At 28:30 he talks about the new concrete product as high in...

At 28:30 he talks about the new concrete product as high in halloysite content so probably this is not coming from this area.

There has been talk about 2 different streams of material supply for the concrete industry.
One is rheology modifier and the other one is graded sand and both of them will be coming from kaolin zone, not from overburden.

The kaolin zone contains a mixture of sand and kaolin. This sand not uniform but comes in a range of sizes.
The wet processing plant (I'm basing it on the flowsheet shown at the miners conference in Adelaide) operates by running wet slurry (material from the kaolin zone) through various separators and series of sets of hydrocylones. At each step particular size range is removed (starting from the largest) until we get no sand left and just very fine kaolin.
This creates a few streams of sand in reasonably controlled particle size ranges.
It's relatively easy to direct a stream of such sand to a pile where the water will drain and we will have a graded sand perfectly suitable for concrete production. This is just plain concrete sand and it's not an expensive product so can be used only by local concrete plants.

The rheology modifier he talks about is high in halloysite and a "byproduct" of some sorts produced during kaolin refining at the wet plant.
Speculative mode on.
1. It is a product removed from slurry stream by hydrocyclones one or two steps before the very fine particle size kaolin suitable for CRM or PRM product is achieved, essentially halloysite kaolin with larger particle size than suitable for CRM or PRM.
2. Some other type of aggregate of sand/kaolin and halloysite that gets removed from slurry much earlier in the process so it is at the large particle size 0.2-0.3mm. Concrete manufacturers don't like very fine particle size in their concrete.