No abstract

In this study, calcined kaolin-white Portland cement geopolymer was investigated for use as biomaterial. Sodium hydroxide and sodium silicate were used as activators. In vitro test was performed with simulated body fluid (SBF) for bioactivity characterization. The formation of hydroxyapatite bio-layer on the 28-day soaked samples surface was tested using SEM, EDS and XRD analyses. The results showed that the morphology of hydroxyapatite was affected by the source material composition, alkali concentration and curing temperature. The calcined kaolin-white Portland cement geopolymer with relatively high compressive strength could be fabricated for use as biomaterial. The mix with 50% white Portland cement and 50% calcined kaolin had 28-day compressive strength of 59.0MPa and the hydroxyapatite bio-layer on the 28-day soaked sample surface was clearly evident.

No abstract

This paper reports that surface treatment with CaCl 2 enhances the bioactivity of a calcined kaolin geopolymer. Calcined kaolin, NaOH solution, sodium silicate solution, and heat curing were used to form geopolymer pastes. A soaked-treatment method was applied to the geopolymer samples using CaCl 2 solution as the ion exchange agent. The bioactivity of the material was determined by the simulated body fluid (SBF) in vitro testing method. Scanning electron microscope images showed a dense apatite formation on the treated geopolymer surface after SBF immersion for only 3 days. The CaCl 2 treatment promoted compressive strength and enhanced bioactivity by accelerating apatite precipitation and slowing down the rise in pH.

This study presents the effects of sodium hydroxide concentration (NH) and sodium silicate to sodium hydroxide ratio (NS/NH) on the mechanical properties and microstructure of geopolymer pastes prepared from calcined kaolin (CK) and white Portland cement (WPC). Different curing conditions viz., ambient curing, temperature curing, and moist curing were used. The results indicated the increasing NH concentration and NS/NH ratio increased the compressive strength of CK-WPC geopolymers and gave the highest compressive strength at NH concentration of 15 molar and NS/NH ratio of 1.0. Furthermore, the use of 50% WPC increased the compressive strength of geopolymer paste. The samples with ambient temperature curing showed high early compressive strength equal to that with temperature curing. For moist curing, the compressive strengths of WPC samples at the later age were continuously developed and were higher than those with ambient and temperature curings. The microstructures of geopolymer paste were tested using SEM images and pattern of XRD (X-ray diffractometer) which showed the denser paste and higher calcium compound in the CK-WPC samples than those in CK samples.

Biomaterials containing calcium phosphate ceramics have been used as bone substitute materials. In this study, the compressive strength and in vitro bioactivity tests of hydroxyapatite (HAp) from golden apple snail shell mixed with calcined kaolin (CK) were investigated for used as bone substitute materials. Mixed paste samples were cured at 23°C and 60°C for 2 days and curing continued at 23°C for 7 days. The effects of HAp:CK weight ratio on compressive strength and apatite formation in simulated body fluid (SBF) were investigated. The good compressive strength was 32.93 MPa at 25 % hydroxyapatite with 75% calcined kaolin at curing temperature of 60°C. Apatite formation was observed on sample surfaces after soaking in SBF for 28 days using SEM, EDS and XRD analyses. It was found that apatite formation took place on the surface of samples, consisting of HAp, after immersion in SBF.

No abstract