Most outranking methods build a preference relation between alternatives evaluated on several attributes using the concordance / non-discordance principle. This principle leads to declaring that an alternative is "superior" to another, if the coalition of attributes supporting this proposition is "sufficiently important" (concordance condition) and if there is no attribute that "strongly rejects" it (non-discordance condition). Such a way of comparing alternatives is simple and rather natural; however, it is well-known that it may produce binary relations that do not possess any remarkable property of transitivity. This paper uses conjoint measurement techniques to obtain an axiomatic characterization of such relations that emphasizes their main distinctive feature, i.e., their very crude way to distinguish various levels of preference differences on each attribute. We focus on outranking methods, such as TACTIC, that produce an asymmetric relation, interpreted as strict preference. The results in this paper may be seen as an attempt to give such outranking methods a sound axiomatic foundation based on conjoint measurement.