Brick Paving has been around since the first roads and have stood the test of time. Quality pavers are among the highest end pavements available. A successful paver project depends almost entirely on the base preparation. Unlike concrete which is rigid and will hold a span, pavers behave like asphalt in the respect it is a non rigid surface and with any deflection, heaving or settling in the base will show up on the surface.
Unlike blacktop or concrete however, pavers will not crack due to freeze thaw cycles and if done correctly, will settle substantially back into place. Poor compaction, poor soils and drainage and base issues in general have caused many a paver project to fail, however many of these failures shouldn't have happened at all. In our experience, pavers are probably the most misunderstood of the projects we undertake so we believe it is helpful to have an understanding of exactly what goes into making a paver project succeed.
The following depicts a paver project we completed, the sequencing, and how we addressed and solved potential base failures.
This picture hows the sequence from excavation to laying pavers. At this paver sidewalk project in Mendota Heights, we encountered poor soil conditions in the last 50' of our sidewalk run. We excavate the soils as seen in this photo. Our quality control has indicated in marking paint areas which need to be remediated.
The excavation was done to 16" and 4" of 1.5" Limestone and portland cement was added to the sub grade. It was a fairly small area so the material was rked in by hand. A sheeps foot drum compactor was then applied to the limestone/portland mix. An additional 2" of gravel was then added to even out the surface and compacted in. Its important to note our compactor is rated for the lift sizes we installed.
Geotextile was then installed over the subgrade and 8" of class 5 base material was placed and compacted.
Excess geotextile was trimmed off and the paver laying could continue. When Striking off sand, we install it to 3/4"-1", which when the pavers are compacted, allows some sand to fill the lower joint of the paver. Too little sand and the lower joints don't interlock, too much and the pavers will sink.
Pavers are then laid with cuts filling in right behind the layer. For dust control reasons, we wet cut all masonry work. We also like to cover our work behind us to make sure the surface remains clean prior to sweeping in joint sand and final compaction.
Unless circumstances present which are out of our control, we edge and compact all the pavers laid that day to approximately 3' from the end of paving. When we begin again the following day, we typically reset the first 3 uncompacted courses of pavers laid the previous day
After the cuts are made and the edging is installed, we run over the pavers with the plate compactor with the paver pad on it once before sweeping in polymeric joint sand. We clean the paver surface with a back pack blower and sweep in sand and compact it in to make sure the joints are filled.
Once all the joints a filled, we sweep off the remaining sand and run the blower over it again using care to make sure we don't blow out the joints. Water is then carefully applied to the surface and the joints to activate the polymeric sand. This is something of an art and takes experience to put on enough water but not so much as to wash out the binder material.
A Quality finished product suitable for golf cart and pedestrian traffic.
In the area behind the retaining wall, we would be unable to achieve adequate compction without blowing out the wall. Our solution in situations like these is to place a self consolidating flowable fill or slurry mix to outside the reinforces zone of the wall.
We frequently integrate portland cement to stabilize areas in the sub grade. We condition it into gravel then sheep's foot compact it in.
Trenches and along structures are particularly difficult to achieve adequate compaction as well. A high percentage of utility trenches settle even when granular material is placed and compacted correctly. In these situations we opt for flowable fill to help assure a stable base.
