Chloride binding in cement paste with calcined Mg-Al-CO3 LDH (CLDH) under different conditions

Geng, J; Pan, C; Wang, Y; Chen, W; Zhu, Y

Abstract

The chloride binding capacity of cement paste with Mg-Al CLDH, obtained through calcining a commercial LDH, is investigated under different chloride concentration, environmental temperature, and concrete pore solution alkalinity conditions. The transformation mechanism of Mg-Al CLDH to Mg-Al-Cl LDH is mainly explored by means of X-ray diffraction (XRD) , Fourier-transform infrared spectroscopy (FT-IR) and Differential thermogravimetric analysis (DTG). There appears to be a threshold chloride concentration of 1.0 mol/L for Mg-Al CLDH (6% incorporation) effectively enhancing the chloride binding capacity of cement paste. Both lowering and raising (>38 °C) the environmental temperature is disadvantage to the transformation of Mg-Al CLDH to Mg-Al-Cl LDH in cement paste, and the amount of bound chloride at different curing temperatures follows as 38 °C > 50 °C ≈ 20 °C > 3 °C. Higher pore solution alkalinity is also adverse to both of the formation of Friedel’s salt and the rehydration of CLDH. With increasing pH from 12.5 to 13.5, the improvement of Mg-Al CLDH on the chloride binding capacity of cement paste became weaker. Mg-Al CLDH improves the chloride binding capacity of cement paste is not only related to the excellent anions exchanging ability of it , but also related to the promotion of Friedel’s salt formation of it.

Citation

Geng, J., Pan, C., Wang, Y., Chen, W., & Zhu, Y. (2021). Chloride binding in cement paste with calcined Mg-Al-CO3 LDH (CLDH) under different conditions. Construction and Building Materials, 273, 121678. https://doi.org/10.1016/j.conbuildmat.2020.121678

• Journal Article Type: Article
• Acceptance Date: Nov 9, 2020
• Online Publication Date: Dec 5, 2020
• Publication Date: Mar 1, 2021
• Deposit Date: Dec 8, 2020
• Publicly Available Date: Dec 5, 2021
• Journal: Construction and Building Materials
• Print ISSN: 0950-0618
• Publisher: Elsevier
• Volume: 273
• Pages: 121678
• DOI: https://doi.org/10.1016/j.conbuildmat.2020.121678
• Publisher URL: https://doi.org/10.1016/j.conbuildmat.2020.121678
• Related Public URLs: http://www.journals.elsevier.com/construction-and-building-materials/
• Additional Information: Funders : Natural Science Foundation of Zhejiang Province;Natural Science Foundation of China;Public welfare foundation of Ningbo city;Natural Science Foundation of Ningbo City; Grant Number: LY17E080017; Grant Number: 51778578; Grant Number: 2019C50015; Grant Number: 2019A610392