01/11/2020
Spraying of phenolphthalein indicator solution to determine the depth of carbonation in alkali-activated concrete specimens

Spraying of phenolphthalein indicator solution to determine the depth of carbonation in alkali-activated concrete specimens

Source: BAM

For the employment of novel, alkali-activated cements it is of utmost importance to be able to assess the durability of concretes made from them under conditions expected to occur during their service life. As all currently standardized durability testing methods relate to Portland cement-based materials, their applicability needs to be assessed, and the test methods modified where required, before these methods can be reliably used to predict the durability of alkali-activated concretes. To address these issues, the Technical Committee 247-DTA “Durability Testing of Alkali-Activated Materials” of the International Union of Laboratories and Experts in Construction Materials, Systems and Structures (RILEM) carried out a round-robin testing program, in which BAM participated together with several laboratories from Europe, North America and Australasia.

Carbonation and chloride penetration test methods where applied to five alkali-activated concretes, based on ground granulated blast furnace slag, fly ash or metakaolin. Both carbonation and chloride penetration are important degradation mechanisms, as both potentially lead to corrosion of steel reinforcement, which is embedded in most concrete elements. The results of the round-robin testing program show that most, but not all, of the employed methods, when applied to alkali-activated concretes, exhibit an intrinsic precision that is comparable to the precision when applied to conventional concretes. Most methods appear to be reliably applicable to evaluate the relative performance of concretes based on binders with similar chemistry, but certain tests gave unexpected rankings when employed to compare binders of different chemistries. In addition, the results indicate that preconditioning of alkali-activated concrete specimens for carbonation testing can cause artifacts which affect the extrapolation of the results to longer service life periods. Taken together, the results show that current durability testing methods can serve as the basis to establish test methods for alkali-activated concretes, but some of these need modifications in certain respects.

RILEM TC 247-DTA round robin test: carbonation and chloride penetration testing of alkali-activated concretes
G. J. G. Gluth, K. Arbi, S. A. Bernal, D. Bondar, A. Castel, S. Chithiraputhiran, A. Dehghan, K. Dombrowski-Daube, A. Dubey, V. Ducman, K. Peterson, P. Pipilikaki, S. L. A. Valcke, G. Ye, Y. Zuo, J. L. Provis
published in Materials and Structures, Vol. 53, article No. 21, 2020
BAM Department Safety of Structures, Division Technology of Construction Materials