Learn The Main Difference Between Epoxy Grout And Injection Mortar

For times when cast-in rebars aren’t planned and placed to connect concrete members, there aren’t many alternatives other than using injection mortar or grout. At first sight, they might look like similar technologies - still talking about chemical products surrounding a rebar installed in a drilled hole, isn’t it? However, these two technologies are far from being similar for several reasons.

You may benchmark and compare the two technologies from different points of view, such as code suitability, productivity, and reliability. Spoiler Alert: Injection mortar outperforms grouts in every aspect.

Let’s deep dive into the comparison based on the regulatory framework for now.

Before we start, it would make sense to clarify a few points. Talking about grouts, we refer to pre-dosed bi-components products that need to be mixed (manually or through a machine) by an operator. The two components are usually contained in cans and after mixing, the grout is poured into the hole using ‘dip-and-stick’ technique.

An example of manual mixing and dip-and-stick installation of a bi-component grout system

Talking about mortar injection systems, we refer again to bi-component products in pre-dosed cartridges (such as HIT-RE 500 V3 and HIT-HY 200-R). The mixing is carried out by a dispenser (by discarding a required number of pumps as per the product manual) The dispenser is also used for the injection of the adhesive blend in the bore-hole.

An example of dispenser-mixing and injection of a chemical mortar

The importance of a technically sound qualification process in place for injection mortars: ETA and ICC-ES Approvals

When dealing with the design of critical and safety-relevant applications there are two important tasks to be accomplished: first, to define the acting loads. Second, to run a proper design to check if the capability is higher, or at least equal, than the demand.

To be safe, and compliant with the international standards used for the design of the rest of the structure, post-installed rebar applications should be carried out by a technology fully covered under these standards. Injection mortar technology from reputed brands and with third-party approvals are suitable for designing your concrete-to-concrete connections according to Eurocode or ACI. Also, we need to ensure that the application conditions such as seismic and fire are covered, if necessary.

On the other hand, when it comes fixing a new concrete member to an existing one with grouts, we can’t achieve a consistent code compliance as per injection mortars.

Imagine designing a concrete-to-concrete connection, for instance, a slab-to-wall. You calculated the overall structure and reinforcement according to Eurocode/ACI. You find a grout product that has been somehow tested for repairing a concrete member or for filling purpose, but the system has not been approved for connecting a new concrete member to an existing one. Perhaps, you might also find some information about its bond strength in the product’s technical datasheet. But without exact resistance values taken from approvals such as ETA and ICC-ES, how would you know that the design or installation you have made with grouts will withhold to the forces that will be transferred through?

Well, let’s stop a while: we cannot simply run a design with that grout system, as the performance has not been determined specifically for post-installed rebar applications. We might be comparing apples with oranges here.

The importance to have a full qualification

such as ETA or ICC-ES in place

for post-installed rebar solutions

To start with your fully-compliant concrete-to-concrete connection design, use a software like our PROFIS Rebar for a quick and reliable support: you can calculate rebar anchorages and splicing with Hilti injection systems according to the most-updated state of the art design codes and Hilti methods.

In case you need more support to understand which qualification fits your application requirement better, please leave a comment on this article or post your question in our Q&A section.