Stamping a concrete mix design
Stamping a concrete mix design
(OP)
I'm working as a consultant to a contractor for a large WWTP upgrade. The design engineers are requiring an engineers stamp on all concrete mix designs. I have been asked to stamp some existing mix designs from the local concrete supplier. Some have historical test results, others do not. My question is what should I look for to responsibly stamp these designs and what is my liability in doing so? I don't see a problem with stamping a design but does that mean I'm certifying it will meet the required strength? What is the accepted design guide for concrete mixes? I'd appreciate any input you all might have.
Bret Rinehart, PE
Rinehart Engineering & Construction
Bret Rinehart, PE
Rinehart Engineering & Construction






RE: Stamping a concrete mix design
That said, if the engineer of record is requiring it on the construction documents/specs, I'd be forthright about it and call him/her up to ask what exactly they are looking for in an "engineered" mix.
What you could do, is write a letter, stating that in your engineering opinion:
1. You have reviewed the mix and found it to meet x, y, and z of the specifications and,
2. That it appears to meet the intent of the specifications and design documents and,
3. You qualify it to state the truth, that past performance of a certain mix does not necessarily mean a guarantee of future performance and,
4. You also refer them to chapter 5 of the ACI code as to acceptance of concrete and that it is typically the engineer of records responsibility to respond to concrete test results with respect to their design.
I'm not sure I'd agree that developing a mix design is truly engineering and requires a stamp. But you can always express an opinion and qualify it in an engineering letter.
RE: Stamping a concrete mix design
As you have mentioned, the mix design will be for a large project. Therefore, this project will have a good specification to go along. The mix design should be developed to satisfy all the requirements specified in the specification. Do not think that the mix that you are going to stamp may meet all these requirements. In fact, it may take revising the mix few times before getting the correct one. More over, the results of the trial mix is going to tell the truth, there is very little to no requirement of a engineer's stamp to certify this.
RE: Stamping a concrete mix design
JAE gave very good advice. Such a letter limits your liability to a review that the design meets x, y, and z provisions of the spec but does not guarantee performance.
RE: Stamping a concrete mix design
RE: Stamping a concrete mix design
RE: Stamping a concrete mix design
I agree with JAE. I've reviewed mix designs but never sealed them; I've treated them like shop drawings as someone above mentioned. What I do is compare the mix with NYSDOT specifications.
RE: Stamping a concrete mix design
RE: Stamping a concrete mix design
RE: Stamping a concrete mix design
Bret Rinehart, PE
Rinehart Engineering & Construction