Limitations of Koch-Steinegger test to evaluate the durability of cement pastes in acid medium

The durability of ordinary Portland cement and ground granulated blast furn ace slag pastes in buffered acetic/acetate medium (pH 4.5) was studied by m eans of the Koch-Steinegger test. Results show that flexural strength measu rement is not a good parameter to evaluate the degradation degree of cement paste in acid medium because two effects take place with opposite conseque nces on flexural strength as a result of acid attack: a densification of th e cement paste in the specimen core and a degradation of the outer surface with loss of resistance. (C) 2000 Elsevier Science Ltd. All rights reserved .