It has been known for a long time that strained, microcrystalline or cryptocrystalline quartz-bearing aggregates may cause alkali-silica reactions in concrete. Studying the relationship between deformation processes and microstructural characteristics of rocks, the reason for this behaviour can be better understood. Orthogneisses from the metamorphic basement of the Sierra Chica, Córdoba (Argentina), which were locally and differentially deformed in ductile shear zones, were used to analyse such behaviour. Petrographic analyses, accelerated mortar bar tests (ASTM C 1260, 2005) and chemical test (ASTM C 289, 1994) were conducted. Furthermore, corrosion tests were performed on polished rock surfaces using 1 N NaOH solution. It was seen that the reactivity of the quartz-bearing mylonites increased by~30% with respect to the non-mylonitised sample due to the increment in the strained quartz content and specially with the extended subgrain development. The mylonitised rock affected by superimposed cataclasis and the development of pseudotachylytic veins incremented its reactivity by~97% with respect to the nonmylonitised sample due to the combined effects of subgrain formation, grain size reduction and the formation of glassy material. It was also the only sample that showed significant differences in surface corrosion confirming the high reactivity of the rock. These results agree with expansion values measured on the accelerated mortar bar test and with silica leached in the chemical test. We believe that the simultaneous use of different tools to evaluate the potential alkali reactivity of the rocks in concrete is a good strategy rather than the use of isolated tools, which could lead to confusing interpretations of the process and therefore result in erroneous decisions.

Isotope (Sr, C) and U-Pb SHRIMP zircon geochronology of marble-1 bearing sedimentary series in the Eastern Sierras Pampeanas, Argentina. with Sr-isotope composition ca. 0.7075 and 0.7085 that are considered stratigraphically significant. 23The first is inferred early Ediacaran, the second late Ediacaran to early Cambrian. The Sierras de 55The Sr-isotope composition of marbles that remain unmodified after sedimentation has been 56 increasingly used for chemical stratigraphy since the seminal work of Burke et al. (1982). These (and S and O-isotope systematics), to constrain the age 63 of paleoclimatic changes (e.g., Derry et al., 1989Derry et al., , 1992 Jacobsen and Kauffman, 1999; Kuznetsov, 64 1998; Kuznetsov et al., 2013; Montañez et al., 2000; Halverson et al., 2007 Halverson et al., , 2010. 65 We focus here on the Sr, C and O-isotope composition of marbles from the Sierras de , 1998; Vujovich et al., 2004; Casquet et al., 2004 Casquet et al., , 2008 Rapela et al., 2010) high-grade metamorphism from ~490 to 430 Ma (Sims et al., 1998;Pankhurst et al., 1998; Rapela 90 et al., 1998a Rapela 90 et al., , 2007 Dahlquist et al., 2008 (Gordillo, 1984; Gordillo and Bonalumi, 1987; Baldo, 1992; Guereschi and 113 Martino, 2002, 2003). Plutonism, deformation and metamorphism took place in the early Cambrian Rapela 114Pampean orogeny (Rapela et al., 1998b). Metamorphism reached medium to high temperature (600-115 800 °C) and intermediate pressure (4-8 kbar) (Gordillo and Lencinas 1979; Rapela et al., 1998b Rapela et al., , 116 2002 Steenken et al., 2010). Marbles are found as lenticular bodies due to stretching, but they can 117 be followed over long distances with thicknesses from a few centimetres to hundreds of metres. Argentina were recognized in the Sierras de Córdoba (Sierra Grande and in northwestern Sierra 122Chica and Sierra Norte) (Fig. 2) on the basis of detrital zircon ages (Escayola et al., 2007; Rapela et 123 al., 2007 Rapela et 123 al., , 2016. The term Puncoviscana Formation in the literature embraces sedimentary rocks 124 probably older, coeval and younger than the Pampean magmatic arc, with the only constraint that 125 they are older than the unconformably overlying middle to late Cambrian Meson Group (e.g., 126Omarini et al., 1999; Adams et al., 2008 Adams et al., , 2011 Escayola et al., 2011, and references therein). We 127 restrict the term here to that part of the siliciclastic succession that is of relevance to the early 128 history of the Puncoviscana sedimentary basin (e.g., Casquet et al., 2012). These rocks host the 129 magmatic arc in the south (540-530 Ma) and can be coeval with syn-orogenic volcanism (ca. 530 130 Ma) in the north (Escayola et al., 2011). 131The detrital zircon age pattern in the Eastern Sierras Pampeanas is almost bimodal with 132 characteristic peaks at ca. 1000 and 600 Ma. The zircon was interpreted as derived from West 133Gondwana sources in the east (Natal-Namaqua belt and probably the Brasiliano-Panafrican orogen 134 and the...