Direct Answer: The core rule of diamond blade bond selection is simple opposites: Hard substrates (like hard granite, river rock concrete, or high-PSI rebar slabs) require a SOFT bond matrix to wear away predictably and continually expose fresh diamond grit. Conversely, soft and highly abrasive substrates (like asphalt or green concrete) require a HARD bond matrix (containing nickel-iron or tungsten-carbide alloys) to withstand abrasive slurry erosion and prevent premature segment stripping.
Diamond saw blades consist of synthetic diamond crystals embedded inside a sintered metal powder matrix (the "bond"). How quickly that metal bond erodes under friction dictates blade cutting speed and lifespan.
The bond will not erode fast enough to release worn diamonds. The blade will glaze over, overheat, lose cutting action, and warp.