Identification of Composite Cement Hydration Products by Means of X-Ray Diffraction

 In this paper the effect of limestone, fly ash, slag and natural pozzolana on the cement hydration products is studied. Four composite cements containing limestone, natural pozzolana from the Milos Island, slag and fly ash have been produced by intergrinding clinker (85%), the above main constituent (15%) and gypsum. The grinding process was designed in order to produce cements of the same 28d compressive strength. The hydrated products, formed after 1–28 days, were studied by means of X-ray diffraction. Unhydrated calcium silicate compounds of clinker and hydration products such as C*H, C*S*H and ettringite are clearly observed. Although there is not significant differentiation among samples hydrated for the same period of time, modifications of calcium aluminate hydrates as well as sulfoaluminate hydrates, are indicated by the XRD patterns. In samples of limestone cement, monocarboaluminate is formed in the first 24 hours and is still present after 28 days.