Impact of acid treatment on the puzzolan activity of natural zeolite tuff

Abstract

Using the methods of thermal gravimetric analysis, and X-ray phase analysis, the puzzolan activity of the natural zeolite tuff of the Lyulinsky deposit of Khanty-Mansiysk Autonomous District -Yugra as a mineral additive to cement was evaluated. Acid modification of natural zeolite tuff was performed. The selection of modification conditions was carried out by varying the concentration of the acid solution, the time of exposure to the reagent, and the temperature. The optimal parameters were: the concentration of hydrochloric acid 3 M, the duration of acid exposure-5 hours, the temperature of 80°C. It was found that the treatment of tuff with 3M hydrochloric acid solution leads to a significant increase in puzzolan activity. The strengthening effect of the modified additive is shown. The strength of cement samples with the addition of zeolite tuff at a similar age increases by 28%. The effect of the addition of zeolite tuff on the phase composition of cement during hydration and hardening is studied. A more significant decrease in the content of portlandite was recorded when using a modified additive compared to the addition of zeolite tuff in its native state, which is consistent with the data obtained from the mass loss curves. At the same time, an increase in the content of ettringite, which contributes to the strengthening of the structure of the binder part of the cement stone, is shown. The degree of hydration of cement was estimated by the change in the content of alite. A complexometric determination of the aluminum content in the washing waters after acid treatment of zeolite tuff was carried out. It is shown that acid treatment leads to its dealuminization, which is associated with the restructuring of the zeolite framework. This, in turn, provides an increase in the number of active acid centers responsible for its adsorption properties and reactivity on the surface of the aluminum-silicate framework of the zeolite.