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11Ground granulated blast furnace slag (GGBS) is the most common industrial by-product used as a 12 precursor for alkali activated binders due to its fast setting, simple curing needs, and good early age 13 strength gain. There are conflicting findings on the chloride penetration resistance of such binders and 14 more information is required regarding the suitability of this type of binder material for chloride 15 environments. This article outlines the findings of investigation of alkali activated slag concretes 16 (AASC), to provide a comprehensive view of the effect of mix design variables on slump, strength, and 17 chloride transport and binding. It is concluded that AASC can be designed for different workability and 18 different grades of concrete. The diffusivity results demonstrate that the addition of excess water does 19 not directly control the pore structure/connectivity in AASC as it does for Portland cement, and 20 therefore AASC can be designed based on the water/binder ratio needed for a specified mechanical 21 performance. The chloride binding capacity increased as the paste content of the concrete and/or the 22 silica content of the activator was increased. 23 Keywords: alkali activated slag concretes (AASC); workability; strength; chloride diffusion and 24 chloride binding capacity 25

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The aim of RILEM TC 247-DTA ‘Durability Testing of Alkali-Activated Materials’ is to identify and validate methodologies for testing the durability of alkali-activated concretes. To underpin the durability testing work of this committee, five alkali-activated concrete mixes were developed based on blast furnace slag, fly ash, and flash-calcined metakaolin. The concretes were designed with different intended performance levels, aiming to assess the capability of test methods to discriminate between concretes on this basis. A total of fifteen laboratories worldwide participated in this round robin test programme, where all concretes were produced with the same mix designs, from single-source aluminosilicate precursors and locally available aggregates. This paper reports the mix designs tested, and the compressive strength results obtained, including critical insight into reasons for the observed variability in strength within and between laboratories.

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