In order to lower the consumption of natural raw materials, to save fuel energy for clinker production and to make appreciable reduction Of CO2 emission, the Morrocan plants cements become to produce some composite cements types by adding some components. This paper describes the production of composite cements by intergrinding clinker, gypsum and limestone with a minor addition of fly ash up to 10%. Physical and mechanical properties are discussed, and the main result is that the addition of fly ash with low quantity acts as grinding agent by reducing the required time to obtain the same percentage of particles retained on an 80 mu m sieve compared to the cement without addition of fly ash. From 28 days to 90 days, the compressive strength increases rapidly in the case of cement with a minor addition of fly ash. (c) 2005 Springer Science + Business Media, Inc.