A discussion of the paper "Low-field [formula omitted]H NMR study on geopolymers: The effect of paramagnetic Fe(III)" by Z. Yu, R. de Oliveira-Silva, Y. Pontikes, and D. Sakellariou.

The recent paper "Low-field 1 H NMR study on geopolymers: The effect of paramagnetic Fe(III)" is discussed. After examining the NMR test method and results, it is deduced that, the relaxation signals of the geopolymers with various Fe(III) contents were inconsistently obtained and interpreted without attention to total intensity. The calibration of surface relaxivity was also questionable. These inappropriate interpretations not only make the experimental results about the effect of Fe(III) loading on spin relaxation unreliable, but also make the discussion about its effect on pore structure of the geopolymers too ambitious, which is further incompatible with current understandings of geopolymerization. [ABSTRACT FROM AUTHOR]