The effect of measuring procedure on the apparent rheological properties of self-compacting concrete

Torque versus time during testing of the rheological properties of fresh concrete has been investigated. The testing was performed in a BML viscometer and on a self-compacting concrete (w/c=0.45, 70% rapid hardening Portland cement, 3% silica fume, 27% fly ash, third generation superplasticizer). The relaxation period needed to obtain steady-state flow may affect the rheological properties estimated and should be taken into account in the selection of measuring procedures. Nonsteady state is likely to cause an overestimation of the plastic viscosity and an underestimation of the yield value. Furthermore, lack of steady state may explain the apparent shear-thickening behaviour of self-compacting concrete reported elsewhere.     

A discussion of the paper “Influence of pre-rusting on steel corrosion in concrete” by P. Novak, R. Mala, and L. Joska

The authors of this paper deserve to be congratulated for their study on the influence of pre-rusting on steel corrosion in concrete. The report of this kind of study is very scarce in the technical literatures. The topic of the study is very interesting as in the actual construction practice generally pre-rusted steel bars are used. We also are planning to do some study on this matter in the near future. After reading this article, we found that the authors did not provide/explain enough information/discussion related to the experimental setup and the experimental results. Further explanation on these matters will be very useful to us and also to other interested readers of the cement and concrete research journal.