Cements with a low clinker content: versatile use of raw materials

Abstract

A model for alkaline activation has recently been designed to develop new cementitious systems known as hybrid alkaline cements. These multi-component systems contain a high percentage of mineral additions (fly ashes, slags (BFS), metakaolin (MK), bentonites (BT) …), low proportions (<30%) of Portland clinker and moderately alkaline solid activators. This study explored the mechanical performance of two sodium carbonate-activated hybrid cements, CEM MK (20% CK + 40% BFS + 40% MK) and CEM BT (20% CK + 40% BFS + 40% BT). The reaction kinetics of the two systems were analyzed by isothermal conduction calorimetry. The hydrated matrices were characterized with XRD, SEM/EDX and ²⁹Si and ²⁷Al NMR. Both systems developed high mechanical strength, for both generated a mix of (N,C)-A-S-H and C-A-S-H gels. The proportions of the gels precipitating vary with system composition and initial reactivity, however.

Keywords:

• geopolymer
• alkaline activation
• hybrid cement
• mechanical strength
• NMR

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was funded by the Spanish Ministry of the Economy and Competitiveness under the projects BIA2013-43293-R and RTC-2014-2351-5. One of the authors worked under a Postgraduate Studies Council grant co-funded by the Spanish National Research Council and the European Social Fund (ESF).