Portland limestone cements

الملخص EN

Portland limestone cements, if produced to the same strength as other Portland cement types, have been shown to give equivalent concrete performance.

This includes fresh concrete performance, and long term durability as demonstrated by fundamental thermodynamic studies, relevant performance testing of cement of concrete, and from several decades’ practical experience where it has been used in most environmental classes in several European countries.

This includes experience in Denmark where, with the exception of the most severe exposure classes, XS3 and XA3, it has been widely used in all applications.

The key hydration reactions in Portland limestone cements are essentially the same as the hydration reactions in CEM I Portland cements which can of course contain up to 5 % limestone.

The limestone reacts with available alumina from the Portland cement to form the mono-carbo aluminate hydrate AFm phase.

This reduces porosity and increases concrete strengths.

When the supply of alumina is exhausted additional carbonate takes no further part in the hydration reactions leading to increased porosity.

Because the same phases that form from the hydration of CEM I Portland cement also form from Portland limestone cements, including the composition of the pore solution (which for example is not the case with pozzolan or slag cements), the same reactions are also involved in the common forms of degradation such as sulfate attack or alkali silica reaction.

Therefore, any comparisons between the durability of CEM I and Portland limestone cements must be made at equal porosity which in most cases also means equal strength.