City of Cardiff Council granted planning permission to construction materials firm Tarmac for its reworking of Creigiau Quarry.
Work stopped at the quarry in 2002 but planning permission already existed allowing extraction to continue until 2042.
According to a planning report, the extension would result in the loss of 6.5 hectares of agricultural land.
The report said that Pentyrch Community Council said it had "significant concerns" over the extension, particularly over road safety, noise and the environment.
Pontyclun Community Council also objected to the application, saying increased traffic would cause distress to residents.
The Campaign for the Protection of Rural Wales raised a formal objection and two petitions of objection were handed over by councillors, totalling more than 1,700 signatures, the report said.
But planning officers said that the principle of the development of the site for quarrying "is firmly established and the application will, importantly, provide a source of minerals that are important for the local economy and for provision of essential infrastructure".
The report added that the extension would "deliver significant environmental protection improvements compared to the existing planning consent to develop the quarry" and noise and traffic could be mitigated to acceptable levels.
The report concluded that planners considered that the proposal was "policy compliant and there are no reasonable grounds for refusal".