The burnt shale
alone develops a strength of 30 MPa, which makes it a valuable low cost cement constituent.
Township roads then were mostly covered with "red dog," the burnt shale
that is left when the pile of discarded stone and coal from a mine tipple goes through spontaneous combustion.
Describing her work on the "terrible beauty" of Durham's coastline, Konttinen wrote: "Coal-black sand frosted with sulphur, purple rocks of burnt shale
, pebbles luminous with iron dioxide.
However, demolition and site clearance identified potential problems in the form of burnt shale
and unfavourable geology.
Kunda Nordic Cement in Kunda, Estonia, and Holcim Dotternhausen cement plant are using burnt shale
as a cement component.
Kikas and coworkers, studying the influence of OSA on the properties of self-stressing shale ash cement, concluded that the concrete made with burnt shale
is characterized by high strength, high frost resistance, and low permeability.
Research on Estonian oil shale ash has shown that the use of burnt shale
as a feedstock in production of cement is very effective.
In Dotternhausen, Germany, for example, clinker (raw meal and oil shale) from the rotary kiln and hydraulic burnt shale
from fluidised bed combustion unit together are used to produce Portland-burnt shale
That means that the burnt shale
, when mixed with water, gets hard and develops strength like cement.