Effect of Li2CO3 on the properties of Portland cement paste

In order to increase the application of CO2 in cementitious materials and to develop new additives for cement-based materials, the effect of lithium carbonate (Li2CO3) on the properties of Portland cement (PC) paste was investigated. The hydration heat of fresh paste was tested and the hydration products were characterized using XRD, TG-DTA, SEM and MIP. The results showed that both the initial and final setting time of the PC paste was prolonged with increasing Li2CO3 content. While, the compressive strength of the hardened PC paste at 1 day, 7 days and 28 days increased initially and then decreased. When the content of Li2CO3 was 0.09wt%, the initial and final setting time was increased by 19.8% and 27.7%, and the compressive strength at the age of 1 day, 7 days and 28 days was increased by 47.6%, 21.2% and 14.0%, respectively. Hydration heat, TG-DTA, XRD, SEM, pore structure and other tests showed that Li2CO3 promoted the formation of AFt, and prolonged the arrival time of hydrated calcium silicate peak, but increased the formation of hydrated calcium silicate. Especially when the Li2CO3 content was below 0.09wt%, the pore structure was also optimized. Based on the above results, when the content of Li2CO3 is not greater than 0.09wt%, not only the setting of the Portland cement paste can be retarded, but also the early strength can be enhanced. This can provide a good reference for the use of Li2CO3 in the preparation of new Portland cement-based material admixtures.

Automated summary

The study found that a small amount of lithium carbonate (Li2CO3) can prolong the setting time of Portland cement paste and increase early strength. Li2CO3 helps promote the formation of AFt, but also increases the formation of hydrated calcium silicate, with a certain optimization effect on pore structure.