The use of several admixtures in a building material formulation can cause undesired interactions. In the worst cases, complete loss of performance is observed . From job sites,many examples for incompatibilities have been reported.For most of them, the reason remains unknown. One well studied example is the effect of sulphate ions on the adsorption of certain polycarboxylates.According to this study, higher charged inorganic anions such as sulphate, but also carbonate orphosphate, can hinder the adsorption of a polycarboxylate with low anionic charge density in the main chain.
The result is a strong reduction of the achievable flow-ability
Corresponding author. Self--levelling underlayments(SLUs) are commonly applied on floor screeds in order to level uneven, rough surfaces. The.mortar levels itself under the influence of gravity and produces aplain and smooth surface. Typically, the binder system for such mortar is OPC (e.g. CEM 142.5 R). If fast setting and high early strength development are required, a rapid hardening mortar containing OPC, CAC and anchorite is used .
The complete formulation of such a dry mortar is shown in Table 1. Rapid setand hardening of this temary binder is caused by massive ettringite formation. The mixing water is bound chemically in the ettringite crystals, resulting in much faster drying. Ettringite alsoprovides excellent shrinkage compensation.
In cementitious SLUS, incompatibility between polycarbon-ylate-based superplasticizers and trisodium citrate retarder is aswell known phenomena.Measurement of mortar spread over time according to DIN EN 12706 revealed that a typical PC functions