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Effects of traffic‐induced vibrations on young concrete: part 1 In the COUNT (Concreting under traffic) research project, the effects of traffic vibrations on young concrete are extensively examined. This research question has recently become more relevant since traffic closures often have to be imposed when bridges are renovated or widened, as there is a concern that the vibrations caused by traffic will damage the young (hardening) concrete. COUNT aims to determine critical vibration values and underlying damage mechanisms based on three test series. Both harmonic and real bridge vibrations due to train, truck and car traffic are adopted, and the effects on the material concrete itself are investigated, as well as on the bond behaviour between concrete and reinforcement, and the contact between existing and new concrete parts. This first part of the article reports on the results of test series 1 and 2, in which small samples were systematically excited by artificial vibrations during hardening. It was found that conventional traffic vibrations do not affect the strength of concrete per se, but that the bond between the concrete and the reinforcement can be weakened if the vibrations are too great. In addition, it was found that (differential) displacements is a more suitable measure for damage assessment than the vibration velocity. [ABSTRACT FROM AUTHOR]

The geochemical conditions conducive to dolomite formation in shallow evaporitic environments along the Triassic Tethyan margin are still poorly understood. Large parts of the Triassic dolomites in the Austroalpine and the southern Alpine realm are affected by late diagenetic or hydrothermal overprinting, but recent studies from the Carnian Travenanzes Formation (southern Alps) provide evidence of primary dolomite. Here a petrographic and geochemical study of dolomites intercalated in a 100 m thick Carnian sequence of distal alluvial plain deposits is presented to gain better insight into the conditions and processes of dolomite formation. The dolomites occur as 10 to 50 cm thick homogeneous beds, millimetre-scale laminated beds, and nodules associated with palaeosols. The dolomite is nearly stoichiometric with slightly attenuated ordering reflections. Sedimentary structures indicate that the initial primary dolomite or precursor phase consisted largely of unlithified mud. Strontium isotope ratios (87Sr/86Sr) of homogeneous and laminated dolomites reflect Triassic seawater composition, suggesting precipitation in evaporating seawater in a coastal ephemeral lake or sabkha system. However, the setting differed from modern sabkha or coastal ephemeral lake systems by being exposed to seasonally wet conditions with significant siliciclastic input and the inhibition of significant lateral groundwater flow by impermeable clay deposits. Thus, the ancient Tethyan margin was different from modern analogues of primary dolomite formation. [ABSTRACT FROM AUTHOR]