Strength retrogression

Silica to reduce or prevent high-temperature strength retrogression Dispersants... 

At the high temperatures encountered in deep wells, pozzolanic admixtures are essential to prevent strength retrogression, as in high-pressure steam curing (Section 11.7). Silica flour (finely ground quartz) and silica sand are the most commonly used. There are few data on the effects of prolonged... 

In the case where other minerals have been added to the formulation, hematite to densify or silica for strength retrogression, sedimentation is compounded with a segregation process. Here, the density gradient created is not just due to a variation in particle concentration but also to the fact that bigger and heavier particles tend to fall faster. For example, the concentration of hematite particles or of coarse silica particles (sand) can be higher at the bottom of a set sample than at the top,... 

Rao, P.B. (1980) Chemistry of arresting strength retrogression in stmctural high alurrtirta cemerrts, ia Proceedings 7th ICCC, Paris, Vol. 3, pp. V51-56. 

The rate at which the material develops its strength is relevant, as it determines the time needed before drilling operations can continue. A retrogression of strength must not occur under the conditions existing in the well. 

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