IN-SITU XRD INVESTIGATION OF OPC HYDRATION

摘要

Rietveld+ calculations of XRD pattern of hydrated OPC pastes are leading to repeatablernresults with true quantitative approach. The first hydration product after stirringrncement powder with water (after 5 min) is Ettringite, with about 10 ma.-% with respectrnto the wet cement paste. C3A, C4AF, and sulfate carriers are decreasing at thernsame time. During the next 2.5 h no significant change in quantitative phase compositionrncould be observed. After about 8.1 h a significant content of Portlandite wasrnobserved. Consequently an increasing amorphous content of CSH phase and a decreasingrncontent of Alite was determined. At the same time C3A and Anhydrite arerndecreasing due to formation of more Ettringite. Until 19 h hydration is continuing andrnleading to an Ettringite content of about 18 ma.-% together with increasing Portlanditernand CSH contents. Belite content is not changing during the hydration until 19.1 h.rnApproximately 45 ma.-% of the paste are hydrated after 19 h. The development ofrnthe phase content is correlating very well with heat flow from calorimetric investigations.rnThe first heat flow maximum correlates with hydration of calcium sulfates andrncalcium aluminates/ferrites. The second heat flow maximum indicates the simultaneousrnhydration of calcium sulfates, calcium aluminates/ferrites and Alite. Crystallinityrnof Ettringite is improved during hydration time. Lattice parameters of Ettringite show arnshift from CO3rn2-/OH-/Fe3+ containing solid solutions towards purernC3A*3CaSO4*32H2O during hydration time.