The bond strength test of AAC (Autoclaved Aerated Concrete) blocks measures the adhesion or bond between AAC blocks and mortar, which is crucial for the structural integrity of masonry walls and constructions. Here’s a detailed explanation of how the bond strength test is conducted:
Purpose of the Bond Strength Test:
The bond strength test assesses the ability of AAC blocks to bond with mortar, ensuring the stability and durability of masonry structures. A strong bond between AAC blocks and mortar is essential to resist stresses such as wind loads, seismic forces, and thermal movements.
Equipment Required:
- AAC Block Specimens: Representative AAC blocks with specified dimensions.
- Mortar: Mortar mix prepared according to standard specifications.
- Testing Machine: A tensile testing machine capable of applying a specified load and measuring the force.
- Measuring Devices: Instruments for measuring dimensions and cracks, such as calipers or vernier scales.
Procedure:
- Preparation of AAC Block Specimens:
- Select representative AAC block specimens that are fully cured and free from visible defects.
- Measure and record the dimensions (length, width, height) of each specimen.
- Preparation of Mortar and Bedding:
- Prepare mortar mix according to standard specifications, ensuring consistency in composition and mixing.
- Bed the AAC block specimen securely in the mortar mix, ensuring full contact between the AAC block and mortar bedding.
- Curing of Specimens:
- Allow the mortar to cure and set according to specified curing conditions (typically 28 days or as per standard procedure) to ensure proper bonding.
- Bond Strength Testing Setup:
- Secure the AAC block specimen in the testing machine setup, ensuring it is aligned properly for tensile testing.
- Apply a tensile load gradually and uniformly to the AAC block specimen.
- Application of Load:
- Apply a specified tensile load at a constant rate until the AAC block separates from the mortar bedding or until failure occurs.
- Record the maximum load applied (P) at the point of separation or failure.
- Calculation of Bond Strength:
- Calculate the bond strength (σ) between the AAC block and mortar using the formula: σ=P/A
where:
- P is the maximum load applied during testing (in Newtons),
- A is the cross-sectional area of the bond interface between the AAC block and mortar (in square meters).
- Repeat and Average:
- To ensure accuracy, repeat the test with multiple AAC block specimens from the same batch or lot.
- Calculate the average bond strength for more reliable results.
Interpretation:
- Higher bond strength values indicate better adhesion between AAC blocks and mortar, ensuring stronger masonry constructions.
- Results from the bond strength test help in selecting appropriate mortar mixes and construction practices to achieve reliable and durable masonry bonds.
Standards:
- The bond strength test of AAC blocks is typically conducted according to international standards such as ASTM C1072 (Standard Test Method for Measurement of Masonry Flexural Bond Strength) or equivalent national standards.
By conducting the bond strength test, manufacturers and engineers can ensure that AAC blocks are used effectively in masonry applications, providing stability, durability, and safety in construction projects.
