Yep it’s termites, not surprising to anyone in the business. If there is a crack in the foundation slab then it is probable that you might get termites breaching the slab. That slab crack serves at a gateway right into your home and very little except termiticide will stop them for good. I suggest Termidor HE,

State-of-the-art molecular technology dramatically improves the transport of the Termidor HE Copack active ingredient into the soil creating an Enhanced Protection Zone.

It utilizes an advanced nonrepellent, or “undetectable,” liquid technology that termites cannot see, smell, taste, or avoid.