I am not of a mind that you will recover the values from pulverized concrete. As Nick mentions it depends on the quantity of gold you lost.
True story, I had a client about 10 years back who set up an acid refining setup for aqua regia work. In the design I included a berm in the room to contain spills and the floor was to be coated with a Novolac epoxy resin to resist attack from the acids and essentially seal the porous concrete. They built a beautiful berm but never coated the concrete. All was fine for a year or so until a loaded 72 liter flask with a working volume of 40 liters broke and spilled on the concrete. The vessel was loaded with acid from a large 14 karat digestion. The concrete did a wonderful job of sopping up the spill and a spot about 6 feet in diameter clearly defined where the acid had been absorbed. They were freaking out because the were looking for about 175 ounces of fine gold from the lot or north of a quarter of a million dollars. The concrete was chipped out and it was easy to see where the values were contained by the color of the concrete. When the entire crater of cement was cleared, it was crushed and made into prepared sweeps. They constantly shipped prepared sweeps anyway so the dust was sampled and shipped. It wasn't an easy assay because the flux had to be adjusted to accommodate the concrete but eventually we got a fusion without any lingering beads and got a reproducible assay. End result was they were paid for all of the expected gold less the fees for processing sweeps, which are higher than processing karat.
So if there is enough gold to justify it, crush and sift it and ship it as a powder. Based solely on the issues with the assay of the crushed concrete I encountered with the clients spill, I think an acid digestion would be a problem.