re SHALE AS ADDITIVE
I don't have access to any studies done with regard to shale as a cement additive but I know that burnt(calcined) shales have been extensively used as a cement additive due to their pozzolanic properties.
At the following website, Holcim claim to have performed comprehensive tests on their shale+limestone cement called "Optimo" ;-
Here is the relevant extract;-
" Holcim's Dotternhausen cement plant near Rottweil in southern Germany has deposits of shale in the immediate vicinity that are unique in Central Europe. This shale contains combustible components that are used to produce electricity; in the process the shale is chemically transformed. The burned shale is chemically reactive, i.e. it is capable of hydraulic and pozzolanic reactions. It is an ideal clinker substitute, to which shale cements already used in Germany impressively testify. Nevertheless, the properties of Holcim Optimo, a mixture of clinker, limestone and burned shale, were meticulously studied in a comprehensive range of pilot tests. These showed that very finely ground shale has a positive impact on several properties of concrete. The new Nano-T® technology increases the effective packing density, and thereby the density of the concrete structure. Certified to SN EN 197-1 for all applications of concrete, Holcim Optimo is the perfect all-rounder and the answer for those looking for a new standard cement with strong eco-compatible properties."