Central Europe Chemistry

Ulrich Schubert, Professor of Inorganic Chemistry at the Materials Chemistry Institute of the Vienna University of Technology, is Euchems president elect. Nachrichten aus der Chemie asked him about his priorities and aims.


Nachrichten aus der Chemie: In a few months you will be president of Euchems: Is this a pleasure or a burden?
Ulrich Schubert: It will probably end up as a mixture of both. But it was gratifying and a great honour to be asked to be a candidate in the first place, and then actually to be chosen. Will the office end up being burdensome? The word burden has a bad aftertaste and I don't believe I could ever feel that way about this position. But the amount of work that is coming my way has already become clear in the few months since the election: in that short time my e-mail has tripled.
Nachrichten: What are the issues topping your agenda?
Schubert: The first priority is to represent Euchems interests vis-à-vis European institutions and authorities, as well as European and international partner organisations. For example, deliberations for the eighth European Framework Research Programme have already begun, and Euchems wants to play a key role in them.
Nachrichten: And what will be priority number two?
Schubert: The second most important assignment for Euchems is networking. In my view, a network of young chemists is especially important. We senior academics already have our networks, but among our juniors there is room for improvement. The very active European Young Chemists Network, EYCN, needs our full support.
Nachrichten: Is there a third construction site?
Schubert: Yes. The lines of communication from Euchems via the national member societies to their individual members and back are in urgent need of upgrading. It's a typical umbrella-organisation predicament. The average member of each national chemistry association knows far too little about the benefits they're getting from Euchems.


<h2>How chemists benefit from Euchems</h2>
Nachrichten: And what does the individual chemist gain from membership? 
Schubert: Well, first I'd have to name the big Euchems conferences like those in Nuremberg, Turin and Budapest, because of their high visibility. Another example are networking possibilities through our divisions and working groups. But there are low-profile benefits, too, such as the lobbying at European institutions by our policy manager in Brussels, where we now have a permanent office. It is also worthwhile reading the Euchems Newsletter and the Euchems Brussels News Updates, both of which are on the Internet at <ext-link ext-link-type="uri"><a href="https://www.euchems.org" target="_blank">www.euchems.org</a></ext-link>.
Nachrichten: But is yet another lobbying organisation actually needed in Brussels? There's already, for instance, Euro-Chemistry, an association of a number of national research organisations. And then there's Cefic, the European Chemical Industry Council — an influential player.
Schubert: You are right about Cefic: it carries much more weight in policy-making than we will ever have, in terms of financial resources alone. But it acts on behalf of other interests too. To put it as succinctly as possible: Cefic speaks for the chemical industry; Euchems for the chemists — as human individuals. Of course their interests overlap to a certain extent and are complementary to those of Euchems. Other associations and organisations such as the European Cooperation in Science and Technology (Cost) and the European Science Foundation (ESF) are not specifically chemically oriented. The same is partially true for Euro-Chemistry. This is a recently founded grouping of a few research organisations centred around the French CNRS. Their objectives are not clear, and it is not clear how these multi-disciplinary organisations could represent chemistry.
Nachrichten: What does lobbying in Brussels actually accomplish anyway?
Schubert: I would not take the word lobbying too literally. It is more of a joint effort to raise awareness about chemistry. An example is the promotion of European research by the European Research Council (ERC), which puts chemistry in a very good light. Still, one thing is a pity: though there are two evaluation panels concerned with chemical applications, neither refers explicitly to chemistry in its title. Here we chemists are ourselves at fault. We are often far too reticent. We should stress that in many fields of research it is chemistry that provides the intellectual leadership. That doesn't mean we should distance ourselves from the other disciplines, but adopting the role of a mere utility for the life sciences or for materials research is a fundamental error. Chemistry has a better standing generally than chemists themselves believe. Many go on insisting that chemistry has an image problem. That may have been true twenty years ago, but today every decision-maker is fully aware that chemistry is a motor for innovation.


<h2>Financial structure needs to be changed</h2>
Nachrichten: Should Euchems do more to raise its profile politically?
Schubert: Basically, yes. We ought to define issues where chemistry is central or could assume a leading role. But Euchems is not a wealthy organisation. If we want Euchems to take on more pan-European functions, we will have to change its present financial structure.
Nachrichten: What changes are needed?
Schubert: Presently the contribution per member of national chemical societies for Euchems membership comes to about two euros — give or take ten per cent. For large organisations like the German Chemical Society this is relatively little, but for some small societies, for example in Eastern Europe, even that much hurts. So simply raising membership fees proportionately is not an option.
Nachrichten: What other solutions do you have in mind?
Schubert: One possibility could be stronger involvement on the part of the chemical industry. We certainly don't want to leave any chemical society — neither a national organisation nor Euchems — depending on drip-feeding by the chemical industry, though the chemical industry in fact benefits substantially from the work of the chemical societies. An alternative would be to discuss whether Euchems should open its doors to other types of members apart from national chemical societies, such as institutional members.
Nachrichten: Would you welcome stronger networking by the various chemical sectors at European level under the umbrella of Euchems?
Schubert: Networking and joining forces is a must in Europe, because of its federal structure. This is true for political Europe as well as for chemistry in Europe. Euchems is the ideal platform for such networking. Europe's chemistry must speak with one voice, and this is only possible if the various players coordinate their activities. Any fragmentation will have a negative impact.
Nachrichten: In concrete terms, what can be done?
Schubert: Let's take the international year of chemistry: many activities, publications and posters developed by the large societies can easily be adapted by the smaller ones. It would be very good if Euchems could act as a catalyst for cooperation among the societies. Also interesting would be for societies to join forces themselves and hold regional conferences. The big European Euchems conference has become an established event — next year the fourth one takes place in Prague.
Nachrichten: Has the biennial Euchems Conference got off to a good start in your opinion?
Schubert: The first three conferences were very successful, with attendance at around 2500: the conferences weren't planned to be much larger than that. Mammoth meetings like the ACS conferences are fragmented into countless sub-conferences. That is no model for us. Still, the last Euchems conference in Nuremberg did bring one problem to light, namely, the greatly disproportionate number of chemists attending from the host country. I am not worried about Prague. That conference will draw plenty of international guests because of its convenient central location and its wealth of tourist attractions. But what will happen when the conference venue is a very small or somewhat remote country? The large societies are needed here: they must see that such conferences find the same acceptance the others do. Solidarity among the individual societies is a necessity.
Nachrichten: You have both a German and an Austrian passport, and you live and work in Vienna, in the heart of Europe. Is Europe more to you than an administrative unit?
Schubert: I belong to a generation that grew up while Europe was growing together. When I was in school, the Franco-German Treaty of Friendship was of the greatest importance. Later it was my privilege to experience at first hand the end of the Cold War and the Eastern Europeans' liberation from Communism. I firmly believe that the countries of this continent are friends who must cooperate. The chemical societies reflect this beautifully. Perhaps it's easier for us scientists to leave national partisanship behind. I've seen this in my own group, which is very international — nothing unusual in Austria: During the Balkan conflict, a Serb and an Albanian from Kosovo did their PhD work in my group. This did not cause any problems. And hopefully both not only experienced chemistry but also other positive sides of human relationships.

Artikel

“Solidarity is a necessity”

Ulrich Schubert, Professor of Inorganic Chemistry at the Materials Chemistry Institute of the Vienna University of Technology, is Euchems president elect. Nachrichten aus der Chemie asked him about his priorities and aims. Nachrichten aus der Chemie: In a few months you will be president of Euc...

The destruction of concrete and mortar in environments rich in sulphates and carbonates is termed sulphate attack: in terms of topical chemical changes, it is attributed to thaumasite<xref rid="bib1" ref-type="ref">1</xref> added to ettringite. The scope of sulphate ingress (as opposed to durability) into concrete has been recorded based on a decrease of flexural strength, changes in length, and observation. Phase changes studies have confirmed beyond doubt the relevance and role of thaumasite and thaumasite sulphate attack (TSA) to concrete, but the latter must not be overestimated. Thus, the amount of thaumasite in destructed concrete bodies, as well as quantification of the TSA portion of overall deterioration caused by sulphate attack on construction material, remain the subjects of ongoing discussion in the research and technology of concrete and mortar.
 The first step in damage to concrete and mortar and the constructions based on them is observable in the formation of ettringite and conjugated mass and volume changes leading to cracks, which enable water to access the original material. Repeated (cyclical) wetting and drying increase both the permeability of the material and the probability of reactions of atmospheric CO2 with sulphates and the C-S-H phase of the original material to form a. o. thaumasite — CS·Cs·Cc·H15.<xref rid="bib1" ref-type="ref">1</xref>—<xref rid="bib3" ref-type="ref">3</xref> One of the preconditions for TSAs on concrete construction materials is relatively low environmental temperatures (below 15o C). The presence of thaumasite, and thus the development of TSAs on concrete, have been confirmed by X-ray phase analysis, thermal analysis and electron microscopies.


<h2>Thaumasite: composition and basic structural features</h2>
Thaumasite rarely occurs as a natural mineral, an alteration product of limestone. The chemical formulae [Ca3Si(OH)6·12 H2O](SO4)(CO3) or CaSiO3·CaCO3· ·CaSO4·15 H2O show the composition and basic structural features of thaumasite: the short-hand cement chemistry notation CS·Cs·Cc·H15 is widely used (also in this text). Although it is generally assumed that a solid solution series between thaumasite and ettringite exists, both substances crystallize within different space groups. A possible discontinuity has been identified and is characterised by a gap in the a-dimension of the solid solution phases,<xref rid="bib4" ref-type="ref">4</xref> while details of the crystal structure of thaumasite were reported much earlier.<xref rid="bib5" ref-type="ref">5</xref> A series of thermal decomposition studies of thaumasite are to be found in the literature.<xref rid="bib6" ref-type="ref">6</xref>—<xref rid="bib10" ref-type="ref">10</xref> The basic outputs may be summarised as part of the data on the decomposition of mineral thaumasite<xref rid="bib5" ref-type="ref">5</xref>—<xref rid="bib8" ref-type="ref">8</xref>, as may proposals of the methodology of thermo-analytical and microstructural investigations of thaumasite as a form of sulphate attack in concrete.<xref rid="bib8" ref-type="ref">8</xref>—<xref rid="bib12" ref-type="ref">12</xref>
Until the end of the 1990s, the destruction of concrete and mortar by sulphate attack was attributed to the formation of two minerals: ettringite (C6As3H32) and gypsum (CsH2).<xref rid="bib1" ref-type="ref">1</xref>—<xref rid="bib3" ref-type="ref">3</xref>,<xref rid="bib12" ref-type="ref">12</xref>,<xref rid="bib13" ref-type="ref">13</xref> This form of destruction is accompanied by a local increase in volume and by the consumption of aluminium within the cement, both obviously in limited quantity in ordinary concrete. The thaumasite form of sulphate attack on concrete and in mortar — TSA — requires a source of sulphate and also of carbonate.<xref rid="bib1" ref-type="ref">1</xref>,<xref rid="bib2" ref-type="ref">2</xref> It tends to form at low temperatures — typically about 4 — 10 oC. Thaumasite results from a reaction by the strength-forming C-S-H phases to sulphate ions or a sulphate-containing compound in the presence of a source of carbonate and water (moisture). Sulphate can be derived from a variety of sources: groundwater or mineral salts are common examples. Carbonate is present in atmospheric CO2 or in limestone present within the concrete or mortar. Although the calcium silicate hydrate in concrete provides most of the strength of concrete, it also becomes a reagent of thaumasite formation. Thus the affected system suffers extreme weakening: concrete severely affected by thaumasite formation can easily be broken with the fingers and the coarse aggregate extracted.
We have earlier reported our findings of the presence and contents of thaumasite in a selection of buildings from several regions in Slovakia that possibly display the characteristics and effects of TSA.<xref rid="bib3" ref-type="ref">3</xref>,<xref rid="bib14" ref-type="ref">14</xref> Our laboratory has also studied and analysed thaumasite formation and TSA itself on model systems using an aggressive attack methodology: a cooled (5 ± 2o C) MgSO4 (1.5 % by mass) and Na2SO4 (5 % by mass) solution, the volume of the solution is 10 times that of the test sample. These extremely aggressive environmental testing conditions were chosen to achieve in a relatively short time data that would take much longer to compile under service conditions.
Changes in X-ray phase analysis, electron microscopy, flexural strength and length were measured and evaluated using routine methodologies. Phase compositions of probes were determined by means of X-ray data (difractometer Philips PW 2235, CuKa radiation), simultaneous thermal analysis (sdt 2960 — T.A. Instruments, TGA &amp; DTA), and electron microscopy (electron microscope Zeiss EVO 40 with the microanalyzer Bruker axs). An assessment of the scope of deterioration was also achieved by visual observation and by standardised measuring of changes in flexural strength and length, and by evaluating the evolution of these over a given period.


<h2>Investigating thaumasite</h2>
The methodology developed<xref rid="bib9" ref-type="ref">9</xref> and used for the indication of thaumasite based on thermo-analytical data depends on analysis of step 1 of the thermal decomposition of thaumasite (cf. eq. 1) exerting characteristic (a) stoichiometry and (b) DTA endoeffect, both taking place from 108 to 128 oC. The mole fraction xth of thaumasite in the inspected sample is straightforwardly expressed (cf. eq. 2) as the ratio of the value of TG mass loss — ΔmI(exp) of probe at the above temperature interval and the value of mass loss from proposed stoichiometry during this step of decomposition — ΔmI(st) = 37.6%. Both the occurrence of the DTA endoeffect between 108 and 128 oC and the value of TG mass loss that are characteristic of step 1 of the thermal decomposition of thaumasite enable an evaluation of the content of thaumasite present in the sample down to as little as 0.1%. Figure 1 illustrates the decomposition (dehydroxylation) of thaumasite as evidenced by the DTA effect (108.7 oC) and thus by relevant TG mass loss (ΔmI(exp)), while the values of ΔmI(exp) had already been widely used for calculation of the content of thaumasite both in the model system and in construction materials in several parts of Slovakia that were inspected for evidence of TSA.
CaSiO3·CaCO3·CaSO4·15 H2O →
→ CaSiO3·CaCO3·CaSO4·2 H2O  + 13 H2O (eq.1)
 xth = ΔmI(exp)/ 37.60 (eq. 2)
The content of thaumasite investigated using the complex methodology above, both in the materials under aggressive attack and in local construction materials, is compared and referred to as an indicator of the evidence and effects of TSA. The reference materials exert values of TG mass losses of 1% to 10% for the temperature interval 110°-130o C; the mol fraction of thaumasite 0.027 &lt; xth &lt; 0.266 was calculated using the eq. 2. The values close to the upper part of the interval of our data were presented<xref rid="bib8" ref-type="ref">8</xref> for samples stored under extreme conditions (UK weather conditions, accessibility of earth sulphates, sulphides and carbonates). A comparison of the relevant values of mol percentages of thaumasite in local construction materials in Slovakia with a possible manifestation and effects of TSA (0.011 &lt; xth &lt; 0.035)<xref rid="bib14" ref-type="ref">14</xref> shows that the content of thaumasite in samples taken from six months to two years following the model aggressive attack attains to and exceeds the level of thaumasite content displayed by construction materials after 30 to 70 years of service under Slovakian weather conditions. Additional studies (i.e., on the improvement of sulphate resistance of concretes, not reported here) have showed that TSA may be delayed if slag or fly ash are used either in the form of blended cements or as a latently hydraulic additive directly applied to the raw mix concrete.
The latest results and studies<xref rid="bib13" ref-type="ref">13</xref>,<xref rid="bib15" ref-type="ref">15</xref> indicate that thaumasite formation is always preceded by expansion and cracking of the sample due to ettringite formation. It has been observed that thaumasite can form within the C-S-H phase, consuming the available carbonate and sulphate, and, given the very slow kinetics of thaumasite formation, is probably facilitated by the opening of the structure due to ettringite-induced cracking. The specific conditions for the formation of thaumasite were also derived by means of thermodynamic calculations and experimental investigations of a laboratory specimen.<xref rid="bib11" ref-type="ref">11</xref>,<xref rid="bib12" ref-type="ref">12</xref> The studies also confirmed that the formation of thaumasite can be prevented through the use of moderate sulphate concentrations, if during the production of concrete a sufficient quantity of pozolanic or latent-hydraulic materials is added. When these materials are admixed, calcium hydroxide is consumed, and the calcium silicon relationship in the C-S-H phases is consequently reduced. These calcium-poor C-S-H phases are more chemically resistant to the formation of thaumasite than are the usual calcium-rich C-S-H phases. If the attack takes place in the presence of the mineral gypsum (and not via sulphate ions), all of the binding agents examined prove to be equally susceptible to damage through the formation of thaumasite. In this case physical resistance should be increased in order to avoid the formation of thaumasite.
Finally, knowledge of phase composition, the formation mechanism and specific formation conditions is completed by microstructural studies (Figure 2, and Lit.<xref rid="bib11" ref-type="ref">11</xref>—<xref rid="bib13" ref-type="ref">13</xref>). Basically, most of the content of monosulphate- and monocarbonate AFm phases is mixed with C-S-H. The transformation to ettringite in the presence of C-S-H leads to the development of expansion stress and the formation of cracks in cement paste and on interfaces with filler particles. Aside from the accessibility of phases, the former mechanism is a necessary precondition for phase changes for the formation of thaumasite in cracks and interfaces, as our experiments have shown. At the same time, a loss of cohesion is observed, i.e., a decrease in strength, the ultimate phenomenon being the destruction of surface material.


<h2>Concluding remarks</h2>
Research on TSA and thaumasite (including our results) shows that thaumasite sulphate attack constitutes a real danger, especially under severe environmental conditions and as a follow-up to delayed ettringite formation. Prevention is effective to a limited extent only.
The time period after which TSA may exert negative effects upon the parameters of concrete under ambient climatic and environmental conditions should not be overestimated. As in the example, the amount of thaumasite, and thus the extent of deterioration after decades of service of construction material under ambient conditions, is usually much less than the level achieved during testing of model systems over two years under extremely aggressive environmental conditions.
Milan Drábik is a senior scientist in the Ceramics Department of the Institute of Inorganic Chemistry, Slovak Academy of Sciences, Bratislava and associate professor in the Department of Inorganic Chemistry, Faculty of Natural Sciences, Comenius University, Bratislava. <a href="mailto:drabik@fns.uniba.sk">drabik@fns.uniba.sk</a>


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“Solidarity is a necessity”

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