"gradual addition" is a correct and usable phrase in written English.
You can use it when describing something that has had elements added over time. For example, "The gradual addition of new technology to the workplace has made operations much more efficient."
One could just as easily argue that it's a matter of gradual addition or accumulation.
A darkly regal atmosphere is created by the gradual addition of strings and woodwinds.
The influences of gradual addition of CuO and melting temperature on the sequence of crystallization and magnetic properties were studied.
An increase in size and the gradual addition of bulk foods to the diet would in turn have affected the habitat and the pattern of locomotion of primates.
A significant enhancement of fluorescence intensities at 531 nm was observed upon gradual addition of nerve agent simulants on excitation at 480 nm.
The current study aimed at the assessment of CuO gradual addition on the crystallization behavior and magnetic properties of ferromagnetic glass ceramic in the system Fe2O3·CaO·ZnO·SiO2.
The animals – each has a name – were gradual additions.
Google has only made small, gradual additions and changes to Gmail in the past, with some changes remaining entirely optional for years for its 425-million-plus users.
Weather Channel executives say most viewers have responded well to the gradual additions of reality shows and even films, although they have acknowledged that "Misery" was a stretch.
Mrs. DeCaumette will give it something of her own twist, with new music and a menu that will continue to provide the usual bar fare, with gradual additions like a smoked trout salad and onion soup.
Just as nature creates the largest tree incrementally from a single seed, the teacher must endeavor to make gradual additions to a child's knowledge in every action taken.
