New Standard Gets to Core of Axis Length
Technicians drill concrete-core samples from structures to find in-place physical properties such as strength, density, cracks, and deterioration.
On Aug. 10, ASTM Committee C09 on Concrete and Concrete Aggregates approved new ASTM C 1542/C 1542M, Standard Test Method for Measuring Length of Concrete Cores. The standard provides two procedures that measure a core along its axis to determine its length, used in:
Absorption, density, and voids analysis;
Cement-content analysis; and
A task group of ASTM Subcommittee C09.69 on Miscellaneous Tests developed the standard. Subcommittee chair Howard (Buck) Barker, PE, a construction materials engineer with RVT Engineering Services, LLC, Wausau, Wis., says the new standard can be used to measure any core along its axis, and explains why its important. The primary (most frequent) use will be calculating compressive strength to investigate the current condition of a structure or to evaluate low strength test results (by American Concrete Institute 318-02 Section 5.6) from compression tests of 6 x 12 cylinders, he says.
Having ASTM C 1542 closes the legal gap that existed and formerly raised questions regarding how compression test specimens (cores) were measured, he continues. In addition, tests that require a volume to be determined now have an accurate way to obtain length, one of the important three dimensions needed for that calculation. It may even be a simple way for companies who drill to obtain core samples to accurately get paid, since many are paid by the inch or by feet of drilling (or some unit of length).
The task group developed new Standard ASTM C 1542/C 1542M to dispel the confusion caused by misunderstood applications of ASTM C 174, Test Method for Measuring Thickness of Concrete Elements Using Drilled Concrete Cores, says Barker. The new standard determines core length but not concrete dimensional tolerances or structural-element thickness often used to establish compliance with design specifications as outlined by ASTM Test Method C 174.
He offers a little history. ASTM C 174, [which] was written during World War II to measure the thickness of airport runways used for military purposes, also measures cores, he says. That method measures the distance between two parallel surfaces (i.e., the ends of the core) regardless of how crooked or out-of-square the ends are from the axis of the core. It has been confused as a method to measure the length of the core along its axis. Technicians performing certain tests such as ASTM C 42, [Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete] needed to know how to measure the length of a core along its axis to perform the calculations necessary to measure compressive strength using ASTM C 39, [Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens] but no method was available until ASTM C 1542.
Members of Subcommittee C09.69, such as engineers specializing in cement and concrete, a petrographer, a chemist, and others developed the standard to provide uniformity in the method used to measure the length of a core, Barker concludes. This will result in greater accuracy in all the other test procedures where measuring the length of a core is required.
For further technical information, contact Howard Buck Barker, PE (phone: 715/675-0700). Committee C09 meets June 15-18 in Denver, Colo. For membership or meeting details, contact Jim Olshefsky, director, Committee Services, ASTM International (phone: 610/832-9714).
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