Influence of Citric Acid on the Hydration of Portland Cement

Citric acid can be used to retard the hydration of cement. Experiments were carried out to investigate the influence of citric acid on the composition of solid and liquid phases during cement hydration. Analyses of the solid phases showed that dissolution of alite and aluminate slowed down while analyses of the pore solution showed that citric acid was removed almost completely from the pore solution within the first hours of hydration. The complexation of the ions by citrate was weak, which could also be confirmed by thermodynamic calculations. Only 2% of the dissolved Ca and 0.001% of the dissolved K formed complexes with citrate during the first hours. Thus, citric acid retards cement hydration not by complex formation, but by slowing down the dissolution of the clinker grains. Thermodynamic calculations did not indicate precipitation of a crystalline citrate species. Thus, it is suggested that citrate sorbed onto the clinker surface and formed a protective layer around the clinker grains retarding their dissolution.

[1]  Carl D. Palmer,et al.  Solubility of ettringite (Ca6[Al(OH)6]2(SO4)3 · 26H2O) at 5–75°C , 1999 .

[2]  T. E. Zelenina,et al.  Complexation of citric and tartaric acids with Na and K ions in aqueous solution , 2005 .

[3]  W. Schwarz.  Novel cement matrices by accelerated hydration of the ferrite phase in portland cement via chemical activation: kinetics and cementitious properties , 1995 .

[4]  C. Wilding,et al.  A classification of inorganic and organic admixtures by conduction calorimetry , 1984 .

[5]  E. Königsberger,et al.  Complexation of iron(III) and iron(II) by citrate. Implications for iron speciation in blood plasma. , 2000, Journal of inorganic biochemistry.

[6]  Ellis Gartner,et al.  Saturation factors for calcium hydroxide and calcium sulfates in fresh portland cement pastes , 1985 .

[7]  V. S. Ramachandran,et al.  Conduction calorimetric investigation of the effect of retarders on the hydration of Portland cement , 1992 .

[8]  S. Goñi,et al.  Calcium Hydroxide Saturation Factors in the Pore Solution of Hydrated Portland Cement Fly Ash Pastes , 1996 .

[9]  O. Pokrovsky,et al.  Experimental study of the effect of organic ligands on diopside dissolution kinetics , 2006 .

[10]  Jeffrey J. Thomas,et al.  Solubility behavior of Ca-, S-, Al-, and Si-bearing solid phases in Portland cement pore solutions as a function of hydration time , 2002 .

[11]  O. Pokrovsky,et al.  Kinetics of brucite dissolution at 25°C in the presence of organic and inorganic ligands and divalent metals , 2005 .

[12]  F. P. Glasser,et al.  Reaction of EDTA, oxalic acid and citric acid with Portland cement , 1999 .

[13]  M. Wilhelm,et al.  Solid state NMR investigations on the role of organic admixtures on the hydration of cement pastes , 2006 .

[14]  André Nonat,et al.  Experimental investigation of calcium silicate hydrate (C-S-H) nucleation , 1999 .

[15]  G. Saoût,et al.  Influence of limestone on the hydration of Portland cements , 2008 .

[16]  B. Lothenbach,et al.  Thermodynamic Modelling of the Effect of Temperature on the Hydration and Porosity of Portland Cement , 2008 .

[17]  T. Chotard,et al.  Effect of malic and citric acid on the crystallisation of gypsum investigated by coupled acoustic emission and electrical conductivity techniques , 2006 .

[18]  Martin Rb.  Citrate binding of Al3+ and Fe3+. , 1986 .

[19]  N. B. Singh,et al.  Hydration Study of the System Ca3Al2O6–CaSO4· 2H2O–Ca(OH)2–H2O with and without Citric Acid , 1990 .

[20]  Jörg-Rüdiger Hill,et al.  Retardation of setting of plaster of Paris by organic acids: Understanding the mechanism through molecular modeling , 2004, J. Comput. Chem..

[21]  J. Tinnea,et al.  Influence of Citric Acid on Reactions in the System 3CaO·Al2O3‐CaSO4·2H2O‐CaO‐H2O , 1977 .

[22]  O. Pokrovsky,et al.  Effect of pH and organic ligands on the kinetics of smectite dissolution at 25 °C , 2006 .

[23]  N. B. Singh,et al.  Effect of citric acid on the hydration of portland cement , 1986 .

[24]  B. Lothenbach,et al.  Thermodynamic modelling of the hydration of Portland cement , 2006 .