Influence of Mineral Addition on the Hydration and the Hardening of Ash-Cement Stone During Heat and Steam Curing

The influence of mineral additives, introduced in an amount of 20% to replace part of the fly ash, on the composition of hydration products and hardening of ash-cement stone after heat and steam curing was studied. The greatest increase in the compressive strength of ash-cement stone is provided by the use of ground granulated blast furnace slag and crushed hornblendite screenings, the introduction of which increases it by 2 times compared to non-additive stone. Differential thermal analysis of ash-cement stone has established that in the presence of blast furnace slag, the basicity of low-basic calcium hydrosilicates of composition CSH(B) decreases, and their amount increases as a result of the binding of portlandite with the active components of the additive and aluminosilicate glass of fly ash. The increased content of low-basic calcium hydrosilicates helps to increase the compressive strength of ash-cement stone. The addition of crushed hornblendite screenings does not change the composition of hydrate formations, and the increase in its strength is due to the high density and strength of rock particles. The introduction of copper smelting slag instead of part of the ash does not contribute to an increase in the content of new hydrate formations in the ash-cement stone, since its components do not interact with the hydration products of portland cement, and the lack of hydraulic activity is due to the low content of calcium and aluminum oxides in it, the presence of a significant amount of chemically inert fayalite and glass phase. The experimental results obtained make it possible to evaluate the effectiveness of the influence of mineral additives on the strength characteristics of ash-cement stone in order to increase the volume and rational use of fly ash from thermal power station as part of composite materials, in the production of foamed aggregate, for example, non-fired fly ash gravel.