The Colloidal Behavior of Lime¹

Abstract

HEN a quicklime is slaked directly to a wet putty, many of its properties are quite different from those of a putty made from the same lime by soaking the dry hydrate. The properties of a putty made from a dry hydrate sometimes change as the time of soaking the hydrate increases. Other differences in the methods of preparation of a lime putty produce differences in the properties of the putty. The causes of these differences have never been satisfactorily explained. Any national theory must account for several known facts. Many theories have been put forth, but only the colloidal theory will be discussed here. Theory for Difference in Lime PuttiesAccording to this theory, lime forms an irreversible colloid, or at least some irreversible colloidal material, during its slaking. If, in the slaking process, only sufficient water is used to produce a dry hydrate, the colloids are destroyed during the drying out of the hydrate and, upon subsequent treatment with water, will not again assume the colloidal state. But if sufficient water is used to leave the slaked lime as a wet putty, the colloidal properties are retained. The col-This would form the colloids necessary for plasticity. These authors have also shown that the magnesia of the quicklimes giving the non-plastic hydrates either completely hydrates during the hydration or else does not hydrate during the soaking. In this case no colloids would be present in the putty to make it plastic. Emleys states that plastic limes can be mixed with more water before they become sloppy or semi-liquid than the non-plastic hydrates. This is another indication of the presence of the colloids in plastic putties, and of their absence in non-plastic ones. The colloidal jelly-like structure of the plastic putty would require more water to Droduce fluidity Many of the properties of hydrated lime can be explained by the assumption that it is a non-reversible colloid. It is thought that the differences between a putty made directly from a quicklime and one made by soaking a dry hydrate may be due to the difference between their colloidal content. In this article it is shown that most putties contain positively charged particles and therefore exhibit cataphoresis to a limited extent. The amount of this cataphoresis is greatest for plastic putties and least for non-plastic putties. The theory is developed that plastic limes owe their plastic properties to their power of forming charged particles upon soaking or slaking. By an adaptation of the theory of Donnan's membrane equilibrium it is shown that the charged particles hold around them a film of solution, which so lubricates the particles as to make the putty plastic.loidal material present modifies the properties of the lime putty and causes the differences observed between the putties made directly from the quicklime and those made by soaking the dry hydrate. It is thought that plasticity, as well as some other properties of lime, depends upon the presence or absence of colloids.This theory explains several of the known facts concer...

Investigation on the hydration of CFBC fly ash

“…The newly created slaked lime cannot immediately precipitate despite its very low solubility for its high reaction rate, but results in irreversible Ca(OH) 2 micelles. The structure of the Ca(OH) 2 micelles is as follows [22]:…”

“…For the oppositive electrical property of fly ash particle and Ca(OH) 2 micelles, electric attraction action occurs, which results in the agglomeration of particles and the setting of A12. If lime is replaced by slaked lime in A15, the micellization process of Ca(OH) 2 cannot occur [20][21][22]. Therefore, A15 cannot set in a short time.…”

Nanoparticles for Cultural Heritage Conservation: Calcium and Barium Hydroxide Nanoparticles for Wall Painting Consolidation

“…Interestingly, it was observed that once hydrate lime putty is dried, it does not recover its initial properties by re-dispersion in water. [15] Many attempts have been carried out to better understand this irreversibility, due to its important scientific and technological implications, particularly in the field of cultural heritage conservation. Short-range van der Waals forces are responsible for the attractive interactions that favour clustering of lime colloids.…”

Microstructure and Rheology of Lime Putty

“…This is the most desirable property of a binder in the fresh state and has a decisive effect on its workability and performance. Despite its importance, studies on the flow behavior of lime putties and pastes, which are known to behave as colloidal suspensions, are scarce. The complex rheology of Ca(OH) 2 suspensions and the difficulty in giving a mechanistic interpretation for the observed flow behavior has been recognized. , Atzeni et al modeled lime putty as a Bingham fluid, although the low number of data points as well as the low value of the correlation coefficient suggest that the Bingham model may not adequately describe the rheological behavior of lime putty, especially at the low shear rates tested.…”