Evaluation of saturation in cemented slags with P-wave velocities

Abstract

The application of the circular economy concept to construction engineering and to transportation geotechnics, brings several challenges associated to the use of non-conventional artificial materials. Steel slags can replace natural raw materials, but a thorough mechanical characterisation is needed to assure an adequate behaviour and quality control parameters. The focus of this paper is a mixture of two types of steel slags (a reducing slag and an oxidizing slag) from electric arc furnace steel production. The mixture has cementing properties, mainly due to the reducing slag, being stable in water after compaction. Due to its high stiffness and reduced permeability, the evaluation of the degree of saturation of the mixture using the conventional Skempton parameter B is not very reliable. In this work, P wave velocity measurements in specimens with different cementation levels (given by amount of reducing slag and curing time) and soaked conditions (before and after submersion) were compared. In addition, the elastic shear stiffness evolution with time obtained by S wave velocity measurements demonstrated a clear increase in stiffness with curing time especially in soaked specimens. The aim of the paper is thus to discuss the advantage of P waves to identify full saturation in stiff specimens that harden with time and water. It was found that it is very difficult to evaluate the degree of saturation of a highly cemented specimen, either with the B value or with the P-wave velocities. However, the usual mechanical evaluation by triaxial compression tests is still valid provided that suction is low.