With the building substantially lifted (less minor adjustments), we focused our attention on the compaction grouting. Much of the same challenges presented themselves similar to the pile installation. Because of the buried concrete chunks, simply driving the piles with percussion were not enough. Again, predrilling was required with a down in the hole hammer.
There were some concerns with creating overburden with too much weight. With 280 holes and an anticipated 10 yards each we initially calculated 11 million pounds of grout to be injected. While we planned to grout down to solid substrate with columns of grout to the surface, minimizing potential for grout induced settlement, we also took steps to minimize the grout weight. We used cinder sand as one of the aggregates and cellular foam additive. This was rather new and innovative and required experimenting with the mix until it was dialed in.
Our initial plan was to have the grout delivered by ready mix trucks since mixing by hand would limit our production. 4 holes per day with 10 yards each would be impossible to do by hand. While this method did give us the volume we needed, it left us dependent on the vagaries of the ready mix availabilities. With the plant being over 45 minutes away, we were left with our crews standing around much of the time. With the project going as long as it has been delays were painful for the owner.
Accordingly we acquired a volumetric mixer by Cementech. We had the Cementech team come out to our jobsite and provide training and calibration for our specific mix design. This greatly sped up our operations. We also acquired a 2nd compaction grouting pump in order to run 2 grouting crews.
The plan was to grout some interior slab locations as well as the parking dock and the retaining wall for the retention basin. Again, we rolled up our sleeves and began work in earnest.
CLARIFICATION ON A RECENT BLOG POST:
I mentioned recently mention Brian Juedes as the chair of the committee for the PTI Guide for perming evaluations for slab on grade. It has come to my attention that Brian’s chairmanship was supported by a team effort at Felten Engineering as well as obviously other members of the committee. Brian is a smart guy but I certainly didn’t want to insinuate that this was a solo effort.