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The implementation of repair works on concrete structures is on the increase since many existing concrete buildings have been exposed for long periods of time to different climates, as well as to other severe conditions, and have consequently deteriorated. Repair mortars need to fulfil the requirements of the EN 1504 series before being used in practice. Different mixtures, based on three different precursors (fly ash, ground granulated blast furnace slag, and metakaolin) and processed by alkali activated technology, have been assessed with regard to their suitability for the repair of concrete. Whereas the slag-based repair mortar delaminated from the substrate, and was thus unsuitable for its intended use, the other two mortars which were based on the precursors fly ash and metakaolin exhibited good mechanical properties and good adhesion. The bond strength of the metakaolin and fly ash mortars ranged from 1.8 to 2.3 N/mm 2 , and thus met these criteria for both structural and non-structural repair mortars. The capillary absorption of all three mixtures was too high to fulfil the criteria of EN 1504-3 for structural repair products, but the fly ash and metakaolin mixtures still have the potential to be used for non-structural repair works. The problem of efflorescence in all three mixtures was also assessed. [ABSTRACT FROM AUTHOR]

The behavior upon exposure to CO 2 of novel cementitious materials prepared with a low clinker cement CEM II/C-M (S-LL) is investigated in this paper. A simplified carbonation model considering the dissolution of a combined Ca-containing hydrate phase (CH, C-S-H, ettringite, monocarbonate, and Si-hydrogarnet) and the precipitation of calcite according to the evolution of phase assemblages calculated with thermodynamic modeling is applied to simulate accelerated carbonation tests in the laboratory. The dissolution rate of the Ca-containing hydrate phase is assumed to be determined by the water saturation degree, the partial pressure of CO 2 , and the fraction of its remaining volume compared to the initial one, which provides a way to predict the precipitation rate of calcite. Two mass conservation equations are considered in the model: water migration through the connected pores and diffusion of carbon dioxide in gaseous phases. Selected physical variables representative of the reactive transport properties are quantified from experimental measurements, including dynamic vapor sorption tests and drying experiments. The model response is compared to experimental data in terms of portlandite profiles from thermogravimetric analysis, and carbonation depth measurements using a pH indicator after specific times of accelerated carbonation. These experiments were also performed on a reference mortar prepared with the CEM II/A-S cement. All experimental results were simulated with the simplified carbonation model and the results compared to the response of the novel material. • Carbonation response of a novel low clinker CEM II/C-M (S-LL) cement is studied. • A simplified carbonation — drying model is coupled with thermodynamic calculations. • Transport properties are identified via DVS tests and drying experiments. • Model is validated against experimental portlandite profiles and carbonation depth. • Performance of the novel CEM II/C-M (S-LL) is compared to existing CEM II/A-S. [ABSTRACT FROM AUTHOR]

• Round robin test (RRT) performed with active participation of 34 laboratories. • All constituting materials shipped to national contact points. • Detailed protocols prepared with preconditioning, mixing and testing procedure. • Consistency, temperature, density, air content and compressive strength analysed. • With the adopted approach possible to prepare a common reference concrete for RRT. Round Robin Testing (RRT) is a well-known method for assessing the reproducibility of a test or verification of a new test procedure of almost any kind. In the EU funded network COST Action TU1404 "Towards the next generation of standards for service life of cement-based materials and structures", an Extended Round Robin Testing program (RRT+) was planned as a fundamental tool to obtain input data for a range of concrete properties and validate non-standardised testing techniques. In this paper, detailed information on the planning, conduction and analysis of Phase 1 of the RRT+ is presented. The aim of Phase 1 was to define and confirm the best practice for creating a comparable reference concrete mix for RRT programmes. With a total of 45 laboratories from Europe, Japan and Canada, RRT+ was one of the most extensive round robin testing programmes targeting cement-based materials. [ABSTRACT FROM AUTHOR]