Investigation of Portland and cement and pure C₃S using 1-D SANS

The effect of contrast matching in ordinary Portland cement (OPC) and pure C₃S has been investigated as a function of time after hydration using the 1-D small-angle scattering technique. The observed scattering response of OPC hydrated with 100% D₂O increased in time, while the response of OPC hydrated with a null water mixture did not. The increase in scattering is therefore attributed to the formation of bubbles in the water-filled pores of the hydrating cement paste. The addition of 1% CaCl₂ to OPC increased the kinetics of bubble formation considerably. Based on similar contrast measurements, we have concluded that bubbles do not form in pure C₃S. However, the addition of 1% CaCl₂ was found to induce bubble formation in the hydrated C₃S compound.