... residual deformation is adsorbed by the concrete, and another part of energy which is proportional to the surface hardness is transmitted to ... to other nondestructive testers, HT-225A concrete strength tester is an economical and practical instrument.Specifications: ModelHT-225ANominal kinetic ... test hammer80+/-2StandardsISO/DIS 8045, EN 12504-2, ENV 206, DIN 1048 part 2, ASTM C 805, ASTM D 5873, ...