ULTRASONIC METHODS APPLIED FOR ASSESSING THE PROGRESSION OF ALKALI-SILICA REACTION IN CONCRETE

摘要

Development of reliable non-destructive methods is needed to assess the damage induced by alkali-silica reaction (ASR) in concrete structures. The aim of this study is to follow the evolution of the ASR-damage in laboratory-made concrete with two procedures based on through-transmission of stress waves: ultrasonic pulse velocity and frequency-domain analysis of ultrasonic waves. Experimental data obtained from both methods are reported here. Variations in mechanical properties of concrete were also assessed. Three reactive concrete mixtures were made with a combination of reactive aggregates, and one mixture incorporating non-reactive aggregates was made as control. Some specimens were placed over water in hermetic plastic pails at laboratory ambient temperature (18-23℃) whereas some were soaked in a 1 mol/l NaOH solution at 38℃. Mechanical testing conducted on reactive concretes showed that the Young modulus was more affected than the compressive strength. Measurements of P-wave pulse-velocity in reactive concrete showed that velocity does not vary significantly with expansion. Frequency-domain analysis of ultrasonic waves, taken into account density and length of specimens, seemed more appropriate for the evaluation of ASR-damage, showing a progressive attenuation with expansion.