It is a pier and beam construction. Is there a product or do you have some ideas on how we can repair this ourselves ? Perhaps an epoxy or grout which can be applied easily ?
If you are noticing actual separation in the piers, or even visible cracking I would suggest a more permanent repair.
Same goes if you notice deflections in the beams or floors above.
The best repair will be to replace the crumbling piers with new ones.
You do that by using jacks to slightly raise and support the beam, remove the old pier, and install a new one.
I am assuming you are talking about pre-cast piers.
If these are the cast in place type you may have to recast the whole thing.
Depending on clearance under the house and how much money you wish to spend
I would suggest going with an expert. They can be quite reasonable.
Check with your homeowner insurance (I hope you have one). It may cover the repair.
If you decide to repair the piers then go with structural epoxy.
But be aware that those require preparation and thorough cleaning of the
cracks which you may not be able to do.
Always call the manufacturer's technical support for recommendations.
I find them very good and helpful.