Mortars for Brickwork and Blockwork (1)

Lime ~ traditional mortars are a combination of lime, sand and water. These mixes are very workable and have sufficient flexibility to accommodate a limited amount of wall movement due to settlement, expansion and contraction. The long term durability of lime mortars is poor as they can break down in the presence of atmospheric contaminants and surface growths. Nevertheless, lime is frequently specified as a supplementary binder with cement, to increase mix workability and to reduce the possibility of joint shrinkage and cracking, a characteristic of stronger cement mortars.

Cement ~ the history of cement type mortar products is extensive. Examples dating back to the Mesopotamians and the Egyptians are not unusual; one of the earliest examples from over 10 000 years ago has been found in Galilee, Israel. Modern mortars are made with Portland cement, the name attributed to a bricklayer named Joseph Aspdin. In 1824 he patented his improved hydraulic lime product as Portland cement, as it resembled Portland stone in appearance. It was not until the 1920s that Portland cement, as we now know it, was first produced commercially by mixing a slurry of clay (silica, alumina and iron-oxides) with limestone (calcium carbonate). The mix is burnt in a furnace (calcinated) and the resulting clinker crushed and bagged.

Mortar ~ mixes for masonry should have the following properties:

• Adequate strength

• Workability

• Water retention during laying

• Plasticity during application

• Adhesion or bond

• Durability

• Good...