Impact of Zn salts on hydration, compressive strength, microstructure, leachability and toxicity of ordinary Portland cement

abstract

English

Ordinary Portland cement (OPC) has been used to solidify of hazardous waste for about 25 years and the effect of waste components on the hydraulic activity is an interesting object for the research. The possible increase of zinc incorporation present in secondary raw materials may lead to changes in behavior of pastes made from OPC. In this study zinc nitrate, chloride and oxide were added to Portland cement. The concentrations of 0.05, 0.1, 0.5 and 1.0 weight percent of zinc in cement were tested. After 1, 7, 28 and 90 days were measured the compressive and flexural strengths. The addition of salts of zinc modifies resulted compressive strength in various ways. The early compressive strength (1 day) decreases in comparison with the reference sample. This difference is probably due to a delay in tricalcium silicate hydration as shown by isothermal and isoperibolic calorimetry. As shown by scanning electron microscopy and X-ray diffraction, zinc is predominantly absorbed in CaZn2(OH)6.2H2O and another crystalline phases according to the additional anion. The possibility of release of zinc were made on all prepared mortars after 1, 7, 28 and 90 days according to ČSN EN 12457. Zinc was not investigated in any made leachates (by ICP-OES). Toxicity is measured on grow of seeds of Sinapis alba.

Portland cement, zinc, hydration, calorimetry, toxicity

KOLÁŘOVÁ, I.; ŠILER, P.; HAVLICA, J.

5. 12. 2014

VUT v Brně FCH

Brno

978-80-214-5077-6

Sborník abstraktů Chemie je život - studentská konference

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