Undermounted sink in concrete countertop

[theCarl]

Hi, I am renovating a kitchen and the plan is to cast a concrete countertop with an undermount sink. Similar to the result in this picture: https://www.ccrye.info/wp-content/u...of-dark-kitchen-cabinets-concrete-counter.jpg

I am thinking of casting bolts on the underside of the countertop. Then I will attach the sink to the bolts with nuts. What I am wondering about is which adhesive/sealant to use in between and how to get a nice joint between the countertop and the sink.

Do you have any tips?

/Carl