Clarify and Confirm

Winter 2017

Industry developing a second ASTM paving slab standard

The industry is dividing paving slabs into two camps based on dimensional
tolerances which are required for certain applications.

By

Clarify and Confirm

Last summer, ASTM approved C1782 Standard Specification for Utility Segmental Concrete Paving Slabs. Needed for decades, the industry now provides a baseline product standard for segmental concrete paving units from 12 x 12 up to 48 x 48 in. (300 x 300 up to 1,200 x 1,200 mm). ASTM C1782, however, was written for paving units that do not require close dimensional tolerances. Such tolerances noted in Table 1 at right are from that standard.

Utility paving slabs often have architectural finishes and are used in residential and some commercial applications for at-grade and roof ballast applications. Architectural finishes include (but are not limited to) blasted, hammered, tumbled, textured and polished surfaces. The Interlocking Concrete Pavement Institute is proposing a second ASTM standard for slabs with closer (tighter) dimensional tolerances. Like products conforming to C1782, products conforming to the proposed standard typically have architectural finishes. However, the main difference between C1782 and the proposed new standard is that the latter has closer dimensional tolerances required for pedestal-set roof applications, as well as for at-grade bitumen-set and some sand-set applications. The new proposed standard formalizes these dimensional tolerances used with architectural paving units for these applications for over 20 years. This proposed new standard below is very similar to ASTM C1782 except for the closer dimensional tolerances shown in Table 2.

Rather than provide optional closer dimensional tolerances within C1782, a new standard is being proposed that differentiates itself from C1782 with higher dimensional tolerances for architectural paving slabs. Also, two distinct paving slab standards (standard and architectural grade) can help reduce confusion between these two groups of paving products among specifiers, contractors, and other users. Freeze-thaw durability and flexural strength requirements are proposed to remain the same as those in C1782. Acceptance of this new standard is anticipated in 2018, but this depends on the outcome of voting by ASTM members.

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