definitions & history

manufacture

hydration

classification

types

TESTS

field examination

lab tests

Unsoundness of cement occurs due to delayed /slow hydration or other reaction of some compounds present in the hardened cement viz. free lime, magnesia and calcium sulphate.

In countries (like U.S) where Magnesia is present in significant quantities in raw materials, more preference is given to Autoclave test.  Autoclave expansion test (ASTM C 151)  provideS an index of potential delayed expansion caused by the hydration of CaO and MgO in hydraulic cements.

In other countries, where Magnesia is rarely present in significant quantities in raw materials, more preference is given to Le Chatelier test.  However, the Le Chatelier procedure determines unsoundness from the hydration of free CaO only, whereas the autoclave procedure measures cement paste expansion from either free CaO, free MgO, or both.