The large-shear digital speckle interferometry are employed to measure the out-of-displacement of concrete structure. Based on the phase-modulation theory of liquid crystal variable retarder, a retarder is an optical device that resolves a light wave into two orthogonal linear polarization components and produces a phase shift between them. The liquid-crystal phase shifter is successfully incorporated into the large-shear digital speckle interferometry system to enhance the measuring sensitivity and accuracy. From the experiment used to measure the out-of-displacement of an object, the optimum performance of the method is confirmed. In the meantime, the new technique is provided to evaluate the mechanical behavior of concrete structure with different curing time with non-contact, high accuracy, full-field, real-time and in-situ. The experimental results show that the strength of concrete structure will be enhanced as its curing time goes on, and after 21 days the strength value will be approaching to the design value.