I was curious about this so I reached out to Lawrence Mayhew who is with the Humic Products Trade Association and an expert on humic substances. Here was his reply:

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Humates make very strong associations with the clay fractions of soils, they are almost inseparable. In sandy soils, they are attracted to soil colloids through weak forces (London forces, hydrogen bonding, vander Waals forces) with silicates and silicon dioxides (quartz, sand, etc.) and hold soil moisture. So, they don’t actually replace anything in the soil space, they add to the volume of soils, which contributes to lowering the density of soils, actually making room for microbial and metal interactions. They provide exchange sites for metal interactions (measured as CEC), but it is not as simple as exchanging a cation tit for tat with other soil components, instead they provide a more complex but stable environment for plant/soil/microbial interactions. For example, they reduce iron (Fe3+) and some bromates (boron-oxygen combinations) into more bioavailable forms by acting as electron shuttles to the electron accepters acting more like Lewis acids than simple ionic interactions.

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In the case of HumaCarb (a product I developed when I was associated with Advancing Eco-Agriculture), I would not expect to see either physical, chemical, or biological changes in a soil treated with the product. The product is intended to be combined with other liquid products to enhance their effectiveness, not to change the bulk soil chemical and physical properties directly.