Alkali aggregate reaction for concrete made with tunnel muck: Experimental investigations

Abstract

The ever decreasing availability of natural aggregates, together with the increase of civil infrastructures such as tunnels and the consequent accessibility of potential natural resources can, following a thorough analysis, lead to tunnel muck being used in concrete. This is possible after evaluating its durability, not only by means of technological testing but also through performance tests. In this paper the following two investigations on Alkali Aggregate Reaction are reported: (1) accelerated expansion tests on mortar bars made by Omegna tunnel muck aggregates (after excavation and after treatment) following the UNI 8520-22 standard. Among the two different kinds of tunnel muck studied, the concrete specimens made with the treated aggregate show a higher average expansion and a lower flexural strength than the simply excavated aggregate. (2) performance accelerated tests of a real concrete mix according to the NF P 18-454 standard on two kinds of aggregates: the first lightly reactive and the second with uncertain alkali-reactivity. The results confirmed the reactivity of the two aggregates and also proved that a small content of pozzolan in cement is not enough to prevent the alkali-silica reaction. .