Measurements used for slump in concrete?

zeilberg, Oct 9, 8:23am
hi all. im trying to pass concrete in my building apprenticeship and failed last time because i didnt know how to order the slump for concrete. i then asked the concrete driver a few weeks later and he said 80 is dry, 100 is standard and 120 is wet? just wondering is this true? thanks
budgel, Oct 9, 8:36am
In the old days 4" slump was standard. That is 100mm, so yes.
It is not strictly a test of wetness, more of workability which can be altered without increasing the amount of water by the use of admixtures.

I'm assuming you know about the slump cone.
aj.2., Oct 9, 8:43am
To really test the slump , you need to fill the cone , then lift it off , and measure the height of the concrete, the wetter that it is , the more it will slump.
80 slump is dry , but it depends on the cement , and if any hardeners have been added.
120 slump is usually for use with a pumping unit.
If it is too dry it blocks in the tube.
zeilberg, Oct 9, 9:19am
yes i do. and i gues that's where i got confused because yeah its not just the water that determines the slump but also the aggregate size/ratio and admixtures like you said. thank you
griev, Oct 9, 9:32am
Have you sussed the answers you req?
If not repost and I will give you a crash course
zeilberg, Oct 12, 7:42am
Bump.
hi griev
This is what im going to say to the bcito coordinator. Slump is purely the work-ability of concrete. what decides this work-ability is the size of aggregates required, mpa rating and ad-mixtures required and then water is adjusted to suit the all the requirements. ? 80mm dry, 100mm standard and 120mm wet.
tintop, Sep 4, 12:16am
Given all the above is correct except there being excessive water and higher slump than the mix design allows, leads to excessive shrinkage - esp on pre/post tensioned work. Disastrous on bridge work where the total shrinkage of the main box section exceeds the space allowed for movement at the free end.