Presentation on theme: "CEMENT DEFINITION Cement is often confused with concrete. Cement is a finely ground, usually grey colored mineral powder. When mixed with water, cement."— Presentation transcript:
CEMENT DEFINITION Cement is often confused with concrete. Cement is a finely ground, usually grey colored mineral powder. When mixed with water, cement acts as a glue to bind together the sand, gravel and crushed stone to form concrete, the most widely used construction material in the world.
TYPES OF CEMENTS Ordinary cement This type of cement is used a lot today, and is still known as OPC (ordinary Portland cement)... It is ground up into a powder to form ordinary OPC Rapid heat cement They generate more heat in the early stages and can be useful in cold weather concreting.... as either rapid-setting or extra rapid hardening may be Low heat cement Low Heat Cement complies with AS 3972, Special Purpose Type LH/SR. It is manufactured from the ingredients of specially selected cement clinker and ground granulated blast furnace slag, that result in significantly lower heat generation during the process of hydration than the comparable Portland Cement.
Portland blast furnace cement The granulated slag made by the rapid chilling of suitable molten slags from blast furnaces forms the basis of another group of constructional cements. A mixture of portland cement and granulated slag, containing up to 65 percent slag, is known in the English-speaking countries as portland blast-furnace (slag) cement. High alumina cement of High Alumina Cement, Alumina Cement, Refractory Cement, Refractory Materails,... Density Corundum Bricks, high alumine cement ca50-G5, G7, G9, fused, ca70, ca80 Expanding cement Expanding and nonshrinking cements expand slightly on hydration, thus offsetting the small contraction that occurs when fresh concrete dries for the first time. Expanding cements were first produced.
Quick setting cement Rapid cure allows for quick access to repaired areas. Garonite anchoring cement sets and e-x-p-a-n-d-s rapidly, curing twice as strong as concrete in one hour. Use indoors or out Air & trading cement Hydrophobic cement Cement is a hydraulic bonding agent used in building construction and civil engineering. It is a fine powder obtained by grinding the clinker of a clay and limestone mixture calcined at high temperatures. When water is added to cement it becomes a slurry that gradually hardens to a stone-like consistency. It can be mixed with sand and gravel (coarse aggregates) to form mortar and concrete.
White cement White portland cement is readily available throughout North America. It has essentially the same properties as gray cement, except for color, which is a very important quality control issue in the industry. The color of white cement depends on raw materials and the manufacturing process. It is the metal oxides (primarily iron and manganese) that influence the whiteness and undertone of the material. White cement is manufactured to conform to ASTM C 150, Specification for Portland Cement. Although Types I, II, III, and V white cements are produced, Types I and III are the most common. White cements produce clean, bright colors, especially for light pastels. Many different colors can be created by adding pigments to concrete made with white portland cement. Two or more pigments can be combined to achieve a wide range of colors. White cement (or a mixture of white and gray cement) can be specified to provide a consistent color of choice. An even greater variety of decorative looks can be achieved by using colored aggregates and varying the surface finish treatment or texture.
STRENGTH OF CEMENT The mechanical strength of hardened cement is the property of the material that is perhaps most obviously required for structural use. The strength of the mortar or concrete depends on the cohesion of the cement paste, on its adhesion to the aggregate particle and other. Strength test: Compression is the most common measure of strength. A 2-in. mortar cube using a 2.75:1 sand/cement ratio with a water/cement ratio of 0.485 - 0.460 is tested. After a certain procedure is followed the specimens are failed. Tensile strength is determined by a direct tensile test. The results are not of much value. Flexural strength is determined by a flexural test of a small rectangular-shaped prism on simple supports with a center load. The flexural strength is directly calculated. This mortar strength does not necessary relate to concrete strength using the same cement; used for quality control.
The composition of Portland cements falls within the range of: 60 to 67 percent lime, 17 to 25 percent silica, 2 to 8 percent alumina, and 0 to 6 percent iron oxide together with 1 to 7 percent sulphur trioxide, derived mainly from the added gypsum, 0.1 to 5 percent magnesia, and 0.1 to 1.5 percent alkalis.
TYPES OF PORTLAND CEMENT Five types of Portland cement are standardized in the U.S. (Standard Specification for Portland Cement C 150 - 97): Ordinary (Type I) - - most common, no special properties Modified (Type II) - - good strength with lower heat of hydration High-early-strength (Type III) - - rapid setting; used in precast work or at low temperatures -- possible tensile cracking due to thermal stress if sections are large. Low-heat (Type IV) - - Used in mass concrete applications-low heat of hydration Sulphate-resisting (Type V) - - provides protection from damage due to exposure to sulfates (seawater, some groundwater supplies, and particularly wetting and drying processes). In other countries Type II is omitted, and Type III is called rapid hardening. Type V is known in some European countries as Ferrari cement.