There are certainly technical and theoretical reasons determining whether an anchorage should be realized with resin or grout. However, in the practical application it is not so easy to define such limit, because of many factors, such as the compatibility with the original materials or simply feasibility problems during the execution. Significant parameters for choosing the type of anchors are:
- type of substrate
- anchorage length
- hole diameter
- setting time and fixing mode
- waiting times for the loading of the anchorage
The thixotropic consistency of the resin, that is useful to prevent from excessive spreading in the interstices of historical buildings, complicates the deep extrusion stage and limits the anchorage length in comparison with the application where the injection is realized with grouts.
The choice of realizing a chemical bond with resin can be very good if one wishes to limit the drilling diameter: in the applications with resin one has to make a hole just a little bigger than the diameter of the steel bar.
Another essential parameter to determine the choice of the binding material is the waiting time necessary before the loading, which, for some applications, must be short: fixing realized with epoxy resin have a curing time of some hours, while for grouting with cement-based mortars one needs 28 days before reaching the characteristic resistance.