatite based on fly ash-geopolymer 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 ash-geopolymer with NaOH and KOH and 2.5% CP.