This article originally appeared in the 2023 Q3 edition of Precast Today.
Questions from the Field is a selection of questions NPCA Technical Services engineers received from calls, emails, plant evaluations and comments on blog posts or magazine articles posted to Precast.org.
Charlie asks: How wide does a crack need to be in reinforced concrete to cause concern?
Some engineers, precast suppliers and customers believe that all cracks are bad. Aesthetically speaking, cracks may not be easy on the eyes. However, there are established guidelines to determine which cracks are not a concern for repair.
As a matter of fact, a lot of concrete needs to crack for stresses to transfer from the concrete to the reinforcing. These cracks are small and self-heal over time. So not all cracks are bad.
In ACI-224, “Control of Cracking in Concrete Structures,” there is a table (4.1) that serves as a good starting point to determine if a crack is a cause for concern.
It is important to note: These are general guidelines.
Jerry asks: I am in quality control at an NPCA-certified plant, and I am aware that we have requirements for retaining product inspection and other documentation for auditor review during the unannounced annual plant inspection. What options do we have for retaining records? Is there a specific format for these? Does it matter how we keep these records and documents?
NPCA technical experts answer:
NPCA certified plants are required to hold inspection records and other such documents for a minimum period of three years. However, the program does not stipulate how the plant retains this information. Plants are free to keep this information in hard copy, electronic form or any combination thereof.
In addition, plants are encouraged to participate in continuous improvement (Section 1.1.4) and to upload certain documents as stated in Section 184.108.40.206 and Part 2.5 of the Plant Terms and
Conditions of the NPCA Quality Control Manual for Precast Concrete Plants. NPCA provides a Certified Plant Information portal (myNPCA) for this purpose.
For more information on continuous improvement or the myNPCA portal, contact NPCA Director of Certification Programs Phillip Cutler, P.E., at [email protected] or (800) 366-7731.