DETERMINATION OF THE MICRO-STRUCTURE OF HYDRATING CEMENT PASTE BY SMALL ANGLE NEUTRON SCATTERING. T M Sabine, W K Bertram, L P Aldridge, F Eichhorn* and I Joffe*, Materials Division, ANSTO, Sydney, Australia, *BENSC, Hahn-Meitner Institute, Berlin, Germany

SANS data from two types of cement show that there is a significant difference in the development of the micro-structure during hydration. Data on hydrating OPC (ordinary Portland cement) and DSP(cement containing silica fume) were collected on the V 12 neutron interferometer at BENSC.

In analysing the data the square of the structure factor, [F(q)]², is expanded in powers of the variable x_j which is defined by the equation

R_j is a parameter with the dimensions of length specifying an average size or correlation length in the scattering object.

The first, second and fourth powers of x_j give excellent approximations to the classical solutions for the rod, disc and sphere respectively while non-integral powers provide the fractal type solutions.

After inclusion of multiple scattering, absorption in the detector crystal, and background, the model is refined by least-squares methods against the raw experimental data.

The results show clearly that the inhomogeneities in OPC are spheroidal while those in DSP are disc like. The growth in size of the inhomogeneities with time is correlated with the evolution of heat.