admixture vs combining

admixture and combining both are nouns.

Word	Noun	Adjective	Verb	Adverb
admixture	Yes	No	No	No
combining	Yes	No	No	No

As nouns, combining is a hypernym of admixture; that is, combining is a word with a broader meaning than admixture:

Other hypernyms of admixture include combination, compounding.

admixture (noun)	combining (noun)
the act of mixing together	the act of combining things to form a new whole
an additional ingredient that is added by mixing with the base	an occurrence that results in things being united
the state of impairing the quality or reducing the value of something