Effect of variety and moisture content on the engineering properties of paddy and rice

The physical properties: shape and size, thousand grain weight, bulk density, particle density, porosity, angle of repose and coefficient of friction on GI and plywood surfaces, were determined for raw paddy, parboiled paddy, raw rice and parboiled rice of ADT 39 and CO 43 varieties at various moisture levels. All these physical properties were found to increase with moisture content. The physical properties of these two varieties differed from each other at equal moisture contents. The length, width, thickness, geometric mean diameter (GMD) and sphericity of raw paddy were observed in the range of 7.070 - 7.754 mm, 2.085 - 2.554 mm, 1.209 -1.556 mm, 2.480 - 3.105 and 0.35 - 0.40, respectively. The thousand-grain weight, bulk density, particle density, porosity, angle of repose, and static coefficient of friction on GI and plywood surfaces of raw paddy were in the range of 18.56 - 25.38 g, 564.9 - 585.3 kg m^-3, 1112 - 1277 kg m^-3, 47.6 - 54.2%, 25.9 - 30.7°, 1.87-2.85 and 1.62-2.46, respectively, in the moisture content range of 14.3 to 25.7%. Among the tested paddy and its constituents, raw paddy had the highest values of porosity and angle of repose, parboiled paddy had the highest values of length, width, thickness, GMD, sphericity and thousand grain weight, raw rice had the highest values of bulk density and, coefficient frictions on both the GI surface and on the plywood surface, and parboiled rice had the highest value of particle density.