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Reinforced masonry can be said to have come into existence as an improvement on the deficiency of Masonry design after series of research and lesson learnt from other construction materials most especially from a similar brittle material Concrete, in which the use of reinforcement steel enhanced it performance thereby zeroing out its limitation. Masonry did not just come into existence, it has from time immemorial being used in building purposes but lost its footing in use to be replaced by steel structures and reinforced concrete structures whose construction were guided by structural codes of practice. With the introduction of codes of practice, experience gathered over the years of use coupled with different researches being performed, Masonry building constructions are in the competitive use in this century as strength, thickness and other calculations pertaining to structural members can be carried out though with preference to some particular country and continents as some underdeveloped countries still make use of the masonry in the old way.
Bricks are components of masonry/reinforced masonry construction made from /of fired clay calcium silicate or concrete of dimensions not exceeding 337.5 x 225 x 112.5 corresponding to the length, width and thickness all in Millimeters (Hendry et al 1997). They are classified into different types according places of application, resistance to frost action and maximum soluble salt content according to Hendry et al (1997) and these are adapted into Table 1 in accordance to the classification criteria or guidelines.
Compressive Strength: Good Compressive strength is required where masonry is to be used for load bearing and this sis to be provided by the Mortar and the Masonry units (bricks and blocks). Compressive strength provided by the mortar is a function of its water- cement ratio and the Cement both in quantity used in proportion and quality. This can be explained in that increase in the quantities of other materials such as sand, Lime, Water content , air entrainment and the reduction in cement volume results in Decrease in the Compressive strength obtained. (Beall 1997).
Bond Strength: Bonding is the complete and sufficient joining of Mortar and the respective masonry elements into a single entity or element avoiding easy separation. The strength attained by good bonding goes a long way in the determination of other performance properties such as durability, water resistance and weather resistance. Just as the above listed properties are dependent on the good bonding for great performance, there are a couple of parameters that determines good bond strength which includes workability, surface textures of the bricks , absorption, Temperature among a couple of others (Beall 1997).
Water Retaining Capacity: This is the ability of mortar to retain water used in the mixing process. Inability of Mortar to retain water results in the loss of water through evaporation or capillary action or suction by dry brick. Early loss of mix water result in insufficiency in what is required for hydration and poor bonding and strength in mortar and overall structure is obtained. The water retaining capacity of mortar is a function of the lime meaning increase in lime results in increase in water retention (Beall 1997). Water ââ‚¬" Cement ration required for the a good mortar mix (in terms of Workability and Retention) is left is left to the discretion of an experience mason or bricklayer as we;; as his ability to judge the loss of that water either through evaporation of Cement Hydration. Water lost by evaporation is allowed to be replaced while that lost through Cement hydration must not be replaced rather the mortar is discarded.
Grout is the mixture of cement and aggregates usually flowing (without segregation) for the ease of placement into cavities provided within masonry units bricks. Grout serves the sole purposes of creating a proper bonding between masonry units and reinforcements for single element behaviour. Grout good bonding is enhanced by its fluidly/flowing consistency with the appropriate water content for provision of proper cover to the reinforcement ,flow into the rough surfaces and recesses not covered by mortar as well as not creating void spaces within the cavities yet with a good compressive strength developed (Beall 1997). The size of the cavity or core determines the maximum size of the aggregate to be used in the grout mix as it being the only constituent material that varies in size and for provision of a flowing, placement ease and void free resultant solid grout (Hendry et al 1997). This Concrete mix for different uses is as specified in the codes.
Reinforcement provides tensile resistance (strength and stiffness) for the masonry structure to the overcome the effect of environmental forces such as wind, seismic movement and air changes to which the structure will be subjected to in application. Its inclusion in masonry reduces or eliminates movement cracks or defects or entire structure failure due to their brittle nature of other constituents of Masonry construction that is in the masonry units, mortar and grout or concrete infill. There are varieties of reinforcing bars available for selection in use ranging from hot rolled , cold- worked to the welded wire fabric where sizes and placement are obtained by service load design analysis and those conforming to design code of practice specification are adhered to (Beall 1997).