Chloride diffusivity of lightweight expanded clay aggregate concretes under compressive stress

Abstract

The lightweight concrete (LWC), whose aggregate is the keramzit (i.e. expanded clay), presents as a potential material for construction in marine environments. However, only a few studies have dealt with the durability of the lightweight expanded clay aggregate concrete and in particular, the chloride diffusion coefficient of this material under service mechanical loading has not been assessed yet. This study aims at investigating experimentally the chloride diffusivity of a LWC under different compressive stresses. The LWC mix has 30.0 MPa compressive strength after 28 days of curing of the cylinder, i.e., the grade of concrete is C30. Rapid Chloride Permeability Testing (RCPT) is used to measure the LWC chloride diffusivity. Chloride migration tests were carried out on cylindrical cores under different stress levels σ varying from 0 % to 75 % of the uniaxial compressive strength σc. The test indicates that the chloride diffusion coefficient firstly decreases by about 15 % when the σ reaches about 20 %σc, and then increases up to about 40 % compared to the initial value when σ increases to 75 %σc. An analysis was performed to have an idea about the water permeability and the gas permeability of the LWC under compressive loading from existing measurements on the ordinary and high-performance concretes. Linear relations between the water permeability, the gas permeability and the chloride diffusivity are resulted from this analysis. The experimental result of this study is significant and useful for the durability assessment of the structures made of LWC and exposed to aggressive environments.