Abstract
The article deals with the issue of gypsum binder quality reduction during its storage and transportation. The study provides the main methods to protect gypsum from unauthorized exposure to moisture and water vapor. The author proposes hydrophobic modification as a perspective method for the preservation of gypsum activity and its water absorption reduction. The substantiation of cement hydrophobization with the bitumen released during peat thermolysis is provided. The author proposes to use this method in the technology of gypsum binder production. The basic idea is to combine the hydrophobization process with the calcination of calcium sulfate dehydrate. This is facilitated by temperature ranges used for dehydration of natural gypsum and the initial stage of thermal decomposition of the organic matter of peat. The author defined experimentally an optimal concentration of the organic component in gypsum binder. After adding 0.5-1% of the peat additive, the gypsum plaster preserved its grade strength and increased its storage time without caking and hydration, also under adverse conditions. The proposed method is adapted to the technological processes presently used in the production and doesn’t require changing any equipment. The price of mineral raw materials and semi-finished products of peat are approximately equal which reduces the probability of increasing of the cost of hydrophobically modified gypsum binder.
Highlights
Gypsum binder, used in the construction industry, is a fine powder obtained from natural gypsum dihydrate by heat treatment in the temperature range 140190°C
The developed method can be well adapted to the process of production of gypsum binder
Basic parameters of gypsum calcination technology [1, 2] meet the basic parameters of the hydrophobic modification process [7]
Summary
Gypsum binder (gypsum hemihydrate), used in the construction industry, is a fine powder obtained from natural gypsum dihydrate by heat treatment in the temperature range 140190°C. Gypsum dihydrate refers to quick-setting and quick-hardening miner binding materials. It is widely used for plastering, manufacturing of gypsum concrete, gypsum building products, castings, forms, and as an additive to other binding materials [1]. One of the main issues of using gypsum binder is its activity reduction over time. The intensity of the absorption of water from the atmosphere depends on the humidity and ambient temperature. This leads to a gradual transformation of gypsum hemihydrate into the dihydrate one during storage, and reduces its activity upon setting and hardening. It does not allow them to be used for exterior works without additional treatment by traditional hydrophobic compounds [2, 3]
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