Influence of lithium-based products proposed for counteracting ASR on the chemistry of pore solution and cement hydrates

Low- and high-alkali cement pastes were made with or without LiNO3 or a Li-bearing glass. The [Li]/[Na+K] molar ratio was kept constant to 0.74. The specimens were stored at 23, 38, and 60 degreesC in sealed containers. After 3, 7, 28, and 91 days, their pore solutions were extracted and analysed, and their residual water contents were obtained by drying. The Li glass was found to react quite slowly, and the corresponding [Li+] in solution progressively increased with time, temperature, fineness (as-received glass vs. ground glass), and the [Na++K+] concentration in solution. This glass increased the pH by about 0.1, and by about 0.2 after it was finely ground. In contrast, LiNO3 decreased the pH by about 0.1, despite significantly increasing the [Na++K+] in the pore solution. The higher the total %Na2O, content (including Li) in the original mixtures, the higher the total alkali content incorporated in the cement hydrates. The [Li+]-[Na++K+] ratio in solution was about half of the initial ratio (0.74), while this ratio in the cement hydrates was always over 1.1. Li is the alkali most preferentially incorporated into the cement hydrates, while K is the least. (C) 2004 Elsevier Ltd. All rights reserved.