First progress made by the CEReM
Mortars are composed essentially of hydraulic binders (cement, lime), polymers, sand and various additives, and they have properties that deserve to be better understood because their use has to satisfy a large number of requirements, some of which are particularly severe. They can be used for facade renderings, tile adhesives, screeds or repair mortars, and users (professionals and individuals) expect that the properties (mechanical strength, bond, etc.) of mortar will remain unchanged in the long term.
The objective that the CEReM has set itself is to pool international knowledge on the subject. It was first set up in 2003 under the driving force of the CSTB, and is composed of mortar manufacturers (like SNMI ), raw material producers (cement, polymers, sand, additives, etc.) and chemistry, mechanics, microstructure research laboratories, etc. The CEReM works with a college type organisation to decide on which studies should be carried out and asks public laboratories such as the Ecole Supérieure de Physique et de Chimie de Paris, the Ecole des Mines de Saint-Etienne, the University of La Rochelle, The Ecole Normale Supérieure de Cachan, the INSA Toulouse and the Ecole Polytechnique Federale de Lausanne to do the work. Four PhD theses and several short studies have already been awarded to them on different research themes (see inset). The results will be presented annually to all members of the CEReM. "One way of sharing knowledge from fundamental research that we would not have the time or financial and human means to carry out ourselves", says Roger Zurbriggen, chemist, from Elotex. Claude Haehnel, CTG (Italcementi Group), cement manufacturer says the same thing: "Our research means are not infinitely expandable and some interesting subjects are not and will not be developed in the short term in our research centres. Our participation in the CEReM enables us to acquire data and knowledge that we would not have been able to acquire otherwise so directly."
Mutual sharing of knowledge without loss of identity
"We needed to find common denominators to initiate collective research interesting to chemists and to end mortar manufacturers", says Daniel Broussaud, scientific adviser for Weber et Broutin. Nadège Blanchard, the CEReM coordinator at the CSTB, says "the objective is not to substitute ourselves for product formulators, but to create an international skills synergy so as to improve knowledge and scientific tools to enable manufacturers to develop even more reliable mortars". "Everyone keeps his own know-how and his recipes to develop his own products", adds Daniel Broussaud.
Everyone benefits from this emulation and contacts are created. Roger Zurbriggen thinks that CEReM meetings help to maintain contact with the market, and research institutes help to understand current trends and to select the most suitable research orientations. "We meet several of our customers in a single place, which provides a very strong commercial opportunity. It is a good way of being in close contact with professionals who face exactly the same problems as ourselves in their every day work."
The CEReM is an opportunity for exchanges between different players, and brings persons who did not necessarily know each other before, around the same table. For Daniel Broussaud, "the CEReM has enabled chemists to get better understanding of formulators' problems, and vice versa." At Lafarge Mortiers, Sabine Royer, scientific coordinator, explains "We expect that progress made by the CEReM will be in the long term" because in the end we are dependent on raw materials suppliers. Most innovations will originate from chemists and cement manufacturers who see specific progress in them. We shall have to wait before studies from formulators have a direct impact on our work."
Advantages for everyone
The CEReM has asked Jérémie Pourchez, PhD student at the Ecole des Mines de Saint-Etienne, to carry out a study on organic admixtures added in cement. He has the same view of this consortium: "a platform for exchanges between actors of the mortars market". He is well aware of the expectations of these actors after four years of theoretical research. "I work on interaction between cellulose ether and cement. Knowing that more than about twenty inorganic and organic constituents are necessary to make a mortar, I am searching to get a better understanding of interactions between the different molecules to explain the setting time and to make the product more easily handled during its implementation."
But what are the advantages for each partner? Because the cement manufacturer, the chemist and the formulator all have different interests? "Actually, says Jérémie Pourchez, due to our research, the chemist can innovate and reduce the costs of organic binders; the cement manufacturer can optimise cement formulas depending on the types of additives that he uses and the mortar formulator can rationalise the use of each product used in the composition of the final product." And everyone benefits ...
A steering committee composed of two representatives from each industry and two laboratory representatives chooses priority research themes, ratifies short and long term study projects, and manages the budget. Research workers in their own place of work are supervised by a supervisor in the host laboratory and a person from the CSTB, and work is monitored by working groups composed of members of the consortium. All publications are ratified by a reading committee.
80 persons are involved from 5 countries. The CEReM's budget is about 90000 Euros per year.
Seven working groups for a common objective
Formulations of cement-based and polymer-based mortars are still relatively empirical and are based on formulators’ know-how and experience. Basic research carried out by the CEReM helps to understand interaction phenomena between the different constituents.
• Working group No. 1: Latex – cement interactions
Research on understanding of phenomena induced by the addition of latex into mortar formulations.
Contact: Nadège Blanchard – blanchard(at)cstb.fr
• Working group No. 2 : Cellulose ether – cement interactions
Research on microscopic mechanisms affecting the setting time induced by cellulose ethers added to cement.
Contact: Bertrand Ruot – b.ruot(at)cstb.fr
• Working group No. 3: Carbonation of mortars
Study of the carbonation phenomenon (formation of calcium carbonate due to the reaction of mortar with carbon dioxide) and its repercussions on durability of the material.
Contact: Agnès Cauchois – agnes.cauchois(at)cstb.fr
• Working group No. 4: Cracking of mortars
Microscopic and macroscopic studies to understand phenomena that govern cracking.
Contact: Christine Gilliot – c.gilliot(at)cstb.fr
• Working group No. 5: Mortar – substrate interactions
Adhesion and stress state analysis in a mortar layer applied to a substrate.
Contact: Bertrand Ruot – b.ruot(at)cstb.fr
• Working group No. 6: Water movements
• Working group No. 7: microstructure