Concrete Mix Design
Concrete Mix Design
(OP)
I am trying to prepare trial mixes to achieve a specified strength class with some given aggregates and CEM1 and I have a couple of questions
1) Is it necessary to weigh the aggregates oven dry (if so, how come the aggregates for batching are not weighed oven dry)?
2) Can I go ahead and perform the mix design without performing a test for absorption on the fine aggregates (the local labs are not equipped to do absorption on fine aggregates)
I also would like to have the reference to the BS EN codes for concrete mix design.
Help would be much appreciated
Thanks
1) Is it necessary to weigh the aggregates oven dry (if so, how come the aggregates for batching are not weighed oven dry)?
2) Can I go ahead and perform the mix design without performing a test for absorption on the fine aggregates (the local labs are not equipped to do absorption on fine aggregates)
I also would like to have the reference to the BS EN codes for concrete mix design.
Help would be much appreciated
Thanks





RE: Concrete Mix Design
Absorption is a simple test. If you have a scale and an oven you can do it. If the laboratory doesn't have at least this minimal equipment, don't use them. In the absence of absorption data, most fine aggregates from a siliceous origin will have an absorption of about 1 percent.
RE: Concrete Mix Design
RE: Concrete Mix Design
Further, I should have given a more complete response to the original post.
A concrete mix design is done under the premise that both the coarse and fine aggregates are in a saturated, surface-dry condition at the time of batching. SSD is a very transient condition which is why we need to know the absorption of the aggregates and their actual moisture content at the time of batching. This allows us to adjust the amount of water that we add to the mix to bring the aggregates back to the SSD condition and maintain the designed water-cement ratio. For example, if the actual moisture content is below the absorption we have to add an amount of water to the mix to compensate for the deficient moisture. Conversely, if the actual moisture content is above the absorption value we reduce the amount of added water so that we don't compromise the water-cement ratio and reduce the strength of the concrete.
RE: Concrete Mix Design
RE: Concrete Mix Design
I believe the equivalent BS is 812; but you should check that.
RE: Concrete Mix Design
Whats the correct mix ratio to acchiev 25Kn/m3 concrete strength?
RE: Concrete Mix Design
RE: Concrete Mix Design
RE: Concrete Mix Design
As far as I know there is no standard for mix design but only literature and practice, as it is obvious
RE: Concrete Mix Design
As mentioned previously there is no EN standard for mix design as such, the closest you will get is BS-EN 8500.