Composite masonry is defined as the walls constructed from two or more building materials are termed as composite walls. The combination may be stone slab in the face work and brick masonry at the backing, or superior stones in the facing with rubble stone masonry at the backing so on. Composite masonry is adopted to improve the appearance of a structure by concealing the inferior work by use of superior quality of material in the desired positions. This results in great saving in cost and, if properly constructed, the structure remains equally strong and durable. Stones, bricks, concrete and tiles and the materials commonly used in such constructions.
Composite Masonry Used in Stone and Bricks
In this type of construction stone slabs are used in the face work and brick masonry is used as backing. Stones may be natural or artificial. The stones are secured to the backing either by means of metal cramps or by projecting the headers in the face work well inside the backing. It is obvious that the number of joints in the backing will be much more than the joints in the facing and as such the bonding between the two faces should be perfect to avoid unequal settlement of the two leaves.
The different types of composite masonry are described below:
1. Brick Backed Ashlar
The work built from carefully dressed stones with accurate bedding and jointing is termed as ashlar masonry.
2. Brick facing with Rubble or Concrete Backing
In this type of construction, special types of glazed tiles or bricks are used as facing material and rubble, concrete or brick is used as backing. Terra- cotta tiles and other such glazed tiles are commonly used in lavatory blocks and other similar situations.
3. Stone facing with Brick, Rubble or concrete Backing
The purpose of this type of masonry is to make a wall constructed in brick to appear as if constructed in stone. It is adopted to improve the appearance of the structure at a lesser cost. The stone slabs seldom exceed 5 to 10 cm. in thickness and are properly secured to the backing.
Cement Concrete Masonry
Cement concrete is largely used for construction purposes on account of its numerous advantages over the building materials. Cement concrete may be used in the form of pre-cast concrete blocks, plain concrete slabs or reinforced concrete slabs.
Hollow units may be defined as those units having core-void areas greater than 25% of their gross area. The blocks may have one or multi core design to suit the choice of manufacturer. The various advantages of hollow concrete block masonry are described below:
1. On account of their regular and uniform size and less weight, concrete blocks afford great facility in masonry construction which ultimately results in rapid execution of work.
2. Hollow blocks of concrete permit adoption of thinner walls thereby achieving increased floor area and hence saving of space.
3. There is a great saving of material on account of the blocks being hollow from inside. The air space (hollow space) in concrete blocks varies from 20 to 40% of their volume.
4. On account of the large size of concrete blocks, the number of joints in a work are lesser and hence there is saving of mortar in this type of masonry.
5. The hollow space in the blocks enables the masonry to have good insulating properties against sound, heat and dampness.
6. On account of good properties of concrete, hollow concrete blocks masonry can safely withstand the atmospheric action and it requires no protective covering as is necessary in case of brick work.
7. Unskilled labor can be employed in this type of work and on account of the light weight of the blocks, the construction is speedy and it results in economy in labor cost and in time.
8. The rough surface of the concrete blocks makes plastering (if needed) easier.
Load Bearing Wall Tiles
There are a variety of shapes for load bearing clay tiles. The tiles may be used for either interior or exterior load bearing walls. As in the case of hollow concrete blocks, the surface of tiles in rough and can be easily plastered if desired. The tiles may be used with or without any backing or facing. The tiles are designed to carry the superimposed load plus the weight of the facing material such as plaster etc.
Glass Block Masonry
There are various shapes and sizes of glass blocks available these days. The blocks are made from structural glass annealed to withstand rigorous use of the material. In addition, the glass used in such that it is impervious to grease, chemicals, moisture and does not change its color with age. The blocks may be made hollow or solid. Glass block panels should never be made to carry loads other than their own weight. They are generally laid in cement lime mortar (1:4). In glass block masonry with blocks more than 30 cm. high, every horizontal joint should be reinforced with galvanized expanded metal strips. The construction is so executed that there is complete freedom of movement of the panel within the en-framing members. Provision for expansion is made along the jambs and the head of each panel and there is proper anchorage of panel at head, sill and jambs.