CG1 and CG2 Grouts Explained

EN 13888 classifies cementitious grouts as CG1 or CG2. The difference is not cosmetic, and it decides which binder and which dosage a formulation needs.

What the Classes Ask

CG1 is the standard class: reduced water absorption and a defined abrasion resistance. CG2 is the improved class, with a tighter water absorption limit and higher abrasion resistance.

The tests are run on hardened specimens after a set curing period, so a grout that looks dense on site can still miss the class if the curing was wrong.

Binder Consequences

Moving from CG1 to CG2 usually means a denser matrix: a defoamed powder, a hydrophobic component and often a lower water-to-binder ratio.

Dosage alone does not get you there. A high dose of a standard powder raises strength but leaves the air voids that the water absorption test finds.

Testing Reality

Water absorption is measured after short and longer immersion, and the longer value is the one that separates formulations. It is also the value that customers notice as staining months later.

Abrasion resistance depends on the surface, so the way the joint is finished and cleaned matters as much as the recipe.