Strong acids are not considered the same as concentrated acids. 

A strong acid is defined as an acid which completely dissociates in an aqueous solution, producing a high concentration of H+ ions and the corresponding anions. Examples of strong acids include HCl, and H2SO4. In contrast, a concentrated acid is defined as an acid which has a high amount of acid molecules in a unit quantity of a mixture (typically water). Concentration is a measure of the amount of solute (acid) present in a solution, relative to the amount of solvent. Thus, a concentrated acid solution always has a high ratio of acid to solvent. A strong acid can be concentrated, but not all concentrated acids are always going to be strong acids. For example, in a concentrated solution of a weak acid (e.g. glacial acetic acid), although the solution has a high concentration of the acid it may not fully dissolve into ions in the same manner as a strong acid does.