Are the specifications and requirements and guides that are relied upon for concrete construction work overly conservative? At the ACI convention last week I attended a technical session on cold weather concreting. Two of the speakers, Dennis Purinton , Purinton Builders, East Granby, Conn., and Kevin MacDonald, Beton Consulting Engineers, Prior Lake, Minn., described why they feel ACI 306R-10, Guide to Cold Weather Concreting, is much too conservative. This too-careful approach forces concrete contractors to protect fresh concrete in situations where doing less would provide adequate protection.
Purinton placed some slabs with little protection under conditions where ACI 306 would dictate extreme protection or even prohibit construction. Those slabs did just fine, although strength gain was slower. MacDonald showed that some of the tables in ACI 306 are based on data developed in the 1950s or earlier. Today’s cements set more quickly and therefore develop enough strength to resist freezing sooner than the guide predicts. Maybe thin black poly film really is effective cold weather protection in some cases, especially for slabs on ground.
But surely this is just one example of an industry standard that imposes unreasonable, overly conservative requirements on the contractor. We all know there are others. Which construction requirements do you find most unreasonable?