I think you would reach toxic levels of Potash before you would change the soils pH much. Sulfur is the usual application to lower a soils pH.
Perhaps this lonk might be of some help.

Here is a link that might be useful: About soil pH

What is your base soil pH? And what did you do to change it opposite what you started with? And what are railway sleepers? Is that what we call railroad ties (big logs cut square about 8-10 inches (25 cm))?