I have been involved with numerous projects in which cement grout would be an acceptable repair and more cost-effective than chemical grout - until the project location gets factored in. Dams are found in many remote locations. The very remote ones are often built using a temporary road that can handle heavy construction traffic. Fast forward some years and these roads no longer can support cement trucks or other heavy vehicles.
Chemical grouting equipment can easily be loaded into a pickup truck or even on the back of an ATV. While the material cost of polyurethane chemical grout is more than cementitious grout, getting polyurethane materials and equipment to a remote site can be a lot less expensive.
Lightweight polyurethane is much easier to mobilize with a small to non-existent footprint. This means it is less disruptive to sensitive sites. (Seawalls are a good example where chemical grouting can be done without tearing up the home owner’s yard with heavy cementitious grouting equipment.)
There are many factors to consider for every grouting job. It helps to have the Grout Geek and Alchemy-Spetec in your corner to help design the right plan for your project.