Testing, testing: In situ crushing resistance test

This month in Testing, testing, we take a look at the in situ crushing resistance test.

What it’s used for?
The in situ crushing resistance test is used to determine the ability of a screed to carry the traffic required of it, and to identify any areas that may not be strong enough so that they may be treated prior to the application of floorcoverings.

Increasingly, this test is used by contractors to detect any inadequacies in mix proportions, mixing or compaction of the screed, and it is advised to use it if there are any suspicions that these problems may be present.

How it’s done?

  • The area of testing should be cleared of any contaminants and the screed, which should be at least 14 days old, surveyed for any defects before placing a BRE screed testing device (see Figure 1) on the area to be tested
  • An annular 4kg (or 2kg, if a floating screed under 75mm is being tested) weight is dropped a distance of 1m down the vertical rod on the device
  • At the bottom of the rod, there is a case hardened steel foot (an anvil) which, when struck, transmits the impact of the weight onto a 500mm2 area of the screed
  • The weight is dropped a further three times onto the same area of screed, and after the fourth consecutive drop the BRE screed testing device is removed. The depth of the resulting indentation in the screed is measured using a depth gauge

Measuring screed performance

Acceptance limits of the indentations vary, depending on the type of screed being tested and the final use of the screed (see table below). For example, a lower strength screed is more acceptable in a domestic, low traffic environment than in areas of heavy traffic, such as a warehouse or public area.

Table 2

Data from www.screedscientist.com

What to do next?
Should the results exceed these acceptance limits, F. Ball’s recently introduced surface reinforcement system, Stopgap SRS, should be applied to strengthen and reinforce the screed. The steps above should be repeated once it has been absorbed by the screed. Typically, indentation readings are less than 1mm following the application of Stopgap SRS, placing it well within acceptance limits.

To find out more about product testing, visit the F. Ball website.