3. CEILING TILES
Ceiling tiles are lightweight tiles used inside buildings. They are placed in an Aluminum grid; they provide title thermal insulation but are generally design to improve the acoustics of a room. Mineral fiber tiles are fabricated from a range of products; wet felt tiles can be manufactured from perlite, mineral wool, and fibers from recycled paper ;stone wool tiles are created by combining molten stone and binders which is then spun to create the tile; gypsum tiles are based on the soft mineral and then finished with vinyl, paper or a decorative face. Ceiling tiles very often have patterns on the front face; these are there in most circumstances to aid with the tiles ability to improve acoustics. Ceiling tiles also provide a barrier to the spread of smoke and fire. Breaking, displacing, or removing ceiling tiles enables hot gases and smoke from a fire to rise and accumulate above detectors and sprinkles. Doing so delays their activation, enabling fires to grow more rapidly.
2.2.2 BLOCKS
Concrete blocks are made from cast concrete, e.g. Portland cement and aggregate, usually sand and fine gravel for high-density blocks. Lower density Blocks may use industrial wastes as an aggregate. Light weight blocks can also be produced using aerated concrete. Concrete blocks may be produced with hollow centers (cores) to reduces weight or improve insulation. This use of block work allows structures to be built in the traditional masonry style with layers (or courses of staggered blocks come in many sizes. In the US, the most common nominal size is 16*8*8 in (4l0mm*200rrcm*200); the block measures a 3/8 in shorter, allowing for Mortar joints. In Ireland and the UK, blocks are usually 440mm215mm*100Mm ( 17.3*8.5 j*39 in) excluding mortar joints . In New Zealand and Canada Blocks are usually 390mm*l9Omm*l9Omm ( 15.4 in*7.5 in *75 in ) excluding Mortar joints. Blocks cores are typically tapered so that the top of the block( as laid) has a Greater surface on which to spread a mortar bed and for easier handling. Most CMU’s have two cores, but three and four core units are also produced. A core also allows for the insertion of steel reinforcement, tying individual blocks together in the assembly, with the goals of greatly increased strength. To hold the reinforcement in proper position and to bond the block of reinforcement, the core must be filled with goals ( concrete ). Reinforcement primarily used to impart greater tensile strength to the assembly, improving its ability to resist lateral forces such as wind load and seismic forces. A variety of specialized shapes exist to allow special construction features.
U-shaped blocks or knockout blocks with notches to allow the construction of bond beams or lintel assemblies, using horizontal reinforcing grouted into place in the cavity. Blocks with a channel on the end, known as “jamb blocks†allowing doors to be secured to wall assemblies. Blocks with grooved ends permit the construction of control joints, allowing a filler material to be anchored between the un-mortared block ends. Other features such as radiuses corners known as “bull noses†may be incorporated. A wide variety of decorative profiles also exist.
2.2.2.1 STATIONARY CONCRETE BLOCK MACHINE
It constitute of the main following segment:
• BLOCK MACHINE: Its function is to receive the concrete from the Concrete batching plant in its hopper. The concrete is then filled into steel molds that rest on production pallets ( pallet can be from steel, wood or composite material). Once filled, a mix of vibration and hydraulic compression forces the green concrete into the shape of the mold. The mound retreats into the block machine leaving the green product on the pallet.
• ELEVATOR: Its function is to stack pallet with green products in its steel forks. Normally ,15-20 levels of pallet are stacked.
• TRANSFER CAR: It takes the stack of pallet from the eIevator in to the curing chamber, where all pallets are placed on the racks. On the way back, the transfer car brings back cured products.
• CURING CHAMBER: Purpose of the curing chamber is to provide
control temperature and humidity to cure the concrete blocks. Blocks are normally kept in curing chamber for 12-24 hours.
• LOWELATOR: The transfer car brings the cured product to lowelator, whose function is just opposite to elevator. One by one, it takes out the pallets with cured blocks, and passes them onto a conveyor.
• CUBER: The steel grab takes concrete blocks from each pallet and starts making a bundle, normally in the form of a cube or a cuboid.
• PACKING MACHINE: The formed cube of concrete blocks is then shrink wrapped, placed on a wooden pallet, and moved by a forklift to the storage yard.
