Coloured mortars

Mortar colour has a profound effect on the overall appearance of the brickwork as, with stretcher bond and a standard 10 mm joint, the mortar accounts for 17% of the brickwork surface area. A wide range of light-fast coloured mortars is available which can be used to match or contrast with the bricks, thus highlighting the bricks as units or creating a unity within the brickwork. The coloured mortars contain inert pigments, which are factory-blended to a tight specification to ensure close colour matching between batches. Occasionally, black mortars may bloom due to lime migration to the surface. Coloured mortars can be used creatively to enhance the visual impact of the brickwork and even create designs on sections of otherwise monochromatic brickwork. The quantity of pigment should not exceed10% by weight of the cement. Mortar colours may also be modified by the use of stains after curing; however, such applications only penetrate 2mm into the surface, and therefore tend to be used more for remedial work. Through-body colours are generally more durable than surface applications.

(From Materials for Architects and Builders)

9 Use the words below to complete the sentences: clay bricks Part I

The main constituents of brick-making clays are silica (sand) and 1) _____, but with varying quantities of chalk, 2) _____, iron oxide and other minor constituents such as fireclay, according to their source.

There are five main processes in the manufacture of 3) _____ bricks: a) extraction of the raw material; b) forming processes; c) drying; d) firing;e) packaging and distribution.

The process begins with the 4) _____ of the raw material from the quarry and its transportation to the works, by conveyor belt or road transport. Topsoil and5) _____ overburden are removed first and used for site reclamation after the 6) _____ clay is removed.

The handmade process involves the throwing of a suit ably sized clot of wet clay into a wooden 7) _____ on a bench. The surplus clay is struck off with a framed wire and the green brick removed. The bricks produced are 8) _____ in shape with soft arises and interestingly folded surfaces. Two variations of the process are 9) _____ moulding and slop moulding.

clay irregular lime unsuitable mould extraction pallet alumina usable

10 Fill in the gaps with derivatives of the words in capitals: clay bricks

Part II

Figure 3.2.Moulds for handmade bricks In pallet moulding, a stock board, the size of the bed face of the brick, is 1) _____ to the bench. The mould fits loosely over the stock board, and is adjusted in 2) _____ to give appropriate thickness to the green brick. The mould and board are sanded to ease removal of the green brick which, is produced with a frog or 3) _____ on one face. In the case of slop moulding, the stock mould is placed directly on the bench, and is usually wetted rather than sanded to allow removal of the green brick which, 4) _____ the pallet moulded brick, is smooth on both bed faces (Figure. 3.2). To prevent cracking and distortion during the firing process, green bricks produced from wet clays must be allowed to dry out and shrink. 5) _____ is typically 10% on each dimension depending upon the moisture content. Drying temperatures and 6) _____ levels are carefully controlled to ensure shrinkage without distortion. Both intermittent and continuous kilns are 7) _____ for firing bricks. The former is a batch process in which the single kiln is loaded, fired, 8) _____ and unloaded. In continuous kilns, the 9) _____ process is always active; either the green bricks are moved through a fixed firing zone, or the fire is gradually moved around a series of 10) _____ chambers to the unfired bricks. Both continuous systems are more energy efficient than the intermittent processes.

FIX HIGH DEPRESS LIKE SHRINK HUMID USE COOL FIRE CONNECT