Portland-limestone cements. Their properties and hydration compared to those of other composite cements

The new European Standard EN 197-1 emphasizes the development of composite cements. In Greece a variety of pozzolanic and/or hydraulic materials are used as cement main constituents. Until now, limestone could be used only as a filler (up to 3% w/w), but since 2001 (application of EN 197-1) it can also be used as a main cement constituent. In this work a comparison between limestone and some of the materials that are already used in Greece is presented. An ordinary Portland cement and three Portland-composite cements containing limestone, natural pozzolana or fly ash were produced. The grinding process was designed in order to produce cements of the same 28 day compressive strength. The mechanical and physical properties of the cements were measured and hydrated products, formed after 1-28 days, were identified by means of XRD. The composite cements present significant differences as far as the clinker fineness, the development of the strength, the water demand and the hydration rate is concerned. The production of Portland-limestone cements seems to be very challenging, due to the satisfactory properties of the limestone cements as well as the low cost and the high availability of limestone in Greece.