Synthesis, characterization, and thermodynamics of alkali-silica reaction products: knowledge transfer from model system to ASR-affected field concrete
Alkali-silica reaction (ASR) can cause expansion and cracking of concrete due to the reaction between alkalis from the cement (i.e. the glue of concrete) and reactive silica from aggregate (i.e. the sand and gravel). The reaction cannot be stopped once it is initiated. Despite tremendous progress over the past 80 years, a breakthrough of understanding the mechanism of ASR and the structure of ASR products has not yet been made. This makes it difficult to predict the occurrence and kinetics of ASR and the resulting expansion of concrete. The main challenge originates from the insufficient characterizations of the ASR products, as they usually form in tiny amounts with very small size (μm range) co-existing with other silica-rich phases in concrete. This is an urgent problem in the field of cement and concrete research for prolonging the service life of concrete infrastructures.
In this project ASR products were synthesized in large quantity in our laboratory, which are chemically and structurally identical to those formed in concrete. Detailed studies showed that the crystalline ASR products formed in concrete are not able to swell even at high relative humidity. The composition, structure and solubility of different ASR products could be measured, which is an important step forward in predicting the conditions of ASR and developing measures to mitigate ASR for prolonging the service life of concrete infrastructures. Currently, we are in the stage of transfer the knowledge obtained from the synthetic system to the concrete samples and meanwhile improving the thermodynamic data of the synthesized products.
The project is conducted by Dr. Zhenguo Shi in the group of Dr. Barbara Lothenbach in collaboration with colleagues from EPFL and PSI. The main contents of the project are as follows:
- Synthesis and characterization of ASR products at different temperatures
- Investigation of the ASR formation conditions such as influence of alkali/Si and Ca/Si ratios
- Mechanisms of ASR mitigation by Al-rich supplementary cementitious materials and Li salts
- Thermodynamic modelling of ASR
- Knowledge transfer from synthetic system to concrete samples
Project Period
2017 - 2021
Funding Organization
SNF Sinergia: Alkali-silica reaction in concrete (ASR), grant number CRSII5_17108
The EMPAPOSTDOCS-II programme has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement number 754364
Shi, Z., Park, S., Lothenbach, B., & Leemann, A. (2020) Formation of shlykovite and ASR-P1 in concrete under accelerated alkali-silica reaction at 60 and 80 °C. Cement and Concrete Research, accepted
Leemann, A., Shi, Z., Wyrzykowski, M., & Winnefeld, F. (2020). Moisture stability of crystalline alkali-silica reaction products formed in concrete exposed to natural environment. Materials & Design, 109066
Leemann, A., Shi, Z., Lindgård, J. (2020) Characterization of amorphous and crystalline ASR products formed in concrete aggregates. Cement and Concrete Research, 137, 106190
Geng, G., Shi, Z., Leemann, A., Glazyrin, K., Kleppe, A., Daisenberger, D., Churakov, S., Lothenbach, B., Wieland, E., Dähn, R. (2020). Mechanical behavior and phase change of alkali-silica reaction products under hydrostatic compression. Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials, 76(4)
Shi, Z., Leemann, A., Rentsch, D., Lothenbach, B. (2020). Synthesis of alkali-silica reaction product structurally identical to that formed in field concrete. Materials & Design, 190, 108562
Geng, G., Shi, Z., Leemann, A., Borca, C., Huthwelker, T., Glazyrin, K., Pekov I.V., Churakov, S., Lothenbach, B., Dähn, R., Wieland E. (2020). Atomistic structure of alkali-silica reaction products refined from X-ray diffraction and micro X-ray absorption data. Cement and Concrete Research, 129, 105958
Shi, Z., Lothenbach, B. (2020). The combined effect of potassium, sodium and calcium on alkali-silica reaction products. Cement and Concrete Research, 127, 105914
Shi, Z., Lothenbach, B. (2019). The role of calcium on the formation of alkali-silica reaction products. Cement and Concrete Research, 126, 105898
Shi, Z., Geng, G., Leemann, A., Lothenbach, B. (2019) Synthesis, characterization, and properties of alkali-silica reaction products. Cement and Concrete Research, 121, 58-71