by Michael Arstall. This paper was first published in GE’s December 2005 issue.
Grout in one form or other is widely used for repairing and sealing but specifications are frequently vague, to say the least. Many so-called “grout jobs” form ineffective seals which could have serious environmental and financial implications for owners, specifiers and contractors.
The reason is partly historical because in the past, most grouting was used in mines to stabilise workings or to repair leaks in formations and structures, ie hard rock grouting for which a cement based slurry was an obvious choice.
However, more and more projects involve drilling holes in soft rock, for a wide range of applications from geothermal, installing piezometers, electrical earthing, water wells and so on. These frequently pierce several geological strata, which in nature are isolated from each other.
The problem is that engineers often have little or no idea of the potential impact of making different strata contiguous, and there is growing concern that many of the grouts currently used may be ineffective in terms of their sealing abilities. In some cases they may even present a real threat to the environment.
A far greater understanding is needed of not only what is trying to be achieved with the grout, but also how these actions can upset the sometimes delicate balance of nature.