Having recently gone through a hip-joint repair, here's a topic I can relate to. Deteriorating joints in industrial floor slabs give concrete (and concrete contractors) a bad name. But the good news is that we are getting much closer to being able to relieve this pain. While it may not seem to you in June like the 2015 World of Concrete is right around the corner, it is for us, and we are actively planning the Quality in Concrete Slabs luncheon. Joints seems to be the place to start.

Forta’s Dan Biddle and I discussed this recently and came up with two potential themes for the luncheon. First, controlling slab shrinkage with chemical means versus mechanical means. In other words, which is more important to placing a slab with durable joints, macrofibers or shrinkage-reducing admixtures? The admixtures are effective but what is the contribution to long-term ductility and durability? What is the proper balance between these two approaches?

The second potential theme Dan and I discussed is mid-panel cracking, or as he says, are all cracks bad? In some cases, slabs with closely spaced tight cracks have performed better than uncracked slabs with wider joints or cracks (even dominant joints) that are curled and unable to transfer loads through aggregate interlock. Wayne Walker and Jerry Holland pointed out in a 2007 article the danger of relying on aggregate interlock, but if joints stay tight is it possible to have durable joints without dowels or plates?

Let me know what you think. Is one of these themes for the luncheon appropriate or should we focus our attention elsewhere?