Influence of the Functionalities of Organic Molecules on the Reactivity and Hydration Kinetics of Cement Phases

Date This project started on 01 November 2012 and ended on 30 October 2015

Status This project is Finished

Univ. Bourgogne-Dijon, FR
Univ. Surrey, UK

The high degree of technology and the specifications of modern concrete construction implies the generalized used of organic chemical admixtures to confer the material specific properties either related to its fresh state (rheology modifiers, accelerators, retarders...) or longer term properties (e.g. strength enhancers, durability improvers....).

Although used since decades those admixtures are often considered from a performance point of view but the underlying mechanisms and their interaction with mineral surfaces are hardly resolved and understood. For instance, the mechanism by which set accelerators or retarders work is more of a guess and strongly relies on empirical knowledge rather than on a sound understanding.

With the extensive diversity of today's cements and the increasing levels of substitution of SCMs in modern concrete, the current lack of knowledge on the interaction between organic molecules and mineral surfaces and their influence on the hydration mechanisms of those phases represent a real limitation in the rational development of new products with increased efficiency and performance.

This research is in line with the objectives of nanocem in the sense that it aims at generating fundamental knowledge on the very first interaction taking place upon hydration of cement between the most important components of concrete : the cement (or binder) itself and the organic chemical admixture. Those later have received very little attention in nanocem and in the Marie Curie projects so far with exception of CP3. All the knowledge generated in nanocem on hydration, reactivity, reaction between cement phases is valuable but remains disconnected from concrete technology since all the mechanisms investigated are strongly influence and modified by the presence of organic molecules which were hardly considered, for simplification of the studied mechanisms.

This project intends to start bringing this lacking complementary knowledge.
Although not of high interest from technological and commercial points of views, the molecules to be used will be chosen as to enable the understanding of simple basic interactions between well defined chemical functionalities and well characterized mineral surfaces.

The proposed core project is an experimental approach of the interaction of chemicals with cement hydration. The main goal is to identify not only how they affect cement hydration but also why and to correlate the observed effect and its intensity to their structural and chemical parameters. It is expected that the results could serve as a basis for more predictive modelling approaches.

For this reason the molecules that will be studied are simple ones and do not have necessary an application in cement industry.. Selected small molecules will differ only in the functional group or their stereochemistry like sugars. No special synthesis work is planned, only commercial product. No large molecules such as PCEs or other SPs will be considered because of pre-competitiveness issues but also because of the extensive higher number of parameters involves (chemistry of backbone, side chains, length, charge density, molecular weight distribution...).

The project aims at generating fundamental knowledge on the ionic specificity of small well defined and controlled chemical functionalities of organic molecules and their effects on the main mechanisms of cement hydration.

The project intends to work with model cement phases and Portland cement together with a broad set of small sugar and amine like molecules differing from each other on the basis of their conformation or ending functionalities such as carboxylates, sulfonates, phosphonates...

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