Methods, systems, and devices for wireless communication are described. A user equipment (UE) may indicate to a base station the number of uplink (UL) component carriers (CCs) that the UE is capable of supporting. A base station may configure the UE for carrier aggregation (CA) and for one or more auxiliary UL CCs. The CA configuration may include CCs for UL data transmissions and the auxiliary UL configuration may include CCs for UL reference signals or random access channel transmissions. The auxiliary UL CCs may thus be used for sounding reference signal (SRS) transmissions even if the UE is otherwise not configured for UL data transmissions on those CCs. UL data transmissions on the CA carriers may be sent at the same time as SRS transmissions or during different transmission time intervals (TTIs), depending on UE capability.