Reactivity of natural volcanic pozzolans for low carbon cement: respective contributions of the vitreous and crystallized phases

The Institute of Mineralogy, Physics of Materials and Cosmo-Chemistry (IMPMC) is a multidisciplinary institute for physics, Earth sciences and biophysics-bioinformatics, located in the heart of Paris within Sorbonne University and the National Museum of Natural History. 

A historic research laboratory in mineralogy, physics and materials science, its research strategy is focused on ambitious projects in condensed matter physics, Earth sciences in the broadest sense and biology, the three fundamental components of the unit.

The main challenge for the global cement industry is to manage its ecological transition, meaning reducing its CO₂ footprint. There are two main levers to play with:

i) the process way (production tool and conditions of production)

ii) the product way (cement composition).

If the first one is not expected before 15 years from now, with high investment costs, the second one may be much faster by mean of standards evolution.

The main objective is to reduce the content of cement hydraulic binder (the clinker) in cement formulation by a maximum of substitution by supplementary cementitious materials (SCMs), possibly with cooperative interactions between them. The challenge is to keep the usual properties ofusage.

Beside recovery materials, natural volcanic pozzolans are good candidates. The classical interpretation stipulates that their reactivity is broadly proportional to their glass content. However, in several cases the measured reactivity does not fully correlate with the glass content, suggesting that the crystalline phases in this volcanic material, may also play a significant role.

Objectives of the internship

The purpose of this internship is to isolate crystalline phases and glassy phase from volcanic rocks (pouzzolans) of different origins by mean of a protocol using safe dense liquids and centrifugation. As the protocol was developed during a previous internship, the aim here is to apply it to treat a large number of rocks in order to determine the respective contribution of glassy and crystalline phases to the global reactivity of pouzzolans. After separation, the glassy and crystalline phases, as well as the initial total rock will be characterized by chemistry (XRF), mineralogy (Optical microscopy, XRD) and reactivity in highly basic aqueous solution (R3 tests, Portlandite consumption).

The working samples were chosen from industrial experience having shown unconventional behavior by mean of reactivity tests. The proportion of crystalline phase will vary from nil (obsidian) to almost fully crystallized rocks (trachyte, phonolite).

This internship's scientific and professional goal is to gather objective data on the reactivity of the glassy and crystalline phases to establish material selection criteria and aid in data interpretation.

Techniques/methods in use : Phase separation by heavy liquids, chemical reactivity in aqueous solution at high pH (pH>12.7), multiscale microscopic analysis, quantitative XRD (Rietveld analysis), chemical composition by XRF, mechanical strength determination on mortar.

Internship location: Sorbonne Université – IMPMC (Paris). Mandatory collaboration with ICB (Dijon).

Applicant skills: Master geochemistry-mineralogy,or inorganic chemistry with knowledge in solid reactivity in aqueous phase and a marked interest for experimentation.

Industrial partnership: Yes, start-up: Reciprocal Network Consulting in connection with industry.

Possibility for a Doctoral thesis: Y/N (specify if already financed): Yes, provided finance accepted.

Applicant skills: Master geochemistry-mineralogy,or inorganic chemistry with knowledge in solid reactivity in aqueous phase and a marked interest for experimentation.