Many people have trouble cutting Hardie because they use the common sense technique to cut it. They try to cut it like drywall. Wrong! Re-read the directions.
You need to score it several times with the carbide scoring tool, then snap up, not down.
Alternatively you can cut it with a 4" side grinder equipped with a basic diamond blade, but lots of dust. Do it inside the garage near the door with a fan blowing behind you to minimize the dust. Wood pallet on the floor, board on pallet, just lightly score then snap. Still wear a proper mask.
Or if you do this often get a pair of the special shears.
Doing a floor? Why 1/2"?
Marble from Italy
DIRECT Containers MARBLE from ITALY - PERLATO di SICILIA - PERLATINO - BOTTICINO - AVORIO - LIMESTONE -- others - Slabs - Tiles - Custom sizes and textures.