ASPECTS OF PORTLAND-CEMENT HYDRATION STUDIED USING ATOMIC-FORCE MICROSCOPY

Aspects of the mechanisms of hydration and microstructural evolution i n Portland cement are still not fully understood. Atomic force microsc opy (AFM) is in many ways a powerful tool for investigating changes in surface structure that accompany the hydration of Portland cement, es pecially because surfaces can be imaged under aqueous solutions at nor mal temperature, pressure and high magnification. We have investigated changes in the surface characteristics of sections of Portland cement clinker immersed initially in saturated calcium hydroxide solution wh ich was then replaced by water, and in sucrose solution. In the case o f the former, the observations are consistent with the early formation of a protective membrane and the subsequent growth of calcium silicat e hydrate (CSH) structures by an osmotic process. The dissolution of t he clinker in sucrose solution has also been directly observed. It is concluded that the use of AFM will help to resolve many questions rela ting to cement hydration.