Concrete Performance Curves
Free for the asking: An Excel workbook for analyzing concrete lab data:
Development of Concrete Mixtures
When developing concrete mixture designs, a series of test batches with varying cementitious content are created for trial batching. In the old days, concrete mix practitioners referred to this as a cement curve containing three to four mixture designs. Concrete mixtures are proportioned with yield, slump, air, admixture dosage, and workability, held consistent. As the cementitious content is increased or decreased, the volume of the concrete mixture is readjusted by proportioning the aggregates to a fixed yield.
There are several methods for proportioning the aggregates to constant yield. The traditional method is to proportion each concrete mixture with the same coarse aggregate content and adjust the sand, referred to as “sand to yield.”
Current concrete mix practitioners often design mixtures with a focus on blended aggregates, complying with a gradation curve or a “Workability / Coarseness factor. In this scenario, the total aggregate package is adjusted for changes in cementitious volume, with a constant sand/stone ratio and total combined aggregate fineness modulus (FM).
Concrete break data for 7- and 28-day strengths are analyzed and plotted, as well as strength vs. water cementitious ratio (w/cm) and strength vs. cementitious content. The attached Excel workbook will plot the data for you. Input your design strength f’c and over design (f’c), and the required w/cmratio and pounds of cementitious will be calculated from the curve.
Utilizing Three of four point curve data, Straight Line or Polynomial curves
It is a great tool for investigating the economics of overdesigning your concrete with too high a cementitious content or the cost of high batch-to-batch variation.
Just contact me and request the "Cement Curve Workbook" free for the asking.