The only reason to do shape optimization is to reduce required material in my case.
Sika 3350 seem to be the way to go, but I think I will have to import it from UK or USA.

I also found this one which is locally available. It specifies YM also:
https://www.chryso.lk/p/8921/3/5636/en

YM = 47
Compressive strength = 85

I am waiting for the pricing from the local agent. If its reasonable, I can use a thick blocks for base and column. But this has a maximum thickness of 100mm. According to datasheet, higher thickness requires addition of aggregates. How does addition of aggregates affect YM and strength? I believe I will have to do some tests and see?