IntroductionMortar is a mixture of sand, a binder such as cement, and water. This mixture is used in masonry construction to fill the gaps between the bricks and blocks used in construction. It is applied as a paste during construction, and then later sets hard, holding the blocks, or bricks together firmly. It can also be used to fix parts of a construction where its original mortar may have been washed away. Currently, mortar can be either mixed on site, or factory-produced ready-to-use mortar can be bought. (Allen, 2003)Ready-to-use mortars are replacing on-site mixed mortars, due to their advantages over on-site mixed mortar. They are made in factories under tightly-controlled conditi ...view middle of the document...
The silo is delivered to site, complete with integral mixer. Once power and water supplies are connected, mortar can be produced as required. The rate at which water is added can be controlled to achieve the required consistency. The silos can either be single-compartment or two-compartment.(http://www.mortar.org.uk/)Since the factory produced silo mortars are of guaranteed composition, and are thoroughly mixed, they will therefore provide satisfactory durability. However, the designer still has theresponsibility to specify the correct mortar designation for the type of structure, exposureconditions and type of masonry units. In hot conditions some stiffening may occur which may be corrected by the addition of a small amount of water followed by trowel mixing on the spot board in the traditional manner. Once the initial set has started the mortar must not be reconstituted in a mechanical mixer or by any other method.The setting of cement is affected by weather and will proceed more slowly when it is colder.This factor is taken into account when the mortars are manufactured but subsequentsignificant reductions in temperature may increase the retardation period and extend theworking life and will have no adverse effect on the masonry. It is inadvisable to proceed with the construction of masonry whilst the temperature is below 3ºC and falling. If the mortar freezes any frozen material or crust should be discarded.Currently Used BindersPortland cement mortar is made by mixing Portland cement, which in this case is the binder, with sand and water. This type of mortar was invented in the mid-nineteenth century, as part of scientific efforts to develop stronger mortars than those that existed at the time. It was popularized during the late nineteenth century. One of its main advantages is that it sets hard and quickly, increasing the speed of construction. However, it is not advisable for it to be used for the repair of older buildings constructed in lime mortar, because this type of binder lacks the flexibility, softness and breathability of lime that is required for such functions for proper function. Sulfate-resisting Portland cement may be used to replace ordinary Portland cement in cement:sand, cement:lime:sand and cement:sand with plasticizer mortars to reduce sulfate attack, in cases where wet conditions might be prolonged in the presence of soluble sulfates either in the ground or in clay bricks.Polymers are other types of binders, which are used in conjunction with cement hydrate binders of conventional cement mortar. The polymeric binders include latexes or emulsions, redispersible polymer powders, water-soluble polymers, liquid resins and monomers. The mortar made using this combination of binders has low permeability, and it reduces cases of drying shrinkage cracking, and its mainly designed for purposes of repairing concrete structures. An example of polymeric binders is MagneLine (Allen, 2003).Masonry cement itself is a pre-mix...
