Tyler Ley, who teaches at Oklahoma State University, is always coming up with new ideas for working with concrete. A few years ago it was his recycled newspaper slurry for curing that he called FiberCure. Now he has tackled the problems that manufactured sands introduce to a mix, especially in terms of finishability, with his so-called Tarantula Curve—an aggregate gradation curve. His motto is, “We are uncovering the black magic of concrete mixture design one mixture at a time.”
On his web site you can take an entire college course in concrete materials and mix design—for free! One interesting development is his test for workability, which is not equivalent to slump. This has always been a point of contention when discussing performance-based specifications, since there has never been a simple way to measure (and specify) finishability. If you ever have problems with workability, pick up Tyler’s Recommended Specification for Optimized Graded Concrete for Flowable Applications.