Biocidal cements with active mineral additive: production and properties

Concrete and reinforced concrete structures are susceptible to the negative effects of bacteria, mycelial fungi, and actinomycetes. The purpose of this research is development of compositions of cement binders with active mineral additives for biocidal concretes creation. For biocidal cements with an active additive manufacture following components were used: Portland cement clinker produced by JSC Mordovcement, two-water gypsum of the Poretsky deposit, fly ash of the Krasnoyarsk CHP-3 and biocidal ingredients: sodium sulfate, sodium fluoride. Biocidal cements were obtained by joint grinding of mineral components and biocidal additives, then an active mineral additive was added. The physico-chemical, physico-mechanical and technological properties of the cements with an active mineral additive and composites based on them were determined in accordance with current regulatory documents. X-ray phase analysis, thermogravimetric analysis, differential thermogravimetry, calorimetry and other methods were used in this work. The features of phase transformations in cement stone are revealed depending on the type and content of biocidal ingredients, active mineral additives and hydration time. The absence of ettringite formation during hydration of cements modified with sodium fluoride and the presence of a new hydroaluminate phase have been established. The curves of TG, DTG and DTA for hydrated biocidal cement with the addition of fly ash modified with sodium sulfate are almost identical to the curves of hydrated ordinary cement. The largest amount of C-S-H gel (40 wt. %) was recorded in formulations with an active mineral additive. Based on the results of the study of normal density and setting time of the cement dough, the strength of samples of biocidal cement stone during compression and bending, regression equations were obtained, graphical dependencies were built and optimal compositions of biocidal cements were determined. Compositions of biocidal cements superior in physical and mechanical properties to ordinary Portland cements, which are recommended for the manufacture of biostable building products, have been obtained.