Shrinkage mechanisms, crack formation and service life of reinforced concrete structures

Shrinkage of concrete is most often at the origin of crack formation. Cracks are preferential paths for ingress of aggressive substances such as chlorides or sulfates into the composite structure of concrete. Reduced shrinkage means generally extended service life of reinforced concrete constructions. It is shown that shrinkage is not due to capillary action but it depends essentially on disjoining pressure in the nanopores of hydration products of Portland cement. All reactions which reduce disjoining pressure, reduce shrinkage. Shrinkage can be minimised by optimisation of the chemical composition of the pore solution.