Alkali activated slag concretes designed for a desired slump, strength and chloride diffusivity

Abstract

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

Recent progress in low-carbon binders

“…Alkali-activated binders are finding rapidly increasing uptake in a growing range of applications, and this section will provide a very brief overview of some of these. The primary route to market for these materials in the short term will almost certainly be as a binder in concretes, and increasingly sophisticated approaches to the design and use of AAM concretes (rather than just directly applying protocols used for Portland cement concretes) are being published for concretes based on alkali-activated GGBS [60,[255][256][257], fly ash [258][259][260], metakaolin [261], and various blends of these materials [259].…”

RILEM TC 247-DTA round robin test: mix design and reproducibility of compressive strength of alkali-activated concretes

“…However, this mix is still prone to issues with washout as were noted above; underwater curing returned the material to a lower performance level, similar to that of S1b. • The parameter selected for controlling the concrete strengths of S3a and S1b was the activator dose, which is more influential at early age due to the kinetic effects of high pH in accelerating slag reaction [13]. Thus, the difference in strength between the two mixes, shown in Fig.…”

“…Additional work reporting material parameters and characterisation of these concretes (and their constituent pastes and mortars), including permeability, porosimetry and more detailed microstructural analysis related to durability, has been published by various participating groups in publications including [5,13,[15][16][17][18][19][20]. In two papers that will follow this publication, round-robin test results for chloride migration/diffusion, carbonation, alkali-silica reaction, sulfate and freeze-thaw/frost-salt resistance, will be presented and discussed.…”

RILEM TC 247-DTA round robin test: carbonation and chloride penetration testing of alkali-activated concretes

“…pH, redox conditions, chloride concentration) at the steel-concrete interface [8,9], and the rates of carbonation and chloride penetration. A considerable number of studies have been conducted concerning the rates of carbonation and chloride penetration in alkali-activated concretes and mortars, for example [1,2,[10][11][12][13][14][15][16][17][18][19][20][21][22][23], but the data currently available do not yet lead to a comprehensive description of the transport and influence of CO 2 and chloride in these materials.…”