Castle Cement is investing a further UK£10m at its Padeswood production plant in north Wales.
It will build a cement mill alongside the UK£63m cement kiln that began production last year. The mill will be capable of producing 100tph of cement and is expected to begin production by early 2008.
The rise in capacity will ensure Castle keep imports to a minimum and continues to manufacture most of its material in the UK.
Castle commercial director Mike Eberlin said: "Using more efficient plant will reduce electricity consumption and the additional capacity will reduce truck movements."