ASTM C1609/C1609M-24
Standard Test Method for Flexural Performance of Fiber-Reinforced Concrete (Using Beam With Third-Point Loading)

Standard No.

ASTM C1609/C1609M-24

Release Date

2024

Published By

American Society for Testing and Materials (ASTM)

Latest

ASTM C1609/C1609M-24

Introduction

Standard Overview and Technological Evolution

ASTM C1609/C1609M-24 is the core standard for evaluating the flexural properties of fiber-reinforced concrete (FRC). It utilizes the third-point loaded beam test method under a

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Test principle and parameter system

Parameter	Definition	Calculation formula	Engineering significance
First peak strength (f₁)	The first extreme point of the load-deflection curve	f₁=P₁L/bd²	Represents the bearing capacity before cracking
Residual strength (f₁₅₀ᴰ)	Residual load at deflection L/150	f₁₅₀ᴰ=P₁₅₀ᴰL/bd²	Evaluation of post-cracking ductility
Equivalent bending strength (fₑ,₁₅₀ᴰ)	Energy absorption conversion strength	fₑ,₁₅₀ᴰ=150T₁₅₀ᴰ/bd²	Comprehensive performance indicators

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Key implementation requirements

Specimen Preparation Specifications

The new standard specifies that: Specimens must be cast in a single layer (7.2.1), the use of vibrators is prohibited (7.2.2), and only external vibration molding is permitted. Typical specimen dimensions are:

• 100×100×350mm (300mm span)
• 150×150×500mm (450mm span)

Test System Configuration

A closed-loop servo-controlled testing machine (6.1) must be used, and the deflection measurement device must eliminate the influence of support system deformation (Figure 1/2). Data acquisition frequency requirements:

• Initial stage (deflection ≤ L/900): ≥2.5Hz
• Subsequent stage: ≥2Hz

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Technical points analysis

Size effect warning: The standard specifically points out (Note 5) that the specimen size will significantly affect the test results, especially when the ratio of fiber length to specimen cross-sectional size is greater than 1/3, the fiber orientation effect will make the data incomparable.

Precision Verification: Single laboratory coefficient of variation (Table 2/3):

• First peak strength COV=8.3%
• Residual strength COV=16-18%

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Engineering application suggestions

1. For steel fiber reinforced concrete, it is recommended to use 150mm standard specimens to reduce size effect
2. The deflection measurement system needs to be calibrated before testing. The measured f₁ deflection should deviate from the theoretical value (Note 11 formula) by less than 10%
3. When cracks are located outside the 1/3 of the span (9.10), the data should be invalidated