Interactions of polymers with salts are of primary importance in industry as well as scientific research. In this paper, we focus on the system of poly(acrylic acid) (PAA) in concentrated sodium carbonate aqueous solutions. From the results obtained by density, static/dynamic light scattering, conductivity, and rheometry, the size/shape of single polymer chains, their effective hydrodynamic region, and the condensation of ionic species were evaluated as a function of salt and PAA concentrations. The formation of special morphological structures of PAA chains in solution and the resultant rheological behavior of the solutions were also examined.