When should cylinders made for determining serviceability of a structure be removed from their molds?

Cylinders made for determining the serviceability of a structure should be removed from their molds at the time of the removal of the form work. This timing is crucial because it allows the concrete to achieve an initial set and sufficient strength to support itself without the mold, while also being reflective of actual conditions encountered during construction.

Molds provide support for the concrete during the initial curing phase, and removing the cylinders too early can lead to deformation and damage, making the data they provide unreliable. Allowing the cylinders to stay in their molds until the formwork is removed ensures that they properly reflect the concrete's properties and conditions experienced on-site, which is essential for accurate assessment of the material's performance and serviceability.

Removing the cylinders at different times could lead to inconsistencies in the test results, which is why it's important to follow established practices like removing them with the formwork, ensuring they are cured properly while maintaining the integrity needed for accurate testing.