HD1500 Defoaming in Dense Grouts

HD1500 is a defoamed hydrophobic VA/VV powder with a minimum film forming temperature of 0 °C. In a dense grout it has to keep the mix compact while still being workable enough to fill a joint.

Why Air Matters

Every bubble left in a hardened grout becomes a pore connected to the surface. Water enters through it, dirt collects in it and the joint loses abrasion resistance.

Defoaming in the powder reduces the air the mixer drags in. The result is a denser matrix with fewer connected pores, which is exactly what a CG2 classification asks for.

Dosage and Mixing

Grouts usually carry 1 to 3 percent of the powder. The defoaming action needs mixing energy to express itself, so a short high-shear step followed by a low-speed homogenisation works better than constant high shear.

Over-mixing defeats the purpose: it re-entrains air after the defoamer has done its work, and the joint ends up with the porosity the powder was chosen to avoid.

Water Uptake in Service

A dense grout with a hydrophobic film reduces capillary uptake, which shows up as less staining and less efflorescence over a season of cleaning.

That performance depends on the joint being properly filled. A joint that is only partly packed holds water regardless of the formulation.