The search for new pozzolan sources for eco-efficient cement manufacture is the main goal of this study, which evaluates the pozzolanic activity of andesitic material existing in large quantities in Algeria. The improvement in the pozzolanic activity of the andesite was also studied by using mechanical and thermal processes. To evaluate the pozzolanic activity of natural and treated andesite, some pozzolanicity tests, namely the Frattini test, the saturated lime test, XRD, TGA and strength activity index, were used. Mortars of blended cements containing CEM I (52.5R and 42.5N) and 0% to 40% of natural or treated andesite were prepared in order to study the pozzolanic performance of andesite blended cement during hardening. The results show that natural andesite has a moderate pozzolanic reactivity enabling blended cements to be developed. Heat treatment at 800 C improved the andesite pozzolanicity but it remained too low in relation to the high cost of the calcination operation. The partial replacement of cement by andesite led to a decrease in the energy needed to produce a ton of binder. From a performance point of view, the energy cost (kW h/MPa) of binders made of andesite is especially interesting when lower performance cements are used. (C) 2013 Elsevier Ltd. All rights reserved.