Gregorian calendar 2.5

If it is plastering mortar, 1:3 or 1: 2.5 is the "volume ratio".

Mortar is divided into masonry mortar and plastering mortar.

Masonry mortar is marked with M or Mb, which has strength requirements, namely M2.5, M5, M7.5, M 10, M 15, M20, etc. Its mix proportion is designed by Code for Design of Mix Proportion of Masonry Mortar (JGJ98-2000), and it is generally expressed directly by mass ratio in construction, which is more convenient for measurement.

Plastering mortar is usually expressed as 1: 3 or 1: 2: 3 (that is, "1: m" or "1: n: m"), which is a volume ratio, and there is generally no requirement for strength grade.

Therefore, masonry mortar adopts mass ratio and plastering mortar adopts volume ratio. Only in practical engineering, in order to save trouble, the measured mass on one side is converted into the mass of this volume, so it is generally mistaken for the volume ratio.