Compatibility issues of NSF-PCE superplasticizers with several lots of different cement types (long term results)

This paper presents the compatibility issue between cement and superplasticizer. Different kinds of chemical admixtures such as naphthalene (NSF) and polycarboxylate-based (PCE) families and five lots of six different cements widely spread in Italy were considered in the experiment. Mortars and concretes were manufactured by varying superplasticizer dosage to achieve a fixed workability at the end of mixing. Flow retention up to 1 h was measured to evaluate the performances in terms of workability loss of each chemical admixture. Compressive strength at 1, 7 and 28 d was also measured. The results show that PCE are higher efficient in terms of water reduction and workability retention with respect to naphthalene-based admixtures. The performance of the NSF products, however, seems to be less dependent on the cement lot/type. The rheological and mechanical properties of concretes showed good agreement with the results collected on mortars.