How do I repair large Linestone bricks

[darrenh]

Hi, All. We have these Pillars built out of what I assume are large limestone bricks, and some of them seem to be disintegrating, eroding away, especially at the bottom. I'm unsure of the cause. Anyway, I need to try to fix this and would appreciate any advice on what to use and how best to go about it. No doubt I'd like to try keep the same or similar colour & texture if I'm to "plaster" it up so it doesn't stand out like a sore thumb

Thank you in advance

Darren