CLC Lime produces a more intimate contact between the masonry units. As a result, it develops a better and stronger bond.  This kind of mortar also tends to "squish" into the crevices and irregularities of the masonry unit, providing a "keying" action which strengthens the bond.  Lime binds better with, and works into, the rough masonry surfaces producing a tight mortar bond which ensures a high resistance to cracking and moisture penetration.

The durability of a wall involves not only durability of the mortar itself, but also the ability of the mortar to assist in compensating for deficiencies of the masonry unit. In high lime content mortars the lime gradually hardens by the absorption of atmospheric carbon dioxide and reverts to stable limestone. Lime is the only material usually contained in mortars which has the ability to fill-in, and actually create bonds with voids and cracks that may exist in the brickwork. 

High lime content mortars resist deflection (wind sway) and lateral pressures better, with less cracking in the bond between the mortar and masonry units. Thus the strong intimate bond, characterised by high lime content mortars, tends to "give a little" under stress. 

There a less volume change (shrinkage) with mortars of lower but adequate strength containing lime. Hard, high-strength mortars tend to shrink during drying and hardening, causing separation cracking between the mortar and masonry units which results in a weaker bond. Of all cementitious materials, lime has the least volume change during drying and setting. 

The prime causes of efflorescence are the presence of sulble salts in the masonry materials. To protect the masonry units, a high lime content mortar provides tight joints and prevents the water entrance of water. Thus the water cannot act as a solvent and dissolve the salts which later dry and crystallize as the unsightly building "bloom" or efflorescence. It is a fact that lime contains less soluble salts than any other masonry material. 

Lime mortars have high water retentivity. They retain water longer and resist suction, through capillary action, by the masonry units. A mortar with low water retentivity loses its moisture rapidly and "pancakes" or stiffens so quickly that an intimate bond is not developed with the masonry unit. 

Lime based mortars increase in strength steadily over a period of many years. Wetting and drying cycles are actually beneficial to such mortars and tend to accelerate this gain in strength - another reason for the durability of lime mortars.