Getting the columns up

After picking up a very large quantity of concrete blocks and totally overloading the van Mark has begun work on the four columns the we need to build. These columns will support the roof in the old barn. The current oak supports are in a poor state of repair. They are leaning and sinking which has allowed the roof to move and drop. If we do not do something then there is a danger that part or all of it will come down which would be very expensive. Each column will have to be about 4.5 metres high which is a lot of blocks. Will will the reinforce each one with a cement and rebar core.