In our paper, https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4148065 we reference the increase in compressive strength that comes from the sequestration of CO2 in the building. 

Any university laboratory and some commercial concrete testing sites will be able to do a compression test. Google "concrete compression test lab"

However, when you are quickly iterating, you will want a cheaper and faster method for getting some initial numbers.

We built a simple test stand out of wood.

We use a 10 Ton bottle jack and a load cell to measure the compressive strength. This is a fast and inexpensive method. You can purchase load cells on Amazon

1. https://www.amazon.com/gp/product/B01HO1GACE/
2. https://www.amazon.com/gp/product/B082MPLRCS/ circuitry to connect to load cell

You will have to calibrate the load cell with a known load cell.