This is a site test to determine the surface texture of concrete pavement and is conducted by the laboratory staff. Most of the concrete pavement ( if without specified surface finishes ) requires a surface texture to provide non-skid resistance to pedestrians or traffic. This surface texture is usually formed with the use of a broom brushing transversely across the rigid pavement while the concrete is still green. The right time for forming this rough texture depends mainly on the site supervisor’s experience.
If brushing is too early while the concrete is still wet, the formed grooves will slump, resulting in no texture or the texture is too light; and if brushing is too late when the concrete is about to set, the broom will scratch off the aggregate and just leaving behind only the mortar on the concrete surface. The right time to brush is to see the fingerprint, not just a dent, after pressing on the green concrete with the thumb.
Before the test, the testing area should be vigorously wire brushed and cleaned. The test is conducted by using an apparatus ( a wooden disc with hard rubber facing ) to trowel the specified volume ( in form of a heap ) of fine sand with a circular motion and fills up the texture until it reaches the top of the concrete surface and the sand circle will not spread outwards anymore. The average diameter of the sand circle is measured to calculate the texture depth to the nearest 0.1 mm. If the texture depth is too light, it will require remedial work such as saw cutting a series of grooves instead.