What is the proper procedure when a concrete cylinder test fails to meet the specified compressive strength?
Correct Answer
C) Order core samples from the structure for testing
When cylinder tests fail, core samples should be taken from the actual structure and tested. Cylinder failures can result from handling, curing, or testing errors, while core samples provide a true indication of in-place concrete strength.
Why This Is the Correct Answer
Core sampling from the actual structure is the proper procedure because cylinder test failures can occur due to improper handling, storage, curing conditions, or testing procedures that don't reflect the actual in-place concrete quality. Core samples provide a direct measurement of the concrete's actual strength within the structure, eliminating variables that could affect cylinder tests. This method gives the most accurate assessment of whether the concrete in the structure meets specifications before making costly decisions about removal or acceptance.
Why the Other Options Are Wrong
Option A: Ignore the result if only one cylinder fails
Ignoring failed cylinder tests is never acceptable as it could compromise structural safety and violate quality control requirements. Even a single failure indicates potential issues that must be investigated.
Option B: Test additional cylinders from the same batch
Testing additional cylinders from the same batch won't provide information about the actual in-place concrete strength, and if the batch itself has issues, more cylinder tests will likely continue to fail.
Option D: Immediately remove and replace the concrete
Immediately removing and replacing concrete is premature and costly without first determining if the in-place concrete actually has strength deficiencies, since cylinder failures may not reflect actual structural concrete quality.
Memory Technique
Think 'CORE before CHORE' - take core samples before doing the chore of removing concrete
Reference Hint
ACI 318 Building Code Requirements for Structural Concrete, Chapter 26 - Quality Control and Testing, or Florida Building Code Chapter 19 - Concrete
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