Geopolymer concrete from hydro removed coal ash

Introduction. Ash dumps put public health at risk, and enterprises forced to store ash and slag waste incur significant financial losses due to the negative impact on the environment, in turn, bottom ash, after some preparation, can serve as the basis for the production of competitive cement-free construction products, which is a scientific task.

Aim. Development of a scientifically based technological solution for the production of geopolymer building materials based on hydro-removed ash and slag waste from thermal power plants.

Materials and methods. The basis for geopolymers were the combined heat and power plants of Vladivostok TPP-2, Primorskaya GRES and Artemovskaya TPP of Primorsky Krai. Modern methods were used for a comprehensive study of raw materials and developed materials: X-ray phase analysis, energy dispersion microanalysis, scanning electron microscopy, differential thermal analysis, and infrared spectroscopy.

Results. The technological solution for the preliminary preparation of ash and slag waste has been improved, on the basis of which an innovative geopolymer binder has been developed. A wide range of geopolymer concrete compositions has been developed through various combinations of ash and slag waste disposal products. Unlike the hydration products of traditional Portland cement concretes, which are represented by the main structure-forming neoplasms of calcium silicate hydrates, the microstructure in the developed geopolymers is composed of calcium and sodium hydroaluminosilicates. In this case, aluminum atoms embedded in the crystal lattice of hydrated neoplasms significantly strengthen it. 

Conclusions. The effectiveness of using ash and slag waste from thermal power plants as a source for producing new environmentally friendly geopolymer concretes of classes up to B60 for compression and Btb10.0 for bending tension has been scientifically substantiated and experimentally proven. The compressive and flexural strength of the developed materials suggests their competitiveness in comparison with traditional Portland cement concretes. The compressive strength of the developed geopolymers is 2 times higher than the same characteristic for materials based on common Portland cement CEM I 32.5N and 1.5 times higher than for high-strength CEM I 42.5N.

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