Pozzolanic Reaction of a Biomass Waste as Mineral Addition to Cement Based Materials: Studies by Nuclear Magnetic Resonance (NMR)

Non-fossil alternative fuels from biomass (agro-industrial, forestry and fodder plants) focus on getting cleaner, cheaper and more environmentally friendly energy sources directly related to the sustainable development of future societies. The resulting ash produced from the biomass calcination is a viable alternative for use as supplementary cementing materials in the construction industry. This study explores the scientific knowledge of calcium-silicate hydrate (C-S-H) gel formation during pozzolanic reaction between the biomass ash and calcium hydroxide through nuclear magnetic resonance technique with two different types of elephant grass ash that have different microstructure. The ash with the highest initial percentage of Q 4 and Q 3 units was found to react most actively and give rise to gels with the greatest inter-tetrahedral connectivity. In contrast, ash with higher content of total SiO 2 , exhibited lower reactivity and the C-S-H gel formed is characterised by low inter-tetrahedral connectivity from the earliest ages. Evaluation of C-S-H gel by nuclear magnetic resonance (NMR), as main hydrated phase for the engineering properties, revealed the potential of this tool to determine the effectiveness of this type of grass as raw material in cementing matrices through the evolution of the microstructure of the gel C-S-H formed.