Electrochemical behavior of Portland cement pastes containing phosphonates

Abstract An impedance measurement technique was used to investigate the effects of aminotri(methylenephosphonic acid) (ATMP), 1-hydroxyethylidene-1, 1-diphosphonic acid (HEDP), and diethylenetriaminepenta (methylenephosphonic acid) (DTPMP) on the hydration process and setting behavior of portland cement pastes. It was demonstrated that the impedance and capacitive responses can be used to characterize setting behavior and microstructural development of the hydrating pastes containing these chemical admixtures. The presence of a long induction period of up to 20 and more than 75 hours is revealed by the impedance curves of pastes containing ATMP, HEDP, and DTPMP at dosages of 0.05% and 0.2%, respectively. This confirms that phosphonates are efficient retarders. These compounds appear to have strong chelating or complexing capability, potentially poisoning CH and C-S-H nucleation. Stabilization of the C-S-H (metastable) film on the surface of cement grains appears to cause retarding effect.

[1]  E. Ebied,et al.  Effect of admixtures on the electrical behaviour of Portland cement , 1993, Journal of Materials Science Letters.

[2]  Some aspects of the electrical properties of cement paste , 1984 .

[3]  V. S. Ramachandran,et al.  The role of phosphonates in the hydration of Portland cement , 1993 .

[4]  F. Tamás.  Electrical conductivity of cement pastes , 1982 .

[5]  V. S. Ramachandran,et al.  Concrete Admixtures Handbook: Properties, Science and Technology , 1996 .

[6]  E. Hekal,et al.  Electrical conductivity of cement pastes in different curing media , 1989 .

[7]  J. Beaudoin,et al.  A rationalized a.c. impedence model for microstructural characterization of hydrating cement systems , 1993 .

[8]  J. Beaudoin,et al.  APPLICATION OF A.C. IMPEDANCE TECHNIQUES IN STUDIES OF POROUS CEMENTITIOUS MATERIALS (II): RELATIONSHIP BETWEEN ACIS BEHAVIOR AND THE POROUS MICROSTRUCTURE , 1993 .

[9]  William John McCarter,et al.  THE ELECTRICAL RESPONSE CHARACTERISTICS OF SETTING CEMENT PASTE , 1984 .

[10]  J. Beaudoin,et al.  Application of A.C. impedance techniques in studies of porous cementitious materials , 1993 .

[11]  D. Roy,et al.  Low-frequency electrical conductivity of cement, clinker and clinker mineral pastes , 1987 .

[12]  James J. Beaudoin,et al.  A study of the hydration and setting behaviour of OPC-HAC pastes , 1994 .

[13]  A. M. Hassan,et al.  Electrical properties of some pyridine complexes , 1993 .

[14]  P. Gu,et al.  Electrochemical behaviour of Portland-cement/high-alumina-cement systems at early hydration times , 1993 .

[15]  M. G. A. E. Wahed.  Electrical conductivity of Portland cement admixed with some azodyes , 1991 .