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Sand Patch Test

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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 the pedestrians or traffic . These 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 of 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 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 finger print , not just a dent , after pressing on the green concrete with the thumb .

Before 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 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 being too light , it will require remedial work such as saw cutting a series of grooves instead .

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