Revision of C78/C78M-22 Standard Test Method for Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading)
Rationale
- Section 9.2 requires the distance between the fracture location and the nearest support for calculation of modulus of rupture, when the line of fracture is outside the middle third. - Section 8 currently specifies width and depth measurements but does not explicitly require measurement or recording of this distance. - Laboratories measure this dimension inconsistently, introducing avoidable variability. - The proposed language mirrors the existing width and depth procedure (three measurements averaged) to maintain internal consistency. - Adding this requirement improves repeatability and aligns precision with existing dimensional measurements (nearest 1 mm [0.05 in.]). - This change clarifies existing practice and does not alter the calculation, equipment, or intent of the test method.
Work Item Status
Date Initiated: 02-09-2026
Technical Contact: Mark Dornak