Hardcore is the material that is placed under the floors. It is used as a sub-base after the foundation wall is built for leveling prior to casting the ground floor concrete slab. Recommended is hard stone ballast or quarry waste that should not pass through a sieve of more than six inches when broken. It should be free of weeds, roots, topsoil, clay, black cotton soil, or other unsuitable materials. Broken stones or brick cutouts can also be used as hardcore.
To place the hard material under the floor beds, use well-sized smaller pieces mixed with fine materials. This will give a dense compact mass after consolidation. This will be layered not to exceed ten inches in consolidated thickness. Sufficient fine materials will be added to each layer to give the necessary gradation to obtain a compact solid mass after lamination. A ten ton flat wheel or two tone vibratory roller should be used to compact each layer.
Compact each layer with eight passes of the roller when placing the hard flooring under the beds. Add enough water to each pass for maximum compaction. To each layer, add a thin layer of sand or quarry powder forced into hardcore by a rolling vibrator. All materials used must always be dry to avoid caking or stickiness. This can allow for air pockets or clearances. This can sag when the hardcore is loaded down with weight. If the sand absorbs into the holes between the ends, continue compacting.
Completely compact the hard padding under the floor beds until the sand is not absorbed. The top surface must be level. The levels are made or graduated according to the required drops. Once this is done, a blinding layer of similar broken materials is added. This is at least an inch thick. A ten ton roller is used to smooth the surface. This hardcore mass is now ready for anti-termite material, waterproofing and mesh reinforcement prior to concreting the ground floor slab.