Phosphonate admixtures

Diaikanol aminoalkyl phenols as admixtures enhance the strength [675]. The additives are useful in very small amounts and do not affect the initial properties of the fluid. The strength additive does not cause set acceleration or early set strength enhancement but provides enhanced compressive strength of the cement in later stages. Addition of small amounts of potassium ferricyanide and nitrile-trimethyl phosphonic acid promotes the formation of complex compounds and thus increases the strength of cement rock [1771]. 

The stabilizer may consist of carboxylic acids and phosphorus-containing organic acid salts such as hexametaphosphates, polyphosphates and phosphonates. The mechanism of action of the stabilizer admixture is thought to be related to the inhibition of CSH and CH nucleation. It is claimed that the nucleation process is controlled more comprehensively than that obtained with conventional retarders [10], Cement hydration is arrested by the admixture acting on all phases of cement hydration including the C3A fraction. The claim is... 

A phosphonate-based admixture, ATMP (amino trimethylene phosphonic acid) in amounts of 0.03-0.05%, was added to C3S and C3A at a w/s ratio of 1.0 and the heat, developed with time, was followed by conduction calorimetry.Phosphonic acid affects the hydration of C3S (Fig. 14). The reference C3S produced a maximum exothermic peak with a heat equivalent to 5.32 cals/g/h at 8.5 hours. Addition of phosphonic acid reduced the amplitude of the peak, delayed the occurrence of the peak, and also modified the appearance of the peak. About 1.79 cals/g /h of heat was developed at 11.5 hours with the addition of 0.03% phosphonic acid, and, at a dosage of 0.04%, an exothermal peak occurred at 31 hours with a heat production of 1.41 cals/g/h. At 0.05% addition, there was practically no heat produced even up to 72 hrs. 

Ramachandran, V. S., and Lowery, M. S., Effect of Phosphonate-Based Compound on the Hydration of Cement and Cement Compounds, 4th CANMET/AClInt Conf. on Superplasticizers and Other Chem. Admixtures in Conor., Montreal, Canada, SP-148 131-151 (1994)... 

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