A Rockwell Hardness Test for Portland Cement Concrete

摘要

The ASTM standard Superficial Rockwell hardness test using a 1/2 inch ball indenter and a 15 kgf Major Loar (15Y test) has been adapted to perform nondestructive hardness tests on portland cement mortars and concrete. Correlations between the compressive strength of both materials and their hardnesses have been found. The correlation for normal concrete and 3 x 6 inches compression cylinders is: 15Y hardness = 73.5 x (log compressive strength in psi) - 187 and has a correlation coefficient of 88%. The test can be performed on samples as thin as 2 mm, on surfaces with a radius of curvature no less than 2 cm and as close to a sample edge as 1 mm. The test uses a standard Rockwell Superficial hardness test instrument but requires a tungsten carbide indenting ball and a sufficiently large sample support to hold the size sample that is being tested.