Materials Man

Does major industry use QA to hide behind? The cement industry appears to have accomplished this, who in the last 40 years remembers testing cement? we all now receive cement certs as a given, never challenged, well how could you? it’s from a factory like an AUDI car, problem is when we have driven the product we can’t sort out why the brochure product is not as advertised, we consumers of ready mix are the ultimate users, denied as real customers by the suppliers who use the powder, no link to powder maker so door shut. Is cement a hugely variable product, unknown to its true, down the line customers ? It’s base line for compliance is so low and set by themselves that it could vary enormously above it’s minimum.

Think about concrete durability for trunk roads in Scotland, all codes are ignored and the employer ’s requirements specify a minimum requirement of a free W/C ratio of 0.4. Does this not tell you about free w/c ratios in actual production and the trust in the ready mix industry?

I would like to see more cement testing, problem is, it will comply, my concern is how variable is it? Don’t see clients specifying this, it would seem to be the province of a ready mix supplier who buys cement from another company. Probably it is happening, but will we users of ready mix ever find out?

Am I too cynical?

How hard can it be to mix four ingredients to produce a stated outcome? aggregate, cement, water and an admixture (or two) We have probably done three of them around the house with a shovel and a board. I once made a whole patio of slabs with my own formwork with embedded red chips floated into the surface. and the real reason for doing it was to prove a mason wrong, whilst having a pint with him he declared, you will never make them frost resistant! Want a bet, I internally cogitated? I was impressed one of his durability factors was frost attack. Most builders still adhere to washing up liquid being a cure all.

I have to admit to having been responsible for several project based concrete mixing plants both here and in the Middle East, so I can answer my own question. Things can and do go wrong. That is what worries me about European specifications where the supplier is in charge of declaring the quality of his own production. Sure we can do identity testing and it’s frequency can be every load if the client wants. It’s not the same as conducting compliance testing to the same spec as the supplier uses, only collecting and using more data. Yes the suppliers have QA and it is third party accredited, they often own the cement source as well so when and if the cement strengths take a tumble, they as internal customers, should be first to know, Aye right! My best supply of concrete has come from small family concerns supplying to medium sized projects, why is it that supply from the majors is so inconsistent? I have sworn never to work with certain suppliers, but when forced to, say 200 miles away from the “we will never work together again” project, they are brand new! this has happened to me several times, and to others who may comment on this post.

Seems to come down to people, not systems, my pint sharing mason couldn’t make durable concrete, where my red slabs outside my back door testify that I can.

Running up to Christmas, just had company Christmas lunch, do you notice when the loud music starts the older guys head for the door? I am part of that congregation.

Anyway I am old enough to remember digging sand replacement densities in lean mix and wondering at the mysteries of comparing them to a theoretical density. Then there used to be a minimum strength, then a minimum and a maximum, then if my memory is correct, a minimum again. Whether it was the blacktop lobby or a diminishing amount of long greenfield road jobs, the good old leanmix was no longer in favour. perhaps also by then enough roads had been built and the resultant transverse cracks were apparent. Again by memory (this site is for conversation, not for me to reel off details checked and verified, thats for you lot!) so memory, was not lean mix a not allowed roadbase on Scottish roads?

I am getting round to HD 26/06 and IAN 73/06, isn’t the IAN wonderful reading? not, but as I see it trunk roads, 80MSA stuff, brings in lean mix, OK it’s HBM now and you have to design it on 365 day results, add PFA, and test beams, cylinders, cubes and any other testable shape, for creep, compression, bending strength, indirect tensile strength and tensile strength, whow. why is it engineers (them with degrees) want to test brittle materials for everything? is it because they can? Flexible materials get of lightly, or did, another post!

where was I? Christmas lunch top up happening! Oh yes back to the past lean mix road bases are in, and the only fight back the blacktop boys have is EME2, how lucky is that that a flexible material is stiff? Trust the French, and why? Well the trunk roads in France are essentially DBFOs (design build finance and operate) so the contractors control the research. Yes, the most Social (with development) part of Europe allows the market place to sort out the roads.

Ask yourself how many “developments” in UK blacktop have come from Germany and France?

Sounds like a bit of a rant, but Talisker makes you type, see what I saying, where’s the leadership is road design? lean mix good, lean mix bad, new lean mix necessary for trunk roads but test it for everything and have design parameters for year old tested specimens.

explain that to an estimating manager!

David?

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, fire in shales. It’s just that spent oil shale is more reliable 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 reamergence of lean mixes (hydrualically bound material) from the stiffnesses required in the design manuals (HD 26/06), spent oil shale should not be omitted as an aggregate.