For erosion service, density results are determined from which of the following specimens?

For linings intended for erosive service, API 936 requires testing that includes specimens that experience real service wear simulation:

“For erosive service, bulk density shall be determined using the abrasion resistance test specimens and the linear change specimens.”

— API Std 936, Section 6.4.3​

Thus, both abrasion plates and linear change bars are used to evaluate density in erosion-sensitive applications.