Different mixes in same placement
Different mixes in same placement
(OP)
We have a large concrete placement planned and the contractor wants to use 2 different batch plants. The issue is each plant has a different proposed mix. Each mix by itself would be acceptable but I don't know if it would be a good idea to mingle the 2 mixes. One mix proposes the use of Type 2 cement while the other is proposing Type 1 with GGBS. In addition, they are using different AE and WR admixtures. Any thoughts would be appreciated. Thanks.






RE: Different mixes in same placement
RE: Different mixes in same placement
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: Different mixes in same placement
RE: Different mixes in same placement
RE: Different mixes in same placement
RE: Different mixes in same placement
I assume the hourly plant capacity of a single plant is not enough. Trucks are not a problem, since most trucks can be used at any plant that is a central mix facility.
If this job is that big, there should be a way to work out a way to upset the normal regular customer demands. Admixtures could be a problem since often the admixture equipment is installed and maintained by the admix supplier that has a long history of testing and documentation. Concrete suppliers often have a loyalty to different suppliers (aggregate, cement, cement replacements and admixtures) and a single job must be big enough to upset the apple-cart. The selection of the date and time of the pour can usually be shifted to early or late hours or a different day of the week to
As a concrete inspector, I was involved in many large pours where I had to be there the day before of materials sampling and often be there at 1:00 AM to 5:00 AM to do the preliminaries for a 500 to 3000 yard pour. There is not enough margin in a single bid project to upset the normal customers. Very often the pour schedule can be adjusted to make the most out of the situation to get a better time frame for traffic.
It is usually a team effort between contractors and suppliers to create a compatible situation. There are always possible problems with large pours that cannot be predicted.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: Different mixes in same placement
RE: Different mixes in same placement
Mike McCann
MMC Engineering
RE: Different mixes in same placement
BA
RE: Different mixes in same placement
Perhaps I am missing something here...
Mike McCann
MMC Engineering
RE: Different mixes in same placement
BA
RE: Different mixes in same placement
Mike McCann
MMC Engineering
RE: Different mixes in same placement
In New York City, that would get them to walk off the job.
In Southern California, they would just add so much water you couldn't tell the mixes were different anyway.
RE: Different mixes in same placement
Maybe the owner needs to be apprised of the risks and be allowed to have some input.