User:DIPANKAR SEKHAR SAIKIA/Difference between portland and aasbestos cement

DIPANKAR SEKHAR SAIKIA/Difference between portland,asphalt and asbestos cement PORTLAND CEMENT....

Portland cement (often referred to as OPC, from Ordinary Portland Cement) is the most common type of cement in general use around the world, because it is a basic ingredient of concrete, mortar, stucco and most non-specialty grout. It is a fine powder produced by grinding Portland cement clinker (more than 90%), a limited amount of calcium sulfate which controls the set time, and up to 5% minor constituents (as allowed by various[which?] standards).[citation needed] As defined by the European Standard EN197.1: “	Portland cement clinker is a hydraulic material which shall consist of at least two-thirds by mass of calcium silicates (3CaO.SiO2 and 2CaO.SiO2), the remainder consisting of aluminium- and iron-containing clinker phases and other compounds. The ratio of CaO to SiO2 shall not be less than 2.0. The magnesium content (MgO) shall not exceed 5.0% by mass.[cite this quote]	”

ASBESTOS CEMENT....

Asbestos cement is a product employed broadly in the past as a building material. It commonly has 10-15% asbestos fibres which are bound in portland cement or calcium silicate and the uncoated sheets are light grey in colour (a number of sheets may have been painted or have a factory applied coating).

Asbestos cement is a well bonded, sheet building material, generally used for roofing and outbuildings like garages. Attention has to be taken not to confuse it with asbestos insulation board which is similar in appearance, but much more dangerous since it is softer.

Despite the rising number of published studies that proved the hazards asbestos imposed on people's health, large companies continued to make use of asbestos despite the fact that safer insulation alternatives, like fiberglass, were obtainable to replace it. Up to the late 1980s, asbestos was broadly employed in construction materials, from asbestos-cement sheeting for ceilings and walls, to corrugated asbestos cements used for roof cladding.

Typically, the existence of asbestos-containing materials is no cause for alarm and you can leave the materials in place. For instance, if internal asbestos sheet walls are in good form and coated with paint, they do not cause a health risk. External roofs and siding do not have to be replaced unless they are broken or the surfaces are damaged. Asbestos-cement construction products could be maintained, removed or disposed of safely, on condition that you take certain precautions to prevent the release of asbestos fibers or dust

ASPHALT CEMENT....

Asphalt concrete, normally known simply as asphalt or AC (in North America), is a composite material commonly used for construction of pavement, highways and parking lots. It consists of asphalt binder and mineral aggregate mixed together then laid down in layers and compacted. Asphalt is a brownish-black liquid petroleum material that hardens when it cools. Asphalt cement poisoning occurs when someone swallows asphalt. Before asphalt hardens, its liquid form can cause burns to the skin and eyes, it can cause lung damage if inhaled, and it can cause severe internal injury if ingested. Asphalt concrete has different performance characteristics in terms of surface durability, tire wear, braking efficiency and roadway noise. The appropriate asphalt performance characteristic is obtained by the traffic level amount in categories A,B,C,D,E, and friction coarse (FC-5). Asphalt concrete generates less roadway noise than Portland cement concrete surfacing, and is typically less noisy than chip seal surfaces. Tire noise effects are amplified at higher operating speeds. The sound energy is generated through rolling friction converting kinetic energy to sound waves. The idea that highway design could be influenced by acoustical engineering considerations including selection of surface paving types arose in the very early 1970s.