Reactions and Surface Interactions of Saccharides in Cement Slurries

Abstract

Glucose, maltodextrin, and sucrose exhibit significant differences in their alkaline reaction properties and interactions in aluminate/silicate cement slurries that result in diverse hydration behaviors of cements. Using 1D solutionand solid-state 13 C nuclear magnetic resonance (NMR), the structures of these closely related saccharides are identified in aqueous cement slurry solutions and as adsorbed on inorganic oxide cement surfaces during the early stages of hydration. Solid-state 1D 29 Si and 2D 27 Al{ 1 H} and 13 C{ 1 H} NMR techniques, including the use of very high magnetic fields (18.8 T), allow the characterization of the hydrating silicate and aluminate surfaces, where interactions with adsorbed organic species influence hydration. These measurements establish the molecular features of the different saccharides that account for their different adsorption behaviors in hydrating cements. Specifically, sucrose is stable in alkaline cement slurries and exhibits selective adsorption at hydrating silicate surfaces but not at aluminate surfaces in cements. In contrast, glucose degrades into linear saccharinic or other carboxylic acids that adsorb relatively weakly and nonselectively on nonhydrated and hydrated cement particle surfaces. Maltodextrin exhibits intermediate reaction and sorption properties because of its oligomeric glucosidic structure that yields linear carboxylic acids and stable ring-containing degradation products that are similar to those of the glucose degradation products and sucrose, respectively. Such different reaction and adsorption behaviors provide insight into the factors responsible for the large differences in the rates at which aluminate and silicate cement species hydrate in the presence of otherwise closely related saccharides. ■ INTRODUCTIONSaccharide reactions and interactions at hydrating inorganic oxide surfaces significantly influence diverse surface chemistry processes that include carbonate formation in marine organisms, biosynthesis at aluminosilicate surfaces, biofuel production over heterogeneous catalysts, corrosion inhibition, and cement hydration. 1−7 The competitive adsorption of organic molecules and water at heterogeneous inorganic oxide surfaces influences reaction mechanisms, kinetics, molecular compositions and structures, and macroscopic material properties. Importantly, saccharide molecules are commonly used to alter the hydration processes and material properties of cements, such as the calcium aluminates and silicates that are widely used in synthetic structural materials. 8 In particular, the hydration kinetics of hydraulic aluminate/ silicate-based cements are critical to concrete construction and oilwell cementing, in which organic additives are often used to slow (inhibit) hydration processes or alter the rheological properties of cement−water mixtures, commonly referred to as cement "slurries". Despite their enormous technological importance, much remains to be known about the physicochemical interactions of the inorganic silicate or alumi...

Influence of bound water layer on the viscosity of oxide nanopowder suspensions

“…47 It was also reported that saccharides affect hydration of cements depending on the reaction and adsorption behavior of saccharides and their degradation products with dissolved species and particle surfaces. 48,49 Similar to the retardation effect of saccharides on aluminate hydration, we observed a decrease in bound water content in the presence of low molecular weight saccharides. 36,38,39 As mentioned earlier, the addition of NaCl did not affect the bound water, while the H + and OH − led to a decrease and increase of the bound water peaks, respectively.…”

Physical, chemical and mineralogical properties of fine recycled aggregates made from concrete waste

“…Vicat needle penetration depth in FRA pastes prepared with different saccharose concentrations. retarder effect [58,59]. This delay increases with increasing saccharose concentration (it is particularly significant above 2%), which suggests a potential chemical reaction.…”

Influences of Dilute Organic Adsorbates on the Hydration of Low-Surface-Area Silicates

“…12,14,21,23−27 Solid-state 2D 13 C{ 1 H}, 29 Si{ 1 H}, and 27 Al{ 1 H} heteronuclear correlation (HETCOR) and 1 H{ 1 H} double-quantum (DQ) NMR measurements of silicates and aluminates hydrated with organic additives (e.g., stabilizers or hydration inhibitors) have established surprisingly diverse influences of closely related organic molecules, such as glucose and sucrose, on the rates of hydration. 13,28,29 Similar 2D NMR methods have also been used to measure the molecular interactions of organic acids adsorbed at much higher concentrations (4−40% bwos) on titania and zirconia nanoparticles that also have high surface areas (50−150 m 2 /g). 30 As conventionally practiced, however, NMR spectroscopy is relatively insensitive, so detecting and resolving the NMR signals from organic molecules and inorganic species in low-surface-area cementitious materials have required concentrations of at least 1% bwos of the organic species, which furthermore must often be isotopically enriched to be feasible.…”