During the renovation of the emergency room entrance to the hospital it was discovered there were 3-4″ voids around the piping that extended through the slab-on-grade to the sub-grade.
After the General Contractor and Geotechnical Engineering company removed some sections of the slab-on-grade for further investigation, they found 4-5″ voids between the bottom of the slab and sub-grade.
It was determined water had entered this area and washed away some of the sub-grade and left the remaining un-compacted and loose.
Due to time line constraints for the ER entrance, it was not feasible from a time standpoint to remove all of the concrete flooring in this area, re-compact the backfills, and pour new concrete. This would have also added major unexpected cost to the project. Leaving the un-compacted fill in place introduces a settlement risk due to the loss of sub-grade support.
Helitech Civil Construction drilled holes through the slab and injected high density polyurethane foam to fill the voids and provide sub-grade support, without increasing the weight on the un-compacted fill.
Helitech Civil Construction was able to complete the job in (1) day and the construction of the emergency entrance was not delayed. This process was very economical considering the alternative was tearing out the existing concrete, compacting the fill and pouring new concrete.