| Abstract |
A quasi-amorphous low-calcium-silicate hydraulic binder, with an overall CaO/SiO2 (C/S) molar ratio of 1.1, was produced. This cementitious material was then hydrated with aqueous solutions containing 3wt\% alkalis (either NaOH, Na2CO3 or Na2SiO3). The evolution of the hydration processes of the samples were monitored by compressive strength testing, XRD, FTIR, Si-29 and Al-27 MAS NMR, isothermal calorimetry and TGA. It was found that the nearly exclusive hydration product formed was a C-S-H phase with a semi-crystalline structure. More importantly, the paste prepared with the Na2SiO3 solution developed compressive strength values similar to those of ordinary portland cements (OPC) with faster early age kinetics. In addition, the isothermal calorimetry results indicated that these new hydraulic binders present much lower heat of hydration values compared with a traditional OPC. The results presented here open the possibility of producing cement with a compressive strength comparable to that of OPC but with lower CO2 emissions during the production process and with lower hydration heat related problems during the production of concrete structures. |
