Degradation Study of an Earthen Historical Rampart of Meknes City (Morocco) Using Ultrasonic Non-destructive Testing

Abstract

The main objectives of this study were to apply the ultrasonic non-destructive testing to a historical rammed earth material in order to identify altered zones and to elaborate a methodology for the health diagnosis and the control of restoration. The ultrasonic surface measurements using a Pundit 54 KHz on chosen panels has led to construct P-wave velocities tomograms. The use of other waveform attributes such as the signal amplitude allowed studying the attenuation and loss of energy related to weathering. The application of the conventional Schmidt hammer test allowed to establish maps of the rebound values R and to assess the mechanical hardness of the raw and the restored panels. These methodologies are well known and applied to concrete, but still not adapted to earth material (pisé). The mean idea is to combine both techniques to estimate a compressive strength through nondestructive tests, and at the end contributing to elaborate a kind of standardized charts. These preliminary in-situ non-invasive measurements and results seem to be very suitable in order to assess the mechanical properties and the structural stability of these historical ramparts, to characterize heterogeneities and to map weak zones.