Projects / Programmes
The Hydration of the System Portland Cement-Limestone-Fly Ash and the Influence of the Final Phase Composition on Sulfate Resistance.
| Code |
Science |
Field |
Subfield |
| 2.02.07 |
Engineering sciences and technologies |
Chemical engineering |
Inorganic products |
| Code |
Science |
Field |
| T440 |
Technological sciences |
Non-metallic mineral technology |
Portland cement; mineral admixtures; limestone; fly ash.
Researchers (4)
Organisations (1)
| no. |
Code |
Research organisation |
City |
Registration number |
No. of publicationsNo. of publications |
| 1. |
0104 |
National Institute of Chemistry |
Ljubljana |
5051592000 |
21,007 |
Abstract
Limestone-containing Portland cement has become in the last twenty years a standard hydraulic system that entirely conforms to both European (EN 197-1) and Slovenian (SIST EN 197-1) standards. The addition of limestone has positive technical, economical and environmental effects on the energy-demanding clinker production. The technical reasons are satisfactory physico-mechanical properties of hardened cement paste and the economic/environmental effect include both energy savings due to decreased clinker production and the reduction of environmental pollution by harmful greenhouse gas CO2. The addition of fly ash enables in the first instance the use of otherwise waste material which in the hydration course under certain conditions even improves chemical, physical and mechanical properties of the final product.
The hydration of cement containing limestone and fly ash is a complex mixture of physico-chemical reactions and their interactions. The course of reactions, their kinetics and specific negative or positive effects on the final phase composition of hardened cement paste have been studied in a majority of cases only in a very general way and, even so, usually only for a certain kinds of a specifically chosen or used system(s).
The purpose of our project is the determination of the time course of hydration reactions and the characterization of the formed phases and, in the final phase of the research, the establishment of the relationships between the addition of limestone and fly ash and the sulfate resistance of hardened cement paste. The sulfate corrosion is one of the main reasons for a serious degradation of concretes where the hardened cement paste represents the main binder with all useful properties. In the presence of SO42- and CO32- anions, moisture and low temperatures a mineral thaumasite, CaO.SiO2.CaCO3.CaSO4.15H2O, forms. Its formation is the main cause for a dramatic decrease of mechanical and physico-chemical properties of a hardened cement paste. The structure of thaumasite includes three types of anions (silicate, sulfate and carbonate) that are taken from the calcium silicate hydrate (3CaO.2SiO2.3H2O), ettringite (3CaO.Al2O3.3CaSO4.26H2O) and tetra calcium monocarboaluminate 11-hydrate (3CaO.Al2O3.CaCO3.11H2O) that are all formed during the hydration of limestone-containing Portland cement.
The final goal of the project is the detailed knowledge of the hydration kinetics, the quantitative determination of the phase composition of hydrated phases and, on the basis of the results obtained, the determination of the optimal formulation of the hydraulic system comprising Portland cement, limestone and fly ash that will demonstrate high sulfate resistance without a significant decrease of important physico-chemical and mechanical properties.
Significance for science
The science of nanomaterials, which includes also hydrated cements with mineral admixtures, is nowadays in a full swing worldwide, although practical issues and the relevance of their usefulness have not yet been adequately exploited. With our research we will join to the international research community that focuses its research effort to that particular field of science. Cements with mineral admixtures that influence their useful properties represent an important class of nanomaterials. All the properties (hydration, the development of hydrated phases, chemical, environmental and, in particular, sulfate resistance) must be thoroughly investigated both on micro- and nano levels.
The important aspects of this research are also the collaboration with the industrial partner and with international research groups and also the publication and dissemination of research results.
Significance for the country
Materials and systems that were investigated in this project are interesting to Slovenian cement producers, particularly to Salonit Anhovo, the largest Slovenian cement producer, with which we have actively collaborated for more than a decade. The production of novel, environmentally-friendly cements with mineral admixtures can effectively decrease the environmental pollution and can also extend the competitivness of the company on the European market.
The improved corrosion and mechanical properties of cements with mineral admixtures are the main reasons for their development and further detailed investigations with a view towards their practical novel applications that altogether represent a sustainable development of novel binders.
The use of fly ash enables in the first instance the consumption of otherwise waste material and in the second instance it reduces the needs for the deponies in the environment. The use of fly ash also reduces the consumption of natural resources and thus helps in their conservation.
Most important scientific results
Annual report
2008,
final report,
complete report on dLib.si
Most important socioeconomically and culturally relevant results
Annual report
2008,
final report,
complete report on dLib.si
