lakeroadster
Well-known member
I’ve tried to use the saying “Trust, but Verify” whenever I am working with a contractor. The following is what I did when the slab was poured on my barn to ensure I received the concrete I asked for. My contractor and I agreed to this, and everything went great. Additionally I had a local testing lab take 5 samples the day of the pour and perform mechanical tests at 14 day, 28 days and 56 days. More on that starting at Post #126 here: https://talk.classicparts.com/threads/lakeroadsters-high-country-barn.22110/page-7
A couple weeks before the pour get a copy of the concrete plants “Trial Mixture Summary Sheet” for the strength that you want. It will look something like this:
Trial Mixture Summary Sheet (see photo below)
Plan ahead.
You’ll want to be at the job site when the concrete truck arrives. Each individual truck that arrives will have a Mix Sheet for the load it is carrying. This Mix Sheet defines the breakdown of the materials and will correlate with the Trial Mixture Summary Sheet. It will look something like this:
Mix Sheet (See pink photo below)
Be up front with your contractor and tell them you are going to do the following:
Once you get the Mix Sheet you can check it against the Trial Mixture Summary Sheet. The critical thing is the Water Ratio to Cementitious Ratio.
That’s why it is critical that you watch to see how much water they add at the job site. If you approve the load and they start adding water, find out how much water and re-run the numbers.
The ratio on the mix sheet is the maximum.
(Note that as the mix strength increases this number drops).
If they add too much water and the ratio increases above the maximum specified number on the Trial Mixture Summary Sheet, that’s too much water, reject the load.
In the above example 4,000 psi Mix Sheet:
1,951.6 lbs = 224 Gallons of water was used
4,540 lbs = Amount of cement
1951.6 / 4540 = 0.43 = which is the Water Ratio to Cementitious Ratio
0.43 is less than the specified 0.49, therefore the Water Ratio to Cementitious Ratio is ok.
A couple weeks before the pour get a copy of the concrete plants “Trial Mixture Summary Sheet” for the strength that you want. It will look something like this:
Trial Mixture Summary Sheet (see photo below)
Plan ahead.
You’ll want to be at the job site when the concrete truck arrives. Each individual truck that arrives will have a Mix Sheet for the load it is carrying. This Mix Sheet defines the breakdown of the materials and will correlate with the Trial Mixture Summary Sheet. It will look something like this:
Mix Sheet (See pink photo below)
Be up front with your contractor and tell them you are going to do the following:
- Be onsite for the entire pour
- Review the mix sheet and the amount of water that will be added.
- Either approve or reject the load of concrete if it doesn’t meet the Trial Mixture Summary
Once you get the Mix Sheet you can check it against the Trial Mixture Summary Sheet. The critical thing is the Water Ratio to Cementitious Ratio.
That’s why it is critical that you watch to see how much water they add at the job site. If you approve the load and they start adding water, find out how much water and re-run the numbers.
The ratio on the mix sheet is the maximum.
(Note that as the mix strength increases this number drops).
If they add too much water and the ratio increases above the maximum specified number on the Trial Mixture Summary Sheet, that’s too much water, reject the load.
In the above example 4,000 psi Mix Sheet:
1,951.6 lbs = 224 Gallons of water was used
4,540 lbs = Amount of cement
1951.6 / 4540 = 0.43 = which is the Water Ratio to Cementitious Ratio
0.43 is less than the specified 0.49, therefore the Water Ratio to Cementitious Ratio is ok.
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