Tag Archives: Chemistry

Proceedings of 13th International Congress on the Chemistry of Cement

Among the conferences taking place every year on cement science, International Congress of Cement Chemistry (ICCC) is almost the most important one. The conference takes place every four years. The latest one is the 13th ICCC hosted in Madrid Spain in 2011 and the next one 14th ICCC will be hosted in Beijing in 2015. During the 13th ICCC, there were more than 900 participants from over 60 countries all over the world, received more than 400 papers on cement science, which cover 9 subjects:

  • 1.- Production process chemistry and engineering
  • 2.- Sustainable production
  • 3.- New cementitious matrix
  • 4.- Hydration and microstructure
  • 5.- Hydration and thermodynamics
  • 6.- Modelling
  • 7.- Properties of fresh and hardened concrete
  • 8.- Concrete durability
  • 9.- Standardization

When reading papers, I saw numerous researchers refer to the information from the papers of ICCC, unfortunately, those proceedings of earlier age are not easy to find, since they are no digital version (like PDF files), or they are not open to the public. Even for the latest proceedings, you have to attend the meetings to get the proceedings, but the cost to attend these meetings is expensive or at least not cheap. What is even worse is that every meeting is definitely not available for all people in the field, due to the difficulties such as travelling and time schedule.

The purpose of conference is to gather people who are interested on some issues in the same field to discuss and share latest results. As a result of meetings, the proceedings paper is a good media to store and spread these information. So we should make these proceedings open for the related researchers rather than close them for a small group of researchers, which is not the REAL Science, Science should be OPEN, and must be OPEN.

I have attended the 13th ICCC thanks to the financial support from my promoter, and got a digital proceedings of the conference. I think it is a good idea to share them with you who are also a researcher on cement science. Just click the link Proceedings of 13th International Congress on the Chemistry of Cement to download them onto your computer or copy the whole folder to your DropBox account.

Share them and make science OPEN.

Chemical reaction of limestone with C3S and C3A

The hydration rate of C3S is accelerated in the presence of limestone probably because of the dilute effect and the multiplied nucleation sites. Jean Pera et al. reported that the total heat resulting from pure C3S hydration was 145 joules while that of the mixture (50%C3S+50%CaCO3) reached 260 joules. Ramachandran’s investigation showed that some calcium carbonate was consumed as the hydration of Portland cement proceeded. The product of the reaction of limestone and C3S is calcium carbosilicate, whose exact type cannot be identified by X-ray diffraction probably due to its amorphous property and small amount of formation.

Besides the reaction with C3S, limestone can reacts with C3A as well. According the investigation of Ingram et al., for a combination of 2% gypsum, 6% limestone, and 92% clinker, CaCO3 reacts with C3A in the clinker. The reaction begins with a C3A·CaCO3·12H2O product, then forms compounds containing a molar ratio of C3A to CaCO3 between 0.5 and 0.25. Later, the product appears to stabilize as C3A·xCaCO3·11H2O, where x ranges from 0.5 to 0.25. Other researchers reported similar results.

Bensted found that in the absence of gypsum CaCO3 in limestone reacts with C3A to form both “hexagonal prism” phase tricarbonate C3A·3CaCO3·30H2O and hexagonal plate phase monocarbonate C3A·CaCO3·11H2O, but the former one tricarbonate is much less stable than AFt at ambient temperature, thus it would not be formed in cement hydration.

The transformation of ettringite to monosulfate in the presence of limestone is delayed and reduced due to the formation of monocarboaluminate. Bentz proposed a possible chemical reaction of this process as follows,

3(CaO)3(Al2O3)·CaSO4·12H2O+2CaCO3 +18H2O →
2(CaO)3(Al2O3)·CaCO3·11H2O + (CaO)3(Al2O3)·3CaSO4·32H2O

G. Kakali et al. concluded that in pastes containing CaCO3, either as a chemical reagent or as a limestone constituent, the ettringite’s transformation to monosulfate is delayed, while calcium aluminate monocarbonate is preferably formed instead of monosulfate even at early ages.

It is should be noted that the formation of ettringite is accelerated by the addition of limestone at the very beginning of hydration (e.g. 30 min) in the presence of gypsum, corresponding with the accelerated conversion of ettringite to monosulphoaluminate due to the incorporation of limestone.