Inspection, evaluation and repair monitoring of cracked concrete floor using NDT methods

•Investigation of causes that have led to extensive cracking on concrete floor surface.•Cracks recording and crack depth estimation by ultrasound pulse velocity measurements.•Investigation for voids under concrete floor slab using the Impulse-Response method.•Concrete floor width estimation using the Impact-Echo method.•Grout injections monitoring using the Impulse-Response method. The objective of the present study is the evaluation of the condition of the concrete floor that suffers from extensive cracking on its surface, through systematic tests using NDT methods. The study contained a thorough visual inspection and recording of cracks, estimation of the crack depth using ultrasonic pulse velocity measurements, investigation for voids between the concrete floor and the underlying aggregate layer using the Impulse-Response method, concrete floor thickness estimation using the Impact-Echo method and concrete quality estimation using cores cutting. The purpose of the study was to investigate the causes that led to extensive cracking on the floor surface in order to plan the repair strategy. The repair method that was chosen was based on grout injections in order to fill the voids located between the concrete and the underlying aggregate layer. The injections were executed in a triangular grid and were monitored using the Impulse-Response method. The area, where the injections took place, was inspected using the method before and after the injections and a secondary grid was designed taken into account the results. After injecting in the secondary grid, the area was inspected again using the Impulse-Response method in order to confirm the successful filling of the voids.