While 구조 refers to structure, 구조화 means structuralisation. In other words, basically, the nouns without the suffix -화 mean the neutral state of the given word, and -화 adds the implication of the process of coming to have that quality. For instance, you could say 난 이 프로그램의 체계가 마음에 들어 (I like the system of this program); and 그는 이 이론을 체계화 했어 (he systematised this theory). And now that I’m giving you these examples, I realise that words with the suffix -화 are often used in verb forms.