Caractérisation en laboratoire du potentiel expansif de granulats de remblais de fondation

Abstract

Pyritic aggregates coming from sedimentary rocks may be subject to expansions when used in subbases, and, in certain cases, may then cause heaving or expansion of concrete slabs with consequences on the structures. This situation occurs in areas where the lack of prime aggregates requires the use of local materials. Swellings are observed and are basically related to the oxidation of sulphides such as pyrite, pyrrhotite, and chalcopyrite, which are present in aggregates. As a result of this oxidation, sulphuric acid is formed and reacts to produce gypsum, which is responsible for the increase of volume. This paper is a contribution to a better understanding of this topical phenomenon and also includes the procedure of characterization used for four aggregates to determine their expansive potential by using an experimental device developed at the laboratory. Different reactivity modes take place involving processes such as swelling and sulphate attack or even the combination of the two modes, which are corroborated by the intrinsic properties of the aggregates used in this study.Key words: subbase, aggregates, pyrite, oxidation, gypsum, swelling.