Canadian Council of Independent Laboratories (CCIL) Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

In the context of using a 100mm x 200mm mould for internal vibration, the focus is on the effectiveness of the vibration process in consolidating the concrete without causing segregation or excessive air entrapment. Typically, the guideline for inserting a vibrator into a mould is to ensure that it penetrates the entire mass but is not inserted too frequently to avoid over-vibration, which can lead to the aforementioned issues.

With a mould of the specified dimensions, allowing for only one insertion ensures that the internal vibration is localized enough to effectively consolidate the concrete while preventing too much disturbance. This approach allows for adequate coverage and ensures that the concrete is properly vibrated throughout the mould's volume without risking improper compaction or weakening of the overall structural integrity.

Each additional insertion would increase the risk of negative effects, hence the recommendation for just one insertion in this case.