The bioactivity of a modified Portland cement (wTC) and a phosphate-doped wTC cement (wTC-P) was studied at 37 Β°C in Dulbecco's Phosphate Buffered Saline (DPBS). The cements, prepared as disks, were analysed at different ageing times (from 1 day to 2 months) by micro-Raman and ATR/FT-IR spectroscopies. The presence of deposits on the surface of the cements and the composition changes as a function of the storage time were investigated.
The presence of an apatite deposit on the surface of both cements was already revealed after one day of ageing in DPBS. The trend of the I 965 /I 991 Raman intensity ratio indicated the formation of a meanly thicker apatite deposit on the wTC-P cement at all the investigated times. This result was confirmed by the trend of the I 1030 /I 945 IR intensity ratio calculated until 14 days of ageing. At 2 months, the thickness of the apatite deposit on wTC and wTC-P was about 200 and 500 lm, respectively, as estimated by micro-Raman spectroscopy, confirming the higher bioactivity of the phosphate-doped cement.
Vibrational techniques allowed to gain more insights into the cement transformation and the different hydration rates of the various cement component. The setting of the cement and the formation of the hydrated silicate gel (C-S-H phase) was spectroscopically monitored through the I 830 /I 945 IR intensity ratio.