Hydration hardening internal stresses

Whereas small amormts of free lime may be cortsidered acceptable, larger amormts may cause expartsiort, strength loss, and cracking of the hardened paste. This is due to a delayed hydration of free calcitrm oxide to calcittm hydroxide, which takes place topochemically and is associated with an increase of volttme and a generation of internal stresses within the paste. Thus excessive amounts of free calcium hydroxide in clinker must be avoided. 

Formation of Contacts between the Particles and the Development of Internal Stresses during the Hydration Hardening of Mineral Binders... 

Internal Stresses in Structures Obtained in the Course of the Hydration Hardening of Various Binders... 

Dependence of Internal Stresses on the Conditions of the Hydration Hardening... 

The effect of hardening conditions on internal stresses (Adid) was studied using specimens of finely disperse Mg(OH)2 with a surface area on the order of tens of mVg. The results indicated a considerable dependence of the internal stresses on the degree of supersaturation, a (a = c/Cq, c, concentration Co, equilibrium solubility), reached in the course of the hydration of a mineral binder in an aqueous slurry. The AdId values increased with both the ino-ease in the degree of dispersion and the decrease in the W/S ratio, as shown in Table 6.12. 

Another possible way to substantially modify the nature of contacts is to use hydration hardening of the magnesium oxide followed by dehydration instead of mechanical pellet pressing (Figure 7.63e) [120,149,160]. This allowed one to establish stronger phase contacts while simultaneously removing the residual internal stresses. 

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