Nephrite-Bearing Mining Waste As a Promising Mineral Additive in the Production of New Cement Types

A growing demand for products made of jewelry and ornamental stones, including nephrite, requires an increase in mining volume. However, only less than 30% of the extracted raw material is suitable for processing. The rest of the low grade nephrites are substandard and unclaimed, and they negatively affect various life spheres. In this regard, their involvement in industrial turnover is an actual task. One of the directions of mining waste use is production of building materials, in particular, cements. The low grade nephrite can act here as mineral additives. In the course of the research, the optimal amount of low grade nephrite waste additive was determined, which is 30% of the cement mass. The grinding time of a raw mix is 10 min. It was found that introduction of the additive affects the hydration activity of cement compositions. Compressive strength of the mixed cement is 25% higher than that of the control sample. At the same time, new phases in the hydrated cement were not recorded. Good physical and mechanical properties of the obtained cements are achieved when hardening in normal humidity conditions. Heat and humidity treatments do not facilitate the hydration processes in binary systems. The conducted studies have shown that low grade nephrite can be used as mineral additives in cement production. This will allow development of not only a new type of product, but also reduction of the negative impact of cement production on the environment.