Made me think of the caravan(s).

We can trace "concrete" back to the Latin verb concrescere, meaning "to grow together."

https://www.merriam-webster.com/dictionary/concrete

History and Etymology for concrescence

borrowed from Latin concrēscentia "coagulation, solidification," noun derivative of concrēscent-, concrēscens, present participle of concrēscere "to coalesce, condense, solidify, harden," from con- CON- + crēscere "to come into existence, increase in size or numbers"

https://www.merriam-webster.com/dictionary/concrescence