The use of ultrasonic pulse velocity to estimate the water permeability of concretes

In this work we investigated the possibility of estimating the water permeability of concrete from the ultrasonic surface wave velocity (Rayleigh's waves). This is a method for the non-destructive permeability diagnosis of the in situ auscultation of a structure. Four ordinary concrete compositions with different W/C ratios and two self compacting concretes SCC were used. This study showed a decrease in of ultrasonic pulse velocity with the increase in the W/C ratio, this is due to the increase in porosity. Curing in air of the concrete specimens produces greater permeability than curing in water. The increase in the permeability with the increase of W/C ratio is more important for curing in water than for the curing in air. SCC1 has a lower permeability than that of SCC2, this difference is respectively 20% and 10 % for curing in air and in water. The study show that permeability estimation with ultrasonic surface waves is more reliable for curing in water mode than tin curing in air. The correlations obtained between the permeability and the indirect ultrasonic velocity are linear, with an inversely proportional relation.

Condition assessment of longitudinal pavement joints using ultrasonic surface waves

Poor-quality longitudinal joints can cause premature failure on asphalt pavements; they are characterized by exhibiting low density and high permeability. These conditions generate surface distresses such as longitudinal cracking. Previous ultrasonic methods for condition assessment, e.g., Fourier and wavelet transmission coefficient, require user input, making the automatic data processing difficult. Furthermore, the coupling between ultrasonic transducers and the asphalt surface is not practical for testing in-service roads. This paper presents a new data analysis technique and the results of an experimental program for the condition assessment of longitudinal asphalt joints using ultrasonic surface waves. A new coupling system between the ultrasonic transducers and the asphalt surface is presented. The new data processing technique reduces user input and increases testing reliability. The new coupling system uses polyurethane foam and calibrated weights to provide a spring action on the transducers. The proposed data analysis technique, called instantaneous transmission coefficient (ITC), is based on the evaluation of instantaneous frequencies and damping ratios. The main advantage of the new procedure is that it can be performed automatically, reducing user input and increasing test repeatability. A laboratory scale asphalt slab is used to show the potential of the new methodology and coupling system. Laboratory validation results show good agreement between the new ITC method and previous methods, and a significant reduction in testing time, while improving test reliability.