ASTM C1812/C1812M-22 PDF

Overview

ASTM C1812/C1812M-22 defines the standard practice for the design of journal bearing supports for use in the flexural testing of fiber-reinforced concrete beams. This standard is crucial for ensuring accurate flexural test results by specifying the roller supports used at each end of the beam during third-point loading test methods, particularly ASTM C1399/C1399M and ASTM C1609/C1609M. The primary aim is to minimize and control the friction at the supports, as inconsistent or excessive friction can artificially increase the measured load resistance and distort test outcomes.

ASTM C1812/C1812M-22 provides guidelines on the selection, design, manufacture, and maintenance of the roller assemblies, including recommendations for materials, surface finish, lubrication, and dimensional tolerances. The standard also includes a method for correcting apparent load resistance values, accounting for the influence of support friction.

Key Topics

• Friction in Beam Supports: Explains how friction at roller supports can affect the apparent load resistance of fiber-reinforced concrete beams during flexural tests.
• Journal Bearing Roller Design: Specifies requirements for rollers featuring metal-on-metal sliding surfaces, lubricated with grease, to ensure low and consistent friction coefficients.
• Applicability to Beam Sizes: Covers roller assemblies for both 150 mm (6 in.) and 100 mm (4 in.) deep beams with square cross-sections.
• Roller Types:
  • One type accommodates rotation parallel to the beam’s longitudinal axis, addressing any warping in test specimens.
  • The other type remains fixed to prevent beam overturning during testing.
• Correction Method: Provides a calculation for adjusting apparent beam load resistance measurements to account for known friction at the supports.
• Maintenance Guidelines: Recommends regular cleaning and greasing schedules to maintain roller function and friction performance.

Applications

• Flexural Testing of Fiber-Reinforced Concrete: Used in labs and quality control environments to ensure accurate measurement of residual strength and post-crack behavior in fiber-reinforced concrete beams.
• Test Method Compliance: Ensures proper support conditions for ASTM C1399/C1399M and ASTM C1609/C1609M, which assess the flexural performance of concrete using third-point loading.
• Structural Materials Research: Supports development and validation of new concrete composites by minimizing systematic error from test setup friction.
• Industry Quality Assurance: Facilitates repeatable, standardized tests across laboratories, supporting regulatory compliance and product certification for concrete containing fibers.

Related Standards

• ASTM C125: Terminology Relating to Concrete and Concrete Aggregates.
• ASTM C1399/C1399M: Test Method for Obtaining Average Residual-Strength of Fiber-Reinforced Concrete.
• ASTM C1609/C1609M: Test Method for Flexural Performance of Fiber-Reinforced Concrete (Using Beam With Third-Point Loading).
• ASTM D4950: Classification and Specification for Automotive Service Greases, referenced for lubrication of roller assemblies.
• SAE J404: Chemical Composition of SAE Alloy Steels, referred for material selection of the roller components.

Keywords: ASTM C1812/C1812M, fiber reinforced concrete, flexural beam test, journal bearing supports, roller supports, test method compliance, concrete testing standards, friction correction, laboratory quality assurance, structural materials testing.

This standard is essential in achieving reliable and consistent results in flexural testing of fiber-reinforced concrete beams by controlling roller support design and minimizing the impact of friction in laboratory environments.