Spent oil Shale is an industrially produced product, unlike blaze, or blase, which is not. Both materials have similar properties as the processes are the same, combustion in shales. It's just that spent oil shale is more reliably burnt  being the tip product from retorts that produced oil. Unlike blaze, which is colliery spoil (shale) which has self ignited. So flying out from Edinburgh you have or could have, great views of spent oil shale, literally mountains of it, bings we call it. It is a "specialist" recyclable product to West Lothian. But here is fact lost in time and now a perceived risk to modern engineers, sulphates, or more precisely sulphate attack. On this first materials and construction blog I am not prepared to reveal all my companies research findings, lets just say the M8 and the M9 have cemented spent oil shale beneath them, either as a road base or a subbase. From our construction of the Newbridge interchange I would say roadbase. However the perceived knowledge drifted down through time is "oh yes cement was added for frost resistance" that is true as spent oil shale is not frost resistant. But to return to the perceived risk of sulphate attack what has happened to the spent oil shale with cement added? It has not dissolved into mush as the M8 and M9 will testify. During a design and build contract we had sufficiently convinced a consultant to adopt spent oil shale as a road base with cement, trust me , this was not easy. The client however was very afraid. No cemented roadbase, lost opportunity. Given the re-emergence of lean mixes (hydraulically bound material) from the stiffnesses required in the design manuals (HD 26/06), spent oil shale should not be omitted as an aggregate.

3 Responses to “Spent Oil Shale”

  1. ThePath December 5, 2008 at 4:07 pm

    So spent oil shale seemingly has a good use and thus will increase in value.

    Shall i buy as much as I can cheaply now or does this materials test have a while to run yet with any surprising results.

    For someone not in the know….enlighten me as to how long the M8 and M9 sections containing spent oil shale as subbase or road base have been in existence?

  2. Ian December 8, 2008 at 1:56 pm

    I suspect all Spent oil shale is in the hands of the landowners and subject to leases. To buy some you would need a quarry operating license, backactors, trucks etc then try and get a lease.

    The M8 and M9 in this area were built in the mid 70s.

    It is not as simple as a single or combined set of tests, with a pass or fail. The problem is they do fail but the sulphates they have are non-reactive, just as the sulphates contained in hardened concrete fail some of the limits but are non-reactive. this can lead to a ridiculous situation of trying to use a crushed concrete backfill to a concrete structure and the sulphate rules preventing the crushed concrete being placed within 500mm of the structure.

  3. Ian May 16, 2011 at 6:32 pm

    Part of this project had an EME2 pavement on a 200MPa stiffness subbase, HRA on type 1, that pavement has survived under the wonkie deflectograph determination of lifespan, but the pavement with a proposed cemented subbase , not roadbase as my post proclaims, has in places zero life. Type 1 with HMB 35 to HD 26/01. Clearly a pavement with zero life is dubious and doubtful but that’s the deflectograph for you, but the same pavement with a cemented subbase ??

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