Message text written by "BP - \"where heavy conservationists hang out\"" >My only question is, does Jahn shrink 11% or 11/100 of 1%. Would seem to me that the .11% you wrote, Mike, is pretty negligible. But if that's too much, it's too much--but is it too much? How does the Jahn shrinkage compare with the Edison-lauded concrete repair products? The structural engineers, whose practice is (almost) limited to repair work, for whom I work have high regard for Sika conc repair material. What say you, Mike? Ralph < 11% would be truly exceptional high shrinkage-- the ICRI Guideline defines high shrinkage as >0.10% and states that based on field experience high shrinkage can lead to significant problems. Though this number may seem small, you have to consider that these materials get placed in large volumes sometimes, and when you take this sort of shrinkage over a larger volume you're almost guaranteeing crack development. While some engineers are not concerned about cracking because they are accustomed to seeing it in perfectly serviceable concrete, it is at the very least unsightly and, after all, these are supposed to be Aesthetic repairs. I happen to be of the persuasion that a cracked patch IS a failing patch, because cracks of only 0.008 inches in width will leak, and as we all know, water infiltration is the primary driving mechanism in deterioration. Shrinkage data I have seen for Edison Custom System 45 patching compounds is on the order of 0.04% ("Low") to 0.06% ("Moderate"). The ICRI guideline describes moderate shrinkage as 0.05% to 0.1% and low shrinkage is less than 0.5%. There is also a "very low" shrinkage category, but there can be a whole different set of problems with products in this category. Sika and Master Builders are two manufacturers whose products have been very effectively marketed and supported for the engineering community, among others. These are usually designed to be structural repair materials, and are not used in aesthetic repair unless the scope of work also includes a paint job. Mike Edison