Perforated bricks

With the arrival of perforated bricks, dies had to be provided with suitable cores, core holders and core holder bows. Tests were made with so-called bow-less dies with the cores fixed to wires, but these proved to be unsuccessful. With the design of dies becoming more and more complicated, die-making developed into a special field within ceramic machinery engineering, and even today there are still a few companies in various countries who manufacture exclusively dies. 

The main purpose of the pressure head, as a connection element between extmsion barrel and die, is to create uniform inflow conditions over the entire die area. To start with, a universal pressure head was employed for all types of clays and products, but it was quickly discovered that plastic materials required a longer pressure head than lean bodies. Also perforated bricks needed longer pressure heads than solid bricks to allow for ample space between core bow and end auger. Therefore a tripartite pressure head was designed, which made it possible to adjust the correct length of the pressure head, for instance in the event of alternating production of solid bricks and perforated bricks. Also there were lubricated pressure heads and those with a lateral cleaning door. 

System A. From right to left sandwich panel air interspace perforated brick 12 bioveid. 

System D. From tight to left certrent perforated brick 8 air interspace perforated brick 12 PVC foam. 

Cellular bricks are usually made by pressing whereas perforated BRICKS (q.v.) are made by extrusion. Cellular Concrete. See aerated concrete. 

Perforated Brick. A building brick made lighter in weight by its being pierced with numerous, relatively small (6-12 mm dia.) holes, usually in the direction of one of the two short axes. In the UK a perforated brick is defined (B.S. 3921) as one in which has holes not exceeding 25% of the volume of the brick with the holes so disposed that solid material is never less than 30% of the width of the... 

An article in The Builder [13] based on testing three types of perforated bricks walls set the low fire resistance with perforated bricks walls compared to solid brick walls was likely due to its cellular structure. Excessive temperature gradients produce a progressive fracture in the hollows of the elements of the walls. 

Other studies [15] also used data from previous researches by adding other tests on walls to show that the load-bearing walls fire resistance is depending on thickness and the performance of perforated bricks is related to the degree of drilling. Previous studies with other materials such as concrete under high temperatures have been used to provide guidelines about the behavior of mortars subjected to the thermal action. 

Safety in case of fire in buildings books also deal with high resistance to fire bricks solid respect to an equivalent thickness of perforated bricks and several of them conclude that due to the amount of air insulation it is not enough to offset the loss of solid material. 

H.L. Malhotra. Eire resistance of perforated brick walls. The Builder, March 9,1962. 

The die produces a column of clay with the desired form and a steel wire cuts it in individual parts. Products made by an extruder bricks (both perforated and not), hollow bricks, large building blocks, drainage pipes, sewer pipes, riven slabs, tiles and roof tiles. The extruder requires the use of a plastic clay. The baked product is characterized by its square shape and smooth surface. 

Liquation. Antimony sulfide is readily but inefficiendy separated from the gangue of comparatively rich sulfide ore by heating the gangue to 550—600°C in perforated pots placed in a brick furnace. The molten sulfide is collected in lower containers. A more efficient method uses a reverberatory furnace and continuous liquation however, a reducing atmosphere must be provided to prevent oxidation and loss by volatilization. The residue, containing 12—30% antimony, is usually treated by the volatilization process to recover additional antimony. The liquated product, called cmde or needle antimony, is sold as such for applications requiring antimony sulfide, or is converted to metallic antimony by iron precipitation or careful roasting to the oxide followed by reduction in a reverberatory furnace. 

Cutting laminations are mainly caused by fixtures in the die. Such fixtures are always unavoidable if a die with cores is employed in order to produce a perforated column, as with pipes, hollow profiles, common bricks, honeycombs, etc. The core bows, which are fitted crosswise to the flow direction, separate the body. If the distance between the core bow and column exit is too narrow or if the flow pressure is too low, the parting planes cannot sufficiently weld together. (5)... 

The sometimes large quantities of additives as commonly used in the brick industry for the production of highly-perforated heat-insulating bricks, together with the varied origin, grain shape and moisture content of these additives, demand optimum body preparation and proportioning a-head of the extruder. 

Considering the relative dryness of the body, it would be practically impossible to extrude good-quality cellular bricks at any reasonable pressure, if the insides (= feed contours) of the pressure head and die are not lubricated. The bricks would almost certainly have dragon s teeth and torn surfaces, and any penetrometric value in excess of roughly 3 would make some compounds stop up the pressure head and die. If, however, the compaction surfaces in the pressure head and die are lubricated, less extrusion pressure is needed, wear is minimized, the throughput capacity increases, and the surface quality of the extrudate improves. Large-format cellular bricks, e.g., 25 x 25 cm, are difficult, if not impossible, to stiff-extrude, because the resistance inside the corebar is simply too high. Smaller formats with up to about 40 % perforations are extrudable if the body has the appropriate properties. 

The characteristics and requirements of the product must also be known, of course, in order to plan optimal evacuation. Hourdis bricks with 60-70 % perforations, for example, are less exacting from the stand point of evacuation than, say, 500 mm compact slugs used for making insulators. 

Construction and Demolition (C D) waste typically consists of concrete, bricks, asphalt, wood, glass, masonry, roofing, siding and plaster, alone or in combinations. Intermediate C D landfills must have a 3-foot-thick clay liner and a leachate collection system. The diameter of leachate collection pipes must be at least six inches. Engineered landfills for municipal and industrial waste are constructed with a base liner and a leachate collection system. The primary purpose of the liner is to prevent grormdwater pollution. The liner may consist of clay only or be a combination of geomembrane and clay (known as a composite liner). The liner is constructed with at least a 2% slope towards perforated leachate collection piping to direct leachate to a collection system. 

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