Theory and Method
Cement mortar strength testing applies a controlled load to a prismatic specimen until fracture occurs, recording peak force to calculate strength. For compression tests, a specimen half (broken from a 40 × 40 × 160 mm prism during the flexural phase) sits between the upper and lower compression plates, and hydraulic pressure builds at a constant preset rate. The controller maintains the target loading rate through closed-loop pressure regulation. Peak load at fracture is divided by the specimen's bearing area to calculate compressive strength.
Flexural testing follows a center-point three-point loading method on the intact 40 × 40 × 160 mm mortar prism. The prism rests on two support rollers at a fixed span, and a single loading roller applies downward force at the midspan until fracture. Tensile stress develops at the prism's bottom face, and fracture initiates from the tension side. The control software captures peak load at fracture and calculates flexural strength (modulus of rupture) from peak load, support span, and cross-sectional dimensions.
The constant loading rate specified in EN 196-1, ASTM C109, C348, and C349 must be maintained throughout each test to obtain repeatable results. Cement mortar exhibits time-dependent deformation at stress levels near failure, so rate deviations shift the recorded fracture load and introduce inter-test variability. The QT-300B / QT-300BD allows the operator to enter the target stress rate in the control software to match each applicable standard exactly. Automatic overload protection disengages the hydraulic system when the preset limit is reached, protecting fixtures and specimens if loading is not stopped promptly after fracture.
