Abstract
Increasing the efficiency of using gypsum binders can be carried out by using not natural gypsum raw materials, but calcium sulfate-containing waste from various industries (phosphogypsum, borogypsum, citrogypsum, etc.). As the main source material in the work, we used gypsum-containing waste from a faience factory in the form of waste molds for casting dishes, souvenirs and plumbing fixtures. It has been established that the optimal binding system is formed by mixing powders of dihydrate technogenic gypsum from a coarse and fine earthenware factory with average particle diameters of 3.473 microns and 3.065 microns in a percentage ratio of 30:70, respectively. Using a computer software developed by the authors, which makes it possible to simulate the microstructure of a raw mixture taking into account the contact interaction of particles and calculate the average coordination number, models of binary packing of particles were constructed at various ratios of their diameters. Studies of the strength of composites obtained on the basis of bidisperse systems have shown the presence of an extremum in the region of mixtures containing 30% coarse powder. With optimal packing, a large number of phase contacts are formed due to the regulation of the grain composition of the bidisperse system. It was revealed that a brick based on the waste of two-water gypsum from earthenware production has 2.5–5 times better characteristics of compressive strength than traditional building wall products based on natural gypsum. At the same time, the strength immediately after molding is more than 3 times higher than that of traditional gypsum products. Even higher indicators are achieved when adding microcalcite in addition to the waste of earthenware production, in this case, the compressive strength is 3–6 times higher, and the strength immediately after molding is almost 3 times higher than that of traditional gypsum products.
Highlights
Traditional methods of producing gypsum building materials provide for the burning of raw materials to obtain a binder, and the molding of products based on it and their subsequent drying [1,2,3]
It is a known method for producing gypsum products by non-firing technology [4,5]
It is necessary to increase the efficiency of using gypsum binders in such regions by using not natural gypsum raw materials, but gypsum-containing waste from various industries [11,12,13]
Summary
Traditional methods of producing gypsum building materials provide for the burning of raw materials to obtain a binder, and the molding of products based on it and their subsequent drying [1,2,3]. In view of the fact that one of the factors determining the formation of the internal structure of a dispersed system is the bulk density, which determines the formation of the maximum number of primary contacts between the particles of gypsum dihydrate, and the number of contacts is determined by pressure, and by the grain size composition. In this regard, the work investigated the bulk density of powdery raw mixtures of various grain size compositions. The microstructure of calcium sulfate dihydrate powders and their mixtures was assessed by electron microscopy using an MBS-1 stereoscopic microscope, and the microstructure of a gypsum stone using a Scan 4 scanning microscope
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