The micro-structural character of limestone and its influence on the formation of phases in calcined products: natural hydraulic limes and cements

0547864 - ÚTAM 2022 RIV NL eng J - Journal Article
Kozlovcev, Petr - Válek, Jan
The micro-structural character of limestone and its influence on the formation of phases in calcined products: natural hydraulic limes and cements.
Materials and Structures. Roč. 54, č. 6 (2021), č. článku 217. ISSN 1359-5997. E-ISSN 1871-6873
R&D Projects: GA MK(CZ) DG20P02OVV028
Keywords : raw materials microstructure * limestone petrography * calcination * belite * natural hydraulic lime—NHL
OECD category: Materials engineering
Impact factor: 4.285, year: 2021
Method of publishing: Limited access
https://doi.org/10.1617/s11527-021-01814-7

The properties of natural hydraulic binders are directly influenced by the composition of the raw materials used in their production. Depending on the specific composition and conditions in the kiln during burning, the process results in the transformation of the natural raw material and the formation of new phases based on chemical interactions between neighbouring mineral components (solid–state ion migration). A series of laboratory experiments was performed in order to compare the characteristics of various limestones with their properties, phase composition and phase-to-phase relationships after burning. The main objective was to thoroughly understand the relationship between the composition of the raw material and the characteristics of the burnt product. A set of 21 limestone samples were first characterised in terms of raw materials (including their chemical composition), and then individually burnt in an electrical furnace to obtain calcined products. Optical microscopy, SEM–EDS, and XRD-QPA were used to assess the micro-structural character of the material before and after calcination, identifying the relationships between the character and amount of the non-carbonate impurities, the size and character of the carbonate matrix, and the constituted phases. The results show that the chemical composition, expressed as the cementation index, can be used to predict the hydraulicity of calcined limes. However, for this to be reliably applied to an unknown limestone, an understanding of the petrographic characteristics is necessary. The paper demonstrates several different types of phase to phase relationships before and after calcination. It also points out the relation between the micritic and sparitic character of raw materials, and the hydraulicity of burnt products.
Permanent Link: http://hdl.handle.net/11104/0324160