Since its inception in 1994, ICPI published 24 Tech Spec technical bulletins. They provide salient advice and best practices for design, specifications, construction and maintenance of interlocking concrete pavements, permeable interlocking concrete pavements, concrete grid pavements and paving slabs. Salient updates and links to each follow:
Several edits include assessment of soil moisture before compacting, managing dust during saw cutting, clarification on sand gradations, and maximum lippage of adjacent pavers. Some images and references are updated in this and in other Tech Specs.
The only change is deletion of references to Lockpave (v16). Originally developed by Dr. Brian Shackel from Australia, ICPI no longer supports this software because it does not run on Windows 10. Additionally, the text notes ICPI’s free Excel-based structural design software that follows Tech Spec 4 and ASCE 58-16 Structural Design of Interlocking Concrete Pavements for Municipal Streets and Roadways.
The new version removed text on temporary, winter-time utility cut repairs in asphalt with concrete pavers as substitute for using cold patch asphalt materials that don’t install well in below-freezing temperatures. This was an innovative repair method initially developed by contractor Mark Gavigan for utility companies cutting into streets owned by the City of London, Ontario. While a cost-effective approach, the City likely left the pavers in place rather than removing them in the spring and patching cuts with asphalt. In keeping with material differences between asphalt and concrete pavers, the asphalt around these small repair areas in pavers quickly deteriorated and utility cuts returned to using cold patch asphalt.
The updated version removes references to open-graded bases and discourages their use under grid paving units when subject to vehicular traffic. Grids are concrete paving slabs (with openings) which should be exposed to limited vehicular traffic, i.e. maximum 7,500 18,000 lb lifetime equivalent single axle loads. This requires the use of a dense-graded aggregate base under the grids and bedding sand. Open-graded bases can introduce some instability under repeated tire traffic. If open-graded bases are needed for stormwater storage and infiltration, permeable interlocking concrete pavement is recommended due to its higher load-bearing capacity and stability.
This revised version includes additional information on testing for the dynamic coefficient of friction of slip resistance per ANSI A137.1-2012 American National Standard Specifications for Ceramic Tile and A326.3-2018: Test Method for Measuring Dynamic Coefficient of Friction for Hard Surface Floor Materials. With other test methods noted in this bulletin, these ANSI standards provide another option for characterizing the slip resistance of concrete paving units. There are no changes to text on skid resistance for vehicles as tire-pavement skid measurement methods and skid resistance of interlocking concrete pavement remains similar to that of asphalt pavements.
Many edits were made that updates content from LEED v4 to v4.1. Most changes are under the Rainwater Management and Materials and Resources credits. Fortunately, the US Green Building Council issued a free, 260-page reference guide for v4.1 in early January 2020 and this document was quoted in this Tech Spec. LEED v4.1 makes earning points easier as the more onerous and complex v4 lost some traction among project owners and design professionals.
This bulletin includes minor edits and updates to a crosswalk section drawing.
Additional information on particle sizes and layer thickness for the asphalt bed under concrete pavers are provided. This gives a wider range of options for asphalt mixes.
Updates include clearer advice on using sand for winter traction, street sweeper effectiveness in removing sediment from paver joints, and addition of recently developed, high-pressure air/vacuum surface cleaning equipment and pictures. The latter cleaning equipment is quite effective in restoring clogged PICP surfaces.