ST2400 in Large-Format Bedding

ST2400 is a hard VAE powder with a minimum film forming temperature of 3 °C. It is used in large-format bedding where the adhesive has to hold a heavy tile without collapsing.

Rib Stability

A notched rib holds its shape if the mortar has enough yield stress. A soft mix spreads under the weight of the tile and leaves voids where the ribs collapse.

A hard polymer film supports the rib structure as the mortar stiffens, which is why large-format adhesives are built on hard grades rather than flexible ones.

Coverage and Contact

Large tiles need high coverage, usually above 80 percent for exterior work. Coverage depends on notch size, trowel angle and how the tile is bedded.

The adhesive also has to transfer load into the ribs when the tile is pressed. A mortar with good wet tack does that without the tile sliding.

Dosage and Workability

Large-format adhesives usually carry 1.5 to 3 percent of ST2400. Above that the mix becomes stiff and harder to notch, and the open time shortens.

Workability matters as much as strength here. A tiler who cannot notch a consistent rib will not achieve the coverage the formulation was designed for.