Alkali-silica reaction – a multidisciplinary approach

Abstract

In the last four years, a multidisciplinary study involving several research groups in Switzerland tackled a number of unsolved, fundamental issues about the alkali-silica reaction (ASR) in concrete. The covered topics include SiO2 dissolution, the characterization of various ASR products formed at different stages of the reaction in both concrete and synthesis, crack formation and propagation. The encompassed scale ranges from nanometers to meters. Apart from conventional techniques, novel methods for the field of ASR have been used, e.g. combination of scanning electron microscopy with dissolution experiments, combination of focused ion beam with transmission electron microscopy, several synchrotron-based methods, synthesis of ASR products for in-depth characterization, time-lapse X-ray micro-tomography combined with contrast-enhancing measures and numerical models of ASR damage based on realistic crack patterns. Key achievements and findings are the quantification of the effect of aluminum on dissolution of different silicates, the variance in morphology and composition of initial ASR products, the differences and similarities between amorphous ASR products and calcium-silicate-hydrate, the link between temperature and the structure of the crystalline ASR products, the behavior of the crystalline ASR products at varying relative humidity, ASR propagation in 4D and numerical modelling based on realistic crack patterns.

Thermal properties of ASR products

“…16 Si 4 O 8 (OH) 2.84 .1.5H 2 O): nanocrystalline products whose atomic structure can be related to defective K-shlykovite with a coherence length of a few nanometers. This product has also been reported as amorphous [19,20] in the literature, but recent molecular simulations [21] show that defective nanocrystalline K-shlykovite reproduces available experimental X-ray diffraction patterns and pair distribution functions better. The comparison of defective nanocrystalline K-shlykovite structure with available experimental data demonstrate that ASR-P1 can be associated with the disordered/ amorphous products reported in previous studies in the literature [22][23][24] Na-and K-rich products are the main ASR products in cement systems, as these are the primary alkalis in the pore solution of cement-based materials [25].…”

Suitability of biochar as supplementary cementitious material (SCM) or filler: waste revalorization, a critical review

“…Thereby, the determination of biochar elemental composition is a top priority when considering its application on the construction industry, given the importance of stability of any component of cementitious matrixes in order to prevent deleterious reactions like alkali-silica reaction (ASRs) or alkali-carbonate reactions (ACRs), which can lead to cracking and fracture over the span of several years of service (Adams & Ideker, 2020;Leemann et al, 2022). For elemental composition characterization the most used techniques are ICP-OES, ICP-MS and CHNS analysis, extremely useful to determine the ratio of heavy metals in biochar composition.…”

The Environmental Degradation of Cement-Based Materials Due to Alkali-Silica Reaction: Case Studies

“…Dams, roadways, walls, and other structures are affected by these phenomena, which can take some time to occur (Latifee, 2016, Thomas et al, 2012Diamond, 1992) and can be severe (Bach et al, 1993;Islam & Ghafoori, 2011;Swamy, 1991). The effect of aluminum on the dissolution of silicates as well as a better characterization of the alkali-silica reaction products and the influence of the temperature and relative humidity are some of the recent findings (Leemann et al, 2021). Several procedures, Keywords: concrete, degradation, cracks, alkali-silica reaction recommendations and tests were developed to assess the AAR susceptibility of cementitious materials (Mene´ndez et An overview of the AAR presence on the infrastructure along the alpine and sub-alpine region in Switzerland indicated the damage to occur in a relatively long period of time and to be variable depending on the geographic region.…”