To construct a wall, bricks and blocks are to be used. Mortar is used to bind th

Question

To construct a wall, bricks and blocks are to be used. Mortar is used to bind the bricks and blocks to form brick wall.

Discuss the mortar use in masonry construction based on following aspect:

(1) The main objective/functions/attributes of mortar in masonry construction; (10 marks)

(2) The mixing proportion and allowable dimension (15 marks)

(3) The mortar constituents - binder (20 marks)

(4)  The mortar constituents - Aggregate (20 marks)

(5)  The mortar constituents - Admixture (20 marks)

(6) The function of hole/perforate/hollow in brick in brick. (15 marks)

Explain briefly each part.

Explanation / Answer

Answer 1-

It binds together stones or bricks to take up loads and to give required strength to structure. It provides a homogeneous mass to structure . It helps to fill up empty joints in masonry and is used for plastering the structure so that an even surface is obtained. Also it provides a weather resisting or durable layer between the different courses of masonry, it should be capable of developing good adhesion with the building units such as bricks, stones etc.It should be capable of developing the designed stresses.It, .It should be capable of resisting penetration of rain water, It should be cheap, It should be durable and It should be easily workable.  

Answer 2-

Quantity of cement mortar is required for rate analysis of brickwork and plaster or estimation of masonry work for a building or structure. Cement mortar is used in various proportions, i.e. 1:1, 1:2, 1:3, 1:4, 1:6, 1:8 etc.

it is easy to estimate the amount of cement consumption required for brick masonry. Remember depending on the class of brickwork of sand cement ratio the total calculation can change. Additionally, a homogeneous mix of sand, cement, and water is the secret of the recipe for a stronger bond between bricks. Therefore, only required a quantity of water should be used, and the mix should be prepared with a mechanical mix to assure the strength of the brick masonry.

Answer 3-

The binder’s job is to hold the sand together, to contribute flexibility for building movement, and to contribute moisture permeability so that water can escape rapidly, The two critical qualities of sand that contribute compressive strength are particle size and particle shape. These can be determined with simple tests, The ratio of binder to sand is critical because too much or too little of the binder will weaken the mortar, The void space in a sand can be determined with a simple test, and will determine the amount of binder to use for that sand.

Answer 4 -

The aggregate or main part of mortar is sand. The sand is dredged from pits or river beds and a good sand should consist of particles ranging up to 5 mm in size, In the ground, sand is usually found mixed with some clay earth which coats the particles of sand. If sand mixed with clay is used for mortar, the clay tends to prevent the cement or lime binding the sand particles together and in time the mortar crumbles. It is therefore important that the sand be thoroughly washed so that there is no more than 5% of clay in the sand delivered to the site.

Answer 5-

Admixtures are natural or manufactured chemicals which are added to the concrete before or during mix- ing. The most often used admixtures are air-entraining agents, water reducers, water-reducing retarders and accelerators. Admixtures are used to give special properties to fresh or hardened concrete.

Chemical admixtures are the ingredients in concrete other than portland cement, water, and aggregate that are added to the mix immediately before or during mixing.

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