Alkali Aggregate Reaction for Concrete Made with Tunnel Muck: Experimental Investigations

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 al-so through performance tests. In this paper the following two investigations on Alkali Aggregate Reaction are reported: -accelerated expansion tests on mortar bars made by Omegna tunnel muck aggregates (after excavation and after treatment) following the UNI 8520-22standard. 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. - performance accelerated tests of a real concrete mix according to the NF P 18-454 standard on two kinds of aggre-gates: 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.