The lime mortar is a highly hetrogeneous material which
can exbibit different types of 
structural and textural features in different parts of the mortar. All
gravity flows are guided by broad planes (>100µm) of structural weakness.  The particle size and particle
size distribution in the lime mortar also depend on the rate of flow of pore
fluids and their evaporation. Similarly smoothness or roughness of the surfaces
bounded around the mineral grains and the specific surface area are also play
critical role  on the rate of flow of
pore-fluid and its evaporation. Increasing effect of lime mortar matrix and
fractures are increased lime mortar permeability. On the other hand,  increasing effect of rock matrix increases
matrix permeability. As per IUPAC (International Union of Pure and Applied Chemistry) pore
size ranges of sorption (1nm-0.1µm), micro pores (1nm-10nm) mesopores (10
nm-100 nm), macro pores (0.1µm to 10cm), capillary pores ranges (1µm -100µm)
and coarse pores ranges 0.1mm  to 10 cm 30.
Capillary transfer of pore fluids play optimum role for dissolution and
precipitation materials in mortar.

A void is an empty space in lime mortar. The type,
size, shape, arrangement and abundance of voids and pores are factors
controlling many important properties. The percentage of air void volume is
generally specified by the design of the mixture of mortar. The
determination of the abundance of the various types of voids is very essential
to study the texture of lime mortar plaster. Air voids present are formed
during the mixing lime mortar. Diffusion of vapourous lime mortar into air
voids may cause free growth of needle-like crystals from inner walls of such
voids as in the crystallization in miarolytic cavities 31 and 32.  Particle size and particle size distibution
in the lime mortar  and the planar
surface on which the lime mortar applied are 
also caused heterogenetity of lime mortar. They may be studied under
scanning electron microscope (SEM).  The
size and shape of the voids can be used as indicators of type and origin of
voids. The luster and texture of the interior of the voids may be used in the
recognition of voids caused by accumulation of water and passageways for water.
The properties on which distinctions may be made between the various types of
voids.  Because these distinctions are
made on the appearance of a void on the surface of a slice, many large voids
will be classified as entrained voids when they are really entrapped voids
(>1mm bubble like (FHWA-RD, 1997). A cross section that is larger than the
defined maximum for entrained voids (100µm – 1mm) must be a section of an entrapped
air void or a water-formed void. A significant number of large cross sections indicate a
great number of large voids. SEM study is a valuable technique to analyze
quantitative determination of the abundance of various types of voids. Air
voids are classified as entrained or entrapped. During recrystallization of
fine-grained minerals into coarse crystalline ones, the whole material tries to
loose the excess of internal energy generated during  the deformation when  the crystal lattice defects occurs. During
such process the shape and size of grains change and the texture of the
material changes. The intergranular boundaries of mineral grains are irregular.
During recrystallization of gypsum and other sulphate minerals, intergranular
boundaries are migrated or rotated (Nimmo, 2004). Adjacent  grains differs in density.The defect poor
gypsum grain bulges into the deffect rich adjacent grain, and shape of the  gypsum grain distorted. It results
spontaneous growth of new grains.