Sand-gravel pad will soften the impact of the soil on the slab
The next step is to create a multi-layer protective cushion, which plays the role of a buffer between the concrete fill and the soil. A layer of coarse sand, gravel or crushed stone with a thickness of 10-15 cm is poured over the ground. It is necessary to alleviate the pressure on the concrete base from the side of the seasonal heaving forces.
The sand-gravel pad after dumping is rammed for greater density by a vibrating plate or by hand tamping in the form of a chock with handles attached to it. When building the foundation on clay or marshy soils before dumping gravel, the soil is covered with geotextile, which will prevent the protective layer from deepening into the soil.
A protective leveling screed made of “lean” concrete, grades M-100… (more…)