Understanding how concrete responds to stress is crucial in construction. One essential property is the Modulus of Elasticity, which relates normal stress to strain within specific limits. While various codes provide formulas, accuracy can be a concern. To address this, ASTM C469 offers a reliable method for precisely determining the modulus of elasticity of concrete.
Two main tools are employed in the ASTM C469 test:
A sturdy machine designed for assessing the modulus of elasticity.
An apparatus attached to the concrete specimen for measuring strain accurately.
Concrete specimens, either molded cylindrical or drilled core, must adhere to specific conditions:
Test within an hour of removal from curing/storage.
Follow the same storage and ambient conditions as molded specimens.
To ensure accurate results, follow these steps:
Maintain a constant temperature throughout the test.
Prioritize the determination of compressive strength using two specimens.
Attach strain-measuring equipment securely to the specimen.
Place the specimen on the lower platen, aligning its axis with the upper bearing block.
Apply the load carefully, observing gauge performance. Correct any abnormal responses.
Apply continuous load and record applied load and longitudinal strain at 50 millionths strain and 40% of the ultimate load.
Using the obtained data, the modulus of elasticity (E) can be calculated using the equation:
E=S1e2
Where:
The modulus of elasticity is computed with an accuracy to the nearest 50000 psi (344.74 MPa), providing a reliable measure for concrete properties.