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?

One Response to “Lean mix full circle?”

  1. January 27, 2009 at 8:47 pm

    I liked Lean Mix when it was nice and simple. I think back to the days of West Adamston Improvement on the A96 and the A94 (now A90) Parkford to Balnabriech Improvement. We quarried our own gravel, mixed it with a sprinkle of cement and a wee drop water in the Steelfields (the white one with the huge red “M” on the side) and hauled it to the paver with 6W tippers. Good old Jim McFarlane was waiting there patiently to lay this grey mixture to perfect line and level before whacking it to death with a dirty big roller then spraying the silver stuff all over it. It was cheap, it was easy but only a few were brave enough to try it. We now have to cope with fancy new names and exotic recipes for the grey stuff. To be honest it’s beyond me. I thank the Lord for the materials men of this world who keep me right in these matters.

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