Fiber cement flat sheets, a combination of inorganic binders and fibers, undergo rigorous acceptance tests to ensure they meet specific standards. This two-part series explores these tests in detail, beginning with Part 1.
Acceptance tests are crucial to determine if a batch of fiber cement flat sheets adheres to defined specifications. Samples are drawn from continuous production or delivered consignments for testing.
In consignments, sheets of identical size, category, and type form a lot. The sample size varies based on the lot size, as indicated in Table 1.
Size of the Lot | Sample Size |
---|---|
≤ 150 | 3 |
151 to 180 | 3 |
181 to 500 | 4 |
501 to 1200 | 5 |
1201 to 3200 | 7 |
3201 to 10000 | 10 |
Two square specimens of 250 mm x 250 mm per sheet are cut from the same part. Conditioning involves seven days in ambient conditions for equilibrium strength and 24 hours in water for wet strength.
A bending test machine, parallel supports, and a micrometer are used. The test piece is loaded, and breakage should occur within 10s to 30s. Modulus of rupture (Rf) is calculated using the formula provided.
Three test specimens are cut, with dimensions of at least 600 mm x 500 mm. A sealed frame is placed on top, and specimens are kept in a controlled environment for at least 7 days.
The frame is filled with water, and the test lasts for 24 hours. Afterward, examine the underface for moisture traces, ensuring no formation of water drops.
Ten sets of paired specimens are cut. Cooling units are used to reach -20°C, 2 hours after starting freezing, with an air circulation unit in the freezing chamber.
Specimens undergo 50 freeze-thaw cycles. Each cycle includes cooling to -20°C, thawing in water, and subsequent freezing. Afterward, specimens are examined for cracks, delamination, or defects.
This comprehensive testing regimen ensures that fiber cement flat sheets meet stringent quality standards. In Part 2, we delve into additional tests to provide a thorough understanding of the evaluation process.