Therecalculation of EDS analyses (Table 5 and 6) of weight percent in the elementform into oxides, the analyses showed a great deficiency of cations withabundance of free anions; indicating that the analyzed material is composed ofsignificant amount of hydroxides and water of crystallization. The analyses are very similar to the chemicalcomposition of saline solutions or groundwater. Normally, a small number ofsubstances constitute the chemical composition of water (major ions), but otherions (minor ions) can also be found in low concentrations.
The identificationof saline minerals based on their morphology of crystal forms was rathercomplex and difficult. They often grow as distorted crystals as needles andradiating aggregates in pore spaces. Owing to their small size in the rangearound 5?m, it is not possible to identify under polarizing microscope. Hydratesare composed with water of crystallization in their structures 6. When ahydrate is heated; it absorbs enormous quantity of heat (endothermic) and formsanhydrous mineral. When an anhydrate is immersed into water; it absorbs waterand releases enormous quantity of heat transforming into a hydrate mineral 6.
In other way, it can be expressed that a hydrate is formed by releasingenormous quantity of heat from its anhydrous product. The heat released mightpromote evaporation of pore fluids. Ice is formed by removing heat from thefreezing water is a typical example for a hydrate transition.
The most hydratesare stable and soluble in water at room temperature. Some hydrates spontaneouslyloss water of crystallization by efflorescence. Others absorb water into theirstructure forming hydroscopic hydrates. Some deliquescent mineral like sodiumhydroxide absorbs huge quantities of water and form as a liquid. Thedecomposition of carbohydrates generally releases water. Thus, water ofcrystallization in a hydrate mineral play critical role on their changes intheir specific gravities and in turns their volumes 7.
Hydration is not areversible reaction, however, the environment in which the crystallization ofhydrates plays critical role for the formation of hydrates and anhydrates 8. Repeated hydration and dehydration changesthe volume of saline minerals which in turn affects the volume of pore spacesand hairline cracks are induced. Most pores are partially or completely filledwith saline pore fluids 9. The evaporation of saline fluids precipitatessaline minerals initially at peripheral portions of saline droplets inside thepores.Figures13-20 provide distribution of ioniccomponents in the pore fluids present in the lime-plaster, derived from EDSanalyses and represent chemical variation of binary components. Theions of various chemical components are calculated on the basis of 6(Cl) ions(Deer.et.al.
5). Rittman’s norm 4 is used to calculate the normativeproportions of calcite, gypsum and halites. linear distributions were seen in the distributions of Alagainst Si, Cl against CO2, Na against Ca (Figures 13-15). A low concentration of sulphate ions in thetri-linear diagram shows a linear distribution of Cl ions against CO2.Figure 16 represents the linear distribution of carbonate ions againstchloride ions in the lime mortar.
Low concentration of gypsum showslinear distribution for normative calcite (Figure 17). NaCl (halite) against Cland aluminum carbonate against silicon carbonate exhibited positive lineardistribution (Figures 18 and 19). The Figure 20 elucidates initial randomdistribution of Na ions against Ca ion and more linear when Na ions enriches atlate stages of crystallization.