Quality control testing reveals that 5% of concrete cylinders from a pour failed strength tests. According to ACI standards, what action is typically required?
Correct Answer
A) Investigate the cause and potentially take core samples
ACI standards require investigation when cylinder tests fail, including potential core sampling to verify in-place concrete strength. The 5% failure rate indicates a potential quality issue that needs assessment.
Why This Is the Correct Answer
According to ACI 318 standards, when concrete cylinder tests fail to meet specified strength requirements, the contractor must investigate the underlying cause rather than simply accepting or rejecting the concrete outright. The investigation process typically includes taking core samples from the actual structure to determine if the in-place concrete strength is adequate, since cylinder test failures don't automatically mean the structural concrete is deficient. This approach allows for a thorough assessment before making costly decisions about concrete removal or structural modifications.
Why the Other Options Are Wrong
Option B: Reject the entire concrete pour immediately
Immediate rejection of the entire pour is premature without proper investigation, as cylinder test failures may not reflect the actual in-place concrete strength due to factors like improper curing of test specimens.
Option C: Accept the concrete if less than 10% failed
While increasing future testing frequency may be prudent, it does not address the immediate concern of the failed tests and does not meet ACI requirements for investigating current quality issues.
Memory Technique
Think 'CSI' - when concrete tests fail, you must investigate like a detective, and Core Sampling Investigation is the key tool.
Reference Hint
ACI 318 Building Code Requirements for Structural Concrete, Chapter 26 - Quality Control and Testing
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