Abstract
The increase of the consumption of gypsum products in construction industry with a limited amount of natural gypsum deposits requires alternative sources of gypsum-containing raw materials. In some countries which have fertilizers industry plants, the problem can be solved using industrial wastes, e.g. phosphorgypsum – a byproduct of fertilizers’ production. Kept in dumps over decades, phosphorgypsum is subjected to the chemical changes due to washing out impurities with rain and other natural factors. However, there are observed deviations of harmful impurities in dumped PG depending on its age., Phosphorgypsum of any age requires chemical treatment to neutralize remains of phosphorus and sulfuric acids, fluorine compounds. According to our researches one of the most simple and effective method of neutralization the impurities is using lime-containing admixtures. The paper presents results of laboratory tests of phosphorgypsum as a component of clinker and non-clinker binders. There were investigated the impact of phosphorgypsum as admixture for clinker binders to substitute natural gypsum. Neutralized phosphorgypsum can be applied as mineralizing admixture in calcination of Portland cement clinker. Adding 2 to 2.5% of phosphorgypsum as setting time regulator resulted in a similar physical and mechanical properties compared to mix made with natural gypsum. Another important area of phosphorgypsum application is sulphate activatoion of low-clinker blast-furnace slag cement (clinker content is less than 19%). According to results, the incorporation of phosphorgypsum as sulphate activator in cement has the better effect as natural gypsum. Other development has been carried out to modify the phosphorgypsum binder properties. Complex additive consisted of polycarboxylate-based superplasticizer and slaked lime permitted an increase mechanical properties of hardened phosphorgypsum binder due to significant a reduction of water consumption. Such modified binder can be used as partial or complete replacement of gypsum binder for filling cements and finishing plasters. It can substitute gypsum in non-clinker binders like supersulphated cements. There were also developed compositions of supersulphated cements based on low-alumina blast furnace slag and phosphorgypsum. Supersulphated cements were tested in normal-weight and light-weight concrete.
Highlights
Synthetic gypsum is applied as an alternative for natural gypsum raw in production of construction materials [1], in the areas of location of fertilizing plants. at insufficient level of wastes recycling and reuse
The only fertilizing plant located in Western Ukraine accumulated around 10 mln tones of accumulated phosphorgypsum (PG) wastes – a by-product of phosphoric acid production, small part of it is offered as agricultural product
The aim of the research was revealing the areas of PG application in production of binders and composites made with PG
Summary
Synthetic gypsum is applied as an alternative for natural gypsum raw in production of construction materials [1], in the areas of location of fertilizing plants. at insufficient level of wastes recycling and reuse. Synthetic gypsum is applied as an alternative for natural gypsum raw in production of construction materials [1], in the areas of location of fertilizing plants. According to data of Florida Institute of Phosphate Research, for each ton of phosphoric acid produced by wet processes in fertilizing plant - approximately 4.5 tons of gypsum generates. At gradual exhausting of the deposits of natural gypsum [3] calcium sulphate containing waste in few decades will become a main raw source for gypsum products. Due to the wet technological processes PG requires drying. Another issue is radioactivity of natural raw for fertilizing plants and PG [5, 6]. One of the most common applications for different PG binders [8] is mortars and different types of concrete [11]
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