Stability of cement grout: Study of sedimentation phenomena: Fid-Bau Portal

Stability of cement grout: Study of sedimentation phenomena

Gelade, P. / Roy, R. Le / Boucenna, I. / Flaud, P.

The grouts are suspensions containing cement used in the technique of pre-stressing by post-tension. Cement, from its chemical nature, protects the wire ropes (strands) from corrosion. To be able to play correctly this protective role, the grout must remain homogeneous and must entirely cover the strands. The lack of stability of the grouts, which results in packing or sedimentation, is a major problem. In this article, we try to correlate the rheological properties of the grout with its capacity to remain homogeneous. We show that an increase in the concentration of superplasticiser, a polymer solution, decreases the thixotropic behaviour of the grout, but on the other hand, increases the effects of sedimentation. We explain this phenomenon by the modification of the structure of a three-dimensional network in relation to the interparticle interactions. The sedimentation phenomenon can be described as follow: without superplasticiser, because of high attractive interactions, cement particles build up a tri-dimensional structure. When interparticle interactions are not strong enough (for the strong superplasticiser concentration), the structure collapse: the cement suspension start to sediment and segregation can be observed. These results show that it is possible to correlate rheological measurements with the sedimentation of the grout: indeed, one can think that a grout with a high yield stress leads to a grout, which does not form a deposit. It now remains to see whether the measurement of the structuration is possible with simpler systems of measurement.