No, there is not. JPQL does have following String functions: CONCAT, LENGTH, LOWER, SUBSTRING, TRIM, and UPPER. Only way in with older JPQL versions is to simply repeat separator between each value in CONCAT:
SELECT CONCAT(se.string1, ';', se.string2)
FROM SomeEntity se
With JPQL in the JPA 2.1 specification implementations it is possible to call database functions as follows (first arguments is name of the function, others are arguments to function):
SELECT FUNCTION('CONCAT_WS', ';', se.string1, se.string2)
FROM SomeEntity se
Older EclipseLink versions have same functionality via FUNC
keyword.