To truly understand certain aspects of sand compactability, it is important to know the simple science behind it. Let\’s get started without further ado!

Do you periodically send green sand to an outside lab for testing to compare testing results?

If you do, you must have noticed that their moisture content is similar to your readings but their compactability number is always lower than yours. You even make sure that the sand is immediately placed it an air tight bag, but the compactability still changes. Have you ever wondered why?

As the sand is placed in an airtight bag, there is no loss of moisture even after several days. Hence, there must be other reasons for compactability drop other than the evaporation of moisture from sand. The key factor affecting this loss is continual absorption of moisture by the clay platelets in the interior and reduction in compactability.

Degree of Loss of compactability after muller depends on the system. The amount of moisture absorption depends on the following variables:

• Amount of clay added at the muller (increased clay addition increases drop in compactability)

• Sand to metal ratio which affects the clay replacement for each cycle of mulling

• Target clay level (Higher the clay level, higher the loss) The target clay level depends on core sand, new sand input, type of molding machine, shakeout, and type of clay used. It also depends on how and where clay is added.

Read more: Factors that affect sand compactability