Galkina D.K.

East-Kazakhstan State Technical University in the name of D. Sericbaev

Anhydrite binder on the basis of technogenic anhydrite

 

One of commonly used constructional materials in construction activity are gypsum and anhydrite binder and their products. Additional source of base material for gypsum and anhydrite binder  production on their basis are sulfate-containing waste, such as phosphogypsum, borogypsum, titanogypsum, flourgypsum, sulfogypsum etc., this helps to economize the best part of natural resources and deal with the problem of environment protection.

The subjects of  study is technogenic anhydrite (CaSO4) – mud coming from fluoric production, appearing in Ulba Metallurgic Plant in East Kazakhstan, and represents  solid acid calcium sulfate wastage.

Acid wastage coming out of baking is granular grey material. Granular size is from 0,3 mm to (40-60) mm. pH level ~ 1,8. The chemical composition of wastage is the following: ÑàÎ – 31; SO3 – 44; Fe2O3 – 0,5; MgO – 0,04; Cr2O3 – 0,01; TiO2 – 0,02; Na2O – 0,02; K2O – 0,02, Ð2Î5 – 0,04. According the results of X-ray phase analysis acid technogenic anhydrite has the following phase composition, mass. %:  CaSO4 – 88,5-98,2; H2SO4 – 10-15; CaF2 – 1-1,5; HF – up to 0,5.

To use acid wastage of fluoric production, first of all it is necessary to saturate extra quantity of acids. The saturation of acid wastage was making till neutral or alkalescent pH level.

During mixing with the water neutralized anhydrite showed subastringent state, as represented generally solventless anhydrite  (AII). For the purpose of   technogenic anhydrite activation ruin was used and additionally grind mixture was produced till specific surface  of cementing component. As a result synthanite  of air hardening on the basis of technogenic anhydrite, specified by the strength aged 28 days: under compression 11,2-17,8 MPa, under curve – 2,2-4,7 MPa, with pH level =10-12, softening factor - 0,4-0,5, water demand – not above 42 % [1].

To develop this sphere of using bonding material, the next stage was research in waterproofing of synthanite  of technogenic origin [2].

Gypsum cement pozzolanic binder (GCPB) [3], received by means of adding gypsum binder and active mineral admixture, except cement. As a pozzolanic admixture it is usually used: bergmeal, ash, granulated blast - furnace  slag. The following mixture GCPB  %  is mostly used  by weght: gypsum binder 75-50, portland cement           15-25, pozzolanic admixture 10-25.

Other subject of study is composition anhydrite  binder  on the basis of technogenic anhydrite, including complex of admixtures, specifically cement, farewell and ash dump mixture. Composition anhydrite  binder of higher water resistant, on the basis of technogenic anhydrite was found after the research, with water requirement not above 38%, with the strength 28 days from 20 to 30 MPa and from                     3,7-6,0 MPa, under compression and curve, with the coefficient  softening from 0,72 till 0,81, depending on the compositional analysis.

The structure of anhydrite binder of air hardening and composition anhydrite  binder of higher water resistant is on the 1st picture.

 

 

 

 

 

 

 

 

 

 

 


                                 à                                                                b            

 

a-air hardening; b-higher water resistance

drawing 1- the structure of anhydrite binder  on the basis of technogenic anhydrite  at the age of 28 days

 

Developed anhydrite binders on the basis of technogenic anhydrite are recommended for the producing of structural material  and its products, including dry plaster- binder of air-hardening,  wall products –binder of higher water resistance.

The using of binder of higher water resistance on the basis of anhydrite wastage allows to extend raw material base of anhydrite binder and additionally utilizes waste. 

 

Literature

 

1.                Rodin A.N. Utilization of gypseous wastage of East Kazakhstan for the purpose of getting binder and structural material on its basis. Report about R-effort  ¹ of gosregistration  0109PK01151/A.N. Rodin, A.A. Hayrullina, D.K.Galkina, and ect. – EKSTU in the name of Serikbaev – 2009.

2.                Galkina D.K. Development of binder of higher water resistance from hydrogen fluoride wastage. D.K Galkina, A.N. Rodin, A.A. Hayrullina // Vestnik             EKSTU, 2010. ¹2.

3.                Volzhensky A.V. Gypsum cement pozzolanic binder, concrete and products./ Volzhensky A.V,V.I.Stambulko, A.V.Ferronskaya –M.: Literature about construction, 1971. p. 319.