The thermal analysis of zinc oxide‑contaminated Portland cement blended with thiocyanates and determination of their effect on hydration and properties

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216305%3A26310%2F22%3APU146092" target="_blank" >RIV/00216305:26310/22:PU146092 - isvavai.cz</a>

Result on the web

<a href="https://link.springer.com/content/pdf/10.1007/s10973-022-11666-0.pdf" target="_blank" >https://link.springer.com/content/pdf/10.1007/s10973-022-11666-0.pdf</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1007/s10973-022-11666-0" target="_blank" >10.1007/s10973-022-11666-0</a>

Result language

angličtina

Original language name

The thermal analysis of zinc oxide‑contaminated Portland cement blended with thiocyanates and determination of their effect on hydration and properties

Original language description

The contamination of cement binders with zinc represents a significant problem due to the negative effects on cement hydration. Zinc compounds cause a drastic increase in setting time due to prolonging the induction period. The currently accepted mechanism behind this effect is the formation of Ca(Zn(OH)3 ) 2 ·2 H 2 O hydrates on the surface of cement grains that deplete Ca 2+ ions from the pore solution and creates a diffusion barrier. Hydration accelerators are commonly employed in the concrete industry to counter long setting time caused by low temperature and contamination by heavy metals. These compounds influence both hydration kinetics and composition of hydration products. The influence of various compounds on the mechanism of cement hydration can be studied using calorimetric methods such as isoperibolic and isothermal calorimetry. The hydration of the material was stopped, and the properties of hydrated cement pastes were studied using differential thermal analysis, X-ray diffraction and scanning electron microscopy. Some setting accelerators have been found to significantly decrease setting time of zinc-contaminated cement. Out of the most used compounds in commercial accelerators, the efficiency of thiocyanates is yet to be determined. The results show that thiocyanates induce a visible change in hydration mechanism of cement to various degrees depending on concentration and on the presence of the specific cation. Alkali thiocyanates drastically retard the hydration of zinc-contaminated OPC. With further retarded hydration of cement, the mechanical properties were negatively impacted. Calcium thiocyanate on the other hand effectively accelerates setting and positively impacts compressive strength at low doses. Main difference between the influence of alkali and calcium thiocyanates on setting is the change in ettringite content. Alkali salt promotes AFm phases at the expense of ettringite content while calcium salt promotes formation of ettringite at ear

Czech name

—

Czech description

—

Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

20101 - Civil engineering

Project

<a href="/en/project/GA19-16646S" target="_blank" >GA19-16646S: The elimination of the negative impact of zinc in Portland cement by accelerating concrete admixtures</a><br>

Continuities

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Publication year

2022

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Journal of Thermal Analysis and Calorimetry

ISSN

1388-6150

e-ISSN

1588-2926

Volume of the periodical

neuveden

Issue of the periodical within the volume

2022-11-13

Country of publishing house

HU - HUNGARY

Number of pages

29

Pages from-to

„“-„“

UT code for WoS article

000877887300004

EID of the result in the Scopus database

2-s2.0-85140989995