Evaluation of non-destructive testing methods for concrete defects in connection components of modular integrated construction

Modular Integrated Construction (MiC) is gaining popularity for high quality, fast construction, and lower pollution. Precast concrete modules are assembled on-site, with cast-in-place shear walls connecting them. However, poor construction and inadequate concrete vibration could cause voids and delamination. Prompt detection of these defects is vital for maintaining structural integrity. This paper examines the detection abilities of impact echo (IE), ultrasonic testing (UT), infrared thermography (IRT), and ground penetrating radar (GPR) for interfacial delamination and internal voids in shear walls between modules. By analyzing variations in the IE dominant frequency, minor delamination (50 mm × 50 mm) and voids (40 mm × 40 mm), as well as deep voids up to 240 mm in depth, can be identified. Defects reduce ultrasonic amplitude and increase time-of-flight. However, UT is less effective for minor and deep defects. By observing surface temperature changes, the IRT can detect shallow defects up to a depth of 60 mm. GPR cannot detect defects due to the dense rebar in the concrete slab. In summary, IE is best suited for detecting defects in shear walls between modules. This study offers a solution for the on-site detection of typical connection components in MiC.