How important are the soil conditions in constructing a good slab-on-grade?
The soil is the support for slabs on grade. Therefore the soil should be as uniform as possible to avoid differential settlement and have good bearing qualities to keep overall deformations to a minimum. The soil should be well compacted. Low compaction grades lead to thicker slabs and higher fibre dosage rates and these extra costs are normally higher than those where additional compaction is carried out. Ruts that remain after vehicle traffic are a sign of poor compaction. Normally point loads are very limited in depth in the soil, so that the most important criterium is a well compacted sub-base. However, for higher uniform distributed loads or in case of heavy rack systems, attention should be paid to possible soft layers which can be located several metres under the finished level of the sub-base. Such layers should always be reported to the designers, as these can lead to significant differential settlement between loaded and unloaded areas, which can result in major longitudinal
