Abstract
The RILEM technical committee TC 247-DTA ‘Durability Testing of Alkali-Activated Materials’ conducted a round robin testing programme to determine the validity of various durability testing methods, originally developed for Portland cement based-concretes, for the assessment of the durability of alkali-activated concretes. The outcomes of the round robin tests evaluating sulfate resistance, alkali-silica reaction (ASR) and freeze–thaw resistance are presented in this contribution. Five different alkali-activated concretes, based on ground granulated blast furnace slag, fly ash, or metakaolin were investigated. The extent of sulfate damage to concretes based on slag or fly ash seems to be limited when exposed to an Na2SO4 solution. The mixture based on metakaolin showed an excessive, very early expansion, followed by a dimensionally stable period, which cannot be explained at present. In the slag-based concretes, MgSO4 caused more expansion and visual damage than Na2SO4; however, the expansion limits defined in the respective standards were not exceeded. Both the ASTM C1293 and RILEM AAR-3.1 test methods for the determination of ASR expansion appear to give essentially reliable identification of expansion caused by highly reactive aggregates. Alkali-activated materials in combination with an unreactive or potentially expansive aggregate were in no case seen to cause larger expansions; only the aggregates of known very high reactivity were seen to be problematic. The results of freeze–thaw testing (with/without deicing salts) of alkali-activated concretes suggest an important influence of the curing conditions and experimental conditions on the test outcomes, which need to be understood before the tests can be reliably applied and interpreted.
Highlights
Alkali-activated concretes have shown sufficient durability to apply them for full-scale application, as demonstrated for Materials and Structures (2020) 53:140 alkali-activated concretes based on ground granulated blast furnace slags [1,2,3]
The mix design of the activated materials (AAMs) tested was different from the mix design specified in ASTM C1012, as described in Sect. 2.2 and shown in Table S1 in the Electronic Supplementary Material
The extent of sulfate damage incurred by AAMs based on slag or fly ash, whether measured by expansion, mass change or visual inspection, seems to be limited
Summary
Alkali-activated concretes have shown sufficient durability to apply them for full-scale application, as demonstrated for Materials and Structures (2020) 53:140 alkali-activated concretes based on ground granulated blast furnace slags [1,2,3]. There are still open questions regarding the long-term durability of alkali-activated materials (AAMs) [4, 5], which are related to the wide range of precursors and activators that can be used. This, in turn, leads to a wide variety in hydrate phase chemistries and microstructural characteristics of these materials. The work of RILEM technical committee (TC) 247-DTA ‘Durability Testing of Alkali-Activated Materials’ has been targeted to perform a round robin testing programme to assess the validity of different durability testing methods concerning alkali-activated concretes. The two previous papers derived from the activities of RILEM TC 247-DTA presented the outcomes of round robin tests on compressive strength [6] and on carbonation and chloride penetration testing [7]. The TC evaluation of testing methodologies for the determination of sulfate resistance, alkali-silica reaction and freeze– thaw resistance is highlighted in this contribution
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