Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 5, pp. 716−721.
Pleiades Publishing, Ltd., 2012.
Original Russian Text © A.S. Brykov, V.V. Danilov, M.V. Mokeev, 2012, published in Zhurnal Prikladnoi Khimii, 2012, Vol. 85, No. 5, pp. 712−717.
AND INDUSTRIAL INORGANIC CHEMISTRY
Effect of Alkali Cations on Silicon Ability to Bind in Cement
Stone by Data of Solid-State
Si NMR Spectroscopy
A. S. Brykov
, V. V. Danilov
, M. V. Mokeev
St. Petersburg State Technological Institute, St. Petersburg, Russia
Institute of Macromolecular Compounds, St. Petersburg, Russia
Received September 6, 2011
Abstract—An effect of additive compounds of sodium and lithium (nitrates and chlorides) on the distribution of
silicon atoms by a degree of connectivity in the cement paste was studied by the solid-state
Si NMR spectros-
copy at different periods of hydration. Simultaneously, we measured the strength of the hardened cement paste
The problem of an inﬂ uence of alkali metal com-
pounds on the properties of Portland cement (PC) formu-
las and concrete is of interest to researchers because there
is still no unambiguous understanding of participation of
these compounds in the process of PC hydration [1, 2].
As it is known, alkaline compounds accelerate the PC
hydration, facilitate rapid taking of cement paste, and
in some cases increase early strength of cement paste
[1–5]. Nevertheless, the presence of alkaline compounds
in high concentrations has a negative impact primarily
on the durability of cement stone, especially in the late
period of hydration [1, 4]. Signiﬁ cant amounts of sodium
and potassium compounds can enter the cement stone or
concrete with the cement, chemical additives, as well as
from external sources: sea water, anti-icing agents, and
industrial efﬂ uents.
The durability of the cement stone is due to formation
of a structure known as C–S–H-gel [6, 7]. The structure
of the C–S–H gel involves polymer silicon–oxygen
fragments formed by successively combining discrete
(monomers or Q
) supplied by silicate
phases of PC, ﬁ rst into dimers Q
and then into polymeric
fragments of a linear structure, in which silicon atoms are
in the degree of connectivity Q
. The formation of
the structure of C–S–H-gel occurs with the participation
of calcium, which connects the silicate fragments.
In the study using the solid-state
Si NMR spectros-
copy we examined the dependence between the distri-
bution of silicon atoms by the degree of connectivity
in the cement paste containing the additive compounds
of sodium and lithium and durability. Researching the
effect of lithium ion on the polymeric state of silicon in
the product of hydration and on durability is of special
interest because lithium compounds are known as the
most effective inhibitors of alkali-silicate reactions in the
body of concrete with the participation of reactive ﬁ llers
and alkalis from the pore ﬂ uid .
Fig. 1. Durability of cement stone R (МПа) vs. time τ (days)
and amount of alkali compounds in it. (1) without additive; (2,
3, 5) Na
O amount (wt %): 0.5, 3, and 6, respectively; (4, 6)
O amount: 1.4 and 2.9, respectively.