WHAT IS SAND PATCH TEST ?

SAND PATCH TEST FOR TEXTURE DEPTH OF CONCRETE PAVEMENT

• Sand patch method is a field method which is used to measure the average macrotexture depth of a pavement surface. The method is based on volumetric approach in which a known volume of sand is spread evenly over the pavement surface to form a circle with the help of a flat wooden disc and subsequent measurement of the total area covered.

• FREQUENCY AND LOCATION OF SAND PATCH  TEST

The test shall be performed at least once for each day’s work and wherever the Engineer considers it necessary at times after construction.

• IDENTIFICATION OF LOCATION

1. A diagonal line is drawn across a lane width between points 50 m apart along the pavement length.
2. Five individual test is performed at least 2 m apart anywhere along the drawn diagonal.
3. No measurement shall be taken within 300 mm of the longitudinal edges of a pavement constructed in one pass.

• APPARATUS

   For sand patch test, following apparatus are used

1. A cylindrical container of 25 ml internal capacity.
2. A flat wooden disc of 64 mm diameter with a hard rubber disc 1.5 mm thick next to one face, the reverse face is provided with a handle.
3. Brushes for cleaning the pavement surface.
4. Dry natural sand with a rounded particle shape passing through 300 micron IS sieve and retained on a 150 micron IS sieve.
5. A ruler or other measuring device to measure the diameter of the area covered by the sand.
6. A suitable wind screen or shield (if required)

PROCEDURE

1. The surface to be measured shall be dried, any extraneous mortar and loose material are removed and the surface swept clean using the wire brush both at right angles and parallel to the length of pavement.
2. The cylindrical container is filled with the sand, tapping the base 3 times on the surface to ensure compaction, and striking off the sand level with the top of the cylinder.
3. The sand is poured into a heap on the surface to be treated and is spread over the pavement surface, working the disc with its face kept flat in a circular motion so that the sand is spread into a circular patch with the surface depressions filled with sand to the level of peaks.
4. Five measurements of the diameter is taken at different angles by rotating at least 45 degrees between each measurement. The mean diameter of the readings is recorded as diameter of the circle, measured to the nearest 5 mm.
5. The texture depth of concrete surface is given as,

MTD =  31000/  mm, (As per IRC : 15-2017)

Where, D = Average diameter of the area covered by the sand, in mm.

Or

            Texture depth is also given as, MTD

Where, MTD = mean texture depth of pavement macrotexture, in mm.

V = Sample volume, in

D = Average diameter of the area covered by the sand, in mm.