What are the meaning and the grammatical role of the cementing?
Consolidated (or cemented) sediments, too, contain millions of minute water-holding pores. This is because the gaps among the original grains are often not totally plugged with cementing chemicals; also, parts of the original grains may become dissolved by percolating groundwater, either while consolidation is taking place or at any time afterwards.
This is because the gaps among the original grains are often not totally plugged with cementing chemicals ...
Grammatically, it's tempting to call "cementing" an adjective, but in fact it is a verb phrase modifying "chemicals", i.e. it's an attributive modifier. Semantically, the phrase "cementing chemicals" presumably means something like 'chemicals that are capable of cementing something'.
Note that "cementing" can't be an adjective for the following reasons:
[1] Unlike most adjectives, it can't be modified by "very": we can't say *"very cementing"
[2] It can't occur as complement to complex-intransitive verbs like "become": we can't say *"It became quite cementing".
[3] It can't occur as complement to complex-transitive verbs like "find": we can't say *"I found it quite cementing".
The range of expressions that can occur as pre-head modifier to a noun is very large and varied: we don't want to call them all adjectives. "Cementing" has none of the properties of indisputable adjectives and hence does not belong in that class. Which is why it is best analysed as a VP here.
The word "cementing" modifies and describes "chemicals". It is a present participle functioning as an adjective. The meaning is related to the verb "to cement"
