ORIGINAL ARTICLE Properties and performance of silane: blended cement systems M. A. Kargol • U. Mu ¨ ller • A. Gardei Received: 3 January 2012 / Accepted: 19 November 2012 / Published online: 27 November 2012 Ó RILEM 2012 Abstract The paper presents the results of a study dealing with the performance of water repellents on hardened blended cement pastes. Since on the Euro- pean market Portland cement does not play the dominant role anymore and due to the new national and European policies concerning Greenhouse Gases and sustainability, cement manufacturers produce more and more blended cements (CEM II–CEM V). Nevertheless, the majority of experience concerning the efficacy of water repellents is gained from Portland cement; therefore knowledge in regard to the interac- tions of blended cement with water repellent agent is minimal. Two silane-based products were applied on ‘fresh’ and carbonated cement substrates containing limestone, fly ash, slag and trass, and were investigated in terms of their functionality. The evaluation of the treatments’ performance and effectiveness were assessed using various laboratory measurements. Hydrophobicity, water absorption, colour changes and the penetration depth of silanes into the substrate were evaluated before and after artificial aging exper- iments. Moreover, the outdoor weathering test was performed to shed light on treated surface appearance in a ‘real’ outdoor environment. The results showed that surface wettability was independent on water ingress or colour variations, especially for cement specimens artificially aged by accelerated carbonation. Cement pastes containing slag and trass seemed to more distinctly affect the water repellents’ surface performance. Keywords Water repellents Á Silanes Á Impregnation Á Aging Á Carbonation Á Durability Á Blended cement Á Fly ash 1 Introduction The service life of concrete structures, in particular engineering structures, depends strongly on the inter- actions of environment, construction materials and loading conditions. The demand for an increased service life is becoming more and more important in the construction sector leading to enhanced require- ments for the mechanical strength and the durability of the materials. To meet these requirements, the improved material properties and applications of sur- face treatments seem to be necessary. Since concrete is a porous material, surface protection systems are applied to prevent harmful substances from entering the pores of the concrete. This is usually done by the application of polymer coatings or impregnates [1] which reduce the ingress of moisture and ions such as chlorides or sulphates. Nowadays a broad range of chemicals are available on the market for the protection of cement based M. A. Kargol (&) Á U. Mu ¨ller Á A. Gardei Federal Institute for Materials Research and Testing, Division 7.1—Building Materials, Unter den Eichen 87, 12205 Berlin, Germany e-mail: marta.a.kargol@gmail.com Materials and Structures (2013) 46:1429–1439 DOI 10.1617/s11527-012-9984-1