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Alkali activation of a novel calcium‐silicate hydraulic binder with CaO/SiO 2 = 1.1

2018; Wiley; Volume: 101; Issue: 9 Linguagem: Inglês

10.1111/jace.15554

1551-2916

Rodrigo Lino Santos, Ricardo Bayão Horta, João R. Pereira, Teresa Nunes, Paulo Novis Rocha, R. Colaço,

Innovative concrete reinforcement materials

Abstract A quasi‐amorphous low‐calcium‐silicate hydraulic binder, with an overall CaO/SiO 2 (C/S) molar ratio of 1.1, was produced. This cementitious material was then hydrated with aqueous solutions containing 3 wt% alkalis (either Na OH , Na 2 CO 3 or Na 2 SiO 3 ). The evolution of the hydration processes of the samples were monitored by compressive strength testing, XRD , FTIR , 29 Si and 27 Al 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 Na 2 SiO 3 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 CO 2 emissions during the production process and with lower hydration heat related problems during the production of concrete structures.