ICPI Interlock Design Issue 3 2019

15 OGB may have the advantage of installation during rain. However, compacting it in saturated soils, even when placed over geotextile, can be difficult and result in an uneven surface, placing and compacting more base, and possible settlement later. Wishful thinking on using stabilized jointing sand is that it will somehow stay in the joints. This only occurs where there is something at the bottom of the pavers keeping it from moving downward over time. As a rule of thumb, the largest particle size of the joint sand gradation must not be smaller than one sieve size less than the largest particle size of the bedding sand gradation. This rule helps prevent the joint sand gradation becoming so small that it works its way downward into the bedding sand. ICPI’s recommendations: 3 3 If OGB will be used, then construct the base, bedding, and pavers with open-graded aggregates as permeable interlocking concrete pavement per ICPI guidelines. See ICPI Tech Spec 18 on PICP construction methods. 3 3 If the pavement isn’t permeable, use dense-graded base or DGB, i.e., state or municipal DOT road base per ICPI guidelines, meaning typically that used under asphalt. This material should not have more than 10% passing the No. 200 sieve. Selecting DGB materials is covered in the ICPI installer course. Use bedding and jointing sand per ICPI guidelines. 3 3 For permeable and non-permeable applications compact the soil subgrade, base, and pavers. Some contractors are reporting success using open- graded bases under sand-filled joints within interlocking concrete pavements, and others have reported almost immediate failures. The ICPI Construction Committee is evaluating projects built with this method to see how they are performing. This may take some time because project owners might be reluctant to open their paver projects to critical inspection. In the meantime, the initial consensus is to never use this method for any pavement subject to vehicles, residential, or commercial.