SKI Perspective Background

repositories for radioactive waste. It is well known that in the hyperalkaline conditions (pH> 12) of standard cement pore fluids, there is potential for deleterious effects upon the host rock and other EBS materials, notably bentonite, in geological repositories. Low pH cements are beginning to be considered as a potential alternative material that Purpose The purpose of the current project is to perform preliminary modelling to investigate the potential impacts of low pH cement water on bentonite. The evolution of a bentonite sample under the influence of several invading cement porewaters over a pH range from 10 to 13.2 will be compared. The porewater compositions will be taken from published calcium-silicate-hydrate (CSH) gel leaching experiments and published cement-bentonite modelling studies. Results The models suggest that the amount of degradation that is likely to be observed when low pH cement water interacts with bentonite is likely to be much less than when OPC (ordinary portland cement) water is the invading fluid. Below pH 11 there was not a