Water in the pores expands when it freezes. A porous stone sheds faces and produces fines. Specifications therefore cap absorption, often at 2 percent by mass, and tighter on frost-exposed lines.
Sound andesite
Sound andesite is typically well below that cap. The certificate, not the rock name, confirms the batch.
Absorption is a durability signal
A low absorption value usually indicates fewer connected pores, but it should be read with freeze-thaw and soundness results where the route is exposed to repeated freezing. A dense-looking surface can still hide altered seams or microcracks that open after wetting and cooling.
Design for the local climate
Drainage, shoulder protection and a clean grading reduce the time water remains around the stone. The quarry certificate should identify the test method and sample date, while the designer sets acceptance limits for the actual climate rather than copying a generic number.
